Devices for venous pressure sensing

Abstract

A device for non-invasive venous pressure sensing comprises: an occlusion element (OC) configured to be applied to a proximal portion of a human limb to apply an occlusion pressure thereto; and an expansion sensing element (VS) configured to be applied to a distal portion of a human limb to detect its expansion degree. The device also comprises a control circuit (10) coupled to the occlusion element (OC) and the expansion sensing element (VS). The control circuit (10) is configured to: -i) control (104, 106) the occlusion element (OC) to apply at least one sub-diastolic occlusion pressure and maintain it for a certain occlusion period; -ii) obtain (108a, 108b) a sensing signal from the expansion sensing element (VS); -iii) check the sensing signal to determine a certain expansion change of the distal portion caused by the removal of the occlusion pressure; and -iv) send a signal (102) to indicate that the venous pressure is lower than the applied occlusion pressure (P) because the check indicates that the expansion change of the distal portion of the limb caused by the removal of the occlusion pressure has occurred. OC ).

Description

Technical Field

[0001] The present disclosure relates to venous pressure (VP) detection (measurement).

[0002] One or more embodiments may be directed to devices for non-invasive venous pressure sensing that may be used not only by professionals in the clinical field, but also by patients themselves at home. Background Art

[0003] The venous pressure at the right atrium, called central venous pressure (CVP), represents an indirect indicator of the volume and pressure of right ventricular filling and has therefore proven to be a useful hemodynamic parameter for the diagnostic and therapeutic management of patients with cardiac decompensation and visceral territorial pathology. To date, for the measurement of CVP, invasive techniques have been widely used in intensive care units, based on the insertion of a disposable catheter connected to a pressure transducer in a large-caliber deep vein (subclavian, jugular or basilic vein). Such procedures can be expensive, poorly tolerated and are not without risks for the patient.

[0004] On the other hand, there is a fairly extensive literature on noninvasive methods for assessing CVP.

[0005] Examples of such documents include the following:

[0006] - Thalhammer C., et al., "Noninvasive central venous pressure measurement by controlled compression sonography at the forearm", J. Amer.College Cardiol., vol. 50, no. 16, pp. 1584—1589, 2007;

[0007] - Thalhammer C., et al., "Non-invasive central venous pressure measurement by compression ultrasound - A step into real life", Resuscitation, vol. 80, no. 10, pp. 1130—1136, 2009;

[0008] - Amar D., Melendez J.A., Zhang H., Dobres C., Leung D.H., PadillaR.E., “Correlation of peripheral venous pressure and central venous pressurein surgical patients”, J. Cardiothorac. Vasc. Anesth., 2001; 15: 40-3;

[0009] - Desjardins R., Denault A.Y., Belisle S., et al. “Can peripheralvenous pressure be interchangeable with central venous pressure in patientsundergoing cardiac surgery?”, Intensive Care Med. 2004; 30: 627-32;

[0010] - Sathish N., “Comparison between noninvasive measurement of centralvenous pressure using near-infrared spectroscopy with an invasive centralvenous pressure monitoring in cardiac surgical Intensive Care Unit”, Ann.Card. Anaesth. 2016 Jul-Sep; 19(3): 405-409;

[0011] - Jassim, H.M., “IJV collapsibility index vs IVC collapsibility indexby point of care ultrasound for estimation of CVP: a comparative study withdirect estimation of CVP”, Open Access Emerg. Med. 2019; 11: 65-75;

[0012] - Ward K.R., et al., “A new noninvasive method to determine centralvenous pressure”, Resuscitation, 2006 Aug.; 70(2): 238-46. Epub 2006 Jul. 3;

[0013] - Ward K.R., et al., “A novel noninvasive impedance-based techniquefor central venous pressure measurement”, Shock, 2010 Mar.; 33(3): 269-73;doi: 10.1097 / SHK.0b013e3181ab9b9b;

[0014] - Halliwill J.R., et al., “Measurement of limb venous compliance inhumans: technical considerations and physiological findings”, J. Appl.Physiol. (1985), 1999 Oct.; 87(4): 1555-63;

[0015] - Christ F., et al., “Relationship between venous pressure and tissuevolume during venous congestion plethysmography in man”, J. Physiol. 1997Sep. 1;503 (Pt. 2): 463-7;

[0016] - Gamble J.F., et al., “A reassessment of mercury in silastic straingauge plethysmography for microvascular permeability assessment in man”, J.Physiol. 1993 May; 464: 407-22;

[0017] - Bauer A., ​​et al., "Influence of different cuff inflation protocols on capillary filtration capacity in human calves - a congestionplethysmography study", J. Physiol. 2002 Sep. 15; 543 (Pt 3): 1025-1031.

[0018] Devices and methods for non-invasively measuring CVP have also been proposed and described in prior art patents and patent applications.

[0019] For example, documents such as US 7 118 534 B2 (corresponding to US 2004 / 0044290 A1), US 2012 / 253209 Al, WO 2017 / 022245 Al, US 6 432 061 Bl, US 4 566 462 A, US 2007 / 0239041 Al, US 5 040540 A, US 8 417 306 B2, US 2017 / 0100044A1 or US 5 904142 A describe various schemes for non-invasively measuring CVP.

