76 Oxygen uptake efficiency slope - a valuable substitute for peak vo2?

IntroductionCardiopulmonary exercise testing (CPEX) provides valuable diagnostic and prognostic cardiopulmonary function data. However, in clinical setting a maximal test is not always achievable. The Oxygen Efficiency Uptake Slope (OUES) has been proposed as a possible submaximal measure of cardiopulmonary function as it remains relatively stable during the final quartile of the exercise test. This study explored the validity of OUES as a surrogate marker for cardiopulmonary function in the event of a submaximal test.METHODS:Four groups of subjects [128 healthy controls (73 M), 44 asymptomatic hypertensive (HT) patients (26 M), 67 adult cardiac congenital heart disease (ACHD) patients (44 M) and 35 Heart Failure with preserved Ejection Fraction (HFpEF) (10M) patients] were recruited after informed consent. All subjects underwent clinical assessment, resting ECG, blood pressure and spirometry prior to a treadmill CPEX to volitional exhaustion and a respiratory exchange ratio (RER) of at least 1.1 using the same testing protocol. Peak VO2 (ml/min) was recorded from the last 5s of the maximal test (RER=1.1) and OUES was calculated from complete (RER=1.1) and truncated (RER=0.9) gas exchange data. The linear relationships between absolute peak VO2 and OUES from complete and truncated gas exchange data were assessed using Pearson’s correlation coefficient. Subsequently, the two correlations obtained in each patient group were compared. Statistical significance was set at p