Postnatal changes in transdiaphragmatic pressure in piglets

Abstract

We examined diaphragmatic force output in 25 anesthetized piglets ranging in postnatal age from 4 to 21 days (weight 1.3-4.0 kg) in order to determine whether the diaphragm produces greater force output with maturation for a given level of neural input. Transdiaphragmatic pressure (Pdi) served as our index of diaphragmatic force output and was measured during "supramaximal" trans-venous phrenic nerve stimulation at 100 Hz in order to control neural drive. Mean Pdi was 53 ± 17 cm H2O and ranged from a minimum of 29 cm H2O to a maximum of 83 cm H2O. A significant positive correlation between Pdi and postnatal age was observed (r = 0.79, p < 0.001). In addition, positive correlations were noted between Pdi and total body weight (r = 0.73, p < 0.001) and Pdi and diaphragmatic wet weight (r = 0.77, p < 0.001). The voltage needed to stimulate the phrenic nerves "supramax-imally" did not correlate with postnatal age (r = 0.02, p = 0.16). We conclude that a developmental pattern of increasing Pdi with increasing postnatal age, total body weight, and diaphragmatic wet weight exists in piglets and occurs within the context of a controlled level of neural drive. © 1986 International Pediatric Research Foundation, Inc.