Automated device for non-invasive measurement of blood pressure and ankle-brachial index

Abstract

The disclosure provides a device for non-invasive blood pressure measurement comprising a blood pressure cuff positioned around a limb with an optical sensor integrated into the distal end. The optical sensor comprises a transmission optical sensor with light source and detector on opposite sides of a digit distal to the inflatable portion. A processing device controls cuff inflation and deflation while capturing successive optical plethysmographic waveforms during deflation. The processing device high-pass filters waveforms to produce filtered signals with equal area above and below baseline, multiplies corresponding points of filtered waveforms to generate product values, and sums products to determine concordance measures. The device detects initial returning pulsations by identifying when initial low-amplitude optical pulsations have same shape as larger amplitude pulsations during deflation. Systolic blood pressure is determined when concordance measures indicate shape concordance between initial and subsequent optical pulsations. The device measures blood pressure and calculates ankle-brachial indices.

Description

Attorney Docket No. 159615-00123AUTOMATED DEVICE FOR NON-INVASIVE MEASUREMENT OF BLOOD PRESSURE AND ANKLE-BRACHIAL INDEXCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 716,109, titled AUTOMATED DEVICE FOR NON-INVASIVE MEASUREMENT OF BLOOD PRESSURE AND ANKLE-BRACHIAL INDEX, filed November 4, 2024, which is hereby incorporated by reference in its entirety. The present application is related to U.S.Patent Application No. 17,399,662, filed August I L 2021, whose disclosure is hereby incorporated by reference in its entirety into the present disclosure.FIELD OF INVENTION

[0002] The present disclosure relates to non-invasive blood pressure measurement systems, and more particularly to an automated device for measuring systolic blood pressure and calculating ankle-brachial indices using plethysmographic techniques with crosscorrelation signal processing.BACKGROUND

[0003] Non-invasive blood pressure measurement has become a cornerstone of modem medical practice, providing healthcare professionals with vital information for diagnosing and managing cardiovascular conditions. Traditional methods for measuring blood pressure typically rely on oscillometric techniques, where pressure oscillations in an inflatable cuff are analyzed to determine systolic and diastolic values. While these methods are widely used and generally effective for routine blood pressure monitoring, they face limitations when more precise measurements are required, particularly in specialized clinical applications.

[0004] The measurement of ankle-brachial index (ABI) represents one such specialized application where enhanced accuracy becomes particularly valuable. ABI is calculated as the ratio of systolic blood pressure measured at the ankle to the systolic blood pressure measured at the arm and serves as an indicator of peripheral arterial disease. When ABI values fall below 0.9, this may suggest the presence of arterial narrowing or blockage in the lower extremities, making ABI measurement a valuable screening tool for vascular health assessment.

[0005] Current methods for obtaining accurate systolic blood pressure measurements for ABI calculations often employ Doppler ultrasound techniques. These approaches involve1159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 placing a Doppler probe distal to an occluding cuff and listening for the return of arterial flow as the cuff is deflated. While this Doppler method can provide accurate systolic pressure measurements, it presents several practical challenges. The procedure requires skilled technicians, involves the application of ultrasound gel, and can be time-consuming to perform. Additionally, the need to manually locate and monitor arterial signals makes the process somewhat subjective and dependent on operator expertise.

[0006] Plethysmographic techniques offer an alternative approach to blood pressure measurement by detecting changes in blood volume within tissues. Various forms of plethysmography, including electrical impedance, optical, and strain gauge methods, have been explored for cardiovascular monitoring applications. These techniques can potentially provide information about blood flow and vascular changes without requiring the manual probe positioning associated with Doppler methods.

[0007] One challenge common to many non-invasive blood pressure measurement techniques is the presence of noise and artifacts in the acquired signals. Physiological signals are often small in amplitude and can be obscured by various sources of interference, including patient movement, electrical noise, and baseline drift. This signal quality issue becomes particularly pronounced when attempting to detect subtle changes in blood flow or volume that occur at the onset of arterial pulsation during cuff deflation.

[0008] The development of automated systems for blood pressure measurement and ABI calculation could address many of the limitations associated with current manual techniques. Such systems could potentially reduce operator dependency, improve measurement consistency, and make these diagnostic procedures more accessible in various clinical settings. However, achieving reliable automation requires robust signal processing methods capable of extracting meaningful physiological information from noisy measurement environments.SUMMARY

[0009] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summan is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.2159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0010] The present disclosure provides a device for non-invasive measurement of blood pressure that may comprise a blood pressure cuff configured to be positioned around a limb, where the blood pressure cuff may have a proximal end and a distal end. The device may include an optical plethysmographic sensor connected to the distal end of the blood pressure cuff, where the optical plethysmographic sensor may be configured to be positioned on a digit distal to an inflatable portion of the blood pressure cuff to acquire optical plethysmographic signals. The optical plethysmographic sensor may comprise a transmission optical sensor with a light source positioned on a first side of the digit and a light detector positioned on an opposite side of the digit. Alternatively, the optical sensor may be a reflectance optical plethysmograph or pulse oximeter integrated into the distal edge of the cuff.

[0011] The device may further comprise a processing device operatively connected to the blood pressure cuff and the optical plethysmographic sensor. The processing device may be configured to control inflation and deflation of the blood pressure cuff and capture successive optical plethysmographic waveforms during deflation of the blood pressure cuff. The processing device may be configured to high-pass filter the successive optical plethysmographic waveforms to produce filtered waveforms having equal area above and below a baseline, multiply corresponding points of the filtered waveforms to generate product values, and sum the product values to determine a concordance measure.

[0012] The processing device may be configured to detect initial returning pulsations of very low amplitude during cuff deflation by identifying when the initial low-amplitude optical pulsations have the same shape as larger amplitude optical pulsations that follow as the cuff pressure continues to decrease. The processing device may determine systolic blood pressure based on detection of the initial returning pulsations when the concordance measure indicates that the initial low-amplitude optical pulsations are concordant with subsequent higher-amplitude optical pulsations.

[0013] In some aspects, the optical plethysmographic sensor integrated into the distal end of the blood pressure cuff may comprise a pulse oximeter sensor. The transmission optical sensor may be configured to be positioned on a finger or toe at the distal end of the blood pressure cuff. The processing device may be configured to multiply corresponding points of an even number of successive filtered optical w aveforms, and in some cases, the processing device may be configured to multiply corresponding points of four successive filtered optical waveforms.3159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0014] The processing device may be further configured to determine diastolic blood pressure by identifying a maximum concordance measure corresponding to mean blood pressure and calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2, or by identifying a maximum arterial pulsation amplitude. The device may further comprise an inflation mechanism operatively connected to the processing device, where the processing device may be configured to control the inflation mechanism to inflate the blood pressure cuff to a predetermined pressure and deflate the blood pressure cuff at a controlled rate during measurement. The processing device may be further configured to detect the initial returning pulsations by monitoring the concordance measure during the controlled deflation to identify the precise moment when blood flow returns as indicated by shape concordance between initial low-amplitude and subsequent higher-amplitude optical pulsations.

[0015] According to another aspect of the present disclosure, a method for automated measurement of ankle-brachial index is provided. The method comprises determining that a first blood pressure cuff is positioned on an arm of a patient. The method comprises determining that a second blood pressure cuff is positioned on an ankle of the patient. The method comprises determining that a first plethysmographic sensor is positioned distal to the first blood pressure cuff. The method comprises determining that a second plethysmographic sensor is positioned distal to the second blood pressure cuff. The method comprises measuring a first systolic blood pressure at the arm by inflating the first blood pressure cuff, deflating the first blood pressure cuff while acquiring first plethysmographic signals from the first plethysmographic sensor, processing the first plethysmographic signals using a crosscorrelation technique to identify onset of concordant waveforms, and determining the first systolic blood pressure based on cuff pressure when concordant waveforms are detected. The method comprises measuring a second systolic blood pressure at the ankle using the second blood pressure cuff and second plethysmographic sensor in a similar manner. The method comprises calculating an ankle-brachial index as a ratio of the second systolic blood pressure to the first systolic blood pressure.

[0016] According to other aspects of the present disclosure, the method may include one or more of the following features. The first plethysmographic sensor and the second plethysmographic sensor may each comprise an optical plethysmographic sensor. The optical plethysmographic sensors may be transmission optical plethysmographic sensors positioned on digits of the patient. Processing the first plethysmographic signals using a crosscorrelation technique may comprise capturing successive plethysmographic waveforms4159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 during deflation, high-pass filtering the successive plethysmographic waveforms to produce filtered waveforms having equal area above and below a baseline, multiplying corresponding points of an even number of the filtered waveforms to generate product values, and summing the product values to determine a concordance measure. Multiplying corresponding points may comprise multiplying corresponding points of successive filtered waveforms. The method may further comprise measuring systolic blood pressure at both arms of the patient and calculating the ankle-brachial index using a higher of the two arm systolic blood pressures. The method may further comprise generating a report displaying the systolic blood pressure measurements for each extremity and the calculated ankle-brachial indices.

[0017] According to another aspect of the present disclosure, a system for automated vascular assessment is provided. The system comprises a plurality of blood pressure cuffs configured for placement on multiple extremities of a patient. The system comprises a plurality of plethysmographic sensors, each configured for placement distal to a corresponding blood pressure cuff. The system comprises a processing unit configured to control sequential inflation and deflation of the plurality' of blood pressure cuffs, acquire plethysmographic data from the plurality of plethysmographic sensors during cuff deflation, apply signal processing to identify systolic blood pressure at each extremity by detecting concordant pulse waveforms through multiplication of high-pass filtered plethysmographic signals, calculate ankle-brachial indices for lower extremities based on measured systolic pressures, and generate a report displaying systolic blood pressures and ankle-brachial indices for the multiple extremities.

[0018] According to other aspects of the present disclosure, the system may include one or more of the following features. The plurality of plethysmographic sensors may comprise optical plethysmographic sensors. The optical plethysmographic sensors may be transmission optical plethysmographic sensors configured for placement on digits of the patient. A pulse oximeter may serve as an optical plethysmograph. The processing unit may be configured to multiply corresponding points of successive high-pass filtered plethysmographic waveforms to generate product values for determining concordant pulse waveforms. The processing unit may be further configured to determine diastolic blood pressure for each extremity by identify ing a maximum concordance measure corresponding to mean blood pressure and calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2. The plurality of blood pressure cuffs may comprise four blood pressure cuffs configured for placement on both arms and both ankles of the patient, and the processing unit may be configured to5159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 calculate bilateral ankle-brachial indices using a higher of the two arm systolic blood pressures as a denominator.

[0019] The foregoing general description of the illustrative embodiments and the following detailed description thereof are merely exemplars’ aspects of the teachings of this disclosure and are not restrictive.BRIEF DESCRIPTION OF FIGURES

[0020] Non-limiting and non-exhaustive examples are described with reference to the following figures.

[0021] FIG. 1 depicts a graph showing pulsation amplitude versus cuff pressure during conventional oscillometric blood pressure measurement.

[0022] FIG. 2 illustrates a conventional Doppler method for determining systolic blood pressure on a patient's arm.

[0023] FIG. 3A illustrates a blood pressure measurement device configured for use on a patient's upper extremity7, according to aspects of the present disclosure.

[0024] FIG. 3B illustrates a blood pressure measurement device configured for use on a patient's lower extremity, according to aspects of the present disclosure.

[0025] FIG. 4A displays a pulse volume curve plotting microliters per centimeter against time over a three-second period, according to aspects of the present disclosure.

[0026] FIG. 4B displays a high-pass filtered pulse volume curve plotting microliters per centimeter against time, according to aspects of the present disclosure.

[0027] FIG. 5A displays a graph showing microliters per centimeter squared versus time for a product of filtered pulse volume waveforms, according to aspects of the present disclosure.

[0028] FIG. 5B displays a noise waveform plotting microliters per centimeter against time, according to aspects of the present disclosure.

[0029] FIG. 5C displays a product of two high-pass filtered noise waveforms, according to aspects of the present disclosure.

[0030] FIG. 6A displays a combined pulse volume and noise waveform plotting microliters per centimeter against time, according to aspects of the present disclosure.6159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0031] FIG. 6B displays a product of two high-pass filtered noisy pulse volume waveforms, according to aspects of the present disclosure.

[0032] FIG. 7 depicts a graph illustrating the relationship between mean blood pressure and calf pulse volume during cuff deflation, according to aspects of the present disclosure.

[0033] FIG. 8 depicts a report displaying systolic blood pressure and ankle-brachial index measurements for multiple extremities, according to aspects of the present disclosure.

[0034] FIG. 9 illustrates a blood pressure cuff with an integrated optical pulse detector, according to aspects of the present disclosure.

[0035] FIG. 10 illustrates a flowchart for an automated method for measuring ankle- brachial index, according to aspects of the present disclosure.

[0036] FIG. 11 illustrates a flowchart for an automated method for non-invasive blood pressure measurement using plethysmographic signal processing, according to aspects of the present disclosure.

[0037] FIG. 12 illustrates a flowchart for an automated method for m ulti -ext remi ty vascular assessment, according to aspects of the present disclosure.

[0038] FIG. 13 illustrates a flowchart for an enhanced bilateral ankle-brachial index measurement method with diastolic blood pressure determination, according to aspects of the present disclosure.DETAILED DESCRIPTION

[0039] The following description sets forth exemplary aspects of the present disclosure. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure. Rather, the description also encompasses combinations and modifications to those exemplary aspects described herein.

[0040] Referring to FIG. 1, conventional oscillometric blood pressure measurement techniques operate by monitoring pulsation amplitude during deflation of a blood pressure cuff from suprasystolic pressure. FIG. 1 illustrates a graph depicting the relationship between pulsation amplitude and cuff pressure during this deflation process. A cuff pressure axis 110 represents the horizontal axis of the graph, showing cuff pressure measured in mmHg ranging from approximately 200 mmHg to 0 mmHg, with values decreasing from left to right to indicate progressive cuff deflation.7159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0041] The graph displays a characteristic bell-shaped curve showing how pulsation amplitude varies as a function of cuff pressure during deflation. An onset of pulsation marker 1 12 indicates the point where pulsations first appear during cuff deflation, which occurs when the cuff pressure has been reduced to some value above systolic pressure. A systolic pressure indicator 102 marks the location corresponding to a systolic pressure value 100 of approximately 102 mmHg on the cuff pressure axis 110. The onset of pulsation marker 112 does not correspond directly to the systolic pressure value 100, demonstrating that the appearance of pulsations occurs at a different pressure than the actual systolic blood pressure.

[0042] As shown in FIG. 1, pulsation amplitude increases as cuff deflation continues, reaching a maximum pulsation value of 104 corresponding to a mean blood pressure value. The maximum pulsation amplitude can correspond to the diastolic blood pressure. The pulsation value 104 corresponds to the peak of the bell-shaped curve where pulsation amplitude reaches its highest point during the deflation process. Following this peak, pulsation amplitude decreases as cuff pressure continues to fall. A diastolic pulsation value 106 marks the point corresponding to a diastolic pressure, positioned on the descending portion of the curve where pulsations continue below diastolic pressure.

[0043] The oscillometric technique requires mathematical algorithms to derive actual systolic and diastolic blood pressure values from the cuff pressure measurements at the onset of pulsation marker 112, the mean pressure value 104, and the termination of pulsations. These algorithms may differ between manufacturers and may introduce inaccuracies when compared to invasive blood pressure measurements obtained with arterial catheters. The pulsations appear as small waveforms that ride on the decreasing mean inflation pressure and may be extracted through high-pass filtering techniques.

[0044] Referring to FIG. 2, a conventional Doppler method for determining systolic blood pressure provides an alternative approach to oscillometric techniques. FIG. 2 illustrates an orthogonal side view of this conventional measurement setup positioned on a patient's arm 200. A blood pressure cuff 202 may be positioned around the upper portion of the arm 200, where the blood pressure cuff 202 may be configured to occlude arterial blood flow when inflated to pressures above systolic blood pressure.

[0045] A Doppler probe 204 may be positioned distal to the blood pressure cuff 202, typically placed over a radial artery location on the forearm or wrist area of the arm 200. The Doppler probe 204 may be configured to detect arterial blood flow through ultrasound8159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 technology, providing direct monitoring of blood flow distal to the occlusion point created by the blood pressure cuff 202. During the measurement process, the blood pressure cuff 202 may be inflated to a pressure above systolic blood pressure to completely occlude blood flow in the arm 200.

