Position and ventilatory response to added dead space in prematurely born infants

Objectives: Prematurely born infants are at increased risk of sudden infant death syndrome (SIDS) if slept prone. Working Hypothesis: Prematurely born infants would have an impaired response to an added dead space and lower respiratory muscle strength in the prone compared to the supine position. Study design: Prospective study. Patient-Subject Selection: Twenty-five infants, median gestational age of 30 (range 26-32) weeks. Methodology: The infants were studied supine and prone at a median of 36 weeks postmenstrual age. Breath by breath minute volume was measured at baseline and after a dead space was incorporated into the breathing circuit; the time constant of the response was calculated. The maximum inspiratory occlusion pressure generated (MIOP) and the pressure generated over the first 100 msec (P0.i) during airway occlusion were assessed. Results: The median time constant was longer (26 (range 8-106) sec vs. 22 (range 6-92) sec (P=0.045)) and the median MIOP (P=0.001) and P0.1 (P=0.003) were lower in the prone compared to the supine position. Conclusion: Prematurely born infants have a dampened response to tube breathing and reduced respiratory muscle strength in the prone compared to the supine position, which may contribute to their increased vulnerability to SIDS in the prone position.