Answer to Question 1
ANS: B
A. Incorrect response: The transairway pressure is the pressure difference (gradient) between the alveolar pressure and the mouth pressure (atmospheric pressure). This pressure gradient is responsible for the flow of air into and out of the lungs during spontaneous breathing and mechanical ventilation.
B. Correct response: An esophageal balloon measures pressure in the midesophagus, which reflects pressure in the pleural space.
C. Incorrect response: During mechanical ventilation, alveolar distending pressure can be estimated by conducting an inspiratory pause. The plateau or static pressure reflects the pressure responsible for maintaining the lungs in an inflated state.
D. Incorrect response: Pressures in the distal endotracheal tube are considered tracheal pressures.
Answer to Question 2
ANS: C
A. Incorrect response: Alveolar distending pressure is the pressure required to maintain the lungs inflated at the end of inspiration. The pressures Pstatic and Pplateau are essentially interchangeable.
B. Incorrect response: The static pressure is the pressure obtained during an inspiratory pause. It is the pressure exerted to main lung inflation at the end of inspiration.
C. Correct response: Airway pressure or airway opening pressure measures the pressure inside the ventilator or within the ventilator tubing.
D. Incorrect response: The transpulmonary pressure is the pressure difference (gradient) between the alveolar pressure and the pleural pressure. It is the pressure responsible for enabling the lungs to fill during inspiration.