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 < 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, body surface area, and the Quetelet index (body weight/length), 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.