Compliance of the total respiratory system in healthy preterm and full-term newborns.

The compliance of the total respiratory system (CRS) was determined by the occlusion technique during expiration in 19 preterm newborns (NB) over 31 weeks of gestational age (mean, 34 +/- 1.5 SD) and in 20 full-term NB. Postnatal age ranged from 1 to 28 days. No sedation was used during the test. In absolute terms, CRS was significantly greater (P less than 0.01) in full-term than in preterm NB (3.17 +/- 0.71 ml/cm H2O vs 2.37 +/- 0.81 ml/cm H2O). When normalized for body weight, length cubed, [corrected] body surface area, and the Quetelet index (body weight/length squared) [corrected], CRS was similar in preterm and full-term NB. These results suggest that, normalized for biometric data, passive elastic properties of the total respiratory system are similar in full-term and preterm NB, at least in the gestation age range studied.