Laser Doppler flowmetry in wearable implementation for the detection of arterial hypertension
Arterial hypertension (AH) is a disease that is characterized by increased blood pressure (BP). Unfortunately, there are often cases when a persistent increase in blood pressure is completely asymptomatic. All this complicates the diagnosis of such a dangerous disease. To detect it, it is necessary to wear a BP monitor during the day. Such a complex and time-consuming diagnostic method requires not only time and special purpose but is also associated with the use of expensive equipment, which is not available in all healthcare institutions. Therefore, the development of new, simple, affordable and fast methods for diagnosing AH is a great practical interest.
Recently the method of laser Doppler flowmetry (LDF) has been successfully used to assess the state of the microvascular bed in arterial hypertension. It was found that patients with arterial hypertension have significant differences in the functional state of microvessels. LDF can also be useful for personalized therapy that takes into account the functional state of resistive microvessels. However, these studies were conducted with stationary table-top devices, but modern technology development allows us to implement the LDF method in wearable devices. This work aimed to study the possibility of using wearable LDF monitors to detect the features of the microcirculatory bed associated with AH.
The study included 89 men aged 27 to 69 years (44,7 ± 9,7). They subjectively considered themselves healthy, did not make any complaints and did not take any medications regularly. The participants were divided into two groups according to the European Society of Cardiology recommendations, depending on the office BP and ambulatory BP monitoring indicators. Group 1 included 30 men with normal BP (43.4 ± 9.8), and group 2 included 59 men with AH (45.5 ± 9.7). The study used a wearable laser Doppler flowmetry monitor “AMT-LAZMA 1” (Aston Medical Technology Ltd., UK). The device was fixated on the back of the left wrist 2-3 cm above the ulnar styloid process.
The insignificant trend of an increase in the skin perfusion in the second group of volunteers relative to the first group (4.55 and 4.89 (p=0.31)) has been revealed. In the amplitudes of oscillations reflecting endothelial activity, there is a slight decrease in the second group relative to the first (0.17 and 0.14 (p=0.14)). In neurogenic, myogenic and cardiac oscillations, there is a statistically significant decrease in the oscillation amplitudes in the second group compared to the first (p=0.027; 0.0026; 0.0011, respectively). The normalized amplitudes of oscillations of the active range and cardiac oscillations are significantly lower in the group with AH relative to the control one (p<0.05 according to the Mann-Whitney test). A decrease in the contribution of cardiac and endothelial mechanisms of blood flow regulation may indicate vascular constriction in volunteers from the second group with AH, which may indicate an increase in BP.
AH was detected for the first time in more than 66% of the volunteers. All the study participants were men of working age, and they considered themselves subjectively healthy, did not observe any specific symptoms of increased BP. The difficult diagnosability of AH is associated with its asymptomatic course, which leads to early disability and mortality of the population. The tested method is promising for assessing the functional state of blood vessels and also for identifying the features of microcirculatory blood flow regulation in AH. The study opens new opportunities for the early detection of AH by the new wearable sensors.
This work was supported by the Russian Foundation for Basic Research (RFBR), grant 20-08-01153А.
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R&D Center of Biomedical Photonics, OSU named after I.S. Turgenev
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