Answer to Question 1
ANS: C
A. Incorrect response: Alveolar pressure is often represented by the plateau, or static, pressure. It is also called the alveolar distending pressure and is used in the calculation of static compliance.
B. Incorrect response: The airway pressure is usually measured in the ventilator breathing circuit.
C. Correct response: Pleural pressure, estimated by esophageal pressure, is the pressure in the pleural space. During spontaneous breathing, pleural pressure is always subatmospheric. However, during positive-pressure mechanical ventilation, pleural pressure becomes supra-atmospheric. Because of its proximity to the major cardiovascular structures (heart, pulmonary circulation vena cava, and aorta), pleural pressure closely reflects the impact imposed by positive-pressure breathing on blood flow.
D. Incorrect response: Transairway pressure is the pressure gradient responsible for the flow of air into and out of the lungs.
Answer to Question 2
ANS: D
A. Incorrect response: See explanation D.
B. Incorrect response: See explanation D.
C. Incorrect response: See explanation D.
D. Correct response: As the lungs inflate, alveolar vessels are compressed and they
experience a decrease vascular capacitance. At the same time, the extra-alveolar vessels experience an increased pulmonary capacitance. If alveolar capillaries are engorged with blood as during a hypervolemic state, inspiration causes a discharge of alveolar-capillary blood volume into the left atrium. However, if alveolar capillaries are less full, as in the case of hydration lung, inflation will result in a transient decrease in pulmonary vessel outflow as blood pools in the enlarged extra-alveolar vessels.