[0020] In particular, in US 7 118 534 B2 / US2004 / 0044290 A1, the central venous pressure (CVP) is simply determined as the pressure P during deflation of the occlusion cuff and at 40-60 mmHg. OC After a single step, the blocking pressure P OC vs. volume curve (indicates the applied blocking pressure P OC The synchronous analysis does not take into account the physiological time constant associated with the RVR, which depends on the patient's specific vein / tissue compliance and determines a variable time offset between the occlusion action (i.e., the pressure signal) and the effect of that action (i.e., the volume signal), thus introducing errors in the determination of CVP due to the variable time relationship between the occlusion pressure curve and the volume curve.

[0021] On the other hand, various non-invasive systems for measuring blood flow / pressure are also known, for example from documents such as US 7 524 290 B2, US 4 204 545 A, US 5 447 161 A, US 6322 515 B1, US 9 474 453 B2, US 6 916 289 B2 or US 6 749 567 B2, with particular attention paid to the occlusive plethysmography technique, which is usually used to measure regional flow (at the level of a limb). This technique envisages the use of an occlusive cuff positioned around the limb in question and an instrument (usually called a "plethysmograph") positioned downstream of the occlusive cuff for measuring the volume changes induced in the distal part of the limb. Measuring plethysmography can be achieved by various systems, including strain gauges, photoplethysmographic sensors, impedance meters, pneumatic cuffs for pressure measurement, inductive systems and capacitive systems.

[0022] In the case of a technique called venous occlusive plethysmography (VOP), an occlusion cuff is inflated to a pressure below arterial diastolic pressure but above venous pressure (range: 40-60 mmHg) to enable arterial blood flow to the limb but restrict its venous return, thereby increasing the pre-existing venous pressure. As a result, positive volume changes occur in the limb segment and venous volume that are detected by the plethysmograph.

[0023] For example, document US Pat. No. 5,447,161 A describes the photoplethysmographic technique, ie the VOP applied to the limb of interest is a photoplethysmograph which measures changes in the volume of blood as the superficial veins underlying the reflectance photoplethysmograph dilate due to the pressure exerted by an occluding cuff.

[0024] Furthermore, documents such as US 5 089 961 A, US 9 125 569 B2, US 2010 / 0292586 A1 or US 6 309359 B1 describe the so-called air plethysmography technique, i.e. the VOP applied to the limb in question is a pneumatic cuff associated with a pressure sensor, which exploits the fact that in a closed system volume and pressure are inversely proportional to each other and that the amount of air in the pneumatic cuff is equal (but of opposite sign) to the volume of the limb it is wrapped around. Therefore, the pressure in the pneumatic cuff is proportional to the volume of the limb in question.

[0025] It may thus be noted that in the prior art various solutions for the non-invasive monitoring of the venous pressure (VP) have been proposed, for example based on the so-called venous occlusion plethysmography (VOP), which envisages the use of an occlusion cuff wrapped around the limb in question and an instrument (generally called a "plethysmograph"), located downstream of the occlusion cuff, for measuring the volume changes induced in the distal part of this limb.

[0026] Briefly, in VOP, an occlusion cuff is inflated to a pressure (usually 40 mmHg) that exceeds venous pressure and thus restricts venous return from the stretched limb downstream of the occlusion cuff, causing expansion (volume change) of that limb segment that is detected by a plethysmograph. As previously mentioned, the plethysmograph can be implemented by a variety of systems, including strain gauges, photoplethysmographic sensors, impedance meters, pneumatic cuffs for pressure measurement, inductive systems, and capacitive systems.

[0027] However, it can be noted from the analysis of the above-mentioned prior art that many methods based on VOP technology need to be evaluated based on the time correspondence between events calculated on the volume change curve of a limb or vein, where the volume change curve of the limb or vein is obtained in response to occlusion and events occurring on the occlusion pressure curve during the dynamic steps of applying and releasing pressure.

[0028] However, in practice, it can be noted that there is a phase shift between the occlusion pressure curve and the volume change curves of the limb and veins, which phase shift is not constant and depends on the venous / tissue compliance (and the corresponding time constant) of the particular subject. Venous / tissue compliance exhibits a wide range of variability between subjects (and between measurements on the same subject), making it extremely difficult in practice to uniquely associate an event in the volume curve with a corresponding measurement of the occlusion pressure to which the estimate of the venous pressure should correspond.

[0029] Therefore, these methods are far from reliable. Summary of the invention

[0030] It is therefore an object of one or more embodiments to provide a rapid and reliable tool for monitoring CVP in a non-invasive manner without central venous access, thereby being usable not only by professionals in the clinical field but also by patients themselves at home.

[0031] According to one or more embodiments, the above objects can be achieved by a device having the characteristics reviewed in the following claims.

[0032] The claims form an integral part of the technical teaching provided herein regarding the embodiments.

[0033] One or more embodiments may provide a device for non-invasively sensing (e.g., measuring) venous pressure (VP) that will be able to overcome the main problems of currently known solutions, in particular regarding lower measurement accuracy and the possibility of (also) home monitoring without the intervention of a specialist.

[0034] One or more embodiments may utilize the widely documented physiopathological findings on venous compliance in the human limb (e.g., see the papers by Halliwill JR. et al., Christ F. et al., Gamble J. et al., Bauer A. et al. cited at the outset), whereby when a cuff is used around the arm, the pressure applied by the cuff, when the applied pressure is above VP, represents the venous pressure (VP) obtained in the forearm.

