Effect of inhaled nitric oxide on respiratory mechanics in ventilated infants with RSV bronchiolitis

Objective: To evaluate the bronchodilator effect of inhaled nitric oxide (N O) in infants with respiratory failure caused by respiratory syncytial viru s (RSV) bronchiolitis and to compare the effect with the one obtained by sa lbutamol. Design: Prospective study. Setting: Pediatric intensive care unit of a university children's hospital. Patients: Twelve acutely ill, intubated infants (mean age 4.5 months, mean weight 4.9 kg) with respiratory failure due to documented RSV bronchiolitis . Interventions: Total respiratory system resistance (Rrs) was measured by si ngle breath occlusion at the baseline and after inhaling NO at 20, 40 and 6 0 ppm for 1 h, and after inhalation of a standard beta(2)-agonist, salbutam ol. Arterial blood gas analysis was performed at each study level on 6 of t he 12 patients, Results: The baseline mean Rrs (SE) was 0.29 (0.04) cm H2O/ml per s. At eac h dose of NO, the mean Rrs (SE) was 0.28 (0.04) cm H2O/ml per s. With salbu tamol, the mean Rrs (SE) was 0.21 (0.03) cm H2O/ml per s. These values were not significantly different from each other (by ANOVA). Inhaled NO produce d a significant decrease in Rrs of greater than 4 times the coefficient of variation of the baseline measurement in 3 of 12 patients. Seven of 12 pati ents had no significant change while two patients had a significant increas e in Rrs, Inhaled salbutamol produced a significant decrease in Rrs in 5 of 11 patients, while 6 showed no change in Rrs. Conclusion: Inhaled NO has no apparent bronchodilator effect in the majorit y of acutely ill infants with RSV bronchiolitis and does not appear to prov ide any additional benefit over the use of salbutamol. The clinical benefit of inhaled NO as a bronchodilator is questionable under these conditions.