[0046] As shown in FIG. 2, the Doppler method operates by gradually deflating the blood pressure cuff 202 while the Doppler probe 204 monitors for the return of arterial flow sounds. When the cuff pressure falls to systolic blood pressure level, blood flow may resume past the occlusion point, and the Doppler probe 204 may detect the onset of pulsatile flow. This detection of flow resumption may indicate the systolic pressure measurement point, providing a direct indication of systolic blood pressure based on actual blood flow rather than pressure oscillations.

[0047] The Doppler technique may provide more accurate systolic blood pressure measurements compared to oscillometric methods because the Doppler probe 204 directly monitors blood flow distal to the blood pressure cuff 202. However, this conventional approach may present several limitations that restrict its practical application. The Doppler method may require application of ultrasound gel at the contact site between the Doppler probe 204 and the skin surface of the arm 200. Additionally, the technique may require skilled technicians who can locate arterial pulse points and maintain proper positioning of the Doppler probe 204 throughout the measurement process.

[0048] With continued reference to FIG. 2, the conventional Doppler method may also require continuous manual monitoring of the pulse while the blood pressure cuff 202 undergoes deflation. This continuous monitoring requirement may make the process tedious and time-consuming compared to automated measurement techniques. Furthermore, the Doppler pulsations detected by the Doppler probe 204 may not disappear with further cuff deflation, rendering this technique unsuitable for measuring diastolic pressure. The combination of these limitations may restrict the widespread adoption of Doppler-based blood pressure measurement in clinical settings where automated, user-friendly measurement systems may be preferred.

[0049] Referring to FIG. 3A, a blood pressure measurement device 300A may provide an automated approach for non-invasive blood pressure measurement that addresses the limitations of conventional Doppler techniques. The blood pressure measurement device 300 A may comprise several interconnected components that work together to acquire and9159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 process plethysmographic signals for accurate blood pressure determination. FIG. 3A illustrates the blood pressure measurement device 300 A configured for use on a patient's upper extremity, demonstrating the positioning and interconnection of the various system components.

[0050] As shown in FIG. 3A, the blood pressure measurement device 300A may include the blood pressure cuff 202 positioned around the patient's upper arm in a manner similar to conventional blood pressure measurement systems. The blood pressure cuff 202 may be configured to be positioned around a limb and may function to occlude blood flow when inflated to pressures above systolic blood pressure. An inflation mechanism 309 may be operatively connected to the blood pressure cuff 202 via tubing, where the inflation mechanism 309 may provide pneumatic control for both inflation and deflation of the blood pressure cuff 202 during the measurement process.

[0051] The blood pressure measurement device 300A may further include a plethysmographic sensor 312 configured to be positioned distal to the blood pressure cuff 202 to acquire plethysmographic signals from tissue located beyond the occlusion point. As illustrated in FIG. 3 A, the plethysmographic sensor 312 may be positioned on the patient's finger, allowing the plethysmographic sensor 312 to detect changes in blood volume or flow characteristics in the tissue distal to the blood pressure cuff 202. The plethysmographic sensor 312 may be connected to other system components via a cable that transmits acquired signals for processing and analysis.

[0052] With continued reference to FIG. 3 A, the plethysmographic sensor 312 may be implemented using various plethysmographic technologies depending on the specific application requirements. In some cases, the plethysmographic sensor 312 may be based on electrical impedance of the limb for acquiring plethysmographic signals, where changes in electrical impedance may correspond to variations in blood volume within the monitored tissue. The plethysmographic sensor 312 may alternatively be based on reflectance optical plethysmography for acquiring plethysmographic signals, where light reflected from tissue may indicate blood volume changes during cardiac cycles. A reflectance optical plethysmograph may be positioned anywhere on the skin distal to the cuff, even on the distal end of the cuff.

[0053] The plethysmographic sensor 312 may also be based on strain gauge plethysmography for acquiring plethysmographic signals, where mechanical strain10159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 measurements may detect volume changes in the monitored limb segment. In some cases, the plethysmographic sensor 312 may be based on volume displacement plethysmography for acquiring plethysmographic signals, where direct measurement of volume changes may provide plethysmographic data. Additionally, the plethysmographic sensor 312 may be a pulse oximeter which may be considered interchangeable with photoplethysmogram for the purposes of this disclosure, where pulse oximeter technology may provide both plethysmographic signals and oxygen saturation measurements.

[0054] As further shown in FIG. 3A, a processor 308 may be operatively connected to both the blood pressure cuff 202 and the plethysmographic sensor 312, where the processor 308 may coordinate the operation of these components during blood pressure measurement procedures. The processor 308 may be configured to control inflation and deflation of the blood pressure cuff 202 through communication with the inflation mechanism 309. The processor 308 may also be configured to capture successive plethysmographic waveforms during deflation of the blood pressure cuff 202, where these waveforms may be acquired from the plethysmographic sensor 312 at regular intervals throughout the deflation process.

[0055] The processor 308 may be further configured to high-pass filter the successive plethysmographic waveforms to produce filtered waveforms having equal area above and below a baseline. This high-pass filtering process may remove low-frequency components and baseline drift from the acquired plethysmographic signals, resulting in filtered waveforms that oscillate symmetrically around a zero baseline. The processor 308 may then multiply corresponding points of the filtered waveforms to generate product values, where corresponding points may represent data points that are equidistant in time from a reference signal such as a cardiac cycle marker.

[0056] With continued reference to FIG. 3A, the processor 308 may be configured to sum the product values to determine a concordance measure that indicates the degree of similarity between successive plethysmographic waveforms. The processor 308 may determine systolic blood pressure based on detection of concordant w aveforms when the concordance measure exceeds a threshold value. When plethysmographic waveforms are concordant, indicating the presence of consistent pulse signals, the product values may be predominantly positive, resulting in a large positive sum that exceeds the threshold value.

[0057] The blood pressure measurement device 300A may include an output 310 connected to the processor 308, where the output 310 may display or transmit measurement11159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 results to medical personnel. The output 310 may provide various forms of feedback and information to operators during the measurement process. In some cases, the processor 308 may be configured to control the inflation mechanism 309 to inflate the blood pressure cuff 202 to a predetermined pressure and deflate the blood pressure cuff 202 at a controlled rate during measurement.

[0058] As show n in FIG. 3 A, the blood pressure cuff 202 may be inflated to a predetermined fixed pressure such as 200 mmHg during operation, providing a standardized starting pressure that may be suitable for most patients. Alternatively, the blood pressure cuff 202 may be inflated to an adaptively determined pressure such as 20 mmHg past when there is no longer a discernible concordant pulse wave, allowing the system to customize the inflation pressure based on individual patient characteristics.

[0059] The blood pressure cuff 202 may be deflated slowly typically at a rate of 2 mmHg per second during measurement to provide sufficient time for accurate plethysmographic signal acquisition and processing. In some cases, the processor 308 may use an initial pneumatic bleed rate that is relatively fast at 5 mmHg / sec to provide a first estimate of systolic pressure, followed by a slower deflation rate for more precise measurement. This two-stage deflation approach may improve measurement efficiency while maintaining accuracy.

[0060] The blood pressure measurement device 300A may provide feedback mechanisms to assist operators in obtaining high-quality measurements. The system may provide visual output of the pulse volume waveform to let the operator know if the patient's limb is relatively motionless and producing a good pulse volume w aveform. Additionally, the system may produce a sound that is reflective of the pulse volume w aveform to indicate if the patient's limb is relatively motionless and producing a good pulse volume waveform. These feedback mechanisms may help ensure optimal measurement conditions by alerting operators to motion artifacts or signal quality issues that could affect measurement accuracy.

[0061] Referring to FIG. 3B, the blood pressure measurement system may be configured for use on a patient's lower extremity to enable ankle blood pressure measurements for ankle- brachial index calculations. FIG. 3B illustrates a perspective view' of the device positioned on a patient's lower extremity, showing the arrangement of components for acquiring plethysmographic signals from the foot while occluding blood flow at the ankle level. This12159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 configuration may enable automated measurement of ankle systolic blood pressure using the same cross-correlation techniques described for upper extremity measurements.

[0062] As shown in FIG. 3B, an occluding cuff 304 may be positioned around the patient's ankle region, where the occluding cuff 304 may be configured to wrap around the ankle and inflate to occlude blood flow in the lower leg during blood pressure measurement. The occluding cuff 304 may function similarly to the blood pressure cuff 202 described for upper extremity measurements, providing controlled occlusion of arterial blood flow when inflated to pressures above systolic blood pressure. The occluding cuff 304 may be sized and shaped to accommodate the anatomical characteristics of the ankle region while providing effective blood flow occlusion.

[0063] A transmission pulse oximeter 306 may be positioned distal to the occluding cuff 304 on the patient's foot, where the transmission pulse oximeter 306 may be configured to acquire plethysmographic signals from tissue located beyond the ankle occlusion point. As illustrated in FIG. 3B, the transmission pulse oximeter 306 may be positioned on a digit of the foot, where the transmission pulse oximeter 306 may detect changes in blood volume by transmitting light through the tissue and measuring the transmitted light intensity. The transmission pulse oximeter 306 may function as an optical plethysmographic sensor that provides plethysmographic signals for processing by the processor 308.

[0064] With continued reference to FIG. 3B, the transmission pulse oximeter 306 may be a transmission optical plethysmographic sensor configured to be positioned on a digit distal to the occluding cuff 304. The transmission pulse oximeter 306 may operate by emitting light from one side of the digit and detecting the transmitted light on the opposite side, where variations in transmitted light intensity' may correspond to changes in blood volume within the digit tissue during cardiac cycles. This transmission-based approach may provide more reliable signal acquisition compared to reflectance-based optical sensors, particularly in challenging measurement environments.

[0065] As further shown in FIG. 3B, wire and tubing 302 may extend from the occluding cuff 304 and connect the transmission pulse oximeter 306 to external monitoring and control equipment. The wire and tubing 302 may provide both pneumatic connection for cuff inflation and electrical connection for signal transmission between the components and the processor 308. The wire and tubing 302 may enable automated control of cuff inflation and13159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 deflation while simultaneously acquiring plethysmographic data from the transmission pulse oximeter 306 for blood pressure determination.

[0066] The wire and tubing 302 may incorporate a shared connection design where optical sensor connections travel along with the inflation tube to the monitor. This shared tube connection approach may reduce the number of separate connections betw een the patient and the monitoring system, which may be desirable in hospital settings where minimizing connection complexity may improve usability and reduce potential failure points. The wire and tubing 302 may house both the pneumatic tubing for cuff inflation and the electrical wiring for the transmission pulse oximeter 306 within a single cable assembly.

[0067] The arrangement of components shown in FIG. 3B may enable measurement of ankle systolic blood pressure by monitoring the return of pulsatile blood flow" distal to the occluding cuff 304 as the cuff undergoes deflation. The processor 308 may control the inflation and deflation of the occluding cuff 304 while processing plethysmographic signals from the transmission pulse oximeter 306 using the same cross-correlation techniques described for upper extremity measurements. When the occluding cuff 304 pressure falls below ankle systolic pressure, concordant pulse waveforms may appear in the signals from the transmission pulse oximeter 306, indicating the resumption of blood flow to the foot.

[0068] The system may be adapted for use on non-human animal patients, where the occluding cuff 304 and transmission pulse oximeter 306 may be positioned on a limb or tail of the animal patient. In veterinary applications, the occluding cuff 304 may be sized and configured to accommodate the anatomical characteristics of various animal species, w hile the transmission pulse oximeter 306 may be positioned on appropriate digits or appendages where reliable plethysmographic signals may be acquired. The processor 308 may apply the same signal processing techniques for determining blood pressure in non-human animal patients, providing automated blood pressure measurement capabilities for veterinary medical applications.

[0069] The signal processing technique implemented by the processor 308 may more precisely be characterized as a cross-correlation process rather than a simple cross-correlation technique, where the cross-correlation approach may provide enhanced accuracy for detecting the precise onset of blood flow resumption during cuff deflation. The crosscorrelation process may typically compare two distinct waveforms rather than comparing multiple successive waveforms of similar characteristics. In this implementation, one14159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 waveform may be the particular low-amplitude waveform being tested for the presence of pulse characteristics, while the other waveform may be an averaged waveform derived from multiple higher-amplitude waveforms that are acquired as cuff deflation continues and pulse amplitude increases.

[0070] The cross-correlation algorithm may operate by initially capturing very low amplitude waveforms that appear during the early phases of cuff deflation when blood flow first begins to resume past the occlusion point. These initial low-amplitude waveforms may be saved in memory by the processor 308 for subsequent comparison operations. As cuff deflation continues and pulse amplitude increases, the processor 308 may acquire multiple full-amplitude waveforms and calculate an averaged waveform that represents the characteristic pulse shape for the particular patient and measurement conditions. The processor 308 may then perform cross-correlation analysis by comparing the saved low- amplitude waveforms against this averaged high-amplitude waveform template.

[0071] The cross-correlation algorithm may effectively operate by going "back in time" to retrospectively identify the first small waveform that exhibits the same morphological characteristics as the higher amplitude waveforms that follow during continued cuff deflation. This retrospective analysis approach may enable the processor 308 to pinpoint the exact moment when blood flow first resumed, corresponding to the precise systolic blood pressure measurement. The cross-correlation technique may provide systolic blood pressure measurements that correspond closely to measurements obtained using conventional Doppler stethoscope techniques, where the correlation between these measurement approaches may validate the accuracy of the optical plethysmographic approach for clinical blood pressure assessment applications.

[0072] Referring to FIG. 4A, the system may acquire pulse volume measurements that demonstrate the characteristic waveform patterns obtained dunng plethysmographic signal acquisition. FIG. 4A displays a pulse volume curve plotting microliters per centimeter 404 on the vertical axis against time measured in seconds on the horizontal axis, with the time scale ranging from 0 to 3 seconds. The microliters per centimeter 404 measurement scale extends from 0 to approximately 450 microliters per centimeter 404, providing quantitative representation of blood volume changes within the monitored tissue segment during cardiac cycles.15159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0073] As shown in FIG. 4A, the pulse volume curve exhibits two complete cardiac cycles within the three-second timeframe, demonstrating the periodic nature of arterial pulsations that may be detected by the plethysmographic sensor 312. The first pulse in the pulse volume curve begins near zero microliters per centimeter 404 at the start of the recording and rises sharply to reach a peak amplitude of approximately 420 microliters per centimeter 404 at around 0.5 seconds. Following this peak, the first pulse descends back toward baseline, reaching approximately 10 microliters per centimeter 404 at around 1.2 seconds, where the pulse volume curve remains near baseline between approximately 1.2 and 1.5 seconds.

[0074] With continued reference to FIG. 4A, the second pulse in the pulse volume curve begins to rise at approximately 1.5 seconds, demonstrating the onset of the subsequent cardiac cycle. The second pulse reaches a peak amplitude of approximately 420 microliters per centimeter 404 at around 2.0 seconds, maintaining consistency with the amplitude characteristics of the first pulse. The second pulse then declines back toward baseline, reaching approximately 10 microliters per centimeter 404 by approximately 2.7 seconds, completing the second cardiac cycle within the measurement timeframe.

[0075] The pulse volume curve shown in FIG. 4A demonstrates smooth, periodic waveforms characteristic of arterial pulsations without significant noise or baseline drift, representing ideal measurement conditions where plethysmographic signals may be acquired with high signal-to-noise ratio. The processor 308 may capture successive plethysmographic waveforms during deflation of the blood pressure cuff 202 by acquiring data similar to that shown in the pulse volume curve of FIG. 4A at regular intervals throughout the cuff deflation process.

[0076] The processor 308 may use various gating techniques to synchronize the capture of successive plethysmographic waveforms with cardiac cycles, ensuring that waveform acquisition occurs at consistent points relative to cardiac activity. In some cases, the processor 308 may use a QRS wave of an electrocardiogram as a gating signal for capturing successive plethysmographic waveforms during deflation of the blood pressure cuff 202. The QRS wave complex may provide a reliable timing reference that occurs at the beginning of each cardiac cycle, allowing the processor 308 to trigger waveform acquisition at consistent cardiac phases.16159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0077] As further shown in FIG. 4A, the processor 308 may alternatively use an identifiable characteristic of a plethysmogram such as exceeding a dV / dt threshold as a gating signal for capturing successive plethysmographic waveforms during deflation of the blood pressure cuff 202. The dV / dt threshold approach may identify specific points in the plethysmographic waveform where the rate of volume change exceeds a predetermined value, such as the rapid upstroke phase of each pulse shown in the pulse volume curve. This gating technique may provide timing synchronization without requiring separate electrocardiogram monitoring equipment.