[0035] Thus, one or more embodiments may contemplate applying a known pressure (P) via an occlusion cuff around the top of the arm including the vein. OC ), resulting in a value in the forearm equal to the pressure P OC Same artificially induced venous pressure.

[0036] In one or more embodiments, by using a known pressure P OC The occlusion cuff is inflated in incremental steps and at each step the rapid volume response (RVR) caused by the artificially induced venous pressure in the forearm is compared with the natural volume already present in the limb. The value of VP can be determined based on an on / off analysis of the RVR signal, which can be measured by means of a volume sensor (degree of distension) of a type known per se. Two possible examples are provided: a pressure signal P can be provided. SC Another sensing cuff is provided, or after the occlusion is relieved, the superficial vein V below VS The volume changes are indicated by the photoplethysmographic sensor.

[0037] For example:

[0038] - If there is a perceptible drop in the pressure signal PSC (a drop that exceeds a programmable threshold, e.g. 0.1 mmHg) or in the volume signal V VS Decreased (indicating a decrease in RVR due to the patient's VP falling below the applied occlusion pressure P OC If the value of VP is lower than X mmHg, the device will be able to indicate that VP is lower than X mmHg (where X mmHg corresponds to the pressure value P set for the test). OC );

[0039] Otherwise, i.e., in case the patient's VP is higher than the applied occlusion pressure P OCThe value of P is not detected and no perceptible pressure signal is detected. SC Decline (fall below the above threshold) or volume signal V VS In case of a drop, the device will be able to indicate that the VP is above X mmHg (off response).

[0040] In addition, the system can automatically or with prior agreement use the pressure P OC Repeat the test for subsequent (higher) values ​​of XX mmHg.

[0041] On the other hand, it should be understood that for the sake of simplicity of explanation, references to upper limbs (arms) should not be construed as limiting the embodiments in any way.

[0042] Indeed, one or more embodiments may be applied to different areas of the body, such as the lower extremities (legs), with protocols that may prove particularly beneficial for bedridden patients. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] One or more embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0044] Figure 1 represents possible implementations of devices according to some embodiments;

[0045] Figure 2 and Figure 3 is a functional block diagram provided by way of example of possible implementations of the embodiment;

[0046] Figure 4 Provides examples of different ways in which one or more embodiments may be implemented; and

[0047] Figure 5 is a flow chart provided by way of example of possible modes of operation of an embodiment. DETAILED DESCRIPTION

[0048] In the following description, various specific details are shown to enable a thorough understanding of various examples of embodiments according to the description. These embodiments may be implemented without one or more of the specific details, or by other methods, components, materials, etc. In other cases, well-known operations, structures, or materials are not shown or described in detail so as not to obscure aspects of these embodiments.

[0049] References to "an embodiment" or "an embodiment" in the framework of this specification are intended to indicate that a particular configuration, structure, or characteristic described with respect to that embodiment is included in at least one embodiment. Thus, phrases such as "in an embodiment" or "in an embodiment" that may be present at various points in this specification are not necessarily referring to exactly the same embodiment. Furthermore, in one or more embodiments, particular configurations, structures, or characteristics may be combined in any appropriate manner.

[0050] The references used herein are provided for convenience only and therefore do not limit the scope of protection or the scope of the embodiments.

[0051] Basically, the device according to some embodiments illustrated herein (see, for example, Figure 1 and 4 ) can include:

[0052] - an occlusive element OC and an element VS for sensing (detecting) dilation, which occlusive element OC and element VS can be respectively arranged on the proximal extension and distal extension of the limb of the subject (patient) P subjected to venous pressure sensing; and

[0053] - A signal processing circuit 10 coupled to the occlusion element OC and the expansion sensing element VS.

[0054] As mentioned above, for simplicity of explanation, references to the upper limbs (arms) should not be construed as limiting the embodiments in any way: one or more embodiments may in fact be applied to different areas of the body, such as to the lower limbs (legs).

[0055] Likewise, again for simplicity of explanation, references to "patient" should not be construed as limiting in any sense the possible use scenarios of the embodiments: one or more embodiments may in fact be applied to use scenarios in which the patient P undergoing venous pressure sensing is not affected by an overt pathological condition, such as an athlete undergoing venous pressure sensing to obtain metrics about his or her athletic performance.

[0056] Furthermore, as will be described more fully below, both the occlusion element OC and the expansion sensing element VS may be implemented by different technical solutions and may be different elements (as shown by way of example herein) or integrated together while maintaining their respective functions.

[0057] Finally, it should be noted that the coupling of the occlusion element OC and the expansion sensing element VS to the processing circuit 10 (here exemplified as being realized via cables or wires) may also be realized in wireless form (eg via a Bluetooth interface or the like).

[0058] like Figure 2 and Figure 3As shown, in one or more embodiments, the signal processing circuit 10 may include a signal processing unit (CPU) 100, which can be, for example, based on Figure 5 A flowchart is used to coordinate the operation of other components of the system.

[0059] A display unit 102 may (according to current standards) be associated with the signal processing unit (CPU) 100 for presenting various signals inherent in the operation of the system and the results of the detection (measurement) actions to a user (which may be the patient P himself).

