Resting lung function in the assessment of the exercise capacity in patients with chronic heart failure

Despite the lung involvement in patients with chronic heart failure (CHF), the significance of lung function abnormalities to functional status in these patients is still controversial. We postulated that in patients with CHF, resting lung function assessment may provide information of clinical relevance on exercise capacity, expressed as peak oxygen uptake (VO2) and ventilatory response to CO2 production (VE/VCO2) during a maximal exercise.

We studied 49 clinically stable patients with CHF (38 men, age range: 25-78 years) (New York Heart Association class range: I-IV) with left ventricular ejection fraction <40%. Patients with chronic obstructive pulmonary disease were excluded. Patients performed pulmonary function tests and maximal incremental exercise test.

Resting spirometry was related to the exercise capacity (P < 0.05), expressed as peak VO2. By means of receiver operating characteristic curve analysis, the forced expiratory volume at first second (FEV1) cutoff point, which better identified patients with a peak VO2 < or =14 mL/kg/min, was <79% of predicted value (0.79 sensitivity and 0.73 specificity). Resting lung diffusion capacity for carbon monoxide and end-tidal pressure of CO2 (PETCO2) were inversely correlated to VE/VCO2 (P < 0.01). The lung diffusion capacity for carbon monoxide and PETCO2 cutoff points, which better identified patients with VE/VCO2 value >34, were <58% of predicted (0.92 sensitivity and 0.42 specificity) and <33 mm Hg (0.67 sensitivity and 0.92 specificity), respectively.

In patients with CHF, resting lung function, including spirometry, lung diffusion capacity, and PETCO2, can provide clinically useful information on exercise capacity, by predicting peak VO2 and VE/VCO2 slope. The results of this study highlight the role of resting lung function in the assessment of the functional status of cardiac patients.