[0078] The gating signals may enable the processor 308 to capture successive plethysmographic waveforms that are temporally aligned with respect to cardiac cycle timing, facilitating subsequent signal processing operations such as waveform averaging and correlation analysis. Each captured waveform may represent a complete cardiac cycle or a portion thereof, where the duration and timing of each captured waveform may be determined by the selected gating approach and the specific characteristics of the patient's cardiac rhythm.

[0079] Referring to FIG. 4B, the processor 308 may apply high-pass filtering to the acquired plethysmographic waveforms to prepare the signals for subsequent cross-correlation processing. FIG. 4B displays a pulse volume curve titled "PULSE VOLUME CURVE - HIGH PASSED FILTERED" that illustrates the result of applying high-pass filtering to plethysmographic data similar to that shown in FIG. 4A. A microliters per centimeter axis label 406 indicates the vertical axis measurement scale, which extends from approximately - 100 to 300 microliters per centimeter 406, demonstrating that the filtered w aveform may exhibit both positive and negative amplitude values relative to a zero baseline.

[0080] As shown in FIG. 4B, a filtered waveform 408 exhibits two complete cardiac cycles within the three-second timeframe, where the filtered waveform 408 oscillates symmetrically above and below a horizontal baseline at 0 microliters per centimeter 406. The processor 308 may be configured to high-pass filter the successive plethysmographic waveforms to produce filtered waveforms having equal area above and below7a baseline, as demonstrated by the filtered waveform 408. This high-pass filtering process may remove low-frequency components and baseline drift from the original plethysmographic signals, resulting in waveforms that maintain the pulse characteristics while centering the signal around zero.17159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0081] The first pulse in the filtered waveform 408 begins near zero at approximately 0.2 seconds and rises sharply to reach a peak amplitude of approximately 240 microliters per centimeter 406 at around 0.5 seconds. Following this positive peak, the filtered waveform 408 descends back through the baseline to reach a negative trough of approximately 200 microliters per centimeter 406 at around 1.0 seconds before returning toward the baseline. This bipolar characteristic of the filtered waveform 408 demonstrates how the high-pass filtering process creates equal area above and below the baseline, where the positive portion of each pulse cycle may be balanced by a corresponding negative portion.

[0082] With continued reference to FIG. 4B, the second pulse in the filtered waveform 408 follows a similar pattern, rising from near zero at approximately 1.5 seconds to reach a peak of approximately 230 microliters per centimeter 406 at around 2.0 seconds. The second pulse then descends through the baseline to reach a negative trough of approximately 200 microliters per centimeter 406 at around 2.5 seconds, maintaining the characteristic bipolar structure created by the high-pass filtering process. A figure number 400 appears in the upper right comer of FIG. 4B, providing identification for this particular waveform representation.

[0083] The filtered waveform 408 demonstrates the characteristic result of high-pass filtering applied to pulse volume data, where the filtering process produces equal area above and below the baseline with the positive and negative portions of each pulse cycle balanced around the zero reference line. This filtering step may prepare the waveforms for subsequent cross-correlation processing by removing baseline variations and low-frequency drift that could interfere with the multiplication and correlation operations performed by the processor 308. The filtered waveform 408 maintains the temporal characteristics and amplitude relationships of the original pulse volume signals while providing a standardized baseline reference for subsequent signal processing operations.

[0084] The high-pass filtering process applied by the processor 308 may ensure that successive plethysmographic waveforms have consistent baseline characteristics, facilitating accurate comparison and correlation betw een w aveforms acquired at different cuff pressures during the deflation process. The filtered waveform 408 shown in FIG. 4B represents the ty pe of signal that may be used by the processor 308 for multiplication operations, where corresponding points of multiple filtered waveforms may be multiplied to generate product values for concordance analysis. The equal area above and below7the baseline characteristic of the filtered w aveform 408 may provide mathematical properties that enhance the18159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 effectiveness of the cross-correlation technique used for detecting concordant pulse waveforms during blood pressure measurement.

[0085] Referring to FIG. 5 A, the processor 308 may multiply corresponding points of the filtered waveforms to generate product values that demonstrate the concordance characteristics of successive plethysmographic waveforms. FIG. 5 A displays a graph plotting microliters per centimeter-squared 504 on the vertical axis against seconds on the horizontal axis, with time ranging from -0.15 to 1.45 seconds. The microliters per centimeter-squared 504 measurement scale extends from 0 to 60000 microliters per centimeter-squared 504, providing quantitative representation of the product values generated through multiplication of corresponding points from high-pass filtered pulse volume waveforms.

[0086] As shown in FIG. 5A, a waveform 502 exhibits two prominent peaks within the timeframe shown, demonstrating the characteristic pattern resulting from multiplication of corresponding points of high-pass filtered pulse volume w aveforms when the w aveforms are concordant. The processor 308 may be configured to multiply corresponding points of an even number of successive filtered waveforms, where corresponding points may represent data points that are equidistant in time from a gating signal such as a QRS complex or an identifiable characteristic of the plethysmographic signal. The waveform 502 demonstrates the result of this multiplication process when applied to concordant pulse volume signals acquired during blood pressure measurement.

[0087] The first major peak in the waveform 502 occurs at approximately 0.65 seconds, reaching a maximum amplitude of approximately 52000 microliters per centimeter-squared 504. This peak represents the product values generated w hen corresponding points of the filtered waveforms are at their maximum concordance during the first cardiac cycle. Following this first peak, the waveform 502 descends to lower values, reaching approximately 0 microliters per centimeter-squared 504 at around 1.05 seconds, indicating the transition period between cardiac cycles where the filtered waveforms may have lower amplitude values.

[0088] With continued reference to FIG. 5A, the second major peak in the waveform 502 begins to rise at approximately 1.15 seconds, reaching a maximum amplitude of approximately 37000 microliters per centimeter-squared 504 at around 1.35 seconds. This second peak demonstrates the product values generated during the second cardiac cycle, where the multiplication of corresponding points produces positive values indicating19159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 concordance between the successive filtered waveforms. Between the two major peaks, the waveform 502 remains near zero with minimal oscillations, corresponding to portions of the cardiac cycles where the filtered waveforms may have lower amplitudes or may be transitioning between positive and negative phases.

[0089] As further shown in FIG. 5A, the waveform 502 remains entirely positive throughout the entire time span, with all values at or above zero microliters per centimeter- squared 504. This characteristic demonstrates that when successive filtered waveforms are concordant, the multiplication of corresponding points produces predominantly positive product values. When two concordant waveforms are multiplied, negative points may be multiplied by negative points and positive points may be multiplied by positive points, resulting in positive products at corresponding time points throughout the waveforms.

[0090] The processor 308 may be configured to multiply corresponding points of successive filtered waveforms to enhance the reliability of concordance detection and minimize the chance of random concordance between noise waveforms. When successive filtered waveforms are multiplied, the resulting product values may provide increased confidence in the detection of true pulse signals compared to multiplication of only two waveforms. The use of successive filtered waveforms may reduce the probability that random noise fluctuations could produce false positive concordance measurements that might be mistaken for actual pulse signals.

[0091] The entirely positive characteristic of the waveform 502 shown in FIG. 5A indicates concordance between the underlying pulse volume signals in the multiplied waveforms, where the consistent phase relationships and amplitude patterns of the filtered waveforms result in positive products when corresponding points are multiplied. The processor 308 may sum the product values represented by the waveform 502 to determine a concordance measure, where the sum of the predominantly positive product values may result in a large positive number that indicates the presence of concordant pulse waveforms.

[0092] The processor 308 may compare the sum of product values to a threshold value to determine when concordant waveforms are detected during cuff deflation. When the sum of product values exceeds the threshold value, the processor 308 may identify this condition as indicating the presence of pulse signals distal to the blood pressure cuff 202, corresponding to the resumption of blood flow as cuff pressure falls below systolic blood pressure. The waveform 502 demonstrates the type of product pattern that may be generated when pulse20159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 volume signals are present and concordant, providing a clear distinction from the product patterns that may be generated when only noise is present in the plethysmographic signals.

[0093] Referring to FIG. 5B, the processor 308 may encounter measurement conditions where plethysmographic signals contain pure noise without discernible pulse volume components, particularly when the blood pressure cuff 202 is inflated to pressures above systolic blood pressure and blood flow is completely occluded. FIG. 5B displays a graph plotting microliters per centimeter on a vertical axis 506 against seconds on the horizontal axis, with time ranging from -0. 15 to 1.45 seconds. The vertical axis 506 extends from approximately -150 to 450 microliters per centimeter, providing a measurement scale for amplitude variations in the acquired signals during periods when no pulse volume signals are present.

[0094] As show n in FIG. 5B, a noise waveform 510 exhibits irregular, random oscillations throughout the time period shown, with amplitudes vary ing rapidly above and below a baseline near zero without any discernible periodic pattern. The noise waveform 510 demonstrates high-frequency fluctuations characteristic of pure noise that may be encountered when the plethysmographic sensor 312 acquires signals from tissue where blood flow has been completely occluded by the blood pressure cuff 202. Unlike the smooth, periodic waveforms shown in previous figures that demonstrate consistent cardiac cycle patterns, the noise waveform 510 lacks any repeating temporal structure or predictable amplitude relationships.

[0095] The noise waveform 510 shows a prominent spike reaching approximately 250 microliters per centimeter at around 0.05 seconds, representing the highest amplitude excursion in the displayed timeframe. This spike demonstrates the unpredictable nature of noise signals, where large amplitude variations may occur randomly without correlation to cardiac activity or blood flow patterns. Following this initial spike, the noise waveform 510 continues with rapid oscillations, reaching approximately 150 microliters per centimeter at around 0.15 seconds, then declining to approximately -50 microliters per centimeter at around 0.25 seconds, illustrating the irregular amplitude variations that characterize pure noise signals.

[0096] With continued reference to FIG. 5B, the noise waveform 510 exhibits fluctuations betw een approximately -100 and 100 microliters per centimeter during the period from approximately 0.3 to 0.5 seconds, followed by oscillations reaching approximately 10021159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 microliters per centimeter between 0.5 and 0.7 seconds. The noise waveform 510 demonstrates variations between approximately -150 and 50 microliters per centimeter from 0.7 to 1.0 seconds, and continues its irregular pattern with amplitudes ranging between approximately -100 and 150 microliters per centimeter from 1.0 to 1.45 seconds. Throughout the entire recording, the noise waveform 510 maintains its random, non-periodic character without any consistent pulse-like features that would indicate the presence of blood flow or cardiac-related signals.

[0097] The noise waveform 510 differs fundamentally from concordant pulse volume waveforms in temporal structure, lacking the periodic patterns and consistent phase relationships that characterize arterial pulsations. When the processor 308 multiplies corresponding points of filtered waveforms derived from signals similar to the noise waveform 510. the resulting product values may be randomly both positive and negative, reflecting the lack of concordance between successive noise waveforms. The processor 308 may sum the product values to determine a concordance measure, where the sum of randomly distributed positive and negative products may result in a small number or potentially a negative number when compared to the sum of products obtained from concordant pulse volume waveforms.

[0098] The random characteristics of the noise waveform 510 may provide a baseline reference for the processor 308 to distinguish between periods when pulse volume signals are present versus periods when only noise is detected by the plethysmographic sensor 312. When the blood pressure cuff 202 is inflated above systolic blood pressure, the plethysmographic signals may resemble the noise waveform 510, producing low concordance measures when processed through the cross-correlation technique. As the blood pressure cuff 202 is deflated and cuff pressure approaches systolic blood pressure, the transition from noise-like signals to concordant pulse volume waveforms may provide a clear indication of blood flow resumption that the processor 308 may detect through changes in the concordance measure.

[0099] Referring to FIG. 5C, the processor 308 may process noise waveforms through the same cross-correlation technique used for concordant pulse volume signals, demonstrating how the multiplication process distinguishes between noise and actual pulse signals. FIG. 5C displays a graph titled "PRODUCT OF TWO HIGH PASS FILTERED NOISE WAVEFORMS" that illustrates the result of multiplying corresponding points of two high-pass filtered noise waveforms similar to the noise waveform 510 described previously.22159615.00123 / 155789766v.1Attorney Docket No. 159615-00123A y-axis 508 indicates the vertical measurement scale, extending from approximately -20000 to 120000 microliters per centimeter-squared, providing quantitative representation of the product values generated through multiplication of corresponding points from noise waveforms.

[0100] As shown in FIG. 5C, a waveform 512 exhibits irregular oscillations throughout the time period shown, with amplitudes varying between approximately -10000 and +20000 microliters per centimeter-squared along the y-axis 508. The waveform 512 demonstrates no consistent periodic pattern or repeating structure characteristic of pulse volume signals, instead showing rapid, unpredictable fluctuations that remain relatively close to the baseline throughout the entire time span from 0 to 1.6 seconds. The predominantly small amplitude variations in the waveform 512, with both positive and negative deflections distributed without any discernible pattern, indicate the result of multiplying two high-pass fdtered noise waveforms that lack concordant pulse volume components.

[0101] With continued reference to FIG. 5C, the waveform 512 demonstrates the fundamental difference between products of noise waveforms and products of concordant pulse volume waveforms. When the processor 308 multiplies corresponding points of fdtered noise waveforms, the resulting product values may be randomly both positive and negative, reflecting the lack of phase relationships or consistent amplitude patterns between successive noise signals. The waveform 512 exhibits this random distribution of positive and negative products, where positive values occur when both corresponding points have the same sign and negative values occur when corresponding points have opposite signs.

[0102] The processor 308 may sum the product values represented by the waveform 512 to determine a concordance measure for noise w aveforms, where the sum of randomly distributed positive and negative products may result in a small number when compared to products of concordant waveforms. Unlike the product of concordant pulse volume waveforms which may show- large positive peaks and result in large positive sums, the waveform 512 remains near zero throughout, w ith the sum of products being a small number that may approach zero or potentially be negative depending on the specific characteristics of the noise signals.

[0103] As further shown in FIG. 5C, the waveform 512 provides a baseline reference that enables the processor 308 to establish a threshold value for distinguishing noise from concordant pulse waveforms during blood pressure measurement. The processor 308 may23159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 determine systolic blood pressure based on detection of concordant waveforms when the concordance measure exceeds a threshold value, where the threshold value may be established based on the characteristic low-amplitude, near-zero sum of products obtained from noise waveforms like the waveform 512. When plethysmographic signals contain only noise, the concordance measure may remain below the threshold value, indicating that blood flow is still occluded by the blood pressure cuff 202.

[0104] The threshold value may be a fixed value determined based on empirical measurements of noise characteristics, or the threshold value may be adaptively determined as a function of corresponding values obtained as the blood pressure cuff 202 is being inflated. In some cases, the threshold value may be established as a fixed percentage of the maximum concordance measure value obtained during the inflation process, providing a dynamic reference that accounts for individual patient characteristics and measurement conditions. The processor 308 may compare the concordance measure to the threshold value throughout the cuff deflation process, where exceeding the threshold value may indicate the transition from noise-dominated signals to concordant pulse volume signals that correspond to blood flow resumption at systolic blood pressure.

[0105] Referring to FIG. 6A, the processor 308 may encounter measurement conditions where plethysmographic signals contain both physiological pulse volume components and noise elements, representing typical real-world measurement environments encountered during clinical blood pressure assessment. FIG. 6A displays a graph titled "PULSE VOLUME + NOISE" that illustrates the characteristics of plethysmographic signals acquired under practical measurement conditions where various sources of interference may be superimposed on the underlying arterial pulsation signals. A y-axis label 604 indicates the vertical measurement scale plotting microliters per centimeter against time, extending from approximately -200 to 700 microliters per centimeter, providing quantitative representation of the amplitude variations present in noisy pulse volume measurements.

[0106] As show n in FIG. 6 A, a combined waveform 602 exhibits two complete cardiac cycles within the three-second timeframe, demonstrating pulse volume signals that contain both physiological pulsations and noise components characteristic of real-world measurement conditions. The combined waveform 602 begins near 200 microliters per centimeter at the start of the recording and rises sharply to reach a peak amplitude of approximately 550 microliters per centimeter at around 0.5 seconds, showing the underlying pulse volume signal pattern while exhibiting irregular fluctuations and baseline variations throughout the trace.24159615.00123 / 155789766v.1Attorney Docket No. 159615-00123These irregular oscillations superimposed on the pulse volume signal may result from various sources including patient movement, electrical interference, sensor positioning variations, or environmental factors that commonly affect plethysmographic measurements in clinical settings.

