Rationale: The relationship between respiratory function at hospital discharge and the severity of later respiratory disease in extremely low gestational age neonates is not well defined. Objectives: To test the hypothesis that tidal breathing measurements near the time of hospital discharge differ between extremely premature infants with BPD or respiratory disease in the first year of life compared to those without these conditions. Methods: Study subjects were part of the Prematurity and Respiratory Outcomes Program (PROP) study, a longitudinal cohort study of infants born <29 gestational weeks followed from birth to 1 year of age. Respiratory inductance plethysmography was used for tidal breathing measurements before and after inhaled albuterol 1 week prior to anticipated hospital discharge. Infants were breathing spontaneously and were receiving ≤1 liter per minute (lpm) nasal cannula flow at 21-100% FiO2. A survey of respiratory morbidity was administered to caregivers at 3, 6, 9, and 12 months corrected age to assess for respiratory disease. We compared tidal breathing measurements in infants with and without bronchopulmonary dysplasia (BPD, oxygen requirement at 36 wk) and with and without respiratory disease in the first year of life. Measurements were also performed in a comparison cohort of term infants. Results: 765 infants survived to 36 weeks post-menstrual age, with research-quality tidal breathing data in 452 out of 564 tested (80.1%). Among these 452 infants, the rate of post-discharge respiratory disease was 65.7%. Compared to a group of 18 term infants, PROP infants had abnormal tidal breathing patterns. However, there were no significant differences in tidal breathing measurements in PROP infants who had BPD or who had respiratory disease in the first year of life compared to those without these diagnoses. Bronchodilator response was not significantly associated with respiratory disease in the first year of life. Conclusions: Extremely premature infants receiving <1 lpm nasal cannula support at 21-100% FiO2 have tidal breathing measurements that differ from term infants, but these measurements do not differentiate those preterm infants who have BPD or will have respiratory disease in the first year of life from those who do not
