Variations of the intraesophageal pressure with maturation in the postnatal piglet

Variations in intraesophageal pressure (Pes) to 5-min exposures of 100% O2, 10% O2, and 6% CO2 were studied in successive days during the first 2 months of 8 piglets. Pressure measurements were integrated over time to obtain mean pressure changes for each minute. Initial exposure to 100% O2 decreased the mean pressure in all piglets followed by an increase over the next 4 test minutes. 5 of 8 piglets demonstrated maximum increases (25--55% above control) at 5 days and between 15 and 22 days; 3 piglets only at 5 days. Initial exposure to 10% O2 increased the pressure in all piglets followed by a decrease pressure (-10%) in the next 4 min when the piglets were less than 22 days, and an increase (15--70%) when above this age. Exposure to 6% CO2 increased the pressure throughout the 5-min test period with the maximum increase (140--160%) at the earliest ages tested of 5 days.