https://www.jstor.org/stable/10.1086/644724

Human Biology and Health

Pulse oximeters require artifact-free clean photoplethysmograph (PPG) signals obtained at red and infrared (IR) wavelengths for the estimation of the level of oxygen saturation ( SpO2) in the arterial blood of a patient. Movement of a patient corrupts a PPG signal with motion artifacts and introduces large errors in the computation of SpO2. A novel method for removing motion artifacts from corrupted PPG signals by applying Fourier series analysis on a cycle-by-cycle basis is presented in this paper. Aside from artifact reduction, the proposed method also provides data compression. Experimental results indicate that the proposed method is insensitive to heart rate variation, introduces negligible error in the processed PPG signals due to the additional processing, preserves all the morphological features of the PPG, provides 35 dB reduction in motion artifacts, and achieves a data compression factor of 12.

Use of Fourier Series Analysis for Motion Artifact Reduction and Data Compression of Photoplethysmographic Signals

Artifact free photoplethysmographic (PPG) signals, obtained with red and infrared (IR) optical sources and detectors are necessary for non-invasive estimation of oxygen saturation (SpO2) in arterial blood. Movement of a patient corrupts the PPGs with motion artifacts, resulting in large errors in the computation of SpO2. This paper presents a novel singular value decomposition (SVD) based method to reduce motion artifacts from corrupted PPG signals. Test results on a prototype incorporating the proposed SVD technique show that stable and reliable SpO2 measurement is achieved even when PPGs are distorted by motion artifacts, thus establishing the efficacy of the proposed method.

Motion Artifact Reduction in Photoplethysmographic Signals using Singular Value Decomposition

In the last few years, the availability of powerful personal computing devices, like smartphones, has opened new scenarios to the so called “Body Area Network” (BAN), i.e., sensor networks specifically designed to monitor physical conditions of the user. The traditional methods adopted to monitor physical parameters, like heart beat rate or exertion level, are not suitable for real-time measurements. However, a continuous monitoring of such kind of parameters would allow the athletes to constantly control their physical conditions, furnishing useful information to prevent overstrain and to improve their performance. In this work, a simple, portable and low-cost system for non-invasive and real-time measurement of physical parameters is proposed and experimentally characterized. It is composed of three units: the sensor apparatus, electronic interface circuit, and the data transmission unit. Two different sensors are combined in a unique structure to be placed in a clip-like fashion on the earlobe or other body part of a person. A photoplethysmographic sensor is used to optically measure the changes of blood volume in the arteries, thus to acquire information about heart beat, blood pressure, and arrhythmias. The second sensor is composed of two electrodes, hence an impedance measurement of the tissue is carried out. The impedance estimation can be used to monitor the dielectric properties of biological tissues and fluids, like blood flow. A commercial battery-operated Bluetooth earphone is used both to transmit sensor data and to provide the power supply for the sensors and the first conditioning electronics. Data transmission is operated by the standard Bluetooth Hands-Free profile; therefore, sensor data can be easily acquired, elaborated and visualized by a broad range of commercial devices. In fact, Hands-Free is the only Bluetooth data communication profile supported by any smartphone, from the low-cost ones to the high-end devices. The experimental characterization of the prototype, performed by using a specifically designed application for Android smartphone systems, has demonstrated the validity of the proposed approach.

Multi-sensor system with Bluetooth connectivity for non-invasive measurements of human body physical parameters

Measurement of blood volumetric changes in human body by photoplethysmographic sensors is used in present study. Objective is to measured different parameters that are heart rate, respiratory rate, BP. PPG signal is acquired by PPG sensor, microcontroller and RS 232. The acquired PPG signal is displayed in MATLAB. Frequency domain analysis of PPG signal shows a two peaks first at around 0.25 to 0.35 Hz and second at around 1 to 1.5 Hz. FFT at 1Hz relates to 60 BPM and FFT at 0.25 Hz relates to 15 respiratory cycles per minute. For BP Measurement, the pulse height of PPG is proportional to the difference between the systolic and the diastolic pressure in the arteries. The standard blood pressure monitoring instrument is used to calculate correlation coefficient. The arterial blood pressure is calculated based on these coefficients. PPG signal is used to detect blood pressure pulsations in a finger and achieved an accuracy of (0.8 ± 7) mmHg and (0.9 ± 6) mmHg for systolic and diastolic pressure, respectively. The developed PPG based method can be used as a noninvasive alternative to the conventional occluding-cuff approaches for long-term and continuous monitoring of blood pressure, heart rate and respiratory rate.

