Many factors are known to influence exhaled nitric oxide (eNO) values. In healthy subjects, eNO levels are known to markedly increase during physical exercise. Spirometric manoeuvres have also been shown to transiently reduce eNO levels. The purpose of this study is to determine whether there is a change in eNO levels after performing six-minute walk tests in patients with chronic obstructive pulmonary disease (COPD).
Twelve consecutive male patients with stable COPD (mean FEV1 50 + 23% predicted) each performed 2 six-minute walk tests with a 30-minute rest period in between. eNO was measured by chemiluminiscence to obtain eNO concentration (FeNO) and output (VNO) at rest 10 minutes before the start and 10 minutes after the end of the 2 six-minute walk tests.
In 6 patients, there were increases in the FeNO and VNO after the exercise tests and in 5 patients there were reduction in FeNO and VNO after the exercise tests. In the remaining patient, the FeNO and VNO were the same after the exercise tests. The overall changes in the mean FeNO (1.1 + 0.3 parts per billion) and in the mean VNO (3.9 + 1.1 parts per billion) after the exercise tests were not significant (P=0.899 and P=0.872 respectively). There was also no significant correlation between the change in FeNO and the six-minute walk distance (r = 0.42, P=0.176) and between the change in VNO and the six-minute walk distance (r = 0.44, P=0.157).
No significant changes in eNO levels were detected after six-minute walk testing in this series of patients with COPD.
In patients with COPD, analysis of eNO may be performed shortly after performance of six-minute walk tests as the eNO levels do not appear to be significantly affected by the exercise testing.
K.C. Ong, None.