The effect of fiberoptic bronchoscopy on exhaled nitric oxide

Nitric oxide has been extensively studied as a noninvasive marker of airway inflammation. Assuming that bronchoscopy can produce not only systemic but also local inflammatory response, we hypothesized that bronchofiberoscopy can be responsible for an increase in nitric oxide synthesis with resulting increase in fractional concentration of exhaled nitric oxide (FE(NO)). Fifty five subjects (F/M-23/32; mean age 53.9 +/-17.3 yr) undergoing diagnostic bronchoscopy participated in the study. The indications for bronchoscopy were as follows: interstitial lung diseases (n=13; 23.6%), lung cancer (n=11; 20.0%), hemoptysis (n=10; 18.2%), differential diagnosis of asthma/dyspnea (n=9; 16.4%), pulmonary infections (n=7; 12.7%), and others (n=5; 9.1%). During bronchoscopy bronchial washing (n=18), bronchoalveolar lavage (BAL) (n=26), and bronchial biopsies (n=24) were performed. FE(NO) was analyzed on-line with chemiluminescence analyzer (NIOX, Aerocrine, Sweden) according to the ATS guidelines, before and at 1, 2, 3 and 24 h after bronchoscopy. The mean FE(NO) before bronchoscopy was 21.0 +/-3.31(SE) ppb, it decreased to 14.8 +/-2.10 ppb 1 h after bronchoscopy, reached a nadir at 2 h (14.4 +/-2.28 ppb; P<0.05), and was not different from baseline 24 h after bronchoscopy (22.8 +/-2.90 ppb). There were no differences in the FE(NO) profile in BAL patients compared with those in whom only the bronchial washing was performed. We conclude that bronchoscopy leads to a decrease in FE(NO). The underlying mechanisms are at present unclear.