Differing patterns of mechanical response to direct fetal hormone treatment

Abstract

A single combined intramuscular dose of betamethasone and l-thyroxine (T4) or placebo was injected into the shoulder of fetal lambs 48 hours prior to delivery at days 121 (n = 14), 128 (n = 25) or 135 (n = 20) of gestation. Respiratory mechanics were calculated using multiple linear regression analysis. Both respiratory system resistance (R(RS)) and elastance (E(RS)) decreased approximately 4 fold between gestational days 121 (D121) and 135 (D135). Both variables were also reduced by hormone treatment. Reduction in E(RS) was due to a reduction in both lung (E(L)) and chest wall (E(W)) components. In absolute terms E(W) decreased with gestational age; however, E(W) as a proportion of total el..