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

Abstract

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

“…For the purposes of this research, the photoplethysmography sensor designed and developed earlier ( Žikić, 2008 ), has been used for continuous and non-invasive recording of the arterial blood flow waveform ( Djuric et al, 2017 ). The sensor was designed in order to eliminate artifacts that were occurring during the phases of respiration, caused by the contraction of the respiratory muscles.…”

“…In the improved design, the light source was two series-connected IR diodes, and the detector was three series-connected NPN phototransistors. Three serially connected silicon NPN phototransistors were used as light intensity change detectors ( Djuric et al, 2017 ).…”

“…The first method is very sensitive (depending on the experience and skills of medical professionals) and cannot provide reliable signals for wave analysis ( Srámek et al, 2000 ; Loizou, 2014 ). On the other hand, the second method is independent from the muscle’s activity, although there is a problem with the signal calibration ( Žikić, 2008 ; Djuric et al, 2017 ).…”

Intravital molecular tagging velocimetry of cerebral blood flow using Evans Blue

“…More specifically, the monitoring of volumetric blood flow rate variations helps to elucidate the fundamental mechanisms of cerebral stroke , myocardial ischemia and optic nerve atrophy . Among the many optical techniques developed for microcirculatory studies, such as photoplethysmography , fluorescent angiography , laser speckle contrast analysis and laser Doppler blood flowmetry , only the flow tracer‐based techniques, namely, PIV , laser Doppler velocimetry and Doppler optical coherence tomography , are capable of intravital measurement of the absolute blood flow velocity in intact blood vessels . In biomedical applications, native red blood cells can be utilized as flow tracing particles, or fluorescence micro beads can be introduced into the circulatory system .…”

Sleep monitoring sensor using flexible metal strain gauge

“…In addition to product, various studies have been carried out to evaluate the state of sleeping. They are inertial sensors and optical sensors based sleep sensor, [17][18][19] ear-electroencephalography (ear-EEG) or ear-ECG based ear wear sensors, [20][21][22][23] strain gauge-based body-mount sensors. 24,25) However, since these sensors are not contactfree, they have the serious disadvantage that they interfere with the user's deep sleeping.…”