Pulse Oximetry Overestimates Oxygen Saturation in COPD.

BACKGROUND Measurement of oxygen saturation with a handheld pulse oximeter is widely practiced as a surrogate to invasive arterial blood gas analysis. Oxygen saturation is an important parameter in cases of COPD, but there are insufficient data on the role of pulse oximetry in patients with COPD, moreso in diseases across its spectrum, such as chronic bronchitis and emphysema. We assessed the performance of pulse oximetry in acute respiratory failure of patients with COPD. METHODS This was a cross-sectional, observational study. We studied 50 subjects with COPD admitted to the Government General Hospital, a 1,000-bed tertiary referral center in Guntur, India, from June 2013 to July 2013. Simultaneous reading of S(pO2) by a handheld pulse oximeter and S(aO2) by an automated arterial blood gas analyzer were taken. RESULTS Pulse oximetry was sufficiently sensitive (84.60%) to hypoxemia in respiratory failure to be used in clinical situations. The mean difference (bias) between SaO2 and S(pO2) was -3.98 (95% CI -4.68 to 3.28). There was less sensitivity (82% vs. 85%) and positive predictive value (69% vs. 85%) of the pulse oximeter to respiratory failure in subjects with chronic bronchitis versus emphysema. CONCLUSIONS Pulse oximetry performed poorly in comparison with the invasive arterial blood gas analysis. The variability of the readings was greater in the subjects with chronic bronchitis than in those with emphysema.