Results:
Forty-three subjects were identified (23 continuous, 20 intermittent dosing). There were no statistically significant differences between groups in gender or gestational age, but higher baseline inspired oxygen (FiO2) and VIS in the continuous group suggested a higher baseline severity of illness (p =0.012). After sildenafil initiation, there were no significant differences in the change in blood pressure, oxygen saturation, FiO2, or VIS between groups, and no difference in the number of subjects requiring discontinuation due to side effects (4 in the continuous group, 1 intermittent, p =0.35). Eight subjects (34.8%) in the continuous group and 3 (15%) in the intermittent group died (p =0.024).