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

Objective: To evaluate the bronchodilator effect of inhaled nitric oxide (NO) in infants with respiratory failure caused by respiratory syncytial virus (RSV) bronchiolitis and to compare the effect with the one obtained by salbutamol. 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 single breath occlusion at the baseline and after inhaling NO at 20, 40 and 60 ppm for 1 h, and after inhalation of a standard β (2)-agonist, salbutamol. Arterial blood gas analysis was performed at each study level on 6 of the 12 patients. Results: The baseline mean Rrs (SE) was 0.29 (0.04) cm H(2)O/ml per s. At each dose of NO, the mean Rrs (SE) was 0.28 (0.04) cm H(2)O/ml per s. With salbutamol, the mean Rrs (SE) was 0.21 (0.03) cm H(2)O/ml per s. These values were not significantly different from each other (by ANOVA). Inhaled NO produced 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 patients had no significant change while two patients had a significant increase 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 majority of acutely ill infants with RSV bronchiolitis and does not appear to provide any additional benefit over the use of salbutamol. The clinical benefit of inhaled NO as a bronchodilator is questionable under these conditions.