[0107] The first pulse in the combined waveform 602 demonstrates the characteristic challenge of extracting pulse volume information from noisy measurement environments, where the underlying periodic pulse pattern may be partially obscured by random noise variations. Following the peak amplitude at 0.5 seconds, the combined waveform 602 descends back toward baseline with noticeable irregular fluctuations, reaching approximately 100 microliters per centimeter at around 1.2 seconds rather than following the smooth decline pattern that may be observed in ideal measurement conditions. The baseline variations and irregular oscillations present in the combined waveform 602 illustrate how noise components may affect the amplitude characteristics and temporal patterns of the acquired plethysmographic signals.

[0108] With continued reference to FIG. 6A, the second pulse in the combined waveform 602 follows a similar pattern, rising from approximately 100 microliters per centimeter to reach a peak of approximately 550 microliters per centimeter at around 2.0 seconds, before declining back toward baseline with continued irregular fluctuations by approximately 2.7 seconds. The combined waveform 602 maintains the fundamental periodic structure associated with cardiac cycles while exhibiting the amplitude variations and baseline drift that may characterize real-world plethysmographic measurements. The presence of noise components in the combined waveform 602 demonstrates the measurement conditions that the processor 308 may encounter during actual blood pressure assessment procedures, where perfect signal conditions may not be achievable.

[0109] The combined waveform 602 illustrates how real-world measurements may exhibit baseline variations that differ from the idealized waveforms shown in previous figures, where noise-free conditions provided clear, smooth pulse volume patterns. The irregular oscillations present throughout the combined waveform 602 may result from physiological factors such as respiratory variations, patient movement, or changes in peripheral circulation, as well as technical factors including sensor sensitivity variations, electrical interference, or mechanical vibrations affecting the measurement system. The processor 308 may be configured to process these noisy pulse volume signals through the same cross-correlation technique described for ideal waveforms, where the multiplication and25159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 summation operations may extract the underlying pulse volume information despite the presence of noise components.

[0110] As further shown in FIG. 6A, the combined waveform 602 represents the type of signal that may be acquired by the plethysmographic sensor 312 during typical clinical measurements, where the underlying pulse volume signal remains detectable despite the superimposed noise components. The processor 308 may apply high-pass filtering to the combined waveform 602 to produce filtered waveforms having equal area above and below a baseline, where the filtering process may help reduce some noise components while preserving the pulse volume characteristics. The filtered versions of signals similar to the combined waveform 602 may then be processed through the multiplication and summation operations to determine concordance measures that indicate the presence of pulse volume signals despite the noisy measurement conditions.[OHl] The combined waveform 602 demonstrates that the cross-correlation technique implemented by the processor 308 may provide robust performance in real- world measurement environments where noise components are present in the plethysmographic signals. When successive waveforms similar to the combined w aveform 602 are processed through the multiplication operations, the underlying pulse volume components may produce predominantly positive products that contribute to large positive concordance measures, while the random noise components may produce randomly distributed positive and negative products that contribute minimally to the overall concordance measure. This characteristic may enable the processor 308 to detect concordant pulse waveforms and determine systolic blood pressure accurately even when the plethysmographic signals contain significant noise components similar to those demonstrated in the combined waveform 602.

[0112] Referring to FIG. 6B, the processor 308 may process real- w orld noisy pulse volume waveforms through the cross-correlation technique to demonstrate how multiplication operations extract concordant pulse information despite the presence of noise components. FIG. 6B displays a graph titled "PRODUCT OF TWO HIGH PASS FILTERED NOISY PULSE VOLUME WAVEFORMS" that illustrates the result of multiplying corresponding points of two high-pass filtered pulse volume waveforms that contain both signal and noise components similar to the combined waveform 602 described previously. A horizontal axis 608 represents time measured in seconds, extending from 0 to 1.6 seconds, providing the temporal reference for the product values generated through the multiplication process.26159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0113] As shown in FIG. 6B, a product waveform 606 exhibits two prominent peaks within the timeframe shown, with the first peak occurring at approximately 0.6 seconds and reaching a maximum amplitude of approximately 100000 microliters per centimeter-squared, and the second peak occurring at approximately 1.2 seconds and reaching a maximum amplitude of approximately 100000 microliters per centimeter-squared. The product waveform 606 demonstrates that multiplication of noisy pulse volume waveforms may produce predominantly positive products when concordant pulse signals are present, where the underlying pulse volume components dominate the multiplication results despite the superimposed noise elements. Between these major peaks, the product waveform 606 descends to near-zero values at approximately 0.9 seconds, corresponding to the transition period between cardiac cycles where the filtered waveforms may have lower amplitude values.

[0114] With continued reference to FIG. 6B, the product waveform 606 demonstrates predominantly positive values throughout most of the recording along the horizontal axis 608, with occasional brief negative deflections reaching approximately -10000 microliters per centimeter-squared. The overall pattern of the product waveform 606 shows two distinct cardiac cycles with high-amplitude positive products indicating concordant waveforms, interspersed with lower-amplitude regions that correspond to portions of the cardiac cycles where the pulse volume signals may have reduced amplitudes. The product waveform 606 results from multiplication of corresponding points of two high-pass filtered pulse volume waveforms that contain both signal and noise components, demonstrating that the signal component dominates the product despite the presence of noise.

[0115] The processor 308 may be configured to multiply corresponding points of successive filtered waveforms to enhance the reliability of concordance detection and minimize the chance of random concordance between noise waveforms. When successive filtered waveforms are processed through the multiplication operations, the probability that random noise fluctuations could produce false positive concordance measurements may be significantly reduced compared to multiplication of only two waveforms. The use of successive filtered waveforms may provide increased confidence in the detection of true pulse signals, where the consistent phase relationships and amplitude patterns of concordant pulse volume signals may be reinforced through the multiplication of additional waveforms.

[0116] The processor 308 may sum the product values represented by the product waveform 606 to determine a concordance measure that indicates the presence of pulse27159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 volume signals despite the noisy measurement conditions. The sum of the predominantly positive product values shown in the product waveform 606 may result in a large positive number that clearly exceeds threshold values established for noise-only conditions, providing reliable detection of concordant pulse waveforms during blood pressure measurement. The processor 308 may compare this concordance measure to a threshold value to determine when concordant waveforms are detected during cuff deflation, where exceeding the threshold may indicate the resumption of blood flow as cuff pressure falls below systolic blood pressure.

[0117] The system may use selective signal averaging where the cuff is held at a series of fixed pressures while averaging takes place to extract pulse information from noisy measurement environments. In this selective signal averaging approach, the processor 308 may maintain the blood pressure cuff 202 at predetermined pressure levels for extended periods, allowing multiple cardiac cycles to be acquired and averaged at each pressure point. The averaged waveform may be flat and without pulsations when the cuff is held above systolic pressure, and may have non-zero pulsations when the cuff is held below systolic pressure, providing clear differentiation between occluded and non-occluded conditions.

[0118] During selective signal averaging operations, the processor 308 may determine that pulse amplitude reaches its maximum when the cuff is held at mean blood pressure, corresponding to the pressure level where plethysmographic measurements achieve peak amplitude during the cardiac cycle. The processor 308 may identify these characteristic pressure points through computational analysis of the averaged waveforms acquired at each fixed pressure level. The selective signal averaging technique may provide an alternative implementation approach that may be used in conjunction with or as an alternative to the continuous deflation method described previously, where the choice of implementation may depend on specific measurement requirements or patient characteristics.

[0119] The selective signal averaging approach may provide enhanced noise rejection compared to continuous deflation methods, where the extended averaging periods at fixed pressures may allow random noise components to cancel out while preserving the consistent pulse volume signals. The processor 308 may capture successive plethysmographic waveforms during the averaging periods at each fixed pressure, where these waveforms may be processed through the same high-pass filtering and multiplication operations described for continuous deflation measurements. The resulting concordance measures obtained at each fixed pressure level may provide clear indication of the pressure points where pulse volume28159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 signals transition from absent to present, corresponding to systolic blood pressure determination.

[0120] The multiplication of corresponding points of successive filtered waveforms may be particularly effective in selective signal averaging implementations, where the extended measurement periods at fixed pressures may provide sufficient time to acquire multiple high- quality waveforms for processing. The processor 308 may generate product values through multiplication of corresponding points of the successive filtered waveforms, where the product values may be summed to determine a concordance measure for each fixed pressure level. The concordance measures obtained through selective signal averaging may demonstrate clear transitions from low values at pressures above systolic blood pressure to high values at pressures below systolic blood pressure, providing reliable systolic blood pressure determination even in challenging measurement environments with significant noise components.

[0121] Referring to FIG. 7, the processor 308 may determine diastolic blood pressure through identification of mean blood pressure during the cuff deflation process, where mean blood pressure corresponds to the point of maximum pulse volume amplitude. FIG. 7 depicts a graph illustrating the relationship between mean blood pressure and calf pulse volume during blood pressure cuff deflation, demonstrating how pulse volume measurements may be used to identify mean blood pressure for subsequent diastolic blood pressure calculations. A figure number 700 appears in the upper right comer of the graph, providing identification for this particular measurement representation. It is understood that this method of determining DBP is an approximation and other methods of determining DBP from the changes in pulse volume that occur during cuff deflation may be employed.

[0122] As shown in FIG. 7, the graph displays two y-axes and one x-axis, where a y-axis label 702 indicates "PERCENT OF BASELINE" ranging from 0 to 120 on the left side of the graph, and ay-axis label 704 indicates "CALF PULSE VOLUME (pl / (cm2))" ranging from 0 to 500 on the right side of the graph. An x-axis label 706 represents cuff pressure or time during deflation, providing the temporal or pressure reference for the measurements acquired during the blood pressure determination process. The dual y-axis configuration allows simultaneous display of different measurement parameters that may be acquired during cuff deflation, where the y-axis label 702 and the y-axis label 704 represent different aspects of the physiological response to changing cuff pressure.29159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0123] With continued reference to FIG. 7, a first waveform plotted against the y-axis label 702 shows percent of baseline values that remain relatively constant at approximately 100% until a certain point, then decrease sharply to lower values as cuff pressure continues to fall. This first waveform may represent baseline impedance or other plethysmographic parameters that remain stable during the initial phases of cuff deflation when blood flow remains occluded, followed by characteristic changes when blood flow resumes as cuff pressure approaches and falls below systolic blood pressure levels.

[0124] A second waveform plotted against the y-axis label 704 shows calf pulse volume measurements that increase from zero to a peak value of approximately 150 pl / (cm2) at a point corresponding to mean blood pressure along the x-axis label 706, then decrease as cuff pressure continues to fall below mean blood pressure levels. The second waveform demonstrates the characteristic relationship between cuff pressure and pulse volume amplitude, where pulse volume reaches its maximum when the cuff pressure equals mean blood pressure. This relationship provides the physiological basis for identifying mean blood pressure through analysis of pulse volume measurements acquired during cuff deflation.

[0125] As further shown in FIG. 7, the peak of the second waveform plotted against the y-axis label 704 corresponds to the point of maximum pulse volume amplitude, which, according to some models, occurs when cuff pressure equals mean blood pressure. The processor 308 may be configured to identify this maximum pulse volume point through analysis of the concordance measures calculated during cuff deflation, where the concordance measure reaches its maximum value when cuff pressure corresponds to mean blood pressure. The processor 308 may monitor the sum of products of corresponding waveform points throughout the deflation process, where the sum of products increases in amplitude until the cuff reaches mean blood pressure, after which point the sum of products decreases.

[0126] The processor 308 may determine the point at which the sum of products is at its maximum and confirm the accuracy of this determination through iteration in a manner similar to the approach used for systolic blood pressure determination. The difference between successive sums of products may be negative as long as the cuff is being deflated between systolic blood pressure and mean blood pressure, indicating that the concordance measure continues to increase as cuff pressure approaches mean blood pressure. After the cuff pressure falls below mean blood pressure, the difference between successive sums of products may be positive, indicating that the concordance measure has begun to decrease from its maximum value.30159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0127] With continued reference to FIG. 7, the processor 308 may seek out the point at which the sum of products is at its maximum, corresponding to the peak pulse volume amplitude shown in the second waveform plotted against the y-axis label 704. This maximum concordance measure point may correspond to mean blood pressure, providing the processor 308 with the mean blood pressure value needed for diastolic blood pressure calculation. The processor 308 may be further configured to determine diastolic blood pressure by identifying a maximum concordance measure corresponding to mean blood pressure and calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2. There are other models which predict that DBP may actually occur closer to a point of maximum pulsations and that may, therefore, be an alternate means of calculating DBP.

[0128] The system may provide user selectabilify between different methods for determining diastolic blood pressure, allowing healthcare providers to choose the most appropriate calculation approach based on clinical requirements, patient characteristics, or institutional preferences. The processor 308 may be configured with a user interface that enables selection between the mathematical relationship DBP = (3MBP - SBP) / 2 derived from mean blood pressure identification, and an alternative point-of-maximum pulsation method that identifies diastolic blood pressure based on the point where arterial pulsation amplitude reaches its maximum during cuff deflation. This user selectability feature may accommodate different clinical protocols and may allow practitioners to compare results obtained through different calculation methods within the same measurement session.

[0129] The selectable diastolic blood pressure calculation methods may be implemented through software configuration options accessible via the output 310 or through dedicated control interfaces on the blood pressure measurement device 300A. When the mathematical formula method is selected, the processor 308 may identify the maximum concordance measure corresponding to mean blood pressure and apply the established physiological relationship to calculate diastolic blood pressure automatically. When the point-of-maximum pulsation method is selected, the processor 308 may monitor the amplitude characteristics of the concordance measures throughout the deflation process and identify diastolic blood pressure at the point where pulsation amplitude reaches its peak value. The system may also provide the option to calculate diastolic blood pressure using both methods simultaneously, displaying comparative results that may assist clinicians in interpreting measurement accuracy and selecting the most clinically relevant value for each individual patient assessment.31159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0130] The mathematical relationship DBP = (3MBP - SBP) / 2 may be derived from the physiological relationship where mean blood pressure is approximately equal to diastolic blood pressure plus one-third of the pulse pressure, expressed as MBP ~ DBP + (SBP - DBP) / 3. By rearranging this relationship algebraically, the processor 308 may calculate diastolic blood pressure using the measured systolic blood pressure and the mean blood pressure identified at the point of maximum concordance measure. This calculation approach may provide automated determination of diastolic blood pressure without requiring separate measurement techniques or additional sensor equipment.

[0131] The processor 308 may apply this diastolic blood pressure calculation method to measurements acquired from multiple extremities, where each extremity measurement may provide both systolic and diastolic blood pressure values through the combined crosscorrelation and mean blood pressure identification techniques. The system may be further configured to determine diastolic blood pressure for each extremity by identifying a maximum concordance measure corresponding to mean blood pressure and calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2. This capability may enable comprehensive vascular assessment that includes both systolic and diastolic blood pressure measurements for all monitored extremities.

[0132] The identification of mean blood pressure through maximum concordance measure detection may provide enhanced accuracy compared to conventional oscillometric techniques that rely on empirical algorithms for mean blood pressure determination. The processor 308 may use the direct measurement of pulse volume amplitude variations to identity' the precise point where pulse volume reaches its maximum, corresponding to the physiological condition where cuff pressure equals mean arterial pressure. This direct measurement approach may reduce the variability and potential inaccuracies associated with algorithmic estimation methods used in conventional blood pressure measurement systems.

[0133] As shown in FIG. 7, error bars are displayed on data points of both waveforms, indicating measurement variability' that may be encountered during actual blood pressure measurements. The processor 308 may account for this measurement variability through iterative confirmation of the maximum concordance measure point, where multiple measurements at pressures near the identified mean blood pressure may be used to verity- the accuracy of the mean blood pressure determination. The processor 308 may hold the estimated mean blood pressure for a period of time, looking for concordant waveforms and32159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 inflating and deflating the cuff above and below that point until a consistent result is obtained through iteration.

