Abstract
Background: The aim of the present study was to compare the end-tidal O2 pressure (PETO2) to end-tidal CO2 pressure (PETCO2) in cardiac patients during rest and during 2 states of exercise: at anaerobic threshold (AT) and at peak. The purpose was to see which metabolic state, PETO2 or PETCO2, best correlated with exercise limitation. Methods and Results: Thirty-eight patients with left ventricular (LV) ejection fraction <40% underwent cardiopulmonary exercise testing (CPX). PETO2 and PETCO2 were measured during CPX, along with peak O2 uptake (VO2), AT, slope of the increase in ventilation (VE) relative to the increase in CO2 output (VCO2) (VE vs. VCO2 slope), and the ratio of the increase in VO2 to the increase in work rate (ΔVO2/ΔWR). Both PETO2 and PETCO2 measured at AT were best correlated with peakVO2, AT, ΔVO2/ΔWR and VE vs. VCO2 slope. PETO2 at AT correlated with reduced peak VO2 (r=-0.60), reduced AT (r=-0.52), reduced ΔVO2/ΔWR (r=-0.55) and increased VE vs. VCO2 slope (r=0.74). PETCO2 at AT correlated with reduced peak VO2 (r=0.67), reduced AT (r=0.61), reduced ΔVO2/ΔWR (r=0.58) and increased VE vs. VCO2 slope (r=-0.80). Conclusions: PETCO2 and PETO2 at AT correlated with peak VO2, AT and ΔVO2/ΔWR, but best correlated with increased VE vs. VCO2 slope. PETO2 and PETCO2 at AT can be used as a prime index of impaired cardiopulmonary function during exercise in patients with LV failure. (Circ J 2012; 76: 79-87)
