Wearable Pulse Oximetry Measurements on the Torso, Arms, and Legs: A Proof of Concept

Abstract

For decades pulse oximeters designed for use on the head, hands, or feet have provided invaluable estimates of oxygen saturation to medical personal attending to combat casualties. However, traditional placement sites are not ideal for the relatively new paradigm of continuous battlefield telemonitoring. To assess the feasibility of oximetry on nontraditional body sites, 42 healthy volunteers were enrolled, consented, and underwent an industry standard induced-hypoxia study. During the study volunteers used prototype wearable oximeters, designed for the torso, arms, and legs. Subsets (size n) of the volunteers had the wearables placed at the following body sites, and achieved accuracies (A, root-mean-square difference) of the following: calf 1.7% (n = 26); bicep 3.1% (n = 12); forearm 3.4% (n = 11); pectoral 2.9% (n = 42); sternum 2.9% (n = 13). In keeping with regulatory guidance calibrations with an A of less than 3.5% are acceptable for potential future development. Additionally, a new method was developed to enable accurate reporting of respiration rate from the pectoral oximeter, A of 1.1 breaths per minute (n = 10). This study demonstrates the feasibility of monitoring oxygen saturation and respiration rate from nontraditional sites via a wearable pulse oximeter.

A Comparison of Reflective Photoplethysmography for Detection of Heart Rate, Blood Oxygen Saturation, and Respiration Rate at Various Anatomical Locations

“…Heart rate, respiration, and SpO 2 are three of the five vital signs indicating the criticality condition of a patient (aside from blood pressure and temperature). If any of these vital signs have deteriorated, it is an indicator that the patient is in immediate need of medical intervention [8,9,10]. With the introduction of PPG based pulse oximeters, heart rate and SpO 2 can easily be monitored using a single device, and respiration is often monitored visually or through separate devices as required.…”

“…With the introduction of PPG based pulse oximeters, heart rate and SpO 2 can easily be monitored using a single device, and respiration is often monitored visually or through separate devices as required. A single device which can monitor all three signs is a desirable diagnostic tool for emergency medicine, as well as for the monitoring and diagnosis of other diseases, such as sleep apnoea [8,9,10].…”

“…While many studies have been previously conducted into the placement of PPG sensors for pulse oximetry [5,10,11,12,13,14,15,16,17], few studies have been conducted for a suitable location to collect heart rate, SpO 2 , and respiration. Kramer et al [10] developed a new pulse oximeter for use at non-traditional anatomical locations for the measurement of heart rate, SpO 2 , and respiration. They tested their device at five anatomical locations (pectoral, sternum, bicep, calf, and forearm) and found that the calf location recorded the most accurate SpO 2 measurement [10].…”

“…Kramer et al [10] developed a new pulse oximeter for use at non-traditional anatomical locations for the measurement of heart rate, SpO 2 , and respiration. They tested their device at five anatomical locations (pectoral, sternum, bicep, calf, and forearm) and found that the calf location recorded the most accurate SpO 2 measurement [10]. Despite respiration artefacts, Kramer et al [10] found that the sternum and pectoral locations demonstrated acceptable SpO 2 accuracy, while the forearm and bicep performance was significantly degraded compared to other tested locations.…”

“…They tested their device at five anatomical locations (pectoral, sternum, bicep, calf, and forearm) and found that the calf location recorded the most accurate SpO 2 measurement [10]. Despite respiration artefacts, Kramer et al [10] found that the sternum and pectoral locations demonstrated acceptable SpO 2 accuracy, while the forearm and bicep performance was significantly degraded compared to other tested locations. It was also shown that the respiration rate could be captured with the sensor located on the pectoral, the only location where the authors attempted respiration data extraction from the PPG waveform [10].…”