Exhaled nitric oxide and exercise in stable COPD patients

Study objective: To evaluate exhaled nitric oxide (eNO) during exercise in patients with stable COPD. Setting: Outpatient evaluation in a rehabilitation center. Patients: Eleven consecutive male patients with stable COPD (age, 65 +/- 6 years; FEV1, 56 +/- 10% predicted). Eight healthy (six men; age, 51 +/- 16 years) nonsmoking, nonatopic volunteers served as control subjects. Methods: In each subject, a symytom-limited cycle ergometry test was peform ed by monitoring eNO with the tidal-breath method to assess eNO concentrati on (FENO) and output (VNo) at rest, peak exercise, and recovery time. Results: Resting FENO (9.8 +/- 5.1 and 14.1 +/- 6.3 parts per billion, resp ectively) and VNo (4.2 +/- 2.0 and 5.9 +/- 3.4 nmol/min, respectively) were lower, although not significantly, in COPD patients than in control subjec ts. In both groups, FENO significantly decreased whereas VNo significantly increased during exercise. Both variables returned to baseline during the r ecovery time. Peak exercise VNO, but not FENO, was significantly lower in C OPD patients than in control subjects (7.9 +/-, 5.4 and 12.7 +/- 6.0 nmol/m in, respectively, p < 0.05). The rise in VNo was weakly correlated to oxyge n consumption (Oo,) both ill control subjects (r = 0.31, p = 0.002) and in COPD patients (r = 0.22, p = 0.03). FENO showed an inverse correlation to l ie, in both groups (r = -0.53, p = 0.000; r = -0.31, p = 0.003 in control s ubjects and COPD patients, respectively). Conclusions: In patients with mild and moderate COPD, eNO during exercise p arallels that observed in normal control subjects. VNO, but not FENO, is si gnificantly reduced at peak exercise in COPD patients as compared with cont rol subjects. The long-term effects of exercise training on erVO has to be evaluated by further studies.