Intraregional gas mixing in humans during high frequency oscillations

We measured the effect of high frequency oscillation (HFO) on gas mixing in the human lung. In seven healthy, seated subjects the alveolar slope of the single breath nitrogen washout was used to assess the effects of HFO on gas mixing. A reduction in slope was interpreted as reflecting improved gas mixing within topographical lung regions. The alveolar slope was measured after 0, 10, 20 and 30 sec of control breathhold or HFO applied at the subject's TLC. We found that HFO reduced the alveolar slope more than did control breathhold. The difference in the slopes was greater with longer durations, increased stroke volume (SV) and frequency (f) of oscillations. The reduction in alveolar slope correlated better with SV than with f. We conclude that to the extend that a change in the slope in the alveolar plateau reflects intraregional mixing, this mixing is more dependent on SV than on f.