Association of bronchopulmonary dysplasia and hypercarbia in ventilated infants with birth weights of 500–1,499 g
Bronchopulmonary dysplasia (BPD) continues to be a major pulmonary complication in very low birth weight (VLBW) and extremely low birth weight (ELBW) survivors of neonatal intensive care units (NICUs). Many factors including partial pressures of carbon dioxide (Paco 2) have been implicated as possible causes. Permissive hypercapnia has become a more common practice in ventilated infants, but its effect on BPD is unclear. The hypothesis of this study was that hypercarbia is associated with increased BPD in infants with birth weights of 500–1,499 g. Nine hospitals were involved in this observational cohort study. Maternal and infant information including socio-demographics, antenatal steroids, gender, race, gestational age, birth weight, intubation and ventilator status, physiologic variables and data on therapies were collected by chart abstraction. SNAP scores were assigned. Candidate BPD risk factors, including cumulative exposures derived from blood gas and ventilation data in the first 6 days of life, were identified. Risk models were developed for 425 preterm infants who survived to 36 weeks post-menstrual age. BPD occurrence was associated with the cumulative burden of MAP >0 cm H2O in the first 6 days of life (P < 0.0001). After adjustment for the burden of MAP, the occurrence of hypercarbia (Paco 2 >50 torr) was associated with a greater incidence of BPD (P = 0.024). Among 293 intubated, mechanically ventilated infants, those with hypercarbia occurring only when MAP ?8 cm H2O, a scenario more comparable to permissive hypercapnia, also had increased BPD incidence compared to infants without hypercarbia (P = 0.0003). Hypercarbia during the first 6 days of life was associated with increased incidence of BPD in these infants. Mechanically ventilated infants with hypercarbia during low MAP also had a significant increase in BPD. Permissive hypercapnia in ventilated infants needs further close review before the practice becomes even more widespread.