[0060] like Figure 2 and Figure 3 As schematically represented by the symbol of the antenna in FIG. , in one or more embodiments, considering the need to remotely transmit various signals inherent in the operation of the system and the detection (measurement) of the results of the actions, the display unit 102 can be replaced by and / or integrated with a communication interface (for example, on a mobile communication network) according to the so-called telemedicine form currently used.

[0061] On the other hand, the signal processing circuit 10 can be implemented in various forms: for example, the signal processing circuit 10 can be "implemented" on a personal computer or the like (for example, in the case of a device for clinical use by professionals), or as a microprocessor or microcontroller (for example, in the case of a mobile device that the patient P himself can also use at home).

[0062] In one or more embodiments, the occlusion element OC may include a (first) pneumatic cuff that is positionable on the proximal extension of the limb and controllable by the circuit 10 (e.g., via the pressure controller 104 in cooperation with the occlusion pressure sensor 106) for applying an occlusion pressure P having an incrementally programmable value (e.g., in the range of about 4 to 24 mmHg or 5 to 35 mmHg). OC .

[0063] This can be done according to standards per se known to the person skilled in the art, for example according to standards which correspond essentially (except for different pressure values ​​applied, which are subdiastolic values) to the standards for the production and use of sphygmomanometers for measuring arterial pressure.

[0064] "Sub-diastolic pressure values" herein refer to values ​​that are significantly lower than diastolic (arterial pressure) values ​​(e.g., in the range of about 4 to 24 mmHg or 5 to 35 mmHg), which can range between 60 mmHg (low pressure) and 100 mmHg (high pressure, a sign of hypertension).

[0065] One or more embodiments may utilize a blocking pressure P OCThe significant correlation between the venous pressure VP and the venous pressure VP makes it possible to generate a corresponding and accurate venous pressure VP in the distal part of the limb (e.g., the patient's forearm) relative to the occluding element OC by acting on the occluding element OC (e.g., a positionable pneumatic cuff).

[0066] In fact, it can be noted that the blocking pressure P OC The effect of the induced venous pressure VP, in case the latter is higher than the patient's venous pressure VP, manifests itself as a volume change (dilatation) of the distal part of the limb, also called rapid volume response (RVR), which is determined by the venous dilatation counteracted only by the resistance of the surrounding tissues.

[0067] Likewise, it has been noted that in order for an RVR to be present that can be used to reliably sense the venous pressure VP, in addition to the pressure P OC It is advantageous to set the pressure P above the patient's venous pressure VP. OC Maintain a certain period of TP OC , so that the RVR can be stabilized.

[0068] Although not wishing to be bound by any specific interpretation in this regard, it is reasonable to assume that this mode of operation prevents the risk of altering the RVR mechanism due to the liquid filtration process, which would vary with the pressure P. OC Occurs as the holding time is extended.

[0069] TP of the above period OC The duration may be selected to be at least several seconds, for example at least 5 seconds.

[0070] It has been observed that in this way, RVR is caused to fully emerge.

[0071] In one or more embodiments, the time period TP OC The duration of the pressure may vary; for example, the duration may be adjustable according to the subdiastolic pressure value P applied via the obstruction element OC. OC to choose.

[0072] For example, for a pressure P of 5 mmHg OC , you can choose a TP of about 10 or 20 seconds OC , and for a pressure P of about 24 or 35 mmHg OC , you can choose a TP of about 30 or 40 seconds OC .

[0073] The TP OC The value has been shown to be Figure 1 It is advantageous in the case of an expansion sensing element VS implemented as shown).

[0074] Likewise, it has been noted that by using as expansion sensing element VS (such as Figure 4 The photoplethysmographic sensor (shown in FIG. 1 ) (which is able to take into account only the volume increase of the blood contained in the superficial vein below it) can also be used to calculate the time period TP OC The duration is reduced to a few seconds (e.g., approximately 5 to 10 seconds) and does not exceed several tens of seconds (i.e., approximately 20 to 40 seconds).

[0075] On the other hand, it should be noted that Figure 1 (cuff or sleeve sensor VS) and Figure 4 The examples illustrated in (photoplethysmographic sensor VS) are only two of the multiple possible implementations of the above-mentioned expansion sensing element: the expansion sensing element VS can actually be implemented in various ways, such as with the help of a pneumatic cuff for pressure measurement, a photoplethysmographic sensor, a strain gauge, a piezoelectric sensor, an impedance meter, an inductive system, a capacitive system and an ultrasonic system.

[0076] Regardless of the technology choice employed in this regard (pressure sensor, photoplethysmographic sensor, etc.), in one or more embodiments, the expansion sensing element VS can be configured to detect an increase in volume (RVR) that may or may not be related to the applied pressure P OC It is related to situations where the patient's venous pressure VP is higher or lower than the patient's venous pressure VP.

[0077] A possible embodiment of the expansion sensing element VS may envisage the use of a (second) pneumatic cuff, similar in structure to the cuff used to implement the occlusion element OC, which can be positioned on the forearm and preloaded to a pressure below the normal value of the venous pressure VP (e.g. 3 mmHg) for providing an indirect measurement of the RVR (P SC )Measurement.

[0078] This mode of use may be achieved by a volume controller / sensor in cooperation with circuit 100 and by Figure 2 The box 108 in FIG. 1 represents that Figure 3 The pressure P can be realized by the pressure controller 108a and the pressure sensor 108b. SC of detection (again to detect possible expansion of distal extension of the limb).

