Ventilation in Extremely Preterm Infants and Respiratory Function at 8 Years

BACKGROUND Assisted ventilation for extremely preterm infants (<28 weeks of gestation) has become less invasive, but it is unclear whether such developments in care are associated with improvements in short-term or long-term lung function. We compared changes over time in the use of assisted ventilation and oxygen therapy during the newborn period and in lung function at 8 years of age in children whose birth was extremely premature. METHODS We conducted longitudinal follow-up of all survivors of extremely preterm birth who were born in Victoria, Australia, in three periods - the years 1991 and 1992 (225 infants), 1997 (151 infants), and 2005 (170 infants). Perinatal data were collected prospectively, including data on the duration and type of assisted ventilation provided, the duration of oxygen therapy, and oxygen requirements at 36 weeks of age. Expiratory airflow was measured at 8 years of age, and values were converted to z scores for age, height, ethnic group, and sex. RESULTS The duration of assisted ventilation rose substantially over time, with a large increase in the duration of nasal continuous positive airway pressure. Despite the increase in the use of less invasive ventilation over time, the duration of oxygen therapy and the rate of oxygen dependence at 36 weeks rose, and airflows at 8 years of age were worse in 2005 than in earlier periods. For instance, for 2005 versus 1991-1992, the mean difference in the z scores for the ratio of forced expiratory volume in 1 second to forced vital capacity was -0.75 (95% confidence interval [CI], -1.07 to -0.44; P<0.001), and for 2005 versus 1997 the mean difference was -0.53 (95% CI, -0.86 to -0.19; P = 0.002). CONCLUSIONS Despite substantial increases in the use of less invasive ventilation after birth, there was no significant decline in oxygen dependence at 36 weeks and no significant improvement in lung function in childhood over time.