The sensitivity of room-air pulse oximetry in the detection of hypercapnia

Objective To estimate the sensitivity of room-air pulse oximetry in the detection of moderate hypercapnia. Methods In this retrospective case-control study, charts were reviewed from patients with and without moderate hypercapnia (Paco2 >50 mm Hg), as determined by analysis of arterial blood gas samples obtained in the ED. Test characteristics (sensitivity, specificity, and likelihood ratios [LR) for room-air pulse oximetry ≤96% to detect hypercapnia were calculated, as were confidence intervals. Results A total of 349 charts were eligible for abstraction—92 cases and 257 controls. A room-air pulse oximetry reading ≤96% detected 88 of 92 cases of hypercapnia. Test characteristics were as follows (with 95% confidence interval): sensitivity, 0.96 (0.89-0.99); specificity, 0.39 (0.33-0.45), LR of a room-air pulse oximetry value >96%, 0.1 (0.04-0.3); and LR of a room-air pulse oximetry value ≤96%, 1.6 (1.4-1.7). Conclusion Room-air pulse oximetry detects moderate hypercapnia with high sensitivity