Ersdal HL, Eilevstjonn J, Perlman J, et al. - Researchers conducted this observational study to characterize initial positive pressure ventilation (PPV), changes in lung compliance and establishment of functional residual capacity (FRC) in near-term/term neonates ≥ 36 weeks gestation at birth. The sample consisted of all neonatal resuscitations between July 1, 2013, and June 30, 2018, in a Tanzanian referral hospital. Trained research assistants observed perinatal events and characteristics, and recorded them.Nineteen thousand five hundred eighty-seven neonates were born, 1,451 received PPV, of these 821 of median (p25,p75) birthweight 3,180 (2844,3500) grams and gestation 38 (37,40) weeks had ≥ 20 ventilations and complete datasets. The combination of rising expired volumes, ECO₂, and heart rate with declining inflation/expired volume ratios and constant peak inflation pressure (PIP) indicates FRC being developed in the first 20 PPVs in near-term/term neonates using a self-inflating bag-mask without positive end-expiratory pressure, the world's most common tool for ventilating non-breathing neonates. The initial lung compliance is low and, with short inflation times, higher than the recommended PIP, it appears necessary to deliver adequate tidal volumes.