Barotrauma, oxygen toxicity, and chronic lung disease

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 H(2)O 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 H(2)O, 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.

Predictors of successful extubation of preterm low-birth-weight infants with respiratory distress syndrome

OBJECTIVE

The aim of the study was to measure pulmonary mechanics in infants with respiratory distress syndrome before extubation and to correlate pulmonary function values with successful extubation.

DESIGN

Clinical study.

SETTING

Neonatal intensive care unit.

PATIENTS

Fifty-one infants (birth weight, 1158.6 +/- 150.6 g; gestational age, 29.1 +/- 2.0 wks).

INTERVENTIONS

Ventilation and daily ventilatory management.

MEASUREMENTS AND MAIN RESULTS

Of the 51 infants studied, 35 (60.8%) were successfully extubated, whereas 16 (39.2%) required reintubation and mechanical ventilation within 72 hrs after extubation. All patients met the clinical and biochemical criteria for extubation. Variables of artificial ventilation before extubation were minimal in all the studied cases (Fio(2) </=0.4, inspiratory pressure </=20 cm H(2)O, ventilatory rate, </=10/min). Pulmonary mechanics were measured before extubation using a noninvasive, mobile VenTrak measuring station.

RESULTS

Significant differences in pulmonary function values between the groups were found. Lower resistance of airways and work of breathing and higher dynamic compliance, tidal volume, and minute ventilation before extubation were associated with successful extubation.

CONCLUSION

On the average, tidal volume values of >6 mL/kg, minute ventilation of >309 mL/kg/min, work of breathing of <0.172 J/L, dynamic compliance of >/=1 mL/cm H(2)O/kg, and resistance of airways of </=176 cm H(2)O/L/sec predicted successful extubation. We recommend measurement of pulmonary function as an assessment tool in determining readiness for extubation.