Time and reliability issues associated with automatic vs. manual measurements of Ankle to Brachial pressure Index (ABI) following heavy load exercise

A cost-effective smartphone-based device for ankle-brachial index (ABI) detection

BACKGROUND AND OBJECTIVE

Detectors of ankle-brachial index (ABI) are commonly used in cardiovascular patients who have high-risk levels of arteriosclerosis. Increased evidences suggest that patients with arteriosclerosis possess many risks of geriatric and chronic diseases. Meanwhile, new chronic treatments trend from the hospitals toward family and community health centers, but for arteriosclerosis cases have delivered benefits far below instrument costs. Compared to traditional devices based on cuff pressure, cuffless and non-invasive measures have wider application potential in home health care, especially in the case of physically-restricted or severely symptomatic patients.

METHODS

In this study, we developed a simple smartphone-based device for non-invasive ABI monitoring, which consists of four wireless cuffless limbs blood sensors. By identifying and tracking blood flow waveform, a multiparameter fusion (MPF) algorithm is used to estimate blood pressure and generate ABI value. An ARM-based chip STM32 has been adopted as the microcontroller. The ABI calculating program is embedded in C++ and executed by the processor. After generating data, ABI information can be delivered to the smartphone by using Bluetooth. Relying on mobile apps to visualize the data and display on the screen, doctors can monitor cardiovascular patients in real time and analyze the risk levels of arteriosclerosis online.

RESULTS

In this paper, the detection conducted by the classical Doppler equipment and prototype were recorded respectively. A statistical evaluation of the verification results obtained from 29 patients and 7 sub-health volunteers is given, which shows that our device can achieve 91.80% and 93.84% accuracy for patients and sub-health volunteers, respectively. In addition, the prototype can be performed stably for a continuous long time monitoring.

CONCLUSIONS

According to our studies, the accuracy of our device is sufficient for home medical and chronic disease monitoring within a certain time interval. The smartphone-based ABI device has several apparent advantages over traditional devices, such as portability, cost-effectiveness and energy-efficiency.

Tissue optical perfusion pressure: a simplified, more reliable, and faster assessment of pedal microcirculation in peripheral artery disease

Oscillometry is an alternative to continuous-wave Doppler (cw-Doppler) to determine peripheral artery disease (PAD) severity using the ankle-brachial index (ABI). cw-Doppler ABI differentiates systolic pressure of ATP and ADP where either one of both values in most patients is higher (high) and the other value is lower (low). In contrast, oscillometric ABI measures the strongest signal and hence misses the lower value. Both do not take pedal perfusion into consideration. Simultaneous determination of tissue microperfusion cares for pedal PAD. ABI was determined by cw-Doppler and oscillometry. Tissue optical perfusion pressure (TOPP) was taken from the first toe using photoplethysmography. 323 patients were evaluated retrospectively in 3 independent groups. group 1 (99 patients) compared TOPP and oscillometric ABI with systolic cw-Doppler-pressure and cw-Doppler ABI. In group 2 (103 patients) TOPP was compared with toe pressure (TP). In group 3 (121 symptomatic patients) TOPP and ABI at rest and after stress were compared (ultrasound examination and magnetic resonance angiography (MRA) or computer tomography angiography (CTA) as control). Bland-Altman-plot analysis presented no significant difference between oscillometric ABI and the high cw-Doppler ABI (group 1). TOPP showed a difference of 26mmHg to the low cw-Doppler-pressure and none to the high cw-Doppler-pressure. In group 2 TOPP correlates to TP but presented a difference of 37 mmHg. group 3 showed weak or no correlation between ABI and walking distance. Oscillometric ABI correlates significantly to TOPP. To conclude, data after stress present a better correlation than at rest. We conclude that TOPP provides absolute values of pedal macro-/microcirculation at rest and after stress tests.NEW & NOTEWORTHY This new application of photoplethysmography investigated the microcirculation in peripheral artery disease at the level of the toe pad and determined the tissue optical perfusion pressure as the first pulsatile signal during automatic cuff deflation at the ankle. It is the first time that this method has been integrated for simultaneous routine examination in an automatic oscillometric ankle-brachial index (ABI) system. This quick and simple measurement technique provides clinical information on the microcirculation downstream the routine ABI measurement at rest and in particular after stress test.

