A photoplethysmography (PPG) signal can provide very useful information about a subject's hemodynamic status in a
hospital or home environment. A newly developed portable multi-spectral photoplethysmography device has been used
for studies of 11 healthy subjects. The developed optical fiber biosensor comprises one multi-wavelength laser diode
(405nm, 660nm and 780nm) and a single photodiode with multi-channel signal output processing and built in Li-ion
accumulator; special software was created for visualization and measuring of the MS-PPG signals. ARM7TDMI-S
LPC2148, NXP (founded by Philips) 32 bit processor with clock frequency of 60 MHz performs measurement and
analysis of the signal.
Two experimental methodologies for human skin optical non-invasive in-vivo assessment have been developed and clinically
tested - imaging of the laser-excited autofluorescence fading rate, and simultaneous recording of the reflectance photoplethysmography signals at several laser wavelengths with different skin penetration depths. Details of both equipments are described along with some measurement results illustrating feasibility of the novel technologies.
Wearable health monitoring sensors may support early detection of abnormal conditions and prevention of their
consequences. Recent designs of three wireless photoplethysmography monitoring devices embedded in hat, glove
and sock, and connected to PC or mobile phone by means of the Bluetooth technology, are described. First results
of distant monitoring of heart rate and pulse wave transit time using the newly developed devices are presented.
A novel technique ensuring parallel recording of reflection photoplethysmography signals in broad spectral range
has been tested for assessment of pressure-induced vascular changes at various depths from the skin surface. PPG
signals have been simultaneously detected at three combinations of the cw laser wavelengths 405 nm, 532 nm, 645
nm, 807 nm and 1064 nm. The PPG baseline responses to the probe-skin contact pressure changes and shapes of the
PPG pulses originated from the same heartbeat but recorded at different wavelengths have been detected and
A four-channel photoplethysmography device was designed and built at University of Latvia to detect signals from
different body parts and to analyze the signal shapes. The device consists of optical contact probes, interface, and a
standard PC. Clinical tests were performed with occlusion patients having vascular problems at arm or leg arteries.
Results showed significant difference in the pulse wave transit time in occluded and nonoccluded part of the body.
The dual-channel photoplethysmography studies of physiological responses during 3-stage orthostatic test were performed. Clear differences in heartbeat rate, pulse wave transit time and blood pressure variations of healthy volunteers and diabetic patients have been observed.
Three portable prototype devices for cardiovascular biosensing based on reflection-type photoplethysmography (PPG) principle have been designed and clinically tested. The single-channel PPG finger sensor provides real-time measurements with fast calculation of the mean single-period PPG signal shape ("cardiovascular fingerprint", potentially useful for recognition). The dual-channel PPG system gives additional possibility to monitor on-line the arterial pulse wave transit time and its responses to physical exercises. The four-channel PPG system proved to be applicable for fast detection of cardiovascular pathologies, e.g. arterial occlusions in extremities. Design principles and software algorithms of the regarded devices will be discussed, as well as the results of recent clinical tests.
Time resolved detection and analysis of the skin back-scattered optical signals (reflection photoplethysmography or PPG) provide information on skin blood volume pulsations and can serve for cardiovascular assessment. The multi-channel PPG concept has been developed and clinically verified in this study. Portable two- and four-channel PPG monitoring devices have been designed for real-time data acquisition and processing. The multi-channel devices were successfully applied for cardiovascular fitness tests and for early detection of arterial occlusions in extremities. The optically measured heartbeat pulse wave propagation made possible to estimate relative arterial resistances for numerous patients and healthy volunteers.
Time resolved detection and analysis of the skin back-scattered optical signals (reflection photoplethysmography or PPG) provide rich information on skin blood volume pulsations and can serve for cardiovascular assessment. The multichannel PPG concept has been developed and clinically verified in this work. Simultaneous data flow from several body locations allows to study the heartbeat pulse wave propagation in real time and to evaluate the vascular resistance. Portable two- and four-channel PPG monitoring devices and special software have been designed for real-time data acquisition and processing. The multi-channel devices were successfully applied for cardiovascular fitness tests and for early detection of arterial occlusions.
A portable sensor device for simultaneous detection and processing of skin-remitted optical signals from any two sites of the body has been developed and tested. The photoplethysmography (PPG) principle was applied to follow the dilatation and contraction of skin blood vessels during the cardiac cycle. The newly developed two-channel approach allows to estimate the vascular blood flow resistance by analysis of time shifts between the PPG pulses detected at different body sites. Potential of the sensor device for express-assessment of human cardio-vascular condition and for body fitness tests has been demonstrated.
A hand-held prototype device for detection and processing of the tissue-remitted optical signals has been developed and tested. The photoplethysmography (PPG) principle was applied to follow the dilation and contraction of skin blood vessels during the cardiac cycle. Cardiovascular condition of the monitored person was assessed by temporal analysis of the recorded PPG signals as well as by shape analysis of the mean single-period PPG signals.
Blood micro-circulation in upper skin layers has been studied experimentally in real time by advanced two-channel photoplethysmography (PPG) techniques. The blood volume changes caused by micro-vessel expansion and dilution during the cardiac cycles have been detected by infrared optical contact sensors. A newly developed portable monitoring device comprising a lap-top computer was used for accumulation and processing of the bio-signals. Shapes of the PPG signals detected at different sites of the body were compared with these obtained by computer modeling.