Figure 8.

Airflow–volume tidal expiratory curves shifted to allow airflow comparisons under isovolumic conditions in three randomly selected animals. Inspiratory positive airway pressure (IPAP) and continuous positive airway pressure (CPAP) produced a leftward parallel shift in the expiratory curves, which is indicative of increases in end-expiratory lung volume (EELV) without changes in expiratory resistance compared with control conditions. Functional residual capacity (FRC) was defined as the EELV during spontaneous breathing (no positive airway pressure). Relative volume represents the increases in EELV above FRC, as defined above.