Objective To investigate a method of minimally invasive surfactant therapy (MIST) to be used in spontaneously breathing preterm infants on continuous positive airway pressure (CPAP), evaluating the feasibility of the technique and the therapeutic benefit after MIST.

Design Non-randomised feasibility study.

Setting Tertiary neonatal intensive care unit.

Patients and interventions Study subjects were preterm infants with respiratory distress supported with CPAP, with early enrolment of 25–28-week infants (n=11) at any CPAP pressure and fractional inspired O₂ concentration (FiO₂), and enrolment of 29–34-week infants (n=14) at CPAP pressure ≥7 cm H₂O and FiO₂ ≥0.35. Without premedication, a 16 gauge vascular catheter was inserted through the vocal cords under direct vision. Porcine surfactant (∼100 mg/kg) was then instilled, followed by reinstitution of CPAP.

Measurements and results Respiratory indices were documented for 4 h following MIST, and neonatal outcomes ascertained. In all cases, surfactant was successfully administered and CPAP re-established. Coughing (32%) and bradycardia (44%) were transiently noted, and 44% received positive pressure inflations. There was a clear surfactant effect, with lower FiO₂ after MIST (pre-MIST: 0.39±0.092 (mean±SD); 4 h: 0.26±0.093; p<0.01), and a modest reduction in CPAP pressure. Adverse outcomes were few: intubation within 72 h (n=3), pneumothorax (n=1), chronic lung disease (n=3) and death (n=1), all in the 25–28-week group. Outcome was otherwise favourable in both gestation groups, with a trend towards reduction in intubation in the first 72 h in the 25–28-week infants compared with historical controls.

Conclusions Surfactant can be effectively delivered via a vascular catheter, and this method of MIST deserves further investigation.