Effect of Minimally Invasive Surfactant Therapy on Lung Volume and Ventilation in Preterm Infants

Objective To assess the changes in (regional) lung volume and gas exchange during minimally invasive surfactant therapy (MIST) in preterm infants with respiratory distress syndrome. Study design In this prospective observational study, infants requiring a fraction of inspired oxygen (FiO2 ) ≥0.30 during nasal continuous positive airway pressure of 6 cmH2 O were eligible for MIST. Surfactant (160-240 mg/kg) was administered in supine position in 1-3 minutes via an umbilical catheter placed 2 cm below the vocal cords. Changes in end-expiratory lung volume (EELV), tidal volume, and its distribution were recorded continuously with electrical impedance tomography before and up to 60 minutes after MIST. Changes in transcutaneous oxygen saturation (SpO2 ) and partial carbon dioxide pressure, FiO2 , respiratory rate, and minute ventilation were recorded. Results A total of 16 preterm infants were included. One patient did not finish study protocol because of severe apnea 10 minutes after MIST. In the remaining infants (gestational age 29.8 ± 2.8 weeks, body weight 1545 ± 481 g) EELV showed a rapid and sustained increase, starting in the dependent lung regions, followed by the nondependent regions approximately 5 minutes later. Oxygenation, expressed as the SpO2 /FiO2 ratio, increased from 233 (IQR 206-257) to 418 (IQR 356-446) after 60 minutes ( P