Abstract
BACKGROUND: Patients with Chronic Heart Failure (CHF) or with COPD may share an increased response in minute ventilation (VE) to carbon dioxide output (VCO2) during exercise.
OBJECTIVE: To ascertain whether or not the VE/VCO2slope and VE/VCO2intercept values may discriminate CHF from COPD patients at equal peak oxygen uptake (VO2peak).
METHODS: We studied 46 patients with CHF (mean age: 61± 9 years) and 46 COPD patients (mean age: 64 ± 8 years), who performed a cardiopulmonary exercise test.
RESULTS: The VE/VCO2slope values were significantly higher in CHF than in COPD patients (39.5±9.5 vs 31.8±7.4; p<0.01) at VO2peak < 16 ml/kg/min, but not ≥ 16 ml/kg/min (28.3±5.3 vs 28.9±6.6). The VE/VCO2intercept values were significantly higher in both subgroups of COPD patients, as compared to the corresponding values of the CHF patients (3.60 L/min ±1.7 vs -0.16 L/min ±1.7; p<0.01 and 3.63 L/min ± 2.7 vs 0.87 L/min ± 1.5; p<0.01). According to ROC curve analysis, when all patients with a VO2peak < 16 ml/kg/min were considered, COPD patients had a highest likelihood to have a VE/VCO2intercept value greater than 2.14 L/min (0.92 sensitivity, 0.96 specificity). Regardless of VO2peak value, the end-tidal pressure of CO2 (PETCO2) values at peak exercise were not different in CHF (p=0.42) and significantly higher in COPD (p<0.01) patients, as compared to the corresponding unloaded PETCO2 values.
CONCLUSIONS: The ventilatory response to VCO2 during exercise was significantly different between CHF and COPD patients in terms of VE/VCO2slope values in patients with moderate to severe reduction in exercise capacity, and in terms of VE/VCO2intercept values, regardless of the exercise capacity.
Footnotes
- Correspondence to: Prof Alfredo Chetta, Unità di Malattie Respiratorie e Funzionalità Polmonare, Università di Parma, Padiglione Rasori, via G. Rasori 10, 43100 Parma, Italy Tel. +39 0521 703475, fax +39 0521 292615 E-mail: chetta{at}unipr.it
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