[0079] Therefore, the device according to one or more embodiments may envision that the time period TP set immediately following SC The pressure value P detected in the appropriate period before the end SC , and then the pressure P OC The pressure value P detected in the appropriate period after the removal or release of SC Make a comparison.

[0080] If it is a cuff or sleeve, the pressure P OC The removal or release can take place, for example, after emptying the blocking element OC.

[0081] In this regard, it should be understood that the occlusion pressure P OC "Removal" does not in any way (even merely implicitly) involve removing the occluding element OC from the limb: as mentioned above, for example in situations where recourse has to be had to an occluding cuff or sleeve, removal or release of the occluding pressure may simply involve deflating the occluding cuff or sleeve remaining on the limb, for example in order to apply a higher occluding pressure, as will be discussed more fully below.

[0082] Thus, the apparatus according to one or more embodiments may conceivably verify whether a pressure signal P occurs. SC decrease (i.e., decrease by a value greater than a programmable threshold value (e.g., 0.1 mmHg)), which indicates that the RVR has decreased after the occlusion has been relieved, thereby indicating that the patient's venous pressure VP is below the applied occlusion pressure value P OC situation.

[0083] Thus, an apparatus according to one or more embodiments may contemplate different situations in which inspection may occur.

[0084] For example:

[0085] - If the pressure signal P is detected SC drop (i.e., by the applied pressure P OC If the device indicates that the venous pressure VP is less than X mmHg (X mmHg corresponds to the pressure P set for this test), the device will indicate (e.g., via unit 102) that the venous pressure VP is less than X mmHg. OC value);

[0086] - On the contrary, if no pressure signal P is detected SC If such a decrease in the venous pressure VP is detected (i.e., no decrease in the degree of extension of the distal extension of the limb is detected), the device will indicate (e.g., again via unit 102) that the venous pressure VP is above the applied occlusion pressure P OC , and automatically or with prior consent, to block the pressure P OC The test is repeated with a subsequent value of XX mmHg which is higher than the value X mmHg set by the system.

[0087] By adopting the same basic criteria, assuming the thresholds are within a range, for example (ThresholdMin=0.10 mmHg, ThresholdMax=0.15 mmHg):

[0088] - If the pressure signal P is detectedSC a decrease (i.e., a reduction in the distension of the distal limb stretch caused by the applied pressure P OC ), is between ThresholdMin and ThresholdMax, the result is positive ("open response"), and the device will indicate (e.g., via unit 102) that the venous pressure VP is equal to X mmHg (X mmHg corresponding to the pressure value P set for the test OC );

[0089] - If a decrease in the pressure signal P SC is greater than ThresholdMax, the result is positive ("open response"), and the device will indicate (e.g., via unit 102) that the venous pressure VP is below X mmHg (X mmHg corresponding to the pressure value P set for the test OC );

[0090] - Conversely, if no decrease in the pressure signal P SC is detected, i.e., P SC < ThresholdMin, the result is negative ("closed response", i.e., no decrease in the degree of distension of the distal limb stretch is detected), the device will indicate (e.g., again via unit 102) that the venous pressure VP is higher than the applied occlusion pressure P OC , and automatically or after prior consent, will repeat the test with a subsequent value XX mmHg of the pressure P OC , which subsequent value is higher or lower than the system-set value X mmHg.

[0091] In short, if the applied occlusion pressure P OC is lower than the existing venous pressure VP, nothing happens: conversely, if the applied occlusion pressure P OC is higher than the existing venous pressure VP, no increase in the volume of the distal limb stretch occurs.

[0092] By checking whether the degree of distension (volume) increases at the end of a certain time period TP OC (e.g., when removing or releasing the pressure P OC by deflating the occlusion cuff or sleeve OC, for example), it is possible to determine a possible increase in distension in a stable equilibrium state relative to the time constant involved. OC For example, after inflating the cuff or sleeve OC to apply the occlusion pressure P

[0093] , at the end of the equilibrium time period TP OC (e.g., approximately equal to 10 seconds or 20 seconds), by deflating the cuff or sleeve OC to remove the occlusion pressure P OC (e.g., when removing or releasing the pressure P OC.

[0094] At this time:

[0095] - If the occlusion pressure P applied via the cuff or cuff OC OC above the venous pressure VP, the sensor VS detects a decrease in the degree of expansion (volume), which indicates that the pressure P OC Higher than venous pressure VP;

[0096] - If the occlusion pressure P applied via the cuff or cuff OC OC Below the venous pressure VP, the sensor VS will detect a decrease in the degree of distension (volume) to zero (or below a minimum predefined threshold), which indicates that the pressure P OC Lower than venous pressure VP: In fact, if the pressure P OC Below the existing venous pressure, there is no reason for the limb volume to increase.

[0097] In the repeated test for the newly set blocking pressure P OC If the result of (XX mmHg) is positive, the system will indicate that the venous pressure VP is lower than XX mmHg and higher than X mmHg, or that the venous pressure VP is between XX mmHg and X mmHg.

[0098] It will be appreciated that the magnitude of the pressure change between XX mmHg and X mmHg (and possibly other subsequent tests) determines the resolution of the detection or measurement action employed.

[0099] In general, similar considerations apply to possible implementations, such as Figure 4 Shown (as the dilation sensitive element VS of a photoplethysmograph).

