EFFECT OF CHESTWALL DISTORTION ON THE MEASUREMENT OF PULMONARY MECHANICS IN PRETERM INFANTS

The purpose of this study was to determine the effect of chestwall dis tortion (CWD) on the measurement of pulmonary compliance (C-L) and res istance (R(L)). Inductance plethysmography was used in 15 preterm infa nts to determine CWD as total compartmental displacement ratio (TCDR) and out of phase movement between ribcage and abdomen as phase shift ( PS). Flow was measured by pneumotachography and esophageal pressure ch ange (Pe) with a water-filled catheter. C-L and R(L) were calculated b y linear regression analysis. Seven infants (mean +/- SD: BW, 1,484 +/ - 186 g, GA 32.4 +/- 2.2 weeks, age 8.7 +/- 4.7 days) had a breathing pattern characterized by episodes with a high degree of CWD, followed by periods with minimal CWD (distortion group). In this group lung fun ction measurements were analyzed separately during periods with and wi thout CWD. The remaining 8 infants (BW, 1,244 +/- 233 g, GA 30.4 +/- 2 .4 weeks, age 7.4 +/- 3.1 days) always breathed with minimal CWD, and the measurements in this group (non-distortion group) were used as a r eference for the values obtained in the distortion group. Measurements of TCDR, PS, C-L, R(L), and tidal volume (V-T) obtained in the absenc e of CWD were not significantly different between distortion and non-d istortion groups. The measurements obtained in the presence of CWD sho wed a significantly higher TCDR and PS, but C-L and R(L) were not sign ificantly different from the C-L and R(L) measurements obtained in the distortion and non-distortion groups in the absence of CWD. The only significant effect of CWD was a reduction in V-T. The results indicate that the moderate degree of CWD observed in the study population does not significantly contribute to the variability in C-L and R(L) measu rements in preterm infants. (C) 1995 Wiley-Liss, Inc.