[0134] The diastolic blood pressure calculation capability may be particularly valuable in clinical applications where both systolic and diastolic blood pressure measurements are needed for comprehensive cardiovascular assessment. The processor 308 may generate reports that include both systolic and diastolic blood pressure values for each monitored extremity, where the diastolic values are calculated using the formula DBP = (3MBP - SBP) / 2 based on the mean blood pressure identified through maximum concordance measure detection. This automated calculation approach may provide complete blood pressure profiles without requiring additional measurement procedures or extended measurement times beyond those needed for systolic blood pressure determination.

[0135] Referring to FIG. 8, the system may generate comprehensive vascular assessment reports that display systolic blood pressure measurements and ankle-brachial indices for multiple extremities in an automated fashion. FIG. 8 depicts a report displaying systolic blood pressure and ankle-brachial index measurements obtained using a pulse flowmeter 802, where the pulse flowmeter 802 may represent the blood pressure measurement device 300A or similar system configured for multi-extremity vascular assessment. A report identifier 800 appears in the upper right comer of the report, providing identification and tracking information for the specific measurement session and patient data.

[0136] As shown in FIG. 8, the report presents a schematic representation of a patient's body with the pulse flowmeter 802 positioned centrally at the top, with branching lines extending to four extremities representing measurement locations where blood pressure cuffs and plethysmographic sensors may be positioned. The processor 308 may be configured to control sequential inflation and deflation of a plurality’ of blood pressure cuffs configured for placement on multiple extremities of a patient, where each blood pressure cuff may be positioned on an arm or ankle location for comprehensive vascular assessment. The system may include a plurality of plethysmographic sensors, each configured for placement distal to a corresponding blood pressure cuff, where the plethysmographic sensors may acquire plethysmographic data during cuff deflation at each extremity location.

[0137] The method for automated measurement of ankle-brachial index may comprise determining that a first blood pressure cuff is positioned on an arm of a patient and determining that a second blood pressure cuff is positioned on an ankle of the patient. The33159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 method may further comprise determining that a first plethysmographic sensor is positioned distal to the first blood pressure cuff and determining that a second plethysmographic sensor is positioned distal to the second blood pressure cuff. The processor 308 may verify proper positioning of the blood pressure cuffs and plethysmographic sensors through initial signal quality assessment or through operator confirmation before initiating the automated measurement sequence.

[0138] With continued reference to FIG. 8, the method may comprise measuring a first systolic blood pressure at the arm by inflating the first blood pressure cuff, deflating the first blood pressure cuff while acquiring first plethysmographic signals from the first plethysmographic sensor, processing the first plethysmographic signals using an crosscorrelation technique to identify onset of concordant waveforms, and determining the first systolic blood pressure based on cuff pressure when concordant waveforms are detected. For the left arm measurement shown in the report, the system displays BP = 120 / 60, indicating a systolic blood pressure of 120 mmHg and a diastolic blood pressure of 60 mmHg, along with additional parameters including Ro = 253 Q representing baseline impedance, PV = 220 pl / cm representing pulse volume amplitude, and PF = 6 pl / min / cm representing pulse flow measurements.

[0139] The method may comprise measuring a second systolic blood pressure at the ankle using the second blood pressure cuff and second plethysmographic sensor in a similar manner, where the same cross-correlation technique may be applied to identify concordant waveforms and determine ankle systolic blood pressure. The method may further comprise calculating an ankle-brachial index as a ratio of the second systolic blood pressure to the first systolic blood pressure. As shown in FIG. 8, the left ankle measurement displays BP = 105 / 60 with an ABI = 0.84, indicating that the ankle-brachial index was calculated by dividing the ankle systolic pressure of 105 mmHg by the arm systolic pressure, resulting in the ratio of 0.84.

[0140] The first plethysmographic sensor and the second plethysmographic sensor may each comprise an optical plethysmographic sensor, where the optical plethysmographic sensors may be transmission optical plethysmographic sensors positioned on digits of the patient. The transmission optical plethysmographic sensors may be positioned on fingers for arm measurements and on toes for ankle measurements, providing reliable plethysmographic signal acquisition distal to the occluding blood pressure cuffs. The processor 308 may apply signal processing to identify systolic blood pressure at each extremity by detecting34159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 concordant pulse waveforms through multiplication of high-pass filtered plethysmographic signals acquired from the optical plethysmographic sensors.

[0141] As further shown in FIG. 8, the method may comprise measuring systolic blood pressure at both arms of the patient and calculating the ankle-brachial index using a higher of the two arm systolic blood pressures. The right arm measurement displays BP = 125 / 65, indicating a systolic blood pressure of 125 mmHg, which may be higher than the left arm systolic blood pressure of 120 mmHg. The processor 308 may be configured to calculate bilateral ankle-brachial indices using the higher of the two arm systolic blood pressures as a denominator, where the higher arm pressure of 125 mmHg may be used for calculating both left and right ankle-brachial indices to provide standardized comparison values.

[0142] The nght ankle measurement shown in FIG. 8 displays BP — 75 / 35 with an ABI — 0.6, indicating a significantly reduced ankle systolic pressure that may suggest peripheral vascular disease. The ankle-brachial index of 0.6 may be calculated by dividing the ankle systolic pressure of 75 mmHg by the higher arm systolic pressure of 125 mmHg, resulting in a ratio that falls below the normal range and may indicate the presence of arterial occlusive disease in the lower extremity. The system may be configured to calculate ankle-brachial indices for lower extremities based on measured systolic pressures acquired through the cross-correlation technique described previously.

[0143] The method may comprise generating a report displaying the systolic blood pressure measurements for each extremity and the calculated ankle-brachial indices, where the report may provide comprehensive vascular assessment information in a standardized format suitable for clinical interpretation. The processor 308 may generate a report displaying systolic blood pressures and ankle-brachial indices for the multiple extremities, where the report may include various physiological parameters and graphical representations that assist in clinical decision-making. The report may include the amplitude of the plethysmographic pulse waveform for each extremity, as demonstrated by the PV values shown for each measurement location in FIG. 8.

[0144] With continued reference to FIG. 8, the report may include a graphic representation of the pulse for each extremity, where pulse volume waveform graphs are positioned below the numerical values for each measurement location. Each pulse volume waveform graph shows amplitude on the vertical axis ranging from 0 to 10, displaying characteristic arterial pulsation patterns with peaks and troughs representing cardiac cycles35159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 acquired during the measurement process. These graphical representations may provide visual indication of pulse quality and waveform characteristics that may assist clinicians in interpreting the measurement results and identifying potential vascular abnormalities.

[0145] The report may include the quantitative pulse volume amplitude of each limb when selective signal averaging is used, where the PV values displayed for each extremity represent quantitative measurements of pulse volume changes during cardiac cycles. The pulse volume measurements may be expressed in microliters per centimeter and may provide standardized quantitative assessment of arterial pulsation amplitude at each measurement location. The processor 308 may calculate these quantitative pulse volume measurements through analysis of the plethysmographic signals acquired during the measurement process, where the pulse volume amplitude may correspond to the maximum change in blood volume detected during each cardiac cycle.

[0146] As shown in FIG. 8, the report may include the value of the limb's baseline impedance for each extremity, where the Ro values displayed represent baseline electrical impedance measurements acquired at each measurement location. The baseline impedance values may provide information about tissue characteristics and blood volume status at each extremity , where variations in baseline impedance may indicate differences in tissue composition, hydration status, or vascular filling characteristics. The left arm shows Ro = 253 , the right arm shows Ro = 241 Q, the left ankle shows Ro = 325 Q, and the right ankle shows Ro = 315 Q, demonstrating the impedance variations that may be observed between different extremity locations.

[0147] The report may include a display of the first derivative of the pulse volume curve which may represent the instantaneous net inflow into the limb segment, where the PF values shown for each extremity may correspond to pulse flow measurements derived from the rate of change of pulse volume during cardiac cycles. The pulse flow measurements may be expressed in microliters per centimeter per minute and may provide information about the rate of arterial inflow during systolic phases of the cardiac cycle. The left arm shows PF = 6 pl / cm / min. the right arm shows PF = 5.7 pl / cm / min, the left ankle shows PF = 4.7 pl / cm / min, and the right ankle shows PF = 3.5 pl / cm / min, demonstrating the flow rate variations that may be observed between different extremity locations and may correlate with vascular health status.36159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0148] The system may comprise a plurality of blood pressure cuffs comprising four blood pressure cuffs configured for placement on both arms and both ankles of the patient, where the four-extremity measurement capability may enable comprehensive bilateral vascular assessment. The processor 308 may coordinate the sequential measurement of all four extremities through automated control of cuff inflation and deflation sequences, where each measurement location may be assessed using the same cross-correlation technique for detecting concordant pulse waveforms. The processor 308 may be configured to multiply corresponding points of successive high-pass filtered plethysmographic waveforms to generate product values for determining concordant pulse waveforms at each measurement location.

[0149] With continued reference to FIG. 8, the report may be packaged in a transmittable computer file that may be sent to a vascular surgeon for consultation and further care. The processor 308 may generate the report in various electronic formats that may facilitate transmission and integration with electronic medical record systems or telemedicine platforms. The transmittable computer file may include all measurement data, graphical representations, calculated indices, and patient identification information in a standardized format that may be readily interpreted by consulting physicians or specialists. The report identifier 800 may provide tracking and identification information that facilitates proper association of the measurement data with the specific patient and measurement session.

[0150] The automated vascular assessment system may provide a comprehensive screening tool suitable for primary' care physicians, cardiologists, podiatrists, and other physicians to identify medical conditions which may require medical or surgical intervention. The combination of automated ankle-brachial index measurements with quantitative pulse volume assessments may constitute a vascular disease screening system that addresses the clinical need for accessible, accurate, and reimbursable vascular assessment procedures. The processor 308 may generate reports that meet the criteria for vascular studies with graphic representation of arterial pulsations, potentially addressing reimbursement requirements that may encourage more widespread adoption of ankle-brachial index screening in primary care settings.

[0151] The pulse flowmeter 802 may represent an integrated system that combines the blood pressure measurement capabilities described previously with comprehensive reporting and data management functions. The pulse flowmeter 802 may coordinate measurements from multiple extremities, process the acquired data through the cross-correlation techniques,37159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 calculate ankle-brachial indices, and generate standardized reports that provide clinically relevant information for vascular assessment. The automated nature of the pulse flowmeter 802 may reduce the technical skill requirements and time commitments associated with conventional Doppler-based ankle-brachial index measurements, potentially enabling more widespread adoption of vascular screening procedures in various clinical settings.

[0152] Referring to FIG. 9, the system may incorporate an integrated cuff design that combines blood pressure occlusion and plethysmographic signal acquisition functions within a single device assembly. FIG. 9 illustrates a top view of a blood pressure cuff 900 configured for placement on a patient's limb, where the blood pressure cuff 900 may provide an alternative implementation approach that reduces the number of separate connections between the patient and the monitoring system. The blood pressure cuff 900 may comprise a fabric cuff body with an inflatable bladder portion and fastening mechanisms for securing the cuff around the limb during measurement procedures.

[0153] As shown in FIG. 9, the blood pressure cuff 900 may include printed instructional graphics on its surface, showing proper positioning and orientation during use to assist operators in achieving optimal measurement conditions. The blood pressure cuff 900 may display measurement range markings and alignment indicators to assist with proper sizing and placement on the patient's limb, where these visual guides may help ensure consistent positioning that may affect measurement accuracy. A tube may extend from the blood pressure cuff 900 for pneumatic connection to an inflation mechanism, providing the necessary' pressure control for cuff inflation and deflation during blood pressure measurement procedures.

[0154] With continued reference to FIG. 9, an optical pulse detector 902 may be positioned on the inside surface of the blood pressure cuff 900, integrated into the distal edge of the cuff body where the optical pulse detector 902 may contact the skin surface distal to the occluding bladder portion. The optical pulse detector 902 may be located such that when the blood pressure cuff 900 is wrapped around a limb, the optical pulse detector 902 may acquire plethysmographic signals from tissue distal to the occluding portion without requiring separate attachment of a sensor to a digit or other distal location. The positioning of the optical pulse detector 902 on the inside surface of the blood pressure cuff 900 may allow' the detector to function as a reflectance optical plethysmographic sensor that provides plethysmographic signals for processing by the processor 308.38159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0155] The optical pulse detector 902 may be connected via wiring that extends along the blood pressure cuff 900 to enable signal transmission to external processing components, where the wiring may be integrated into the cuff structure to provide a streamlined connection approach. The optical pulse detector 902 may be positioned to avoid compression during cuff inflation, where the location at the distal edge of the blood pressure cuff 900 may ensure that the optical pulse detector 902 remains in proper contact with the skin surface without being subjected to the high pressures generated within the occluding bladder portion. This positioning may enable the optical pulse detector 902 to maintain consistent signal acquisition throughout the cuff inflation and deflation process.

[0156] The blood pressure cuff 900 and the optical pulse detector 902 may be fabricated into a single cuff with two distinct sections comprising a proximal occluding bladder and a distal sensor region, where this integrated design may eliminate the need for separate sensor placement procedures. The proximal occluding bladder section of the blood pressure cuff 900 may provide the pressure occlusion function similar to conventional blood pressure cuffs, while the distal sensor region may house the optical pulse detector 902 and associated wiring. The processor 308 may control inflation and deflation of the proximal occluding bladder while simultaneously acquiring plethysmographic signals from the optical pulse detector 902 positioned in the distal sensor region.

[0157] As further shown in FIG. 9, the integrated cuff design may provide advantages in clinical settings where minimizing connection complexity may improve usability' and reduce potential failure points. The optical pulse detector 902 may share the connection with the inflation tube to the monitor, where both the pneumatic tubing for cuff inflation and the electrical wiring for the optical pulse detector 902 may be housed within a single cable assembly extending from the blood pressure cuff 900. This shared connection design may reduce the number of separate connections between the patient and the monitoring system, which may be desirable in hospital settings where simplified setup procedures may improve workflow efficiency.

[0158] The optical pulse detector 902 may function as a reflectance optical plethysmographic sensor that operates by emitting light into the tissue and detecting the reflected light intensity’ variations that correspond to changes in blood volume during cardiac cycles. The reflectance-based approach may be suitable for the integrated cuff design where the optical pulse detector 902 may be positioned on the same side of the tissue as the light source, eliminating the need for transmission-based sensor configurations that require light39159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 sources and detectors on opposite sides of the monitored tissue. The processor 308 may process signals from the optical pulse detector 902 using the same cross-correlation techniques described previously, where the reflectance optical plethysmographic signals may be high-pass filtered and multiplied to detect concordant waveforms indicating blood flow resumption.

[0159] The system may incorporate alternative sensor configurations where the plethysmographic sensor may be a bipolar impedance electrode rather than quadripolar for detecting the pulse when only presence or absence of concordant pulse is needed for blood pressure determination. The bipolar impedance electrode approach may provide a simplified sensor design that may be suitable for applications where quantitative pulse volume measurements are not required, focusing instead on the detection of pulse presence or absence for systolic blood pressure determination. The processor 308 may process signals from bipolar impedance electrodes using the same multiplication and summation techniques to determine concordance measures that indicate when pulse signals are present distal to the occluding cuff.

[0160] In some cases, the plethysmographic sensor may use pressure pulsations in a partially occluded cuff for detecting the pulse, where a secondary cuff positioned distal to the primary occluding cuff may be maintained at a partially inflated pressure level that allows detection of pressure variations corresponding to arterial pulsations. The partially occluded cuff approach may provide an alternative plethysmographic sensing method that does not require optical sensors or impedance electrodes, instead relying on pressure transduction to detect the presence or absence of arterial pulsations distal to the primary occluding cuff. The processor 308 may monitor pressure variations within the partially occluded cuff and apply the same cross-correlation processing techniques to identify concordant pressure waveforms that indicate blood flow resumption.

[0161] The blood pressure cuff 900 and plethysmographic sensor may be fabricated into a single cuff with two distinct sections comprising a proximal occluding bladder and a distal quadripolar electrode, where the quadripolar electrode configuration may provide quantitative pulse volume measurements in addition to pulse presence detection. The quadripolar electrode approach may enable measurement of both blood pressure and quantitative pulse volume characteristics using a single integrated device, where the distal quadripolar electrode section may acquire impedance plethysmographic signals while the proximal occluding bladder provides pressure occlusion. The processor 308 may coordinate the operation of both40159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 sections, controlling cuff inflation and deflation while processing impedance signals from the quadripolar electrodes to determine both systolic blood pressure and pulse volume amplitude.

