1849 TOTAL RESPIRATORY SYSTEM COMPLIANCE IN INFANTS WITH CYSTIC FIBROSIS

Abstract

In the only study to measure dynamic pulmonary compliance (C) in cystic fibrosis infants (CFI) it was low. Esophageal catheters were used, but these are invasive and may be inaccurate due to chest wall distortion. We evaluated weighted spirometry technique for measuring total respiratory system compliance (Crs) in CFI. We studied during sleep 5 CFI and 9 normal controls (NC) mean ages 6.1 and 6.2 months. We tested respiratory rate (RR), functional residual capacity (FRC) by helium dilution, mixing index (MI), specific total respiratory system compliance, Crs'=Crs/FRC, and size corrected flows (VmaxFRC/FRC) by rapid chest compression.CFI had lower Crs' than NC but similar flows. In the absence of small airways dysfunction, the low Crs' and higher RR in CFI could result from increased elastic recoil since Crs' should be quasi static after equilibration of pressure to all lung units. However, the low MI and high FRC in CFI indicates small airway dysfunction. Thus, the low Crs may be secondary to frequency dependence. We conclude that Crs is low in CFI and represents a non-invasive method for assessing early pulmonary dysfunction. Supported by NIH Grant #HL01322-01, HL990-03 and ALA Fellowship.