[0100] For example, by applying a blocking pressure P via the blocking element OC OC (e.g., a pressure of 8 mmHg, which is subdiastolic pressure or in any case lower than the arterial pressure which is usually about 120 mmHg), maintaining the occlusion pressure for a certain period of time TP OC , and then quickly returning this occlusion pressure to zero (thereby removing the occlusion pressure), two different behaviors of the photoplethysmographic sensor VS can be noticed:

[0101] - If the blocking pressure P OC Above the venous pressure VP, a signal generated by the sensor VS will be recorded, which indicates that the venous volume downstream of the occluding element OC has increased due to the obstruction of the return flow and that by removing the pressure P OC , venous return has been restored, so that the volume of the above-mentioned vein decreases, and the (rapid) decrease in volume causes the signal of the sensor VS to return to zero (or reference level);

[0102] - If the pressure P OC Below the venous pressure VP, no evolution of the type described will be observed in the signal of the sensor VS: due to the occlusion pressure P set via the occlusion element OC OC Below venous pressure VP, venous return from the distal end of the stretched limb will not be blocked. Pressure P OC Obviously blocked, so once the blocking pressure P OC If it is removed, no increase in venous volume will be detected.

[0103] In this case, too, by varying the blocking pressure P OC Continuous measurements at different values ​​will make it possible to determine the venous pressure VP value using successive approximations, the approximation of which is sufficient / acceptable for clinical diagnosis.

[0104] Figure 5 The flowchart of the embodiment illustrates a possible operation form of the embodiment: In this regard, it should be understood that Figure 5 The actions illustrated in the flowchart (for the purpose of providing a non-limiting example only) are as follows: OC (Signal TC input to block 204) selectively changes the period TP OC The possibility of a duration of ) is largely independent of the specific choice of implementation, for example at the level of the expansion sensing element VS.

[0105] Figure 5 The boxes in the figure illustrate the following possible actions:

[0106] 200: START;

[0107] 201: Setting a baseline value for the expansion sensing element VS;

[0108] 202: Starting from the initial minimum value, determine the blocking pressure P OC (subdiastolic blood pressure) value;

[0109] 203: The blocking pressure P is reduced via the blocking element OC. OC Values ​​applied to the proximal stretch of the limb;

[0110] 204: During the waiting time TP OC During this period, the above blocking pressure P is maintained OC The waiting time may be variable, for example, it may be adjusted according to the applied pressure value (signal TC from circuit 100);

[0111] 205: Removing the obstruction, for example by (at least partially) deflation of the obstruction element OC;

[0112] 206: Detecting a possible extension change of the distal extension of the limb via the controller 108 (or 108a, 108b) associated with the sensor VS (eg, via a set time period TP immediately following the SC The pressure value P detected in block 108b before the end SC , where the pressure value P SC is detected in a suitable period immediately after the obstruction element OC has completed deflation);

[0113] 207: Resetting the expansion sensing element VS to a baseline value, for example, after (at least partial) deflation of the corresponding cuff;

[0114] 208: Compare the value detected in block 206 with a threshold value Th to verify whether a perceptible change has occurred in the extension of the distal end of the limb (eg, pressure signal P SC a certain degree of decline);

[0115] 209: In the case where the comparison result in block 208 is negative (N) (ie, because the applied blocking pressure P OC is lower than the venous pressure VP, so the distal end of the limb stretches without expansion), which will block the pressure P OC The value of (subdiastolic pressure) is reset to a value higher than previously applied (in the case of the above example, from X mmHg to XX mmHg);

[0116] 210: If the comparison result in block 208 is positive (Y) (ie, because the applied blocking pressure P OC Higher than the venous pressure VP, so after removing the obstruction pressure P OC Later, distal extension of the limb tends to reduce its degree of expansion after the previous expansion), indicating that the pressure VP is lower than the previously applied occlusion pressure P OC The value of VP <P OC ) (in the case of the above example, X mmHg);

[0117] 211: STOP

[0118] Thus, one or more embodiments may contemplate applying a series of occlusion pressures (P OC ) Square wave pulse.

[0119] At each pulse, the pressure P OC The magnitude at a given blocking time (TP OC ) to facilitate stabilization of the rapid volume response (RVR) in the forearm. At each pulse, after the stabilization time, the pressure P OCSet to zero and evaluate RVR: When a significant change in RVR is detected (e.g., by a threshold check), it is determined that the venous pressure (VP) is below the applied pressure pulse P OC If no significant change in RVR is detected, then a pressure pulse P with increasing amplitude of set value is applied. OC This process is repeated until a significant change in RVR is recorded, thereby determining the pressure value P corresponding to the venous pressure VP. OC .

[0120] The venous pressure VP is generated from the pressure P OC A single constant pulse amplitude is obtained.

[0121] This aspect is important as it helps to reliably determine VP values, possibly taking into account the physiological time constant Tau (depending on the patient's venous / tissue compliance) in order to have a significant and stable RVR (see, e.g., Gamble J., Gartside I., Christ F., “A reassessment of mercury in silastic strain gaugeplethysmography for microvascular permeability assessment in man”, J. Physiol. 1993 May; 464:407-22, cited above).

[0122] Experiments carried out by the applicant have highlighted the reasons for the advantages associated with various possible aspects of the embodiments.