[0162] The integrated cuff design may provide particular advantages for ankle measurements where the blood pressure cuff 900 may be positioned around the ankle with the optical pulse detector 902 or alternative sensor configuration positioned to acquire signals from the foot region. The single-cuff approach may simplify the setup procedure for ankle- brachial index measurements, where operators may position a single integrated device rather than coordinating the placement of separate cuffs and sensors. The processor 308 may apply the same cross-correlation processing techniques to signals acquired from the integrated ankle cuff, where concordant waveform detection may indicate ankle systolic blood pressure for subsequent ankle-brachial index calculations.

[0163] The alternative sensor configurations may provide flexibility in system implementation depending on specific clinical requirements and measurement objectives. When quantitative pulse volume measurements are desired along with blood pressure determination, the quadripolar electrode configuration may provide comprehensive vascular assessment capabilities within the integrated cuff design. When only blood pressure determination is required, the bipolar impedance electrode or partially occluded cuff approaches may provide simplified sensor implementations that may reduce system complexity and cost while maintaining the accuracy of the cross-correlation-based blood pressure measurement technique.

[0164] The processor 308 may be configured to work with any of these alternative sensor configurations, where the same high-pass filtering, multiplication, and summation operations may be applied to signals acquired from optical sensors, impedance electrodes, or pressure transducers. The concordance detection approach may remain consistent across different sensor types, where the processor 308 may identify the transition from noise-dominated signals to concordant pulse waveforms regardless of the specific plethysmographic sensing method employed. This flexibility may enable the system to be adapted for various clinical applications and measurement requirements while maintaining the automated, accurate blood pressure determination capabilities described throughout this disclosure.

[0165] Referring to FIG. 10, a method 1000 for automated measurement of ankle- brachial index may provide a systematic approach for acquiring accurate vascular assessment data from multiple extremities using the cross-correlation techniques described previously.41159615.00123 / 155789766v.1Attorney Docket No. 159615-00123The method 1000 may comprise a series of sequential steps that coordinate the positioning verification, blood pressure measurement, and index calculation procedures to enable automated ankle-brachial index determination without requiring skilled technician intervention. FIG. 10 illustrates a flowchart that demonstrates the logical progression of operations performed by the processor 308 during automated ankle-brachial index measurement procedures.

[0166] As shown in FIG. 10, the method 1000 may begin with a step 1002, where the system determines that a first blood pressure cuff is positioned on an arm of a patient. The step 1002 may involve verification procedures that confirm proper placement and sizing of the first blood pressure cuff on the patient's arm, where the processor 308 may assess initial signal quality or receive operator confirmation that the first blood pressure cuff has been correctly positioned around the upper arm region. The step 1002 may include checks for appropriate cuff sizing relative to arm circumference and verification that the cuff bladder is properly aligned over the brachial artery location to ensure effective blood flow occlusion during subsequent measurement procedures.

[0167] The method 1000 may then proceed to a step 1004, where the system determines that a second blood pressure cuff is positioned on an ankle of the patient. The step 1004 may involve similar verification procedures for the ankle measurement location, where the processor 308 may confirm that the second blood pressure cuff has been property positioned around the ankle region with appropriate sizing and alignment for effective arterial occlusion. The step 1004 may include assessment of cuff placement relative to the posterior tibial or dorsalis pedis arterial locations to ensure that the second blood pressure cuff may provide adequate pressure transmission for occluding ankle blood flow during measurement procedures.

[0168] With continued reference to FIG. 10, the method 1000 may continue to a step 1006, where the system determines that a first plethysmographic sensor is positioned distal to the first blood pressure cuff. The step 1006 may involve verification that the first plethysmographic sensor has been properly positioned on a digit or other location distal to the first blood pressure cuff, where the first plethysmographic sensor may be configured to acquire plethysmographic signals from tissue beyond the arm occlusion point. The step 1006 may include signal quality7assessment to confirm that the first plethysmographic sensor is making adequate contact with the skin surface and is capable of detecting blood volume changes during cardiac cycles.42159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0169] The method 1000 may proceed to a step 1008, where the system determines that a second plethysmographic sensor is positioned distal to the second blood pressure cuff. The step 1008 may involve verification procedures for the ankle measurement sensor, where the processor 308 may confirm that the second plethysmographic sensor has been properly positioned on a toe or other location distal to the second blood pressure cuff positioned at the ankle. The step 1008 may include assessment of sensor contact quality and signal acquisition capability to ensure that the second plethysmographic sensor may detect blood volume changes in the foot region during subsequent measurement procedures.

[0170] As further shown in FIG. 10, the method 1000 may advance to a step 1010, where the system measures a first systolic blood pressure at the arm by inflating the first blood pressure cuff. The step 1010 may initiate the blood pressure measurement sequence for the arm location, where the processor 308 may control the inflation mechanism 309 to inflate the first blood pressure cuff to a predetermined pressure level that exceeds the expected systolic blood pressure. The step 1010 may involve inflating the first blood pressure cuff to a fixed pressure such as 200 mmHg or to an adaptively determined pressure based on initial pulse detection characteristics, ensuring complete occlusion of arterial blood flow in the arm.

[0171] The method 1000 may continue to a step 1012, where the system deflates the first blood pressure cuff while acquiring first plethysmographic signals from the first plethysmographic sensor. The step 1012 may involve controlled deflation of the first blood pressure cuff at a predetermined rate such as 2 mmHg per second while the processor 308 simultaneously acquires plethysmographic data from the first plethysmographic sensor positioned distal to the first blood pressure cuff. The step 1012 may include continuous monitoring of signal quality and patient motion to ensure optimal measurement conditions during the deflation and signal acquisition process.

[0172] With continued reference to FIG. 10, the method 1000 may proceed to a step 1014, where the system processes the first plethysmographic signals using an crosscorrelation technique to identify onset of concordant waveforms. The step 1014 may involve the signal processing operations described previously, where the processor 308 may capture successive plethysmographic waveforms during deflation, high-pass filter the successive plethysmographic waveforms to produce filtered waveforms having equal area above and below a baseline, multiply corresponding points of an even number of the filtered waveforms to generate product values, and sum the product values to determine a concordance measure. The step 1014 may include multiplying corresponding points of successive filtered43159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 waveforms to enhance the reliability of concordance detection and minimize the chance of random concordance between noise waveforms.

[0173] The method 1000 may continue to a step 1016, where the system determines the first systolic blood pressure based on cuff pressure when concordant waveforms are detected. The step 1016 may involve comparing the concordance measure to a threshold value, where the processor 308 may identify the cuff pressure level at which the concordance measure exceeds the threshold value, indicating the resumption of blood flow distal to the first blood pressure cuff. The step 1016 may include iterative confirmation procedures where the processor 308 may hold the estimated systolic pressure for a period of time, looking for concordant waveforms and inflating and deflating the first blood pressure cuff above and below that point until a consistent result is obtained.

[0174] As shown in FIG. 10, the method 1000 may proceed to a step 1018, where the system measures a second sy stolic blood pressure at the ankle using the second blood pressure cuff and second plethysmographic sensor in a similar manner. The step 1018 may involve applying the same measurement sequence described for the arm location to the ankle measurement site, where the processor 308 may control inflation and deflation of the second blood pressure cuff while processing plethysmographic signals from the second plethysmographic sensor using the same cross-correlation technique. The step 1018 may include the same signal processing operations of capturing successive plethysmographic waveforms, high-pass filtering, multiplying corresponding points, and summing product values to determine concordance measures for the ankle measurement location.

[0175] The method 1000 may conclude with a step 1020, where the system calculates an ankle-brachial index as a ratio of the second systolic blood pressure to the first systolic blood pressure. The step 1020 may involve mathematical calculation of the ankle-brachial index by dividing the ankle systolic blood pressure measured in the step 1018 by the arm systolic blood pressure measured in the step 1016, where the resulting ratio may provide quantitative assessment of peripheral vascular health. The step 1020 may include comparison of the calculated ankle-brachial index to established clinical reference ranges, where values below 0.9 may indicate peripheral arterial disease and values below 0.5 may indicate severe arterial occlusive disease.

[0176] The first plethysmographic sensor and the second plethysmographic sensor may each comprise an optical plethysmographic sensor, where the optical plethysmographic44159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 sensors may provide reliable signal acquisition for the cross-correlation processing operations performed in the step 1014 and the step 1018. The optical plethysmographic sensors may be transmission optical plethysmographic sensors positioned on digits of the patient, where the transmission optical plethysmographic sensors may be positioned on a finger for arm measurements and on a toe for ankle measurements. The transmission optical plethysmographic sensors may operate by transmitting light through the digit tissue and detecting variations in transmitted light intensity that correspond to blood volume changes during cardiac cycles.

[0177] The method 1000 may further comprise measuring systolic blood pressure at both arms of the patient and calculating the ankle-brachial index using a higher of the two arm systolic blood pressures. This bilateral arm measurement approach may provide enhanced accuracy for ankle-brachial index calculations, where the processor 308 may perform the measurement sequence described in the step 1010 through the step 1016 for both arm locations to determine systolic blood pressure values for the left and right arms. The processor 308 may identify the higher of the two arm systolic blood pressures and use this higher value as the denominator for calculating bilateral ankle-brachial indices, ensuring that the ankle-brachial index calculations reflect the maximum available arterial pressure in the upper extremities.

[0178] The method 1000 may further comprise generating a report displaying the systolic blood pressure measurements for each extremity and the calculated ankle-brachial indices, where the report may provide comprehensive documentation of the vascular assessment results in a format suitable for clinical interpretation and record-keeping. The processor 308 may generate the report automatically following completion of the measurement sequence, where the report may include numerical values for systolic blood pressure at each measurement location, calculated ankle-brachial indices for both lower extremities, and graphical representations of the pulse volume waveforms acquired during the measurement process. The report may be displayed on the output 310 or transmitted electronically to medical record systems or consulting physicians for further evaluation and clinical decision-making.

[0179] The method 1000 may provide significant advantages over conventional Dopplerbased ankle-brachial index measurement techniques by eliminating the need for skilled technician intervention, ultrasound gel application, and manual pulse detection procedures. The automated nature of the method 1000 may enable widespread adoption of ankle-brachial45159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 index screening in primary care settings where conventional techniques may be impractical due to time constraints, technical skill requirements, or equipment limitations. The processor 308 may coordinate all aspects of the measurement sequence automatically, from initial positioning verification through final index calculation and report generation, providing a comprehensive vascular assessment system that may improve access to peripheral vascular disease screening procedures.

[0180] Referring to FIG. 11, a method 1100 for non-invasive blood pressure measurement using plethysmographic signal processing may provide a systematic approach for detecting concordant pulse waveforms through cross-correlation techniques. The method 1100 may demonstrate the sequential processing steps that enable the processor 308 to distinguish between noise-dominated signals and actual pulse volume signals during blood pressure cuff deflation. FIG. 11 illustrates a flowchart that shows the logical progression of signal acquisition, filtering, multiplication, and threshold comparison operations that may be performed by the processor 308 to determine systolic blood pressure automatically.

[0181] As shown in FIG. 11, the method 1100 may begin with a step 1 102, where the system controls inflation of a blood pressure cuff positioned around a limb. The step 1102 may involve the processor 308 controlling the inflation mechanism 309 to inflate the blood pressure cuff 202 to a pressure level that exceeds systolic blood pressure, ensuring complete occlusion of arterial blood flow in the monitored limb. The step 1 102 may include inflating the blood pressure cuff 202 to a predetermined fixed pressure such as 200 mmHg or to an adaptively determined pressure that may be established based on initial pulse detection characteristics or patient-specific factors.

[0182] The method 1100 may then proceed to a step 1104, where the system controls deflation of the blood pressure cuff. The step 1104 may involve the processor 308 controlling the inflation mechanism 309 to deflate the blood pressure cuff 202 at a controlled rate during measurement, where the deflation rate may be approximately 2 mmHg per second to provide sufficient time for accurate plethysmographic signal acquisition and processing. The step 1104 may include monitoring the deflation process to ensure consistent pressure reduction throughout the measurement sequence, where variations in deflation rate could affect the accuracy of blood pressure determination.

[0183] With continued reference to FIG. 11, the method 1100 may continue to a step 1 106, where the system captures successive plethysmographic waveforms during deflation46159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 using a plethysmographic sensor positioned distal to the cuff. The step 1106 may involve the processor 308 acquiring plethysmographic signals from the plethysmographic sensor 312 at regular intervals throughout the deflation process, where each captured waveform may represent a complete cardiac cycle or a portion thereof. The step 1106 may include using gating signals such as QRS wave complexes or identifiable characteristics of the plethysmographic signals to synchronize waveform capture with cardiac cycle timing.

[0184] The method 1100 may advance to a step 1108, where the system high-pass filters the successive plethysmographic waveforms to produce filtered waveforms having equal area above and below a baseline. The step 1108 may involve the processor 308 applying high-pass filtering operations that remove low-frequency components and baseline drift from the acquired plethysmographic signals, resulting in the filtered waveform 408 characteristics described previously. The step 1108 may ensure that the filtered waveforms oscillate symmetrically around a zero baseline, where the positive and negative portions of each pulse cycle may be balanced to facilitate subsequent multiplication operations.

[0185] As further shown in FIG. 11, the method 1100 may proceed to a step 1110, where the system multiplies corresponding points of the filtered waveforms to generate product values. The step 1110 may involve the processor 308 multiplying corresponding points of an even number of successive filtered waveforms, where corresponding points may represent data points that are equidistant in time from a gating signal or reference point within each cardiac cycle. The step 1110 may include multiplying corresponding points of successive filtered waveforms to enhance the reliability of concordance detection and minimize the chance of random concordance between noise waveforms.

[0186] The method 1100 may continue to a step 1112, where the system sums the product values to determine a concordance measure. The step 1112 may involve the processor 308 calculating the sum of all product values generated through the multiplication operations performed in the step 1110, where the concordance measure may provide a quantitative indication of the degree of similarity between successive plethysmographic waveforms. The step 1112 may result in large positive concordance measures when the filtered waveforms are concordant, indicating the presence of consistent pulse signals, or small concordance measures when the filtered waveforms contain primarily noise components.47159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0187] With continued reference to FIG. 11, the method 1100 may reach a step 1114, which presents a decision point where the system determines whether the concordance measure exceeds a threshold value. The step 1 114 may involve the processor 308 comparing the concordance measure calculated in the step 1112 to a predetermined threshold value that distinguishes between noise-dominated signals and concordant pulse waveforms. The threshold value may be a fixed value established based on empirical measurements of noise characteristics, or the threshold value may be adaptively determined as a function of corresponding values obtained during cuff inflation or based on patient-specific measurement conditions.

[0188] If the concordance measure exceeds the threshold value in the step 1114, the method 1100 may proceed along a "Yes" branch to a step 1116, where the system determines systolic blood pressure based on detection of concordant waveforms. The step 1116 may involve the processor 308 identifying the cuff pressure level at which concordant waveforms are first detected during deflation, where this pressure level may correspond to systolic blood pressure. The step 1116 may include recording the cuff pressure at the time when the concordance measure exceeds the threshold value, providing an automated determination of systolic blood pressure without requiring manual interpretation or skilled technician intervention.

[0189] If the concordance measure does not exceed the threshold value in the step 1114, the method 1 100 may proceed along a "No" branch to a step 11 18, where the system continues cuff deflation and repeats waveform capture, returning to the signal acquisition and processing sequence. The step 1118 may involve the processor 308 continuing the controlled deflation of the blood pressure cuff 202 while maintaining the signal acquisition and processing operations described in the step 1106 through the step 1 112. The step 1 118 may create a feedback loop that ensures continuous monitoring of the concordance measure throughout the deflation process until concordant waveforms are detected or the deflation sequence is completed.

[0190] As shown in FIG. 11, the method 1100 demonstrates the sequential processing steps for automated blood pressure measurement using cross-correlation techniques that maybe implemented by the processor 308. The method 1100 may incorporate a decision-making mechanism in the step 1114 that distinguishes between noise-dominated signals and concordant pulse waveforms through threshold comparison of the concordance measure. When plethysmographic signals contain only noise, such as when the blood pressure cuff 20248159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 is inflated above systolic blood pressure, the concordance measure may remain below the threshold value, and the method 1100 may continue through the step 1118 to maintain signal acquisition and processing operations.

