Figure 8.

Flow profiles during inspiratory flow limitation. Positive flow represents expiration [E], whereas negative flow represents inspiration [I]. (A) During inspiratory flow limitation, minute ventilation (dark shaded area) can be approximated by the product of maximal inspiratory flow (V_Imax, dashed line) and inspiratory time (t_I). Minute ventilation can be increased by increasing inspiratory duty cycle (IDC) (t_I/t_tot), as demonstrated by the arrow and dotted line; (B) in contrast, increasing the respiratory rate does not increase minute ventilation (the sum of dark shaded areas in B is equal to A) when t_I/t_tot remains constant. Adapted from Schneider et al. 2009 (108).