Am. J. Respir. Crit. Care Med.,
Volume 162, Number 3, September 2000, 1087-1094
Pulmonary Interstitial Emphysema 24 Hours after
Antenatal Betamethasone Treatment in Preterm Sheep
KAREN E.
WILLET,
ALAN H.
JOBE,
MACHIKO
IKEGAMI,
JOHN
NEWNHAM,
and
PETER D.
SLY
Division of Clinical Sciences, TVW Telethon Institute for Child Health Research, Perth, Australia; Division of Pulmonary Biology, Children's Hospital
Medical Center, Cincinnati, Ohio; and Department of Obstetrics, University of Western Australia, Perth, Australia
During a series of studies investigating the maturational response
to antenatal glucocorticoids, we observed that 70% of lambs delivered at 128 d gestation (term = 150 d), 24 h after a single injection of 0.5 mg/kg betamethasone or betamethasone + L-thyroxine (15 µg/kg), developed pulmonary interstitial emphysema (PIE), compared with less than 5% of control animals or animals delivered 48 h or 7 d after hormone treatment. This study examined
whether the lungs of animals that developed PIE were functionally
or structurally different from those that did not. Lambs were mechanically ventilated for 40 min after cesarean section delivery.
Hormone-treated animals with PIE were ventilated at similar peak
inspiratory pressure (PIP) to control animals, whereas those without PIE were able to be ventilated at significantly lower PIP. Volume-dependent elastance (E2V), which provides an index of overdistension during mechanical ventilation, was lowest in PIE animals.
Alveolar architecture was distorted in almost all ventilated animals, the most severe distortion occurring in PIE animals. There
was no evidence of excessive alveolar wall thinning in PIE animals,
although parenchymal collagen was 30% lower, and elastin 120%
higher than in control animals. PIE was associated with structural
differences, but not with overventilation.
