Speckleplethysmographic (SPG) Estimation of Heart Rate Variability During an Orthostatic Challenge

Abstract

Heart rate variability (HRV) provides insight into cardiovascular health and autonomic function. Electrocardiography (ECG) provides gold standard HRV measurements but is inconvenient for continuous acquisition when monitored from the extremities. Optical techniques such as photoplethysmography (PPG), often found in health and wellness trackers for heart rate measurements, have been used to estimate HRV peripherally but decline in accuracy during increased physical stress. Speckleplethysmography (SPG) is a recently introduced optical technique that provides benefits over PPG, such as increased signal amplitude and reduced susceptibility to temperature-induced vasoconstriction. In this research, we compare SPG and PPG to ECG for estimation of HRV during an orthostatic challenge performed by 17 subjects. We find that SPG estimations of HRV are highly correlated to ECG HRV for both time and frequency domain parameters and provide increased accuracy over PPG estimations of HRV. The results suggest SPG measurements are a viable alternative for HRV estimation when ECG measurements are impractical.

Continuous Non-Invasive Blood Pressure Monitoring: A Methodological Review on Measurement Techniques

“…Speckleplethysmogram (SPG) has been recently used as an alternative to PPG for measuring heart rate variability (HRV) [52], [53]. SPG is an optical method based on laser speckle contrast imaging (LSCI) to monitor changes in blood flow [54].…”

“…The amount of speckles detected in the image correlates to the volume of blood present at that time point, and the change over time forms the SPG waveform. Studies comparing the signal to PPG report a higher signal to ratio (SNR) to the latter in situations with more motion and colder climates [52], [53].…”

“…With attached electrodes and LED/photo detector sensors on a subject, the BP compared to the reference sphygmomanometer had a mean and standard deviation of -0.34±3.1 mmHg [22]. This method demonstrates PTT from ECG and PPG as an easier method of measuring for the comfort of patients and portability for continuous, long term monitoring; [84] an optical technique that measures the change of blood volume by photoelectric technique as well as measures the oxygen saturation in the blood Transmission Mode: earlobe, fingertip, toe Reflectance Mode: forehead, forearm, supraorbital artery, under the legs, and the wrist [46] slope transit time [81], arterial PTT [82], blocking-free opticaloscillometry [83], arteriolar PTT [84] inexpensive, simple set up external light and cold temperatures can add noise to data Speckle plethysmography (SPG) [52]- [55] an optical technique using laser speckle contrast imaging (LSCI) to monitor changes in blood flow finger [52], [53], wrist [54], [55] Laser Speckle Contrast Imaging [52]- [55] higher SNR compared to PPG in situations with more motion and cold climates, wearable sensors [52], [53] External Light can affect data and add noise [52], [53] Mechanicalbased [56]- [62] measuring the ejection of blood into the aorta and its transmission throughout the arterial system and it is expanded in response to the blood volume change through vessel; mechanical-based BP measurements include capacitive, ferroelectric, or piezoresistivesensors carotid artery, brachial artery, radial artery PTT [61], [62] [66], [85] an electrical impedance based noninvasive medical diagnostic procedure which measures small changes in the blood volume in terms of its electrical bioimpedance of a body part finger [44], [85], wrist [66] PTT (with Proximal or Distal Signals) [44], [66], ...…”

“…ECG is measured via sensors on the chest of the subjects and compared in real time to SPG and PPG. The studies investigating SPG in vitro have shown an improved SNR and robustness to motion artifacts and temperature tests compared to PPG, where the latter produces noisy waveforms [52], [53].…”

Fast pulsatile blood flow measurement in deep tissue through a multimode detection fiber

“…23 Another method, speckle plethysmography, was developed for fast measurement of in vivo blood flow waveform and PPG waveform. 22,24,25 The SM detection fiber is the main reason that fiber-based DSCA system cannot achieve fast blood flow measurement. 13,17,26 A CCD camera is utilized as the detector in the fiber-based DSCA system.…”