PULMONARY FUNCTION IN THE NEWBORN INFANT. V. TRAPPED GAS IN THE NORMAL INFANT'S LUNG*

Abstract

Total thoracic gas volume (TGV) and its ventilated component, the functional residual capacity (FRC) have been measured concurrently in 23 normal newborn infants; TGV was measured by a plethysmographic technique based on Boyle''s Law and FRC was measured by nitrogen dilution. TGV was significantly larger than FRC in 10 babies, indicating the presence of a very poorly ventilated portion of lung amounting to 25 to 60% of the total TGV. This poorly ventilated gas is probably trapped in terminal lung units that are intermittently nonventilated, especially during quiet breathing.