Figure 1.

Pressure and volume tracings from a patient with elevated pleural pressures. (A) Airway pressure (P_AO) measuring total respiratory system pressure. End-inspiratory hold pressure (plateau) and end-expiratory pressure hold (PEEPtotal) are shown. Respiratory system driving pressure (∆P_RS) was calculated as the plateau pressure minus the PEEPtotal; (B) esophageal pressure (P_ES) estimates the trans-chest wall pressure. Chest wall driving pressure (∆P_CW) was calculated as the end-inspiratory hold P_ES minus end-expiratory hold P_ES; (C) transpulmonary pressure (P_L) was calculated as P_AO minus P_ES. Transpulmonary driving pressure (∆P_L) also known as the cyclical stress was calculated as the end-inspiratory hold P_L minus the end-expiratory hold PL; (D) lung volumes during tidal breathing and during expiratory and inspiratory holds; (E) pressure-volume (P-V) curves during tidal breathing with P-V measurements following respiratory system pressures (P_AO), transpulmonary pressures (P_L), and chest wall pressures (P_ES). Dotted lines represent the static compliance of the respiratory system and lung as measured by the slope between end-inspiratory holds and end-expiratory holds (stars on the graphs). Arrows indicate the direction of the inspiration and expiration.