[0191] The method 1100 may provide a systematic approach for detecting the resumption of blood flow distal to an occluding cuff through signal processing of plethysmographic waveforms acquired by the plethysmographic sensor 312. The processor 308 may be configured to control inflation and deflation of the blood pressure cuff 202 while simultaneously performing the signal processing operations described in the method 1100. where the automated coordination of pressure control and signal analysis may enable accurate blood pressure determination without manual intervention. The method 1100 may be applied to measurements at various anatomical locations, including arm and ankle sites for comprehensive vascular assessment procedures.

[0192] The decision point represented by the step 1114 may provide the fundamental mechanism for automated blood pressure determination, where the processor 308 may continuously evaluate the concordance measure against the threshold value throughout the deflation process. When concordant waveforms are detected through exceeding the threshold value, the method 1100 may proceed to the step 1116 for systolic blood pressure determination. When concordant waveforms are not detected, the method 1100 may continue through the step 1118 to maintain the measurement process until blood flow resumption is identified or the measurement sequence is completed.

[0193] The method 1100 may be particularly effective when the processor 308 is configured to multiply corresponding points of successive filtered waveforms in the step 1110, where the use of four waveforms may significantly reduce the probability that random noise fluctuations could produce false positive concordance measurements. The multiplication of successive filtered waveforms may provide enhanced reliability compared to multiplication of only two waveforms, where the increased number of waveforms may reinforce the detection of true pulse signals while minimizing the influence of random noise components that could interfere with accurate blood pressure determination.

[0194] The method 1100 may support the determination of diastolic blood pressure through identification of maximum concordance measures during the deflation process, where the processor 308 may be further configured to determine diastolic blood pressure by identifying a maximum concordance measure corresponding to mean blood pressure and49159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2. The step 1112 may provide concordance measures throughout the deflation process that reach maximum values when cuff pressure equals mean blood pressure, enabling the processor 308 to identify mean blood pressure for subsequent diastolic blood pressure calculations using the mathematical relationship between systolic, diastolic, and mean blood pressures.

[0195] The method 1100 may be implemented using various types of plethysmographic sensors, where the plethysmographic sensor 312 may comprise an optical plethysmographic sensor that provides reliable signal acquisition for the processing operations described in the step 1106 through the step 1112. The optical plethysmographic sensor may be a transmission optical plethysmographic sensor configured to be positioned on a digit distal to the blood pressure cuff 202, where the transmission optical plethysmographic sensor may operate bytransmitting light through digit tissue and detecting variations in transmitted light intensity that correspond to blood volume changes during cardiac cycles. The processor 308 may process signals from the transmission optical plethysmographic sensor using the same filtering, multiplication, and summation operations described in the method 1100, providing accurate blood pressure determination regardless of the specific plethysmographic sensing technology employed.

[0196] Referring to FIG. 12, a method 1200 for automated vascular assessment may provide a comprehensive approach for coordinating measurements across multiple extremities while maintaining consistent signal processing techniques for each measurement location. The method 1200 may demonstrate the sequential processing approach for multiextremity vascular assessment, incorporating a feedback loop that ensures comprehensive measurement of all designated extremities before proceeding to index calculations and report generation. FIG. 12 illustrates a flowchart that shows the logical progression of operations performed by the processor 308 during automated vascular assessment procedures that may include measurements from both upper and lower extremities.

[0197] As show n in FIG. 12, the method 1200 may begin with a step 1202, where the system controls sequential inflation and deflation of a plurality of blood pressure cuffs configured for placement on multiple extremities. The step 1202 may involve the processor 308 coordinating the operation of multiple blood pressure cuffs positioned on various extremity- locations, where each blood pressure cuff may be inflated and deflated in a predetermined sequence to enable systematic vascular assessment. The step 1202 may include controlling the inflation mechanism 309 to inflate each blood pressure cuff to50159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 appropriate pressure levels that exceed systolic blood pressure at each measurement location, ensuring complete arterial occlusion during the measurement process.

[0198] The method 1200 may then proceed to a step 1204, where plethysmographic data is acquired from a plurality' of plethysmographic sensors during cuff deflation. The step 1204 may involve the processor 308 acquiring plethysmographic signals from multiple plethysmographic sensors positioned distal to the corresponding blood pressure cuffs, where each plethysmographic sensor may provide signals for processing during the deflation of its associated blood pressure cuff. The step 1204 may include coordinating the timing of signal acquisition with the deflation sequences controlled in the step 1202, ensuring that plethysmographic data collection occurs during appropriate phases of the measurement process for each extremity location.

[0199] With continued reference to FIG. 12, the method 1200 may continue to a step 1206, where signal processing is applied to identify systolic blood pressure at each extremity by detecting concordant pulse waveforms. The step 1206 may involve the processor 308 applying the cross-correlation techniques described previously to the plethysmographic data acquired from each measurement location, where the same signal processing operations may be performed for each extremity to ensure consistent measurement methodology. The step 1206 may include capturing successive plethysmographic waveforms during deflation, high- pass filtering the waveforms, and processing the filtered signals to identify concordant pulse patterns that indicate blood flow resumption at each measurement site.

[0200] The method 1200 may advance to a step 1208, where high-pass filtered plethysmographic signals are multiplied to detect concordant waveforms. The step 1208 may involve the processor 308 multiplying corresponding points of the filtered waveforms to generate product values for each extremity measurement, where the multiplication operations may be performed using an even number of successive filtered waveforms to enhance concordance detection reliability. The step 1208 may include multiplying corresponding points of successive high-pass filtered plethysmographic waveforms to generate product values for determining concordant pulse waveforms at each measurement location, where the use of four waveforms may minimize the chance of random concordance between noise waveforms.

[0201] As further shown in FIG. 12, the method 1200 may proceed to a decision point at a step 1210, where the system determines whether measurements are complete for all51159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 extremities. The step 1210 may involve the processor 308 evaluating the status of measurements across all designated extremity locations, where the processor 308 may track which measurement sites have completed the signal processing sequence and which sites may require additional data acquisition. The step 1210 may include checking whether systolic blood pressure has been successfully determined for each extremity location through detection of concordant waveforms and threshold comparison of concordance measures.

[0202] If measurements are complete for all extremities in the step 1210, the method1200 may advance along a "Yes" branch to a step 1212. where ankle-brachial indices are calculated for lower extremities based on measured systolic pressures. The step 1212 may involve the processor 308 performing mathematical calculations to determine ankle-brachial indices by dividing ankle systolic blood pressures by arm systolic blood pressures, where the calculations may use the higher of the two arm systolic blood pressures as the denominator for bilateral ankle-brachial index determination. The step 1212 may include comparing the calculated ankle-brachial indices to established clinical reference ranges to provide interpretive information for clinical decision-making.

[0203] With continued reference to FIG. 12, if measurements are not complete for all extremities in the step 1210, the method 1200 may proceed along a "No" branch to a step 1214, where sequential measurements continue on remaining extremities. The step 1214 may involve the processor 308 continuing the measurement sequence for extremity locations that have not yet completed the signal processing operations, where the processor 308 may maintain cuff deflation and signal acquisition procedures for the remaining measurement sites. The step 1214 may create a feedback loop that returns the method 1200 to the step 1204 to acquire additional plethysmographic data from the remaining extremities that require continued measurement procedures.

[0204] From the step 1214, the method 1200 may return to the step 1204 to acquire additional plethysmographic data from the remaining extremities, where the processor 308 may continue the coordinated measurement sequence until all designated extremity locations have completed the signal processing operations. This feedback loop may ensure that no measurement locations are omitted from the comprehensive vascular assessment, where the processor 308 may systematically process each extremity through the complete measurement sequence before proceeding to index calculations and report generation.52159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0205] Following completion of ankle-brachial index calculations in the step 1212, the method 1200 may continue to a step 1216, where a report is generated displaying systolic blood pressures and ankle-brachial indices for the multiple extremities. The step 1216 may involve the processor 308 compiling measurement results from all extremity locations into a comprehensive report format that provides clinical information suitable for vascular assessment interpretation. The step 1216 may include generating graphical representations of pulse volume waveforms, numerical displays of systolic blood pressure values, calculated ankle-brachial indices, and additional physiological parameters acquired during the measurement process.

[0206] The method 1200 may provide an automated approach for coordinating measurements across multiple limbs while maintaining consistent signal processing techniques for each measurement location, where the processor 308 may apply the same cross-correlation processing operations to signals acquired from each extremity. The sequential processing approach demonstrated by the method 1200 may enable comprehensive vascular assessment without requiring manual coordination of multiple measurement devices or separate processing procedures for different extremity locations. The processor 308 may coordinate all aspects of the multi-extremity measurement sequence, from initial cuff inflation through final report generation, providing a systematic approach for automated vascular disease screening.

[0207] The method 1200 may be implemented using a system for automated vascular assessment that may comprise a plurality7of blood pressure cuffs configured for placement on multiple extremities of a patient and a plurality of plethysmographic sensors, each configured for placement distal to a corresponding blood pressure cuff. The plurality of plethysmographic sensors may comprise optical plethysmographic sensors that provide reliable signal acquisition for the processing operations described in the step 1204 through the step 1208. The optical plethysmographic sensors may be transmission optical plethysmographic sensors configured for placement on digits of the patient, where the transmission optical plethysmographic sensors may be positioned on fingers for arm measurements and on toes for ankle measurements.

[0208] The system may include a processing unit configured to control sequential inflation and deflation of the plurality of blood pressure cuffs, acquire plethysmographic data from the plurality of plethysmographic sensors during cuff deflation, apply signal processing to identify systolic blood pressure at each extremity by detecting concordant pulse waveforms53159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 through multiplication of high-pass filtered plethysmographic signals, calculate ankle- brachial indices for lower extremities based on measured systolic pressures, and generate a report displaying systolic blood pressures and ankle-brachial indices for the multiple extremities. The processing unit may correspond to the processor 308 described previously, where the same signal processing capabilities may be applied to multiple measurement locations simultaneously or sequentially.

[0209] The processing unit may be configured to multiply corresponding points of successive high-pass filtered plethysmographic waveforms to generate product values for determining concordant pulse waveforms at each measurement location, where the use of successive waveforms may provide enhanced reliability’ for concordance detection across all extremity measurements. The processing unit may be further configured to determine diastolic blood pressure for each extremity by identifying a maximum concordance measure corresponding to mean blood pressure and calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2. This diastolic blood pressure calculation capability’ may enable the system to provide comprehensive blood pressure profiles for all monitored extremities, where both systolic and diastolic values may be determined through the same cross-correlation processing approach.

[0210] The plurality of blood pressure cuffs may comprise four blood pressure cuffs configured for placement on both arms and both ankles of the patient, where the four- extremity measurement capability may enable comprehensive bilateral vascular assessment through the method 1200. The processing unit may be configured to calculate bilateral ankle- brachial indices using a higher of the two arm systolic blood pressures as a denominator, ensuring that ankle-brachial index calculations reflect the maximum available arterial pressure in the upper extremities. This approach may provide standardized ankle-brachial index values that account for potential differences between left and right arm blood pressures, where the higher arm pressure may serve as the reference value for both ankle measurements.

[0211] The method 1200 may provide significant clinical advantages by enabling comprehensive vascular assessment through a single automated measurement session, where multiple extremity locations may be evaluated using consistent measurement techniques and signal processing operations. The systematic approach demonstrated by the method 1200 may reduce the time and technical skill requirements associated with conventional multi-extremity vascular assessment procedures, where manual coordination of multiple measurement devices and separate processing operations for each extremity location may be eliminated. The54159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 processor 308 may coordinate all aspects of the multi-extremity measurement sequence automatically, providing healthcare providers with comprehensive vascular assessment capabilities that may improve access to peripheral vascular disease screening in various clinical settings.

[0212] Referring to FIG. 13, a method 1300 for enhanced bilateral ankle-brachial index measurement may provide a comprehensive approach for obtaining complete vascular assessment data from multiple extremities, incorporating both systolic and diastolic blood pressure measurements along with bilateral ankle-brachial index calculations in an automated fashion. The method 1300 may demonstrate the sequential processing approach for obtaining comprehensive vascular assessment data from multiple extremities, where the processor 308 may coordinate measurements across both upper and lower extremities while calculating both systolic and diastolic blood pressure values for each measurement location. FIG. 13 illustrates a flowchart that shows the logical progression of operations performed by the processor 308 during enhanced bilateral ankle-brachial index measurement procedures that may include complete blood pressure profiles for all monitored extremities.

[0213] As show n in FIG. 13, the method 1300 may begin with a step 1302, where systolic blood pressure is measured at both arms of the patient. The step 1302 may involve the processor 308 coordinating bilateral arm measurements using the cross-correlation techniques described previously, where blood pressure cuffs may be positioned on both the left and right arms with corresponding plethysmographic sensors positioned distal to each cuff. The step 1302 may include inflating each arm cuff to appropriate pressure levels, deflating the cuffs while acquiring plethysmographic signals, processing the signals using cross-correlation techniques to identify onset of concordant waveforms, and determining systolic blood pressure based on cuff pressure when concordant waveforms are detected for each arm location.

[0214] The method 1300 may then proceed to a step 1304, which involves identifying the higher of the two arm systolic blood pressures. The step 1304 may involve the processor 308 comparing the systolic blood pressure values obtained from both arm measurements in the step 1302 and selecting the higher value for use in subsequent ankle-brachial index calculations. The step 1304 may provide enhanced accuracy for ankle-brachial index calculations by ensuring that the denominator represents the maximum available arterial pressure in the upper extremities, accounting for potential differences between left and right arm blood pressures that may occur due to anatomical variations or vascular conditions.55159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0215] With continued reference to FIG. 13, the method 1300 may move to a step 1306, where systolic blood pressure is measured at both ankles using the cross-correlation technique described in the disclosure. The step 1306 may involve the processor 308 applying the same measurement sequence used for arm measurements to both ankle locations, where blood pressure cuffs may be positioned around each ankle with plethysmographic sensors positioned distal to the cuffs on the feet. The step 1306 may include the same signal processing operations of capturing successive plethysmographic waveforms during cuff deflation, high-pass filtering the waveforms, multiplying corresponding points of filtered waveforms, and summing product values to determine concordance measures for both ankle measurement locations.

[0216] The method 1300 may continue to a step 1308, where the maximum concordance measure corresponding to mean blood pressure is identified for each extremity. The step 1308 may involve the processor 308 analyzing the concordance measures calculated throughout the deflation process for each measurement location, where the concordance measures may reach maximum values when cuff pressure equals mean blood pressure at each extremity. The step 1308 may enable identification of mean blood pressure through direct measurement of pulse volume amplitude variations, where the processor 308 may monitor the sum of products of corresponding waveform points and identity’ the point at which the sum of products reaches its maximum value during cuff deflation.

[0217] As further shown in FIG. 13, the method 1300 may proceed to a step 1310, which involves calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2. The step 1310 may involve the processor 308 applying this mathematical relationship to determine diastolic blood pressure for each extremity based on the mean blood pressure identified in the step 1308 and the systolic blood pressure measured in the step 1302 and the step 1306. The step 1310 may provide automated determination of diastolic blood pressure without requiring separate measurement techniques or additional sensor equipment, where the formula DBP = (3MBP - SBP) / 2 may be derived from the physiological relationship where mean blood pressure is approximately equal to diastolic blood pressure plus one-third of the pulse pressure.

[0218] The method 1300 may then advance to a step 1312, where bilateral ankle-brachial indices are calculated using the higher arm systolic blood pressure as the denominator. The step 1312 may involve the processor 308 performing mathematical calculations to determine ankle-brachial indices by dividing each ankle systolic blood pressure measured in the step56159615.00123 / 155789766v.1Attorney Docket No. 159615-001231306 by the higher arm systolic blood pressure identified in the step 1304. The step 1312 may ensure that both left and right ankle-brachial indices are calculated using the same denominator value, providing standardized comparison values that account for potential differences between arm blood pressures and enable consistent interpretation of peripheral vascular health status.

[0219] With continued reference to FIG. 13, the method 1300 may proceed to a step 1314, which involves generating a comprehensive report displaying systolic and diastolic blood pressure measurements for each extremity. The step 1314 may involve the processor 308 compiling measurement results from all extremity locations into a comprehensive report format that includes both systolic and diastolic blood pressure values determined through the cross-correlation and mean blood pressure identification techniques. The step 1314 may provide complete blood pressure profiles for all monitored extremities, where the report may include numerical displays of systolic and diastolic blood pressure values, baseline impedance measurements, pulse volume amplitudes, and graphical representations of pulse volume waveforms acquired during the measurement process.

