ABSTRACT
Objective:
To explore the effects of prenatal
dexamethasone (DEX), postnatal
pulmonary surfactant (PS) and respiratory support on the
lung fluid clearance in premature
rabbits at
gestational age (GA) of 25-28 d (full term 31 d) and their relationship with dynamic
compliance of
respiratory system (Cdyn), pulmonary morphology and other
parameters.
Methods:
In our previous
publications, premature
rabbits were divided into four groups according to the intervention strategy
control group, PS-only group, DEX-only group and DEX+PS group in which data of several
parameters including wet-to-dry
lung weight ratio (W/D), Cdyn and volume density of alveoli (Vv) were retrieved and the
lung tissue sections were scanned to recalculate the ratio of perivascular sheath to vascular sectional area (S/V) and
lung injury scores-
edema (LIS-E). W/D, LIS-E, S/V and Vv were adjusted for
birth weight (BW) (divided by BW, represented as W/D/BW, LIS-E/BW, S/V/BW and Vv/BW) and mean Cdyn (Cdyn-m) was adopted. Based on the grouping of previous studies, the intervention groups in this study were divided as DEX group and non-DEX group, and PS group and non-PS group to analyze the influence of DEX and PS on the above
parameters. Two independent samples t-test, one-way
analysis of variance,
LSD test, Kruskal-Wallis H
test, Mann-Whitney U test and Pearson correlation
analysis were used for
statistical analysis.
Results:
A total of 196
newborn rabbits receiving
mechanical ventilation after
birth were included in this study. (1) Effects of DEX compared with the non-DEX group, the DEX group showed increased W/D/BW (489±69 vs 421±113, t=－2.09), LIS-E/BW (188±57 vs 138±55, t=－2.61) and Vv/BW (20.1±4.9 vs 14.2±4.7, t=－3.60), but decreased S/V (0.33±0.23 vs 0.51±0.25, t=2.23) and S/V/W/D (0.05±0.03 vs 0.07±0.04, t=2.22) at 25 d of
gestation; at 26 d of
gestation, W/D/BW (472±76 vs 303±44, t=－8.75), LIS-E/BW (189±63 vs 106±36, t=－5.23), Cdyn-m [(0.16±0.07) vs (0.05±0.03) ml/(kg?cmH 2O), 1 cmH 2O=0.098 kPa; t=－7.29] and Vv/BW increased (22.4±5.0 vs 12.2±3.8, t=－7.46), while S/V (0.23±0.19 vs 0.62±0.38, t=4.10), S/V/BW (15.7±12.4 vs 25.7±17.3, t=2.20), S/V/W/D (0.03±0.03 vs 0.08±0.05, t=3.92) and
propensity scores decreased [(12.5±1.2) vs (15.1±1.2) scores, t=7.00]; at 27 d of
gestation, Cdyn-m increased [(0.23±0.12) vs (0.16±0.07) ml/(kg?cmH 2O), t=－2.43], but S/V (0.32±0.23 vs 0.57±0.39, t=2.57) and S/V/W/D decreased (0.05±0.04 vs 0.09±0.06, t=2.55); at 28 d of
gestation, W/D/BW (270±64 vs 162±33, t=－8.09), LIS-E/BW (72±32 vs 35±20, t=－5.17), S/V (0.90±0.60 vs 0.59±0.48, t=－2.81), S/V/BW (34.0±23.6 vs 15.2±12.7, t=－3.77) and Vv/BW increased (16.9±4.3 vs 9.2±2.9, t=－8.04); the differences were all statistically significant (all P<0.05). (2) Effects of PS compared with the non-PS group, the PS group had decreased LIS-E/BW at 25, 26 and 27 d of
gestation, increased Cdyn-m and Vv/BW at 25 and 27 d of
gestation and higher
propensity scores at 25 d of
gestation (all P<0.05). (3) The correlation between
gestational age and each index
gestational age was positively correlated with S/V ( r=0.31, P<0.05), but negatively correlated with W/D/BW and LIS-E/BW ( r=－0.73 and－0.63, both P<0.05).
Conclusions:
The pharmacological action of prenatal DEX on
lung fluid clearance is mainly confined to preterm
rabbits at the GA of 28 d which is supported by
mechanical ventilation. Prenatal
treatment with DEX and/or postnatal PS can improve the early respiratory function in preterm
rabbits between GA of 25-27 d, but had no substantial impact on
lung fluid clearance. The GA-related
lung maturation appears to
play a crucial
role, in comparison with medications, in
lung fluid clearance.
