Abstract
Healthy subjects took breaths of ∼200 ml or ∼600 ml, from functional residual capacity, of a mixture of He, Ar, SF 6 (∼7% each), 21% O 2, balance N 2. Without breath-holding they expired steadily to residual volume. Concentrations of He, Ar and SF 6 were measured continuously near the lips and expressed in each case as a fraction of the inspired concentration. After the bigger breaths the order in phase 2 was SF 6 > Ar > He and at the end of phase 3 He > SF 6, in agreement with other workers. After small breaths, and especially with low inspiratory flows, the early part of phase 2 showed, in a highly significant number of experiments, the order He > Ar > SF 6; in these cases phase 3 still showed He > SF 6. these results are fully consistent with the occurrence, during inspiration, of Taylor laminar dispersion (TLD) in airways situated within about 200 ml from the lips. They show (1) that the end of phase 3 cannot be used to infer the presence or absence of TLD, and (2) that correction for the response of the mass spectrometer is of crucial importance in the interpretation of phase 2.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call