Cath Lab Digest

Comparison of Doppler Ultrasound, Photoplethysmographic, and Pulse-Oximetric Calculated Pressure Indices To Detect Peripheral Arterial Occlusive Disease

authors:
Usman Jaffer, MD, Mohammed Aslam, MD, Nigel Standfield, MD

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Abstract

Objectives. Doppler ankle-brachial pressure index (ABI) is considered the non-invasive screening test of choice to detect peripheral arterial disease (PAD). Photoplethysmography (PPG) and pulse oximetry (PO) are also suitable alternatives; however, correlation and validation are yet to be established. We compare Doppler ABI, PPG-derived and PO-derived indices to detect PAD. Design. Prospective case control study. Methods. Forty-six subjects were evaluated by PO, PPG, and Doppler ABI. Twenty-three patients had known PAD and 24 were healthy subjects with no signs of PAD. Pressure in arms, fingers, toes, and ankles were measured, and different pressure indices calculated. Results. Groups of control participants and patients with peripheral vascular disease were significantly different with regards to age, prevalence of diabetes, and prevalence of hypertension. Doppler ABI was most sensitive (81.4%) to diagnose PAD in the main study group (n = 46). In patients with diabetes and/or chronic renal failure, Doppler ABI had lower sensitivity (69.2–71.4%) and was comparable to the other diagnostic tests; photoplethysmography toe-finger index (TFI) achieved the highest sensitivity in these patients. (84.6–85.7%). Conclusions. Doppler ABI had the highest sensitivity to diagnose PAD overall. In patients with diabetes and/or chronic renal failure, Doppler ABI had lower sensitivity and was comparable to most of the other diagnostic tests. PPG TFI may provide greater sensitivity in the screening of patients with diabetes and CRF for PVD. This pilot study is relatively small and findings should be further investigated with a larger trial.

Introduction

Peripheral arterial disease (PAD) is an important health problem worldwide, causing significant morbidity and decreasing quality of life. Diabetic patients warrant special consideration, since they are more likely to develop PAD. Also, diabetics are at risk of premature development of minor and major morbidity, including amputation.

There are many non-invasive tests to evaluate patients with limb ischemia.

1. Peripheral arterial duplex scanning is reliable on a single-patient basis.1 However, the high cost of this test and the complexity of its performance make it inadequate for screening (Table 1).

2. Doppler ankle-brachial pressure index (ABI) is the method of choice to screen for PAD. However, its reliability may be questioned since data supporting its validity mainly arises from studies on symptomatic patients.2,3 Also, validity of ABI is diminished in diabetes and dependent on technique.4,5

3. Pulse oximetry (PO) toe-brachial pressure index (PO-TBI)6 and PPG toe-brachial pressure index (PPG-TBI)7 may be alternative screening tests for PAD. Their reliability and effectiveness has been widely demonstrated and as a result, these tests have gained recognition in assessment of chronic limb ischemia. As opposed to PPG, PO uses simple equipment available in many clinical settings. Additionally, most health care personnel are familiar with the use of pulse oximeters.

Since Doppler ABI is unreliable in diabetes and renal failure, it is necessary to establish a simple, non-invasive and low-cost screening test for PAD. This study compares Doppler ultrasound, PO, and PPG limb pressure indices to detect PAD in asymptomatic, healthy volunteers and symptomatic patients with PAD.

Patients and Methods

Healthy volunteers and patients with symptoms of peripheral arterial disease who had previously been diagnosed using Doppler ABI, PPG toe pressures, or duplex ultrasonography were invited to participate in this prospective case control study. Informed consent and ethical approval was obtained. Participants were evaluated by pulse oximetric, photoplethysmographic, and Doppler ultrasonic measurement of ankle, brachial, finger, and toe blood pressures (Figure 1).

Doppler ankle-brachial pressure index (ABPI). ABPI was measured with a handheld Multi Dopplex II bi-directional Doppler (Huntleigh Healthcare Ltd., Cardiff, United Kingdom). A 8-MHz Doppler probe was used. A standard 14-cm pressure cuff (Speidel & Keller, Welch Allyn, Ltd., Jungingen, Germany) and an analogue sphygmomanometer (FemoStop, Radi Medical Systems, Uppsala, Sweden) were used.

Pulse oximetry (PO). Measurement of PO toe and finger pressures was performed with a handheld pulse oximeter (Biox 3700e, Ohmeda, Louisville, Colorado), two pulse oximetry probes (Viamed P867RA, West Yorkshire, United Kingdom), a 95-mm long pressure cuff (Hokanson, Bellevue, Washington), and a sphygmomanometer (FemoStop). The 95-mm pressure cuffs were selected from three different sizes according to the toe or finger length, and diameter (16 mm, 19 mm, and 25 mm wide). The 14-cm pressure cuff, and a sphygmomanometer were used to measure ankle and brachial pressures.

Photoplethysmography (PPG). PPG is based on detecting changes in blood filling of the digit. The PPG sensor emits infrared light which is then reflected back from red blood cells. The more red blood cells present, the greater the reflected signal.

A photoplethysmography device and two PPG probes (Dopplex Assist Range: PPG Assist, APPG10A00007-00; Huntleigh Healthcare, Ltd.), a 95-mm long pressure cuff, and a sphygmomanometer were used to measure toe and finger pressures. The 95-mm pressure cuffs were chosen from three different sizes according to the toe or finger length, and diameter (16 mm, 19 mm, and 25 mm wide). The PPG signal is displayed on an electronic display and recorded on a paper recorder.