Tidal breathing in preterm infants receiving and weaning from continuous positive airway pressure.

OBJECTIVE: To compare tidal breathing on different continuous positive airway pressure (CPAP) devices and pressures and to serially measure tidal breathing during weaning off CPAP using electromagnetic inductive plethysmography. STUDY DESIGN: Using electromagnetic inductive plethysmography, tidal breathing was measured in 29 preterm infants receiving CPAP, gestational age 28 ± 2 weeks. Variable-flow nasal CPAP (nCPAP), bubble CPAP (bCPAP) at pressures of 5, 7, and 9 cmH2O, nasal bi-level positive airway pressure (nBiPAP) system at pressures of 5, 7/5, and 9/5 cmH2O, and unsupported breathing were studied. Twenty-one infants had weekly tidal breathing measurements on and off nCPAP. RESULTS: Minute volume (MV/kg) was similar between all devices (0.30-0.33 L/kg/min). On bCPAP, weight corrected tidal volume (VT/kg) was the least, changing little with increasing pressures. On nCPAP and nBiPAP, VT/kg increased with increasing pressure and the respiratory rate (fR) decreased. The delivered pressure varied slightly from the set pressure being most dissimilar on nBiPAP and similar on bCPAP. Compared with unsupported breathing, all devices decreased VT/kg, MV/kg, and phase angle, but did not alter fR. Serial tidal breathing measurements showed decreasing difference for VT/kg over time on and off nCPAP. CONCLUSIONS: At different pressure settings, on all CPAP devices the measured MV/kg was similar either through increasing VT/kg and decreasing fR (nCPAP and nBiPAP) or maintaining both (bCPAP). Serial tidal breathing measurements may aid weaning from CPAP.

Cardiovascular function in children who had chronic lung disease of prematurity.

OBJECTIVES: Although increased pulmonary arterial pressure is common in infancy in preterm infants who develop chronic lung disease of prematurity (CLD), it is unknown if the increase persists into childhood. We, therefore, assessed if 8-12-year-old children with documented CLD in infancy had evidence of right ventricular dysfunction or pulmonary arterial hypertension at rest or in response to acute hypoxia when compared to preterm and term-born controls. METHODS: We studied 90 children: 60 born at ≤32 weeks of gestation (28 with CLD and 32 preterm controls), and 30 term-born controls. All had echocardiography including myocardial velocity imaging, at rest and while breathing 15% oxygen and 12% oxygen for 20 min each. RESULTS: Baseline oxygen saturation, heart rate, blood pressure and echocardiographic markers of left and right ventricular function were similar in all three groups. While breathing 12% oxygen, the oxygen saturation decreased to 81.9% in the CLD group compared to 85.1% (p<0.05) and 84.7% (p<0.01) in the preterm and term controls, respectively. In response to hypoxia, all three groups showed increases in velocity of tricuspid regurgitation, end-diastolic velocity of pulmonary regurgitation, and right ventricular relaxation time; and decreases in pulmonary arterial acceleration time and the ratio of right ventricular acceleration time to ejection time. However, there were no differences between groups. CONCLUSIONS: Childhood survivors of CLD have comparable left and right ventricular function at 8-12 years of age to preterm and term-born children, and no evidence of increased pulmonary arterial pressure even after hypoxic exposure.