Fig. 5.

Epiglottic pressure vs. inspiratory flow in 3 subjects, exhibiting the different patterns of negative effort dependence. In all cases, flow initially increases with increasing effort. However, above a certain inspiratory effort, three patterns are seen. A: no negative effort dependence. Subject behaves as a perfect Starling resistor. B: negative effort dependence within a single breath. After reaching a maximum, flow decreases within a breath as epiglottic pressure becomes more negative. Note that each successive breath reaches the same peak inspiratory flow. C: negative effort within and across breaths. As in B, flow decreases within each separate breath, but the peak flow is also reduced with each successive breath.