Pulse Oximetry: Theory and Applications for Noninvasive Monitoring

Abstract

Noninvasive measurement of arterial oxygen saturation (SaO2) by pulse oximetry is widely acknowledged to be one of the most important technological advances in monitoring clinical patients. Pulse oximeters compute SaO2 by measuring differences in the visible and near infrared absorbances of fully oxygenated and deoxygenated arterial blood. Unlike clinical blood gas analyzers, which require a sample of blood from the patient and can provide only intermittent measurement of patient oxygenation, pulse oximeters provide continuous, safe, and instantaneous measurement of blood oxygenation. Here I review the theoretical background behind this advanced technology, instrumentation requirements, practical instrument calibration, common features of commercial pulse oximeters, specific clinical applications, and performance limitations of pulse oximeters.

Assessment of clinical application of pulse oximetry probes in llamas and alpacas

“…Variations in probes, anatomical locations and clinical conditions can influence pulse oximetry (Shaughnessy & Hofmeister 2010;Chaffin et al 1996;Matthews et al 2003). The pulse oximeter depends on detection of pulsatile waveforms for determination of S a O 2 (Clark et al 1992 ;Mendelson 1992). If pulsatile flow cannot be detected, the pulse oximeter will not read a value or will read an erroneous value.…”

Hemoglobin lansing: A novel hemoglobin variant causing falsely decreased oxygen saturation by pulse oximetry

“…Theoretically, low oxygen affinity hemoglobins could lead to increased tissue unloading of oxygen resulting in low SpO 2. However, this cannot explain the discrepancy between SpO 2 and arterial oxygen saturation [5,10].…”

“…Our case illustrates the importance of understanding the limitations of pulse oximetry and of awareness that low SpO 2 in otherwise healthy patients could be secondary to hemoglobin variants. The pulse oximeters emit light at 660 nm and 940 nm wavelengths and assume that absorbance at these wavelengths is from either deoxyhemoglobin or oxyhemoglobin [5]. Hemoglobin variants may interfere with pulse oximetry by having different spectral properties at 660 nm and 940 nm or by having varying oxygen affinities.…”

Analysing the effects of cold, normal, and warm digits on transmittance pulse oximetry

“…Pulse oximetry uses photoplethysmographic (PPG) signals acquired by an optical sensor, typically mounted on a finger, toe, or ear-lobe to optically detect blood volume changes in the tissue. Conventional pulse oximetry relies on the pulsatile nature of arterial blood and differential absorption of oxyhaemoglobin and de-oxyhaemoglobin at red (RD) and infrared (IR) wavelengths to estimate SpO2 and HR [4,5].…”