Pressure-volume curves, static compliances and gas exchange in hyaline membrane disease during conventional mechanical and high-frequency ventilation

Abstract

Eight premature infants with hyaline membrane disease needing artificial ventilation were studied at a mean age of 26.5 h. After a preparative phase they were randomly assigned either first to conventional mechanical ventilation (CMV; delivered by a Siemens Servo 900 C), followed by high-frequency ventilation (HFV; delivered by Percussionaire VDR 1 at 10 Hz) or vice versa, each period lasting 4h. At the end of each period, arterial blood gases, lung volumes and alveolar pressures (Palv) during CMV or HFV and pressure-volume (P-V) curves of the total respiratory system were determined. Expiratory volumes were measured spirometrically, Palv by the clamping method, and the P-V curve was constructed by the syringe method. Single point static compliance at end-inspiration was higher during HFV (0.40±0.10 vs. 0.32±0.08 ml/cmH₂O·kg^-1; p=0.02), whereas at end-expiration no difference was noted. Two points static compliances were also better during HFV than during CMV (0.32±0.08 vs. 0.24±0.06 ml/cmH₂O·kg^-1; p=0.01). Static compliances derived from the steepest part of the inflation limb of the P-V curve were 0.55±0.12 after CMV and 0.50±0.12 ml/cmH₂O·kg^-1 after HFV (n.s.). Compared to CMV, HFV resulted in similar oxygenation and CO₂-elimination at equal mean lung volumes, but at significantly lower mean Palv. It is concluded that recruitment of lung volume is achieved with less static recoil pressure by HFV. These findings are explained by differences in inspiration allowing more time for volume recruitment during HFV.