Pulmonary function tests, part 2: Using pulse oximetry

Pulse oximetry can be useful in the detection of hypoxemia in a variety of clinical settings, such as the evaluation of unexplained dyspnea. Arterial oxygen saturation (SaO₂) can be measured either at rest or during exertion; desaturation of more than 4% during exertion suggests a gas exchange abnormality. Overnight continuous pulse oximetry can be a valuable tool in the evaluation of sleep-disordered breathing, although its sensitivity and specificity are affected by a number of patient- and device-related variables. When interpreting the results of pulse oximetry, remember that readings can be inaccurate as a result of motion artifact, hypotension, or poor perfusion. Also, SaO₂ is not a reliable guide to ventilation, and arterial blood gas analysis is necessary to identify hypercapnia.