Pta equals Paw minus Palv. This describes which type of pressure?

• A. Transpulmonary Pressure
• B. Transairway Pressure
• C. Transrespiratory Pressure
• D. Transthoracic Pressure

Answer: (B)

The main idea here is the pressure drop across the conducting airways that drives airflow. Pta is defined as the difference between the pressure at the airway opening (Paw) and the pressure inside the alveoli (Palv). That difference represents the pressure the respiratory system must overcome to push air through the conducting airways, i.e., the pressure across the airway walls.

Because this relationship uses Paw and Palv, it specifically describes transairway pressure—the pressure change across the airways themselves. This is distinct from transpulmonary pressure, which uses pleural pressure (Ppl) to reflect the distending pressure across the lung wall (Paw or Palv minus Ppl). It’s also not primarily about chest wall or whole-respiratory-system pressures, which is why the other terms don’t match this equation.

So the correct concept is transairway pressure.