The effect of aminophylline on the excursions of the diaphragm in preterm neonates. A randomized double-blind controlled study.

Aminophylline is used to treat apnoea and to facilitate weaning from assisted ventilation in preterm infants. Aminophylline is thought to increase respiratory drive centrally. We performed a randomized controlled double-blind study to determine if aminophylline increases the excursions of the diaphragm indicating a possible direct peripheral effect. Twenty-two neonates were randomized to treatment with intravenous aminophylline (n = 11) or to no treatment (n = 11). An ultrasonographer, who was blinded to the group assignment, studied the diaphragmatic excursions using a real time sector scanner. The posterior one-third of the right hemidiaphragm was localized and M-mode was used to record the diaphragmatic excursions on paper. The neonates were studied in an awake but quiet state. Aminophylline resulted in an increase (43%) in the excursions of the diaphragm (p = 0.012) with no change in respiratory rate or pCO2. These findings indicate that aminophylline had a measurable effect on the diaphragmatic motion. Further studies combining this technique with other techniques are needed to determine if the main effect of aminophylline in the prevention of apnoea is mainly central or peripheral.