title: The effect of gestational age on the effective elastance of the respiratory system in neonates.
abstract: We measured the effective elastance of the respiratory system (E'RS) in 38 "healthy" neonates, gestational ages ranging from 28-42 weeks. E'RS was calculated by dividing the inspiratory pressure generated after nasal occlusion by the tidal volume of the breath preceding occlusion (E'RS = P/VT). E'RS decreased from 790 +/- 0.070 cm H2O/liter at 30.4 +/- 0.4 weeks of gestation to 520 +/- 0.030 at 34.5 +/- 0.3 weeks (P less than 0.01); then to 340 +/- 0.020 at 40 +/- 0.2 weeks (P less than 0.01). E'RS corrected for lung volume ("specific" E'RS) were 32 +/- 2,32 +/- 4, and 28 +/- 2 cm H2O at the above gestational ages, respectively (P greater than 0.05). We suggest: (1) the increased E'RS observed in preterm infants is lung volume dependent. Changes in lung volume may alter the geometry of the thorax, and therefore, the force/length characteristics of the respiratory muscles; (2) this increased E'RS is not of much benefit to preterm infants who have little respiratory stability when E'RS is maximum; and (3) if E'RS is an index of mechanical stability, apnea in preterm infants is independent of the mechanical properties of the respiratory system.
mesh_terms: D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007320:Inspiratory Capacity; D008176:Lung Volume Measurements; D012119:Respiration; D012143:Respiratory Physiological Phenomena