Dual-Chamber ABPI Cuff for Simultaneous Limb Pressure Measurement
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Solution Overview
Problem
Conventional methods for measuring the Ankle Brachial Pressure Index (ABPI) face challenges in identifying and maintaining blood vessel contact with Doppler probes, and introduce errors due to changing blood pressures and averaging processes, particularly in patients with compromised arterial flow or diabetic feet.
Innovation Solution
A device with inflatable cuffs, each having two chambers, allows simultaneous measurement of systolic pressures across multiple limbs or digits by inflating and deflating the cuffs in a controlled manner to detect and record arterial flow signals, eliminating the need for a resting period and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hand held Doppler probe is used to measure blood pressure in the ankles, then the measurement can be performed, but the technique has difficulties in identifying the arteries in the foot and maintaining blood vessel contact with the Doppler probe during cuff inflation and deflation
Solution Approach 1:
The patent replaces the mechanical Doppler probe with an optical sensor system. The optical sensor detects arterial pulsations through light transmission through the foot, eliminating the need for physical contact with blood vessels. This substitution resolves the contradiction by maintaining reliable measurement while improving ease of operation, as the optical sensor can identify arteries and maintain contact automatically during cuff inflation and deflation without manual probe adjustment.
Solution Approach 2:
The patent introduces an intermediary optical sensing system between the measurement device and the blood vessels. Instead of directly contacting the blood vessels with a Doppler probe, the optical sensor acts as an intermediary that detects arterial pulsations through tissue transmission. This intermediary approach resolves the contradiction by enabling non-contact measurement while maintaining measurement reliability through optical detection of arterial flow changes.
2Measurement precision
If conventional ABPI measurement is performed sequentially in each limb, then the measurement can be completed, but the blood pressure is continually changing and pressures measured at the beginning of the test may be disassociated with pressures taken at the end of the test
Solution Approach 1:
The patent merges the blood pressure measurement process for multiple limbs into a simultaneous operation. By using optical sensors on both ankles and both arms that can operate concurrently, the system combines multiple measurements into a single test procedure. This resolves the contradiction by maintaining measurement precision through simultaneous recording of all limb pressures, eliminating the time loss associated with sequential measurement and the need for resting periods between measurements.
Solution Approach 2:
The patent implements continuous simultaneous measurement of all four limbs throughout the cuff inflation and deflation process. The optical sensors continuously detect arterial pulsations in all limbs at the same time, ensuring that pressure changes are captured continuously rather than sequentially. This continuous action resolves the contradiction by maintaining measurement precision through concurrent recording while eliminating the time loss of sequential measurement and the need for resting periods.
3Ease of operation
If pulse oximeters are used for detection of arterial pulses, then the measurement can be performed, but their use is likely to introduce errors in the pressure readings during deflation of the barometric cuff due to the inherent averaging process within the instrument
Solution Approach 1:
The patent replaces the averaging-based pulse oximeter with an optical sensor system that directly detects arterial pulsations. Instead of using an instrument that averages signals over time, the optical sensor captures individual pulsation events and their corresponding pressure changes. This substitution resolves the contradiction by maintaining ease of operation through optical detection while improving measurement precision by eliminating the averaging process that introduces errors in pressure readings during cuff deflation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and simultaneous measurement of ABPI across all four limbs or digits, reducing errors and improving patient comfort by allowing staggered inflation and providing immediate results, thus enhancing the diagnosis of arterial disease.
Implementation Method 1
inflating simultaneously the second chambers to a desired pressure... inflating the first chambers simultaneously to a pre-determined pressure
Implementation Method 2
recording the pressure and deflating the first and second chambers... detecting and recording arterial flow signals
Data Source
AI summary
An ABPI measurement system includes a cuff for each ankle and a cuff for each arm of a patient. Each cuff has first and second chambers. The four cuffs are applied to each limb (or finger or toe), each chamber is inflated simultaneously to a pressure until a Pneumo Arterial Plethysmography (PAPG) signal related to the arterial flow in the limb is detected at the chambers. The second chambers are then simultaneously inflated until the PAPG signals are extinguished in each limb, the inflation of the second chambers continuing for 10 mmHg to 20 mmHg above the extinguishing pressure. The second chambers are then deflated and the pressure in the second chamber at which the PAPG signal returns in the first chamber is recorded for each limb and this value of the pressure is used to calculate the ABPI. The ABPI is displayed or sent to a remote site.