Nitrogen exchange across the lungs in resting man

The relationship between the partial pressure of N2 in the inspired air (PIN2), and the nitrogen transfer across the lungs (VN2), has been examined in 8 resting subjects, and a study made of the effect of diet upon this relationship. Alterations in PIN2, over the range 60 mm Hg below, to 20 mm Hg above ambient PIN2, caused changes in VN2 which could be described by a linear equation. These changes agreed both in magnitude and direction with those predicted by a four-compartment electrical analogue of the body N2 stores. They were not affected by the protein content of a meal taken 3/4 hr before the start of measurements of VN2. The study has shown that any imbalance in N2 transfer across the lungs is very small and that the open-circuit method of measuring O2 consumption is valid.