Resonance frequency in respiratory distress syndrome

Aim-To observe how the resonance frequency changes with the course of respi ratory distress syndrome (RDS), by examining the effect of changing static compliance on the resonance frequency in premature infants. Methods-In 12 ventilated premature infants with RDS (mean gestational age 2 6.6 weeks, mean birth weight 0.84 kg), resonance frequency and static compl iance were determined serially using phase analysis and single breath mecha nics technique respectively in the first seven days of life. Results-The minimum number of measurements done in any one baby was three a nd maximum was five in this seven day study period. The first measurement i n each baby was done within the first 72 hours of life. The increase in com pliance in this period varied from 27% to 179%. The variation in the corres ponding resonance frequency was within 2 Hz in eight babies and within 6 Hz in all recruited babies. Conclusions-The resonance frequency of the respiratory system in preterm in fants with RDS remains remarkably constant in the early stages of the illne ss, despite relatively large changes in static compliance.