An improved design of optical sensor for long-term measurement of arterial blood flow waveform.

We present here the improved design and development of optical sensor for non-invasive measurements of arterial blood flow waveform. The sensor is based on a physical principle of reflective photoplethysmography (PPG). As the light source we used serially connected infrared diodes whereas NPN silicon phototransistors were used as light detectors. The electronic components were molded into square package and poured with silicone. Such preparation produced an elastic superficies that allowed excellent attachment of the sensor on the skin's surface. Moreover, a serial connection of infrared diodes and phototransistors completely eliminated signal artifacts caused by minor muscle contractions. The sensor recording performances were examined at the photoplethysmographic sites on three different arteries; the commune carotid, femoral and radial and, on each site the sensor demonstrated remarkable capability to make a consistent, reproducible measurements. Because of the advantageous physical and electrical properties, the new sensor is suitable for various cardiovascular diagnostics procedures, especially when long-term measurements of arterial blood flow waveform are required, for monitoring of different parameters in cardiovascular units and for research.

Using the photoplethysmography method to monitor age-related changes in the cardiovascular system.

Introduction: Aging is a physiological process characterized by progressive changes in all organ systems. In the last few decades, the elderly population has been growing, so the scientific community is focusing on the investigation of the aging process, all in order to improve the quality of life in elderly. One of the biggest challenges in studying the impact of the aging on the human body represents the monitoring of the changes that inevitably occur in arterial blood vessels. Therefore, the medical community has invested a great deal of effort in studying and discovering new methods and tools that could be used to monitor the changes in arterial blood vessels caused by the aging process. The goal of our research was to develop a new diagnostic method using a photoplethysmographic sensor and to examine the impact of the aging process on the cardiovascular system in adults. Long-term recorded arterial blood flow waveforms were analyzed using detrended fluctuation analysis. Materials and Methods: The study included 117 respondents, aged 20-70 years. The waveform of the arterial blood flow was recorded for 5 min, with an optical sensor placed above the left common carotid artery, simultaneously with a single-channel ECG. For each cardiac cycle, the blood flow amplitude was determined, and a new time series was formed, which was analyzed non-linearly (DFA method). The values of the scalar coefficients α 1 and α 2, particularly their ratio (α 1/α 2) were obtained, which were then monitored in relation to the age of the subjects. Result: The values of the scalar ratio (α 1/α 2) were significantly different between the subjects older and younger than 50 years. The value of the α 1/α 2 decreased exponentially with the aging. In the population of middle-aged adults, this ratio had a value around 1, in young adults the value was exclusively higher than 1 and in older adults the value was exclusively lower than 1. Conclusion: The results of this study indicated that the aging led to a decrease in the α 1/α 2 in the population of healthy subjects. With this non-invasive method, changes in the cardiovascular system due to aging can be detected and monitored.

Heart rate recovery in elite athletes: the impact of age and exercise capacity.

There is compelling evidence that postexercise heart rate recovery (HRR) is a valid indicator of sympaticovagal balance. It is also used in prescription and monitoring of athletic training. The purpose of our study was to determine HRR after maximal exercise among elite athletes with respect to age. A total of 274 elite male Caucasian athletes were randomly selected from the larger sample and divided into two groups: adolescent (group Y) and adult athletes (≥18 years; group A). They performed maximal cardiopulmonary exercise testing on a treadmill. Heart rate recovery was calculated as the rate of decline of HR from peak exercise to rates 1, 2 and 3 min after cessation of exercise (HRR1, HRR2 and HRR3). A significantly higher HRR1 was found in group A (29·5 ± 15·6 versus 22·4 ± 10·8, P<0·001), but HRR3 was higher in group Y (82·7 ± 10·2 versus 79·9 ± 12·25; P = 0·04). Stepwise multivariate linear regression analysis showed that, among all subjects, the HRR1 alone was independently associated with age (P<0·001). The maximal oxygen consumption (VO2 max) was in a negative relationship with HRR1 and in a positive one with HRR3 (P<0·05) with respect to all athletes. The HRR during 3 min postexercise should be reported for the purpose of better assessing functional adaptation to exercise among elite athletes as well as the age-associated differences in recovery. Higher values of HRR1 should be expected in older athletes, and HRR3 could be used as an index of aerobic capacity, irrespective of age.