Respiratory water loss in fullterm infants on their first day after birth.

Measurements of water loss from the airways, oxygen consumption and carbon dioxide production were made in 12 fullterm, newborn infants on their first day after birth, using an open flow-through system. The system includes a mass spectrometer, specially equipped with a water channel, for analysis of gas concentrations. To avoid condensation of water vapour, the tubing in the flow-through system is heated. Respiratory water loss was 4.9 +/- 1.2 (SD) mg/kg min, which meant an insensible water loss from the respiratory tract of 25.4 +/- 6.9 (SD) g per infant and 24 h at rest, at an ambient temperature of 32.2 degrees C and with an ambient humidity of 50%. Oxygen consumption was 6.0 +/- 0.8 (SD) ml/kg min. An inverse relationship was found between respiratory water loss and ambient humidity, with higher losses at a low than at a high humidity. Oxygen consumption did not change very much with ambient humidity.