Bonnie S. Siner

Early randomized intervention with high-frequency jet ventilation in respiratory distress syndrome

To determine whether early use of high-frequency jet ventilation reduces neonatal mortality or pulmonary morbidity rates, we randomly selected 42 infants with clinical and radiographic evidence of severe respiratory distress syndrome to receive either high-frequency jet ventilation or conventional ventilation. Separate sequential analyses (two-sided, alpha = 0.05, power = 0.95 to detect 85:15 advantage) were performed for mortality rates, air leaks, bronchopulmonary dysplasia, intraventricular hemorrhage, and assignment crossover, and a combined analysis was performed, with death overriding other outcome variables. Enrollment was completed when the combined analysis reached the sequential design boundary indicating no treatment difference. Mortality rates (19% among infants receiving high-frequency jet ventilation vs 24% among infants receiving conventional ventilation), the incidence of air leaks (48% vs 52%), bronchopulmonary dysplasia (39% vs 41%), and intraventricular hemorrhage (33% vs 43%), and assignment crossovers (14% vs 24%) did not differs significantly between the treatment groups. We conclude that early use of high-frequency jet ventilation does not prevent or substantially reduce mortality or morbidity rates associated with assisted ventilation.

Effect of head position on distribution of nasal airflow in preterm infants

Supine preterm infants characteristically adopt a lateral head position; however, it is not known whether this influences the distribution of nasal airflow. Ventilation was measured in 12 healthy preterm infants (postconceptional age 34 +/- 2 weeks) by employing a nasal mask pneumotachygraph that separated airflow between the left and right nasal passages. In the midline supine position, the percent of total tidal volume (%VT) through the right nasal passage ranged from 31% to 64% and varied by less than 5% between active and quiet sleep in any infant. Lateral positioning of the head caused %VT to increase on the dependent side and decrease through the upper nasal passage. When the right side was dependent, mean %VT on that side increased from 52 +/- 9% to 67 +/- 14% (P less than 0.01) and decreased to 43 +/- 10% (P less than 0.05) when the right side was up. In the midline position, the presence of a nasogastric tube caused %VT through the nasal passage with the tube to fall from 54 +/- 8% to 39 +/- 8% (P less than 0.01). The %VT fell farther, to 25 +/- 10% (P less than 0.01), when the nasal passage with the nasogastric tube was up. Despite these changes in VT distribution, total VT remained constant during these maneuvers. We speculate that when supine preterm infants adopt a lateral head position, the decrease in airflow through the upper nasal passage results from partial obstruction of the oropharyngeal or nasopharyngeal airway on that side.