Respiratory outcome in preterm ventilated infants: importance of early respiratory system resistance

Abstract

Since severity of acute respiratory distress syndrome (RDS) has been decreasing, the aetiology of long-term respiratory problems may have changed in preterm infants. We investigated whether early neonatal respiratory resistance (Rrs) and compliance (Crs) were important determinants of respiratory morbidity and lung function abnormalities during the 1st year of life in ventilated preterm infants. In 70 infants of less than 37 weeks gestation, mechanically ventilated within 24 h after birth, Rrs and Crs were assessed daily during the first 3 days of life and medians were calculated subsequently (Rrsneo and Crsneo). Rrs and Crs were reassessed 1 year later in 57 of 70 infants (Rrs(1 year) and Crs(1 year)). After correction for endotracheal tube size, increased Rrsneo was significantly related to respiratory morbidity during the 1st year of life (OR 1.20, 95% CI 1.04 to 1.38; P = 0.013), increased Rrs(1 year) (multiplicative beta per kPa/l x s 1.017, 95% CI 1.000 to 1.034; P = 0.045), and decreased Crs(1 year) (multiplicative beta per kPa/l x s 0.986, 95% CI 0.974 to 0.998; P = 0.023). Associations were not adversely affected by degree of prematurity, neonatal disease and treatment. Crsneo did not show any significant associations. In the current surfactant era, increased Rrsneo, and not Crsneo was associated with poor respiratory outcome during the 1st year of life in preterm ventilated infants. Relationships were not adversely affected by measures reflecting degree of prematurity, neonatal disease, and ventilator conditions.

Conclusion: our results indicate that inborn properties of the respiratory system have become increasingly important in relation to respiratory outcome instead of neonatal disease and treatment conditions.