Closure of patent ductus arteriosus and respiratory function changes in ventilated preterm infants

Active treatment of a haemodynamically significant patent ductus arteriosus (PDA) can be undertaken either pharmacologically or surgically. The effect of PDA treatment on respiratory function and ventilation parameters has not been adequately described. We aimed to report respiratory function changes following PDA treatment using composite respiratory physiological indices.

Retrospective cohort study of ventilated infants born before 30 weeks of gestational age, over two years at the tertiary Neonatal Unit of King's College Hospital, London, UK. The fraction of inspired oxygen (F_IO₂), ventilation to perfusion ratio (V_A/Q), right-to-left shunt and arterial to end tidal carbon dioxide gradient were calculated before and after successful pharmacological or surgical treatment of PDA.

Thirty-nine infants (21 male) were included with a median (IQR) gestational age of 24.8 (23.6 - 26.1) weeks, and birth weight of 685 (580 - 820) gr. The infants were treated for PDA on the 9th (6th - 12th) day of life. The F_IO₂ significantly increased post-treatment [0.42 (0.27 - 0.62)] compared to pre-treatment [0.30 (0.25 - 0.38), p = 0.010]. The V_A/Q and shunt significantly decreased post-treatment compared to pre-treatment [0.27 (0.17 - 0.43) versus 0.40 (0.26 - 0.57), p = 0.034 and 0 (0 - 3) % versus 5 (1 - 11) % respectively]. The carbon dioxide gradient was not significantly different post-treatment compared to pre-treatment.

PDA treatment in ventilated preterm infants was associated with an increase in the oxygen requirement during ventilation, a worsening of the ventilation to perfusion matching while it had a positive effect in reducing the level of the intrapulmonary right-to-left shunting.