Respiratory rate, heart rate and continuous measurement of BP using PPG

This paper presents the design and development of a virtual instrument for the measurement of haemo-dynamic parameters namely, pulse rate and oxygen saturation in arterial blood based on the popular photoplethysmographic (PPG) principle. A clip-on sensor, housing red and infrared (IR) light emitting diodes and suitable photo detectors is developed. The sensor is interfaced to a PC utilizing the audio channel of the sound card, thus dispensing with expensive analog to digital converter hardware. Since the frequency response of the audio channel is not suitable for the PPG waveforms of red and IR, FM modulation and demodulation are employed. An empirical relationship is developed for the computation of the oxygen saturation in arterial blood using the red and IR PPG data and the well-known and well-established extinction coefficients of haemoglobin with and without oxygen. Data acquisition and processing are accomplished under LabVIEW virtual environment.

Virtual Instrument for the Measurement of Haemo-dynamic Parameters Using Photoplethysmograph

Magneto plethysmo gram (MPG), like the Photo plethysmo gram (PPG) is a signal that carries information on blood volume flow and is obtained noninvasively. Unlike PPG, MPG is obtained from a peripheral artery, such as radial, carotid or brachial. The magnetic flux required for obtaining an MPG is generated by a permanent magnet placed on the wrist surface such that the generated flux couples with the blood flow in the artery. In this work it is shown that maximum coupling of flux with the blood flow in radial artery occurs when the distance between the open end of the U shaped probe is 12 mm. In order to attain this result, first the probe is simulated using the finite element method. The distance between the pole faces is varied in steps of 1 mm. Simulation results clearly indicate that the optimal distance is 12mm. Next experiments were conducted with prototype probes of varying distances between the pole faces on 20 volunteers of different age and gender. The experimental results validate the result obtained by the simulation study.

Optimal Design to Ensure Maximum Coupling Between Magnetic Flux and Arterial Blood in a Magneto Plethysmo Gram Sensor Head

A novel magnetoplethysmogram (MPG) system is designed and developed for the real time, noninvasive monitoring of hemoglobin concentration in arterial blood. The basic principle of modulated magnetic signature of blood (MMSB), is validated with clinical trial. The MPG probe consists of a permanent magnet and a Giant Magneto Resistance (GMR) sensor. A strap and stand design enable reliable capture of continuous cycles of MPG with relative ease. Clinical validation with data from 64 patients carried out at the institute hospital of IIT Madras, using the proposed system gave a worst-case error of 6.5% in the measurement of hemoglobin concentration in arterial blood. Linear regression analysis using least square method, exhibited a standard deviation of 0.64 g/dL. Results from the clinical validation establish the practicability of the proffered MPG system.

Use of Magneto Plethysmogram Sensor for Real-Time Estimation of Hemoglobin Concentration

A method for determining the concentration of hemoglobin in arterial blood, non invasively, is explored in this paper. A permanent magnet is placed just above the radial artery of a person whose hemoglobin concentration is to be ascertained. The flux produced by the permanent magnet (that links with the blood flow in the radial artery) is sensed to obtain a signal called magnetic plethysmogram (MPG). In this paper, an analytical model for a magnetic plethysmogram is derived. Using the proposed analytical model, a method of estimation of the concentration of hemoglobin in arterial blood is derived. The proposed method is then validated through a limited clinical study. The results of the clinical study establish the viability of measuring hemoglobin concentration, noninvasively, using magnetic plethysmogram.

J. Rezuana Bai

Papers

Virtual Instrument for the Measurement of Haemo-dynamic Parameters Using Photoplethysmograph

Optimal Design to Ensure Maximum Coupling Between Magnetic Flux and Arterial Blood in a Magneto Plethysmo Gram Sensor Head

Use of Magneto Plethysmogram Sensor for Real-Time Estimation of Hemoglobin Concentration

Non-invasive measurement of hemoglobin concentration using magnetic plethysmo gram