Post-exercise ankle blood pressure and ankle to brachial index after heavy load bicycle exercise

The American Heart Association (AHA) recommendations for diagnosing peripheral artery disease (PAD) after exercise are a decrease >20% of ankle brachial index (ABI) or >30 mm Hg of ankle systolic blood pressure (ASBP) from resting values. We evaluated ABI and ASBP values during incremental maximal exercise in physically active and asymptomatic patients. Patients (n = 726) underwent incremental bicycle tests with pre- and post-exercise recording of all four limbs arterial pressures simultaneously. Univariate and multivariate analyses were performed to define the correlation between post-exercise ABI with various clinical factors, including age. Thereafter, the population was divided into groups of age: less than 40 (G < 40), from 40 to 44 (G40/44) from 45 to 49 (G45/49), from 50 to 54 (G50/54), from 55 to 59 (G55/59), from 60 to 64 (G60/64), and 65 and above (G ≥ 65) years. Results are mean ± SD. * is two-tailed P < .05 for ANOVA with Dunnett's post-hoc test from G40. Changes from rest in ASBP were -3 ± 22 (G < 40), -2 ± 20 (G40/44), 4 ± 22* (G45/49), 10 ± 25* (G50/54), 18 ± 21* (G55/59), 23 ± 27* (G60/64), and 16 ± 22* (G ≥ 65) mm Hg. Decreases from rest in ABI were 32 ± 9 (G < 40), 33 ± 9 (G40/44), 29 ± 8 (G45/49), 27 ± 10* (G50/54), 24 ± 7* (G55/59), 22 ± 12* (G60/64), and 21 ± 12* (G ≥ 65) % of resting ABI. Maximal incremental exercise results in ABI and ASBP changes are mostly dependent on age. The AHA limits for post-exercise ABI are inadequate following maximal incremental bicycle testing. Future studies detecting PAD in active patients should account for the effect of age.

Ankle to brachial systolic pressure index at rest increases with age in asymptomatic physically active participants

BACKGROUND

It is commonly acknowledged that the ability to use the ankle-brachial index (ABI), a reliable way to diagnose atherosclerosis, decreases with age in the general population. The aim of this study was to determine the relationship between resting ABI and age in different populations.

METHODS

674 physically active participants with (active high risk, ACT_HR) or without (active low risk, ACT_LR) cardiovascular risk factors or/and sedentary (SED) subjects, aged 20-70 years. Systolic arterial pressure was recorded at rest and simultaneously with automatic sphygmomanometers at the arms and ankles. ABI was calculated as the ratio of the lowest, highest or mean ankle pressure to the highest arm pressure.

RESULTS

Proportion of ABI_min<0.90 was 10.3% in SED_HR subjects versus 0.5% and 1.2%, respectively, in ACT_HR and ACT_LR groups. The averaged ABI value of each group was in the normal range in all groups (ABI>0.90) but was significantly lower in SED_HR compared with all active participants (p<0.001). Regression lines from ABI_mean versus age could lead to approximately +0.05 every 15 years of age in apparently healthy active participants (ACT_LR).

CONCLUSION

ABI at rest increases with the increase in age in the groups of low-risk asymptomatic middle-aged trained adults. The previously reported decrease in ABI with age is found only in SED_HR subjects, and is very likely to rely on the increased prevalence of asymptomatic arterial disease in this group. The increase of ABI with age is consistent with the 'physiological' stiffness observed in ageing arteries even in the absence of 'pathological' atherosclerotic lesions.

TRIAL REGISTRATION NUMBER

NIH clinicaltrial.gov: NCT01812343.