Which formula represents transpulmonary pressure?

Which formula represents transpulmonary pressure?

• A. Pes - Paw
• B. Paw - Pes
• C. Paw + Pes
• D. Pes / Paw

Answer: (B)

Transpulmonary pressure is the pressure gradient across the lung that distends it, from inside the alveoli to the pleural space. To estimate the pleural pressure, we use esophageal pressure, and the pressure in the airways gives the airway pressure. The distending gradient across the lung is therefore the airway pressure minus the esophageal (pleural) pressure. That makes Paw − Pes the correct representation of transpulmonary pressure. For example, with Paw at 20 cmH2O and Pes at -5 cmH2O, the transpulmonary pressure is 25 cmH2O. Using the opposite order, a sum, or a ratio would not reflect the actual distending pressure across the lung.

Transpulmonary pressure is the pressure gradient across the lung that distends it, from inside the alveoli to the pleural space. To estimate the pleural pressure, we use esophageal pressure, and the pressure in the airways gives the airway pressure. The distending gradient across the lung is therefore the airway pressure minus the esophageal (pleural) pressure. That makes Paw − Pes the correct representation of transpulmonary pressure. For example, with Paw at 20 cmH2O and Pes at -5 cmH2O, the transpulmonary pressure is 25 cmH2O. Using the opposite order, a sum, or a ratio would not reflect the actual distending pressure across the lung.