Edgars Kviesis-Kipge

Wearable wireless photoplethysmography sensors

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.

Effect of probe contact pressure on the photoplethysmographic assessment of conduit artery stiffness

Abstract. Currently, photoplethysmography (PPG) is a frequently studied optical blood pulsation detection technique among biophotonic and biomedical researchers due to the fact that it shows high potential for estimating the arterial stiffness (AS). The extraction of diagnostically useful information requires standardized measurement procedure with good repeatability. However, the effects of a crucially important factor—the optimal contact pressure (CP) of the probe—are often ignored. Also, CP values are not reported to evaluate those effects. It is hypothesized that AS estimated from PPG pulse wave 2nd derivative parameter b/a is strongly inconsistent when recorded at nonoptimal probe CP. Our pilot study confirmed this during in vivo PPG recordings from conduit artery sites on five healthy subjects at variable probe CP (0 to 15 kPa) by using 880 nm reflectance type sensor, force transducer, and PPG alternating current (AC) signal pulse area derived optimal CP criterion. The b/a values, calculated from PPG with variable CP, showed variation >300  percent. In contrast, at the optimal CP, the b/a showed high repeatability (coefficient of variability <5  percent). The effect has been explained with exponential pulse pressure-volume relationship model which indicates the optimal CP range.

Optical Studies of the Capillary Refill Kinetics in Fingertips

A new methodology for temporal analysis of the capillary refill processes by means of photoplethysmography (PPG) contact probe operating in the blue region of spectrum has been developed. A corresponding prototype device for finger measurements has been created and clinically tested. Results demonstrated that both AC and DC components of the blue PPG bio-signals are sensitive to the capillary occlusion and refill. Real-time measurements of the skin capillary refill kinetics by this technology can be used for noninvasive diag- nostics of the peripheral perfusion disorders.

Multi-spectral photoplethysmography biosensor

A photoplethysmography (PPG) signal can provide very useful information about a subjects 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.

Reliability of Hemodynamic Parameters Measured by a Novel Photoplethysmography Device

Three channel photoplethysmography (PPG) signal pulse wave studies of the leg’s conduit arteries during rest conditions were performed. The obtained data of each channel showed similar values, proving arterial PPG as a reliable and repeatable method to assess arterial waveform parameters. A validation experiment was carried out by acquiring signals from three identical IR PPG sensors, which were placed on different sites over the leg’s conduit arteries during rest conditions. Coefficients of variation (CV) were calculated at a 95% confidence interval by comparing results of each subject during multiple attempts. This data processing leads us to certain criteria of improvements in our methodology. Results show that the arterial PPG technique can give trusted and accurate information about the changes in hemodynamics, and therefore, makes it promising for early diagnostics of vascular disease.

Multi-spectral photoplethysmography technique for parallel monitoring of pulse shapes at different tissue depths

A photoplethysmography (PPG) signal can provide very useful information about a subjects 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. Multi-spectral photoplethysmography (MS-PPG) biosensor intended for analysis of peripheral blood volume pulsations at different vascular depths has been designed and experimentally tested. Multispectral monitoring was performed by means of a three-wavelengths (405 nm, 660 nm and 780 nm) laser diode and a single photodiode with multi-channel signal output processing. The proposed methodology and potential clinical applications are discussed.

Express RGB mapping of three to five skin chromophores

Skin melanin, oxy- and deoxy-hemoglobin were snapshot-mapped under simultaneous 448-532-659 nm laser illumination by a smartphone RGB camera. Experimental prototypes for double-snapshot RGB mapping of four (melanin, bilirubin, oxy- and deoxy-hemoglobin) and five (melanin, bilirubin, lipids, oxy- and deoxy-hemoglobin) skin chromophores with reduced laser speckle artefacts have been developed and tested. A set of 405-448-532-659 nm lasers were used for four chromophores mapping, and a set of 405-448-532-659-842 nm lasers for five chromophores mapping. Clinical tests confirmed functionality of the developed devices.

Wireless photoplethysmography finger sensor probe

A sensitive, digital, wireless sensor probe has been developed for photoplethysmography (PPG) measurements. It uses standard light emitting source and detector. The main advantage of this approach is to measure discharge time of the photodiode as amplitude of PPG signal. It reduces the cost, dimensions, power consumption and filtering of the device. First results of distant monitoring of heart rate using the newly developed sensor probe are presented.

Real-time analysis of skin capillary-refill processes using blue LED

A method for analysis of skin capillary-refill processes in real time by means of reflection photoplethysmography (PPG) contact probe operating in the blue (438nm ± 30 nm) and infrared (938 nm ± 20 nm) regions of spectrum is proposed. The corresponding prototype hardware and software for measurements have been developed and tested in laboratory. Realtime measurements of finger capillary refill kinetics by this technology have been taken and analyzed. Results demonstrated that both AC and DC components of the blue PPG biosignal are sensitive to capillary occlusion and refill.

Miniature wireless photoplethysmography devices: integration in garments and test measurements

Wireless PPG devices were developed and embedded in everyday clothes (bandage, scarf, cycling glove and wrist strap) to monitor cardiovascular state of free-moving persons. The corresponding software for measurements also has been developed and tested in laboratory. Real-time measurements of PPG signals were taken in parallel with a professional ECG reference device, and high correlation was demonstrated.