Exercise-induced oxygen desaturation in COPD patients without resting hypoxemia

Abstract

Exercise-induced oxygen desaturation (EID) is associated with increased risk of mortality in chronic obstructive pulmonary disease (COPD). Several screening tests have been proposed to predict EID, including FEV1, DLCO and baseline-SpO2. We aimed to validate a proposed cut-off of baseline-SpO2 ≤95% as simple screening procedure to predict EID during six-minute walk test (6MWT). In addition, we studied the prevalence and characteristics of patients exhibited EID to SpO2nadir ≤88%. 402 non-hypoxemic COPD patients performed 6MWT. Sensitivity and specificity of baseline SpO2 ≤95% as a cut-off to predict EID and determinants of EID were investigated. 158 patients (39%) exhibited EID. The sensitivity of baseline-SpO2 ≤95% to predict EID was 81.0%, specificity 49.2%, positive and negative predictive values were 50.8% and 80.0%, respectively. In a multivariate model, DLCO <50%, FEV1 <45%, PaO2 <10kPa, baseline-SpO2 <95%, and female sex were the strongest determinants of EID. Baseline oxygen saturation solely is inaccurate to predict EID. A combination of clinical characteristics (DLCO, FEV1, PaO2, baseline-SpO2, sex) increases the odds for EID in COPD.

Keywords: 6MWD; 6MWT; AUC; BMI; COPD; DLCO; EID; Exercise testing; FEV(1); FEV(1)/FVC; FFMI; FM; FRC; FVC; MRC; Oximetry; Oxygen saturation; PaCO(2); PaO(2); ROC; SaO(2); Six-minute walk test; SpO(2); TLC; WDS; area under the receiver operating characteristic (ROC) curve; body mass index; chronic obstructive pulmonary disease; diffusion capacity for carbon monoxide; exercise-induced oxygen desaturation; fat free mass index; fat mass; force expiratory volume in 1s; forced vital capacity; functional residual capacity; medical research council dyspnea scale; partial arterial pressure of carbon dioxide; partial arterial pressure of oxygen; receiver operating characteristic curves; saturation of arterial oxygen (hemoglobin); saturation of peripheral oxygen; six-minute walk distance; six-minute walk test; the ratio (r) of forced expiratory volume in 1s and forced vital capacity; total lung capacity; walking desaturation score.