[0123] For example, the holding time TP of the occlusion pressure can be determined OC To help achieve a stable RVR determined by the compliance of the vein and surrounding tissues mechanically involved in the dilation (e.g., by P SC The waiting time is long enough (e.g., tens of seconds) but does not reach values ​​of several minutes to cause changes in the interstitial volume secondary to the vein's own filtration of fluid.

[0124] Similarly, the blocking pressure P OC (See Figure 5 The value of the signal TC) changes at time TP OC It has also been proven to be beneficial.

[0125] As mentioned above, a useful range of values ​​may be, for example, around 10 or 20 seconds TP OC (For a P of approximately 5 mmHg OC ) to about 30 or 40 seconds TPOC (For a P of approximately 24 or 35 mmHg OC ), and other possible values ​​are proportional.

[0126] In this way, the test time can be reduced and, especially for tests at 10 mmHg (the statistically most frequent test), the test time can become very short, which is a clear advantage for the user.

[0127] Likewise, as described above, when using a photoplethysmographic sensor (which will be able to consider only the increase in blood volume contained in the superficial vein below it) as the expansion sensing element (VS in the figure), even the period TP OC The duration of the event (assuming the same occluding pressure is applied) is reduced to a few seconds and does not exceed several tens of seconds.

[0128] As for the pressure P SC The calculation process of the decline ( Figure 4 In action 206), for example, the pressure value P detected within a specific period of time before the command to deflate the blocking element OC can be calculated. SC The average value ( Figure 4 action 205) and the pressure value P detected after the obstruction element OC is deflated SC The difference between the average values ​​of .

[0129] In addition, the pressure P OC Automatically increment the logic ( Figure 5 Action 209 in may follow different rules, with the goal of simply determining the VP value range (low, normal, critical, high, very high), and may take fine incremental steps as needed to achieve high resolution.

[0130] For example, for Figure 4 In the comparison process of action 208, it is assumed that a threshold is adopted such that:

[0131] - If the value P OC Pressure P SC If the change in is 10 mmHg, there is no decrease (the result of block 208 is negative);

[0132] - At pressure P OC Pressure P SC If the change is 15 mmHg, there is a decrease (the result of block 208 is positive),

[0133] exist Figure 4 In action 209, subsequent measurements at 12.5 mmHg may be set, which helps to obtain higher measurement clarity or resolution.

[0134] Likewise, advantages have been noted in connection with the use of a cuff (sleeve, the terms here may be considered synonymous) VS preloaded at a starting pressure (e.g., 3 mmHg) and / or pre-inflated by the presence of foam rubber. It has been noted that the presence of a material such as foam rubber facilitates a uniform distribution of the pressure in contact with the limb, without the need to apply an initial pressure level as described above.

[0135] Likewise, advantages have been noted associated with the use of a cuff OC and / or VS that incorporates a mechanism for pre-tensioning at a preset tightness to facilitate proper positioning thereof.

[0136] As in conventional procedures, in electronic sphygmomanometers, the implementation of a software control system for detecting conditions of too loose and / or too tight cuff positioning (based on the calculation of the time required to reach a predetermined target pressure value) is also conceivable.

[0137] In the device described here by way of example, in addition to the measurement of the venous pressure, the standard measurement of the arterial systolic and diastolic pressure can also be integrated.

[0138] The equipment described in this article may include:

[0139] - an occluding element (e.g., OC) configured to be applied to a proximal portion of a human limb to apply an occluding pressure thereto;

[0140] - an expansion sensing element (e.g., VS) configured to be applied to a distal portion of a human limb to detect the extent of expansion thereof; and

[0141] - a control circuit (e.g., 10), coupled to the blocking element and the expansion sensing element, the control circuit being configured to:

[0142] -i) controlling (e.g., 104, 106) the blocking element to apply (e.g., 203) at least one subdiastolic blocking pressure (e.g., P OC ), and maintaining (eg, 204) the at least one subdiastolic occlusion pressure for a certain occlusion period (eg, TP OC );

[0143] -ii) acquiring (e.g., 108; 108a, 108b) a sensing signal from an expansion sensing element;

[0144] -iii) examining (e.g. 208) said sensed signal to determine a certain change in expansion of said distal portion of the human limb due to removal (or release, e.g. by deflating an occlusion cuff or cuff) of said at least one sub-diastolic occlusion pressure after said occlusion period; and

[0145] -iv) issuing a signal indicating a certain change in dilation of said distal portion of the human limb due to said examination indicating removal of said at least one sub-diastolic occluding pressure after said occluding period, the venous pressure in said human limb being lower than said applied at least one sub-diastolic occluding pressure.

[0146] As noted above, "subdiastolic pressure" is intended herein to mean a pressure value (e.g., in the range of approximately 5 to 35 mmHg or 4 to 24 mmHg) that is significantly lower than diastolic (arterial pressure) values, which can range between 60 mmHg (low pressure) and 100 mmHg (high pressure, a sign of hypertension).

[0147] In the device illustrated in this article, since the examination fails to indicate that the removal of the at least one sub-diastolic blocking pressure after the blocking period has caused the certain expansion change of the distal portion of the human limb, the control circuit can be configured to repeat the actions i) to iv) by controlling the blocking element to apply at least one other blocking pressure higher than the at least one sub-diastolic blocking pressure.

