Ventilation in Preterm Infants and Respiratory Function

Andrea is a 30-year-old primigravida who is admitted to the hospital after premature rupture of membranes at 27 weeks’ gestation. You come to the floor to advise Andrea and her husband about how the baby (known to be a boy) will be monitored and managed, depending on how quickly Andrea goes into labor. We’ve come a long way in caring for neonates born at <28 weeks of gestation. You explain that the baby has a good chance of survival, but Andrea and her husband are understandably anxious and ask a lot of questions. In particular, they want to understand as much as they can about the long-term effects of the interventions that their baby might receive in the NICU.       

In this week’s issue of NEJM, Doyle et al. address at least one aspect of these concerns. The authors prospectively followed preterm infants (born at <28 weeks of gestation) in Victoria, Australia during three time periods: 1991-92 (n=225), 1997 (n=151), and 2005 (n=170). They collected data on the duration and modality of assisted ventilation and oxygen therapy requirements and assessed pulmonary function after 8 years.

Although the use of more invasive ventilation decreased over time (i.e., fewer patients were intubated), the duration of assisted ventilation increased, with a greater increase in the duration of nasal continuous positive airway pressure in infants born in later years. Oxygen dependence at 36 weeks and pulmonary function tests at age 8 years were worse in children born in 2005 than in those born in earlier years, indicating that lung function did not improve as the use of less invasive ventilation increased.       

The authors speculate that despite less invasive ventilation techniques, lung function outcomes are worsening over time in NICU survivors because the duration of assisted ventilation in premature infants has increased and physicians are initiating assisted ventilation at lower thresholds. They further speculate that longer periods of high oxygen delivery increase oxygen dependence and subsequently lead to worse lung function.

These results highlight the need for careful analyses of interventions that are performed in this early critical period of life. Even as interventions become less invasive, the damaging effects of new techniques are hard to predict. For now, you can reassure Andrea and her husband that you will do your best to minimize the duration of assisted ventilation (invasive or noninvasive), while still maintaining adequate oxygenation and aim to avert the long-term effects of neonatal interventions on lung function.

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Rachel is a fifth-year MD/PhD student at Harvard Medical School. She is originally from Okemos, MI, and graduated from Stanford University in 2011. For her PhD research, she is studying the regulation of cell growth in response to nutrients.