REPRODUCIBILITY OF MEASUREMENTS OF BLOOD- GAS EXCHANGE ON EXERCISE INMILD CARDIAC-FAILURE - NEED FOR A PRELIMINARY TEST

The reproducibility of blood gas exchange measurements on exercise in chronic cardiac failure has already been established in patients famil iar with this technique. The aim of this prospective study was to eval uate the reproducibility of cardiopulmonary parameters on exercise in a population of patients who had never undergone this type of investig ation. Twenty patients with chronic cardiac failure in classes I to II I of the NYHA classification, with a mean age of 55+/-11.5 years and a mean LV ejection fraction of 31.2+/-9%, underwent two cardiopulmonary exercise tests (CPX Medgraphic) performed on a bicycle ergometer. Pat ients underwent maximal exercise stress testing attaining 89% of the t heoretical maximal heart rate and 1.14 of the respiratory quotient dur ing the first test. There was no significant change in peak VO2 (22.5 ml/min/kg vs 22.6 ml/min/kg) or in ventilatory anaerobic threshold (12 .8 ml/min/kg vs 12.7 ml/min/kg) between the two tests. The ventilatory anaerobic threshold could not be measured in one patient and seemed l ess reproducible than peak VO2 with a standard deviation of relative d ifferences (T2-T1/T1) of 10.4 versus 7.8%. There was a significant inc rease in the duration of exercise (7.4+/-9.2%; p <0.002) and in ventil atory flow (4.5+/-7.5%, p=0.03). This study shows that peak VO2 is a r eproducible measurement in mild to moderate chronic cardiac failure, e ven in the absence of a preliminary test to familiarise the patient wi th the equipment. The reproducibility of the ventricular anaerobic thr eshold is less satisfactory than that of peak VO2. The increase in the duration of exercise is more dependant on motivation and should not b e taken into account alone in the functional evaluation of chronic car diac failure.