[0148] In the device illustrated herein, the duration of the occlusion period may be no less than 5 seconds, optionally between about 10 seconds and about 30 seconds, or between about 20 seconds and about 40 seconds (for example, when element VS is used as a pressure sensor), or between about 5 seconds and about 10 seconds (for example, when element VS is used as a photoplethysmography sensor).

[0149] In devices similar to those illustrated herein, the control circuitry may be configured to control the occlusion element to apply an occlusion pressure within a range of approximately 5 mmHg to 35 mmHg, or approximately 4 mmHg to 24 mmHg.

[0150] In the devices exemplified herein, the control circuit may be configured (e.g., Figure 5 TC) is used to optionally change the duration of the occlusion period according to the applied occlusion pressure.

[0151] In the devices exemplified herein, the expansion sensing element may include a pressure sensor (e.g., Figure 3 VS, 108a, 108b, wherein the sensing signal includes a pressure signal (P SC ).

[0152] In the devices exemplified herein, the expansion sensing element (e.g., Figure 4 The VS in may include a photoplethysmographic sensor, wherein the sensing signal includes a photoplethysmographic signal to indicate volume changes of a superficial vein thereunder.

[0153] In the device exemplified herein, the control circuit may be configured to detect (e.g., 208) a change in magnitude greater than a change threshold (e.g., a decrease in pressure magnitude greater than a certain pressure drop threshold) in the sensed signal (e.g., a pressure sensed signal or a plethysmographic sensed signal), and to issue the signal to indicate that due to the detection of a change in magnitude greater than the change threshold in the sensed signal, the venous pressure in the human limb is lower than the at least one subdiastolic occlusive pressure (VP <P OC ).

[0154] In the devices exemplified herein, at least one of the occluding element and the expansion sensing element may include a cuff configured to be applied to a human limb, the cuff being optionally pre-inflated and / or pre-loaded to a certain wrapping density.

[0155] Without prejudice to the underlying principle, the details of construction and of embodiment may even vary significantly with respect to what is described herein purely by way of non-limiting example, without departing from the scope of protection, as this is determined by the appended claims.

Claims

1. A device for venous pressure sensing, comprising: an occluding element configured to be applied to a proximal portion of a human limb to apply an occluding pressure to the proximal portion of the human limb, an expansion sensing element configured to be applied to a distal portion of a human limb to sense the extent of expansion of the distal portion of the human limb, A control circuit is coupled to the blocking element and the expansion sensing element, the control circuit being configured to perform the following actions: (i) controlling the obstruction element to apply at least one sub-diastolic obstruction pressure and maintain the at least one sub-diastolic obstruction pressure for a certain obstruction period; (ii) acquiring a sensing signal from the expansion sensing element; (iii) examining the sensed signals to determine a change in dilation of the distal portion of the human limb resulting from removal of the at least one subdiastolic occluding pressure after the occlusion period; (iv) issuing a signal indicating that venous pressure in said human limb is less than said at least one sub-diastolic occluding pressure applied due to said examination indicating that removal of said at least one sub-diastolic occluding pressure after said occluding period has resulted in said certain change in dilation of said distal portion of said human limb; Wherein, since the examination fails to indicate that the removal of the at least one sub-diastolic blocking pressure after the blocking period causes the certain expansion change of the distal portion of the human limb, the control circuit is configured to apply at least one blocking pressure higher than the at least one sub-diastolic blocking pressure by controlling the blocking element, and repeating actions (i) to (iv). 2 . The device for venous pressure sensing according to claim 1 , wherein the duration of the occlusion period is not less than 5 seconds.

3. The device for venous pressure sensing according to claim 2, wherein the occlusion period is between 10 seconds and 30 seconds. 4 . The device for venous pressure sensing according to claim 2 , wherein the occlusion period is between 20 seconds and 40 seconds, or between 5 seconds and 10 seconds.

5. The device for venous pressure sensing according to any one of claims 1-4, wherein the control circuit is configured to control the occlusion element to apply an occlusion pressure in the range of 5 mmHg to 35 mmHg.

6. The device for venous pressure sensing according to any one of claims 1-4, wherein the control circuit is configured to control the occlusion element to apply an occlusion pressure in the range of 4 mmHg to 24 mmHg.

7. The device for venous pressure sensing according to any one of claims 1-4, wherein the control circuit is configured to vary the duration of the occlusion period according to the applied occlusion pressure.

8. The device for venous pressure sensing according to any one of claims 1-4, wherein the expansion sensing element comprises a pressure sensor (108a, 108b), wherein the sensing signal comprises a pressure signal.

9. The apparatus for venous pressure sensing according to any one of claims 1-4, wherein the dilation sensing element comprises a photoplethysmographic sensor, wherein the sensing signal comprises a photoplethysmographic signal.

10. A device for venous pressure sensing according to any one of claims 1-4, wherein the control circuit is configured to detect a quantitative change in the sensing signal that exceeds a change threshold, and to issue a signal to indicate that the venous pressure in the human limb is lower than the at least one subdiastolic occlusive pressure due to a quantitative change in the sensing signal that exceeds the change threshold.

11. A device for venous pressure sensing according to any one of claims 1-4, wherein at least one of the occlusion element and the expansion sensing element comprises a cuff configured to be applied to a human limb, the cuff being pre-inflated and / or pre-biased with a certain wrapping strength.

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