Chest Wall Compliance (Ccw) is estimated by which formula?

Chest Wall Compliance (Ccw) is estimated by which formula?

• A. ΔV/(Pplat - PEEP)
• B. ΔV/ΔPes
• C. ΔPes/ΔV
• D. Pes/VT

Answer: (B)

Chest wall compliance is the amount of volume change produced by a given change in pleural pressure. Because direct pleural pressure measurement is invasive, esophageal pressure is used as a surrogate for pleural pressure. The chest wall’s compliance is represented by the slope of the volume change versus pleural pressure change, so it is estimated as Ccw = ΔV/ΔPes. In practice, you look at the breath's tidal volume (ΔV) and the corresponding change in esophageal (pleural) pressure (ΔPes); a larger pressure swing for the same volume means a stiffer chest wall (lower Ccw). This differs from the overall respiratory system compliance, which uses the driving pressure across the entire system (Pplat − PEEP). The other expressions either describe the whole system’s compliance, its inverse, or are not standard measures.

Chest wall compliance is the amount of volume change produced by a given change in pleural pressure. Because direct pleural pressure measurement is invasive, esophageal pressure is used as a surrogate for pleural pressure. The chest wall’s compliance is represented by the slope of the volume change versus pleural pressure change, so it is estimated as Ccw = ΔV/ΔPes. In practice, you look at the breath's tidal volume (ΔV) and the corresponding change in esophageal (pleural) pressure (ΔPes); a larger pressure swing for the same volume means a stiffer chest wall (lower Ccw). This differs from the overall respiratory system compliance, which uses the driving pressure across the entire system (Pplat − PEEP). The other expressions either describe the whole system’s compliance, its inverse, or are not standard measures.