Pitfalls in spirometry: Clinical relevance

Figure 4 Effects of increased lung elastic recoil on maximal flow in a healthy subject (dashed lines) and a patients affected by pulmonary fibrosis (continuous lines). Upper panel: transpulmonary pressure (Ptp) is plotted vs lung volume; Lower panel: flow is plotted vs volume. With the increase in Ptp, maximal flow increases. This compensates for the decrease in FEV₁ expected from the decrease in total lung capacity (TLC).