[0220] The method 1300 may conclude with a step 1316, where the calculated ankle- brachial indices for both lower extremities are displayed in the report. The step 1316 may involve the processor 308 including the bilateral ankle-brachial index values calculated in the step 1312 within the comprehensive report generated in the step 1314, where the ankle- brachial indices may be displayed alongside the blood pressure measurements and other physiological parameters. The step 1316 may provide clinicians with complete vascular assessment information that includes both hemodynamic measurements and calculated indices suitable for peripheral vascular disease screening and diagnosis.

[0221] The method 1300 may provide a comprehensive approach for bilateral ankle- brachial index measurement that incorporates enhanced measurement accuracy through bilateral arm pressure assessment and complete blood pressure profiling through automated diastolic pressure calculation. The processor 308 may coordinate all aspects of the enhanced measurement sequence, from bilateral arm and ankle measurements through final report generation with complete blood pressure profiles and bilateral ankle-brachial indices. The method 1300 may enable healthcare providers to obtain comprehensive vascular assessment data through a single automated measurement session, where both systolic and diastolic blood pressure values may be determined for all extremities along with standardized ankle- brachial index calculations.57159615.00123 / 155789766v.1Attorney Docket No. 159615-00123

[0222] The method 1300 may support the device described previously, where the processing device may be further configured to determine diastolic blood pressure by identifying a maximum concordance measure corresponding to mean blood pressure and calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2. The step 1308 and the step 1310 may demonstrate how the processor 308 may implement this diastolic blood pressure determination capability, where the same cross-correlation processing techniques used for systolic blood pressure measurement may be extended to identify mean blood pressure points for subsequent diastolic pressure calculations.

[0223] The method 1300 may also support the system for automated vascular assessment described previously, where the processing unit may be further configured to determine diastolic blood pressure for each extremity by identifying a maximum concordance measure corresponding to mean blood pressure and calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2. The step 1308 through the step 1316 may demonstrate how the processing unit may implement comprehensive vascular assessment capabilities that include both systolic and diastolic blood pressure measurements along with bilateral ankle- brachial index calculations using standardized reference values.

[0224] As shown in FIG. 13, the method 1300 may support the system where the plurality of blood pressure cuffs comprises four blood pressure cuffs configured for placement on both arms and both ankles of the patient, and the processing unit is configured to calculate bilateral ankle-brachial indices using a higher of the tw o arm systolic blood pressures as a denominator. The step 1302 through the step 1312 may demonstrate the sequential measurement and calculation approach that enables four-extremity vascular assessment with standardized ankle-brachial index calculations, where the higher arm systolic blood pressure identified in the step 1304 may serve as the reference denominator for both ankle measurements.

[0225] The method 1300 may' provide significant clinical advantages by enabling comprehensive bilateral vascular assessment through automated measurement procedures that require minimal operator intervention and technical expertise. The enhanced measurement approach demonstrated by the method 1300 may address the clinical need for accurate, reproducible ankle-brachial index measurements that may be suitable for widespread adoption in primary care settings where conventional Doppler-based techniques may be impractical due to time constraints, technical skill requirements, or equipment limitations. The processor 308 may coordinate all aspects of the enhanced bilateral measurement58159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 sequence automatically, providing healthcare providers with comprehensive vascular assessment capabilities that may improve access to peripheral vascular disease screening and diagnosis in various clinical environments.

[0226] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.59159615.00123 / 155789766v.1

Claims

Attorney Docket No. 159615-00123CLAIMS1. A device for non-invasive measurement of blood pressure, comprising: a blood pressure cuff configured to be positioned around a limb, the blood pressure cuff having a proximal end and a distal end; an optical plethysmographic sensor integrated into the distal end of the blood pressure cuff and configured to acquire optical plethysmographic signals from tissue distal to an inflatable portion of the blood pressure cuff; and a processing device operatively connected to the blood pressure cuff and the optical plethysmographic sensor, the processing device configured to: control inflation and deflation of the blood pressure cuff, capture successive optical plethysmographic waveforms during deflation of the blood pressure cuff, high-pass filter the successive optical plethysmographic waveforms to produce filtered waveforms having equal area above and below a baseline, multiply corresponding points of the filtered waveforms to generate product values, sum the product values to determine a concordance measure, detect initial returning pulsations of very low amplitude during cuff deflation by identifying when the initial low-amplitude optical pulsations have the same shape as larger amplitude optical pulsations that follow as the cuff pressure continues to decrease, and determine systolic blood pressure based on detection of the initial returning pulsations when the concordance measure indicates that the initial low-amplitude optical pulsations are concordant with subsequent higher-amplitude optical pulsations.

2. The device of claim 1, wherein the optical plethysmographic sensor comprises a transmission optical sensor with a light source positioned on a first side of a digit and a light detector positioned on an opposite side of the digit, and wherein the optical plethysmographic60159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 sensor is configured to be positioned on the digit distal to the inflatable portion of the blood pressure cuff.

3. The device of claim 1, wherein the transmission optical sensor is configured to be positioned on a finger or toe at the distal end of the blood pressure cuff.

4. The device of claim 1, wherein the processing device is further configured to: multiply corresponding points of an even number of successive filtered waveforms.

5. The device of claim 4, wherein the processing device is further configured to: multiply corresponding points of successive filtered waveforms.

6. The device of claim 1, wherein the processing device is further configured to: determine diastolic blood pressure by: identifying a maximum concordance measure corresponding to mean blood pressure and calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2, or identifying a maximum arterial pulsation amplitude.

7. The device of claim 1, further comprising an inflation mechanism operatively connected to the processing device, wherein the processing device is configured to control the inflation mechanism to inflate the blood pressure cuff to a predetermined pressure and deflate the blood pressure cuff at a controlled rate during measurement.

8. The device of claim 7, wherein the processing device is further configured to: detect the initial returning pulsations by monitoring the concordance measure during the controlled deflation to identify the precise moment when blood flow returns as indicated by shape concordance between initial low-amplitude and subsequent higher- amplitude optical pulsations.

9. A method for automated measurement of ankle-brachial index, comprising: determining that a first blood pressure cuff is positioned on an arm of a patient; determining that a second blood pressure cuff is positioned on an ankle of the patient; determining that a first plethysmographic sensor is positioned distal to the first blood pressure cuff;61159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 determining that a second plethysmographic sensor is positioned distal to the second blood pressure cuff; measuring a first systolic blood pressure at the arm by: inflating the first blood pressure cuff, deflating the first blood pressure cuff while acquiring first plethysmographic signals from the first plethy smographic sensor, processing the first plethysmographic signals using an crosscorrelation technique to identify onset of concordant waveforms, and determining the first systolic blood pressure based on cuff pressure when concordant waveforms are detected; measuring a second systolic blood pressure at the ankle using the second blood pressure cuff and second plethysmographic sensor in a similar manner; and calculating an ankle-brachial index as a ratio of the second systolic blood pressure to the first systolic blood pressure.

10. The method of claim 9, wherein the first plethysmographic sensor and the second plethysmographic sensor each comprise an optical plethysmographic sensor.

11. The method of claim 10, wherein the optical plethysmographic sensors are transmission optical plethysmographic sensors positioned on digits of the patient.

12. The method of claim 9, wherein processing the first plethysmographic signals using an cross-correlation technique comprises: capturing successive plethysmographic waveforms during deflation; high-pass filtering the successive plethysmographic waveforms to produce filtered waveforms having equal area above and below a baseline; multiplying corresponding points of an even number of the filtered waveforms to generate product values; and summing the product values to determine a concordance measure.

13. The method of claim 12, wherein multiplying corresponding points comprises multiplying corresponding points of successive filtered waveforms.62159615.00123 / 155789766v.1Attorney Docket No. 159615-0012314. The method of claim 9, further comprising measuring systolic blood pressure at both arms of the patient and calculating the ankle-brachial index using a higher of the two arm systolic blood pressures.

15. The method of claim 14, further comprising generating a report displaying the systolic blood pressure measurements for each extremity and the calculated ankle-brachial indices.

16. A system for automated vascular assessment, comprising: a plurality of blood pressure cuffs configured for placement on multiple extremities of a patient; a plurality of plethysmographic sensors, each configured for placement distal to a corresponding blood pressure cuff; and a processing unit configured to: control sequential inflation and deflation of the plurality of blood pressure cuffs, acquire plethysmographic data from the plurality of plethysmographic sensors during cuff deflation, apply signal processing to identify systolic blood pressure at each extremity by detecting concordant pulse waveforms through multiplication of high-pass filtered plethysmographic signals. calculate ankle-brachial indices for lower extremities based on measured systolic pressures, and generate a report displaying systolic blood pressures and ankle- brachial indices for the multiple extremities.

17. The system of claim 16, wherein the plurality of plethysmographic sensors comprise optical plethysmographic sensors.

18. The system of claim 17, wherein the optical plethysmographic sensors are transmission optical plethysmographic sensors configured for placement on digits of the patient.

19. The system of claim 16, wherein the processing unit is configured to:63159615.00123 / 155789766v.1Attorney Docket No. 159615-00123 multiply corresponding points of successive high-pass filtered plethysmographic waveforms to generate product values for determining concordant pulse waveforms.

20. The system of claim 19, wherein the processing unit is further configured to: determine diastolic blood pressure for each extremity by identifying a maximum concordance measure corresponding to mean blood pressure and calculating diastolic blood pressure using the formula DBP = (3MBP - SBP) / 2, or identifying a maximum arterial pulsation amplitude.

21. The system of claim 16, wherein the plurality of blood pressure cuffs comprises four blood pressure cuffs configured for placement on both arms and both ankles of the patient, and the processing unit is configured to calculate bilateral ankle-brachial indices using a higher of the two arm systolic blood pressures as a denominator.

22. A multi-extremity vascular assessment device, comprising: a plurality of blood pressure cuffs, each cuff configured to be positioned around a different extremity of a patient and having a proximal end and a distal end; a plurality of optical plethysmographic sensors, each sensor integrated into the distal end of a respective blood pressure cuff and configured to acquire optical plethysmographic signals from a digit distal to an inflatable portion of the respective cuff; a processing unit operatively connected to the plurality of blood pressure cuffs and the plurality of optical plethysmographic sensors, the processing unit configured to: sequentially control inflation and deflation of each blood pressure cuff, capture successive optical plethysmographic waveforms from each sensor during deflation of the respective cuff, apply cross-correlation signal processing to detect initial returning pulsations at each extremity by identifying shape concordance between initial low-amplitude optical pulsations and subsequent higher-amplitude optical pulsations, determine systolic blood pressure for each extremity based on detection of the initial returning pulsations, and calculate ankle-brachial indices using the determined systolic blood pressures.

23. The device of claim 22, comprising four blood pressure cuffs configured for placement on both arms and both ankles of the patient.64159615.00123 / 155789766v.1Attorney Docket No. 159615-0012324. The device of claim 23, wherein the processing unit is configured to calculate bilateral ankle-brachial indices using a higher of the two arm systolic blood pressures as a denominator.

25. The device of claim 22, wherein each optical plethysmographic sensor comprises a transmission optical sensor with a light source and a light detector positioned on opposite sides of a digit.

26. The device of claim 22, wherein the processing unit is further configured to determine diastolic blood pressure for each extremity by identifying a maximum: concordance measure and applying the formula DBP = (3MBP - SBP) / 2, or arterial pulsation amplitude.

27. A blood pressure measurement device with integrated optical sensing, comprising: a blood pressure cuff assembly comprising: an inflatable bladder configured to occlude blood flow in a limb, a distal extension portion extending beyond the inflatable bladder, and an optical plethysmographic sensor integrated into the distal extension portion; wherein the optical plethysmographic sensor comprises a pulse oximeter configured to detect optical plethysmographic signals from a digit positioned within the distal extension portion; and a signal processing module configured to: apply high-pass filtering to successive optical plethysmographic waveforms to produce filtered waveforms with equal area above and below a baseline, perform cross-correlation analysis by multiplying corresponding points of the filtered waveforms, detect onset of concordant optical pulsations indicating return of blood flow, and determine blood pressure based on cuff pressure at onset of concordant optical pulsations.65159615.00123 / 155789766v.1Attorney Docket No. 159615-0012328. The device of claim 27, wherein the distal extension portion comprises a finger sleeve or toe sleeve configured to position the digit for optical measurement.

29. The device of claim 27, wherein the pulse oximeter comprises red and infrared light sources and a photodetector.

30. The device of claim 27, wherein the signal processing module is configured to distinguish between concordant pulse waveforms and random noise by comparing sums of multiplication products to a threshold value.

31. A method for automated non-invasive blood pressure measurement using optical plethysmography, comprising: positioning a blood pressure cuff around a limb of a patient, the cuff having an optical plethysmographic sensor integrated into a distal end of the cuff; positioning a digit of the patient within the optical plethysmographic sensor at the distal end of the cuff; inflating the blood pressure cuff to occlude blood flow in the limb; gradually deflating the blood pressure cuff while continuously acquiring optical plethysmographic signals from the digit; and processing the optical plethysmographic signals using cross-correlation analysis comprising: high-pass filtering successive optical plethysmographic waveforms to produce filtered waveforms having equal area above and below a baseline, multiplying corresponding points of the filtered waveforms to generate product values, and summing the product values to determine a concordance measure; detecting initial returning pulsations by identifying when initial low- amplitude optical pulsations exhibit shape concordance with subsequent higher-amplitude optical pulsations as indicated by the concordance measure; and determining systolic blood pressure based on cuff pressure at the time of detecting the initial returning pulsations.66159615.00123 / 155789766v.1Attorney Docket No. 159615-0012332. The method of claim 31, wherein multiplying corresponding points comprises multiplying corresponding points of successive filtered waveforms.

33. The method of claim 31, further comprising determining diastolic blood pressure by identifying a maximum concordance measure corresponding to mean blood pressure and calculating diastolic blood pressure using DBP = (3MBP - SBP) / 2, or a maximum arterial pulsation amplitude.

34. The method of claim 31, wherein the optical plethysmographic sensor comprises a transmission pulse oximeter with light sources positioned on one side of the digit and a photodetector positioned on an opposite side of the digit.

35. A method for automated ankle-brachial index measurement using integrated optical sensors, comprising: positioning blood pressure cuffs on an arm and an ankle of a patient, each cuff having an optical plethysmographic sensor integrated into a distal end thereof; positioning digits of the patient within the respective optical plethysmographic sensors; sequentially measuring systolic blood pressure at the arm and ankle by: inflating each cuff to occlude blood flow, deflating each cuff while acquiring optical plethysmographic signals, applying cross-correlation signal processing to detect shape concordance between initial low-amplitude and subsequent higher-amplitude optical pulsations, and determining systolic blood pressure based on detection of initial returning pulsations; calculating an ankle-brachial index as a ratio of ankle systolic blood pressure to arm systolic blood pressure; and generating a report displaying the measured systolic blood pressures and calculated ankle-brachial index.

36. The method of claim 35, further comprising measuring systolic blood pressure at both arms and both ankles to generate bilateral ankle-brachial indices.67159615.00123 / 155789766v.1Attorney Docket No. 159615-0012337. The method of claim 35, wherein calculating the ankle-brachial indices comprises using a higher of the two arm systolic blood pressures as a denominator.

38. The method of claim 34, wherein the cross-correlation signal processing comprises high-pass filtering the optical plethysmographic signals and multiplying corresponding points of successive filtered waveforms.

39. A method for distinguishing pulse signals from noise in optical plethysmography, comprising: acquiring optical plethysmographic signals from a digit during blood pressure cuff deflation; capturing a plurality of successive optical plethysmographic waveforms gated to cardiac cycles; high-pass filtering each waveform to produce filtered waveforms with equal area above and below a baseline; performing cross-correlation analysis by multiplying corresponding time points of the filtered waveforms to generate product values; summing the product values to obtain a concordance measure; comparing the concordance measure to a threshold to distinguish between: concordant optical pulse waveforms that produce large positive concordance measures, and random noise waveforms that produce small or negative concordance measures; and identifying onset of blood flow based on detection of concordant optical pulse waveforms.

40. The method of claim 39, wherein the threshold is dynamically determined based on a percentage of a maximum concordance measure observed during the measurement.

41. The method of claim 39, wherein multiplying corresponding time points comprises multiplying points from successive filtered waveforms to minimize random concordance between noise waveforms.68159615.00123 / 155789766v.1

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