Time course of changes in lung mechanics following fetal steroid treatment

Lanteri, C.J., Willet, K.E., Kano, S., Jobe, A.H., Ikegami, M., Polk, D.H., Newnham, J.P., Kohan, R., Kelly, R. and Sly, P.D. (1994) Time course of changes in lung mechanics following fetal steroid treatment. American Journal of Respiratory and Critical Care Medicine, 150 3: 759-765.

Author Lanteri, C.J.
Willet, K.E.
Kano, S.
Jobe, A.H.
Ikegami, M.
Polk, D.H.
Newnham, J.P.
Kohan, R.
Kelly, R.
Sly, P.D.
Title Time course of changes in lung mechanics following fetal steroid treatment
Journal name American Journal of Respiratory and Critical Care Medicine   Check publisher's open access policy
ISSN 1073-449X
1535-4970
Publication date 1994-09
Sub-type Article (original research)
Volume 150
Issue 3
Start page 759
End page 765
Total pages 7
Place of publication New York, NY, United States
Publisher American Thoracic Society
Language eng
Formatted 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 betamethasone 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 (τ) 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. These animals were analyzed separately. The lambs receiving medium- or high-dose (24 and 48 h predelivery) betamethasone had significantly lower elastance and a trend toward lower resistance when compared with the control groups. Ten minutes after delivery, the animals that developed PIE all had elastance values comparable to that of the control animals despite corticosteroid treatment. When mechanics were corrected for absolute lung volume, only the high-dose group treated 24 h predelivery demonstrated a difference in specific elastance and specific resistance. This suggests that the changes in mechanics observed after prenatal corticosteroid treatment are due to an increase in lung size rather than a change in the properties of the tissues. This conclusion is supported by the similarities in τ. Furthermore, these data suggest that improvements in resistance from corticosteroid treatment may be due to an increase in lung volume rather than an increase in absolute airway size.
Keyword Rabbit lung
Corticosteroids
Responses
Ventilation
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Medicine Publications
 
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Created: Wed, 17 Nov 2010, 11:37:10 EST