VULNERABILITY OF RESPIRATORY CONTROL IN HEALTHY PRETERM INFANTS PLACED SUPINE

Objective: We tested the hypothesis that healthy preterm infants have attenuated ventilatory responses to hypercapnia, associated with a dec reased rib cage contribution to ventilation, in the supine versus pron e position. Study design: We elicited hypercapnic ventilatory response s from 19 healthy pre-term infants (postconceptional age 35 +/- 1 week s) who were being prepared for hospital discharge, The O-2 saturation was continuously monitored. Before and during CO2 rebreathing, ventila tion was measured with a nasal mask pneumotachygraph and was derived f rom chest wall motion as determined by respiratory inductance plethysm ograph. This measuring method allowed us to compare both ventilation a nd the percentage rib cage contribution to ventilation between supine and prone positions, Statistical analysis employed analysis of varianc e with repeated measures. Results: The supine position was associated with a higher respiratory rate (p <0.02) and lower O-2 saturation (p < 0.007) than the prone position. The increase in ventilation in respons e to hypercapnia was lower in the supine than in the prone position. T his was statistically significant for the respiratory inductance pleth ysmograph (p <.008) but not the pneumotachygraph (p=0.077), and was as sociated with a smaller rib cage contribution to ventilation in the su pine than in the prone position (p <0.0001). Conclusion: Respiratory c ontrol may be vulnerable when healthy preterm infants are placed supin e. Widespread avoidance of the prone position may not be appropriate f or such patients.