Preterm rabbit lung tissue mechanics: maturational changes and effect of antenatal steroids.
OBJECTIVE
Describe lung tissue and central airway mechanics using forced oscillation in preterm rabbits at different gestational ages and after maternal administration of betamethasone (BM).


METHODS
One hundred twelve fetuses from 54 does were studied. Ventilation was done using a Flexivent (Scireq, Montreal, Canada). Resistance (Rrs), compliance/bodyweight (Crs/bw), Newtonian resistance (Rn), tissue damping (G(L)), and elastance (H(L)) were assessed. Maturational changes were studied in normal controls at days 27-31. The effect of BM (0.05 mg/kg on days 25 and 26) or placebo was studied in preterm fetuses at days 27, 28, and 29.


RESULTS
In unmanipulated control fetuses, Rrs decreased and Crs/bw increased with advancing gestation. Rn remained stable while G(L) and H(L) decreased. After day 29 no differences in pulmonary mechanics were observed. At 28 days Rrs and Crs/bw in BM and placebo fetuses were better compared to controls. At 29 days, Crs/bw and Rrs were higher, respectively, lower in control fetuses than BM or placebo exposed pups.


CONCLUSIONS
Maturational changes in preterm rabbits occur mainly up to day 29 of gestation and are largely due to changes in tissue mechanics. Maternal BM injection improves lung mechanics at 28 days but placebo has equal effects.
Centre for Surgical Technologies, Faculty of Medicine, Katholieke Universiteit Leuven, Leuven, Belgium.
Anne
A
Debeer
Andreas W
AW
Flemmer
Paul J
PJ
Lewi
Stijn
S
Beheydt
Frederik
F
De Buck
Luc J
LJ
Zimmermann
Gunnar
G
Naulaers
Jan A
JA
Deprest
D000818:Animals; D001623:Betamethasone / Q000494:pharmacology*; D005865:Gestational Age; D005938:Glucocorticoids / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects* / Q000196:embryology*; D023421:Models, Animal; D011817:Rabbits; D011897:Random Allocation; D012016:Reference Values; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*
D005938:Glucocorticoids; D001623:Betamethasone