Figure 9.

Dynamic lung elastance (E_L) plotted versus time for a healthy subject (A) and an asthmatic subject (B). E_L reflects a change in the fraction of lung tissue participating in breathing, where a decrease in E_L would represent airway re-opening (or recruitment) and an increase would represent airway closure (or de-recruitment). In the asthmatic subject (B), E_L increases after MCh challenge, but shows little change after DI. In the healthy subject (A), E_L increases much greater when DIs are prohibited before MCh challenge. However, a DI after MCh challenge causes a substantially drop in E_L. This suggests that the amplified reactivity that occurs in healthy subjects by prohibiting DIs is a consequence of heterogeneous airway closures and/or severe narrowings that occur simply by withholding DIs, but can be mostly ablated with a DI (reproduced from Black et al., 2004 with permission).