How safe is intermittent positive pressure ventilation in preterm babies ventilated from delivery to newborn intensive care unit?

Abstract

Objectives: To examine whether clinically determined ventilator settings will produce acceptable arterial blood gas values on arrival, in preterm infants ventilated from delivery to the newborn intensive care unit (NICU). Further, to examine the usefulness of tidal volume and minute ventilation measurements at this time.

Design: A prospective observational cohort study in a tertiary level 3 NICU.

Patients: Twenty six preterm infants requiring intubation and mechanical ventilation at the point of delivery to the NICU.

Setting: Infants who required mechanical ventilation were monitored with a blinded Ventrak 1550 dynamic lung function monitor from the point of delivery to the NICU. A Dräger Babylog 2000 transport ventilator was set up to achieve adequate chest wall movement, and Fio₂ was adjusted to achieve preductal Sao₂ of 90–98%. Dynamic lung function monitoring data were recorded and related to the arterial blood gas taken on arrival.

Results: Mean gestation was 28 weeks (range 23–34) and mean birth weight was 1180 g (range 480–4200). A quarter (26% (95% confidence interval (CI) 12% to 48%)) were hypocarbic, with 20% (95% CI 7% to 39%) below 25 mm Hg, and 38% (95% CI 20% to 60%) had hyperoxia. Some (20% (95% CI 7% to 39%)) were both hypocarbic and hyperoxic. Total minute ventilation per kilogram correlated significantly with the inverse of Paco₂ (p < 0.001).

Conclusions: Clinically determining appropriate mechanical ventilation settings from the point of delivery to the NICU is difficult, and inadvertent overventilation may be common. Severe hyperoxia can occur in spite of adjustment of the Fio₂ concentration to achieve an Sao₂ range of 90–98%. Limiting minute ventilation during resuscitation may prevent hypocarbia.