Predictive value of measurements of respiratory mechanics in preterm infants with HMD

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Abstract
Conventional methods for measuring respiratory mechanics model the respiratory system as a single compartment. The interrupter technique allows the respiratory system to be considered as a two compartment model with “flow resistance” of the conducting airways (Pinit), calculated from the initial pressure drop (Pinit), considered separately from Pdiff, as a measure of the viscoelastic properties of the lung and chest wall and any pendelluft present. The pulmonary mechanics of 50 intubated and mechanically ventilated preterm infants (≤1500 g) were studied during the first week of life using conventional methods and the interrupter technique to determine whether it was possible to predict which infants would develop bronchopulmonary dysplasia (BPD). Pulmonary mechanics of preterm infants intubated and ventilated for apnea of prematurity were also studied. The dynamic compliance of the respiratory system (Crsdyn) was significantly lower on day 1 (PPrs), Rinit, or Pdiff between BPD and no‐BPD groups. However, Pdiff was significantly higher in infants with HMD, regardless of the outcome, when compared to the infants ventilated for apnea of prematurity. This suggests that the pathology of HMD is distal to the conducting airways and significantly alters the viscoelastic properties of the lung on day 1. Using stepwise logistic regression, Crsdum on day 1 and birth weight or gestational age were significant independent predictors of the development of BPD, correctly classifying 92% of infants. Due to the correlation between birth weight and gestational age (r = 0.72, Prsdyn is a better independent predictor of the development of BPD in preterm infants with HMD than gestational age or birth weight. Pediatr Pulmonol. 1993; 16:116–123.