Postnatal dexamethasone (DEX) increases Functional Residual Capacity (FRC) and respiratory compliance (CRS) in both preterm females and males

We have previously reported that preterm intubated infants demonstrate a significant increase in FRC and CRS when given a 7 day weaning course of DEX (Ped Res1996;39:229). To our knowledge the effect of gender on UK response to DEX in terms of FRC or CRS has not been reported. We reviewed gender response to DEX in an ongoing blinded, randomized trial comparing the eftect of two dosing regimes of DEX (7 day weaning courses, starting at 0.5 mg/kg/day vs 0.2 mg/kg/day) on FRC and CRS given to intubated very low birth weight (VLBW) infants at 7 to 14 days of age. Twenty-two infants were female (mean BW=710 g; GA=25.6 wks; 64% Caucasian; 32% treated with prenatal corticosteroids; postnatal age =10.1 d; 50% getting 0.5 mg course of DEX; mean airway pressure=6.7 cm H2O; mean FIO₂>30%) and 26 were male (mean BW=847g; GA=25.7 wks, 50% Caucasian; 32% treated with prenatal corticosteroids; postnatal age =8.8 d; 62% getting 0.5 mg DEX; mean airway pressure=8.0 cm H₂O: mean FIO₂> 30%). Pulmonary function testing was done prior to DEX, and on days 2,5, and 7. FRC was measured with the nitrogen washout technique. A minimum of two measurements were performed with the neonate supine and quiet. A study was acceptable if the measurement had a coefficient of variation (CV) of < 10%.Crs was measured with the single breath occlusion technique (SensorMedics 2600). A minimum of 10 breaths with a C V of <20%. Values mean ± SEM. Baseline Day 2 Day 5 Day 7 FRC CRS FRC CRS FRC CRS FRC CRS Female 18.1 1.06 30.5* 1.51* 33.4* 1.61* 34.7* 1.80* Male 19.0 0.95 29.2* 1.28* 32.0* 1.22* 34.6* 1.68* *p<0.01 when compared to baseline for each measurement, FRC in ml/kg; Crs in ml/cm H2O/kg Our preliminary findings indicate that both intubated VLBW females and males show a significant increase in FRC and CRS during a one week weaning course of dexamethasone. We speculate that gender dose not appear to be an important factor on the response of VLBW infants to postnatal dexamethasone.