Abstract
The relationship of pulmonary minute volume to the prevailing oxygen consumption (V1/VO2), the convection requirement (CR) is a useful index of the overall efficiency of ventilation. This study was undertaken to determine the CR of healthy infants and the relationship of CR to the size and age of the infant. Continuous concurrent measurements of V1(bias flow pneumotachometry)and VO2 (open circuit indirect calorimetry) were made for 100 to 150 min. in 31 healthy infants, wt. 650 to 3380 grams, postconceptual age (PA)30 to 42 weeks. Spontaneous changes in V1 and VO2 followed changes in activity and feeding. Data were divided into 3 min. intervals and linear regression analysis of mean V1 vs mean VO2 and first differences, (ΔV1 vs ΔVO2)were performed following time series correction for lags. All infants showed significant positive correlations(V1 vs VO2 r=.79, mean slope=46, ΔV1 vs ΔVO2 r=.64, mean slope=37.2).
Mean regression analysis of the relationship between the slope of individual V1 vs VO2 regression lines(S) & the infants BW,age,PA,GA & study wt. demonstrated significant negative correlations between S & several indices of the size & age of the infant. The V1 associated with VO2=8.5 ml/min.kg for individual infants was also negatively correlated with size and wt.
We conclude that smaller & younger infants are at a relative disadvantage because of high CR,ie.they require a larger V1 for a given VO2 & relatively greater increases in V1 to meet increases in VO2. Measurement of CR should prove useful as a pulmonary function test in neonates with & without respiratory diseases.
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Schulze, K., Stefanski, M. & James, L. 1720 YENTILATORY EFFICIENCY OF NEONATES. Pediatr Res 15 (Suppl 4), 730 (1981). https://doi.org/10.1203/00006450-198104001-01739
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DOI: https://doi.org/10.1203/00006450-198104001-01739