Exhaled nitric oxide and exercise performance in heart failure

Background. In heart failure abnormalities of pulmonary function are frequently observed particularly during exercise, which is characterized by hyperpnea, low tidal volume, early expiratory flow limitation and reduced lung compliance. Exhaled nitric oxide (NO) is increased in asthma. We evaluated whether a correlation between exhaled NO and lung mechanics exists during exercise in heart failure. Methods. We studied 33 chronic heart failure patients and 11 healthy subjects with: a) standard pulmonary function, b) lung diffusion for carbon monoxide (DLCO) including its subcomponents, capillary volume and membrane resistance and eNO both at rest and during light exercise, c) maximal cycloergometer cardiopulmonary exercise test. Results. Forced expiratory volume in 1 second (FEV₁) was reduced in heart failure patients (83 ± 17% of predicted) as was DLCO (75 ± 18% of predicted) due to reduced membrane resistance (32.6 ± 10.3 ml/mmHg/min vs. 39.9 ± 6.9 in patients vs. controls, p <0.02). eNO was lower in patients vs. controls (9.7 ± 5.4ppm vs. 14.4 ± 6.4, p <0.05) and was, during exercise, constant in patients and reduced in controls. No significant correlation was found between eNO and lung function. Vice-versa eNO changes during exercise were correlated with peak exercise oxygen consumption (r = 0.560, p <0.001). Conclusions. The hypothesis of a link between eNO and lung function in heart failure was not proved. The correlation between eNO changes during exercise and peak VO₂ might be due to hemoglobin oxygenation which binds NO to hemoglobin.