Change of nitric oxide concentration in exhaled gas after lung resection

Nitric oxide (NO) has been shown to have a diversity of biological functions. In patients who undergo lung resection such as lobectomy and pneumonectomy, the vascular bed and its ventilation area are reduced. Few patients, however, develop pulmonary hypertension. Endogenous NO may play a role in stabilizing pulmonary circulation after major lung resection. To evaluate endogenous NO production, NO in exhaled gas was analyzed. From August to December 1996, eight patients with a mean age of 62 years who underwent lung resection (seven lobectomies and one pneumonectomy) were examined. NO concentration in their exhaled gas and minute ventilation volume was measured once in the preoperative period, on postoperative days 1 and 3, and once 1 week after surgery. Patients breathed pure oxygen, which contained no NO, through a mouthpiece; exhaled gas was introduced directly to the NO analyzer. NO concentration was analyzed continuously by the chemiluminescence method and recorded. Mean concentration of exhaled NO and total NO in exhaled gas in 1 min were calculated. For minute ventilation volume, there was a significant increase between preoperative examination and postoperative day 1. A significant increase in NO concentration in exhaled gas was observed at 1 day after lung resection. To standardize the change of NO concentration and total exhalation volume, the ratio compared to preoperative data was evaluated. The ratio of NO concentration compared to preoperative data changed 191% +/- 109%, 296% +/- 152%, and 93.7% +/- 65.0% at postoperative days 1 and 3 and at 1 week postoperatively, respectively. The ratio of NO production changed 230% +/- 119%, 363% +/- 205%, and 119% +/- 86.2% at postoperative days 1 and 3 and 1 week, respectively. There was a significant difference in NO concentration between preoperative data and postoperative day 3, and significant differences in total NO volume exhaled in 1 min between preoperative data and postoperative days 1 and 3. In conclusion, we showed that after lung resection, NO in the exhaled gas increases in concentration and total volume in unit time, which might be an important factor that prevents alteration of pulmonary circulation. Further careful study is necessary to clarify the mechanism and role of increased NO in exhaled gas after lung resection.