Effect of body position on tidal volume and minute ventilation in very low birthweight infants

Background: To progress the clinical treatment of neonates, especially in the management of respiration, we have to be able to measure their pulmonary function appropriately. Various methods have been developed, but little is known about the pulmonary function of very low birthweight infants (VLBWI) because of the difficulty in taking their measurements with existing equipment. We have developed a very low dead space pneumotachograph to measure lung function in VLBWI. Methods and results: We used our pneumotachograph on 30 infants each weighing less than 1500 g at birth. The infants were intubated with endotracheal tubes of 2.5 or 2.0 mm diameter to measure tidal volume and minute ventilation in the prone and supine position. The tidal volume in the supine position was 6.99 ± 0.42 mL/kg and 7.58 ± 0.38 mL/kg in the prone position (mean ± SE). The tidal volume was significantly larger in the prone than the supine position (P < 0.05). However, no significant difference was observed in minute ventilation and respiratory rates. Conclusion: The tidal volume significantly increased in the prone position in VBLWI, confirming the previous observation of larger healthy infants is also applicable to the very low birthweight infants.