Time course of changes in lung mechanics following fetal steroid treatment

American Journal of Respiratory and Critical Care Medicine
C J LanteriP Sly

Abstract

We studied the effect of a single-dose, corticosteroid treatment on preterm lambs (gestational age: 128 d). A low, medium, or high betamethasone dose (0.1, 0.5, and 2.0 mg/kg) or saline control was administered directly to the fetus by ultrasound-guided intramuscular injection 48 h before delivery. A second group received either the high dose of betamethasome or saline 24 h before delivery. The lambs were delivered at 128 d gestation, anesthetized with ketamine, and ventilated for 50 min. Respiratory system elastance and resistance were measured at 10-min intervals using multiple linear regression analysis of pressure, flow, and volume. Similarly, estimates of lung mechanics were calculated from transpulmonary pressure. The viscoelastic time constant (tau) was calculated by fitting an exponential to the pressure changes occurring after occluding the airway during expiration. Excised lung volume at 40 cm H2O and lung weight were used to calculate specific elastance and resistance correcting for lung size using volume or weight, respectively. Of the 13 lambs in the 48-h high-dose betamethasone group, five developed pulmonary interstitial emphysema (PIE) as did 3 of 11 animals in the high-dose group treated 24 h before delivery. T...Continue Reading

Citations

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