Answer to Question 1
ANS: C
A. Incorrect response: See explanation C.
B. Incorrect response: See explanation C.
C. Correct response: During an acute crisis, COPD and asthma patients tend to avoid lying supine. In one study of patients having acute asthmatic episodes, no asthmatic having a peak flow of less than 150 L/min chose to be recumbent. Reasons for this choice include the increase in airway resistance while assuming the supine position, and recruitment and optimization of accessory muscles of inspiration and expiration in the upright position.
In the absence of data for mechanically ventilated COPD patients, therapists extrapolate what is known about nonventilated patients with airflow obstruction to ventilated COPD patients. Consequently, the recommendation is to place actively weaning COPD patients in a semirecumbent (upright) position.
D. Incorrect response: See explanation C.
Answer to Question 2
ANS: B
A. Incorrect response: See explanation B.
B. Correct response: Three conditions favor the delivery of ventilation preferentially to nondependent portions of the lung relative to the dependent lung regions. First, ventilation at low tidal volumes shifts the pressure-volume relationships between the dependent and the nondependent areas of the lung in such a manner as to favor alveoli in the nondependent lung.
Second, a high inspiratory flow or the use of accessory respiratory muscles preferentially distributes ventilation to nondependent regions. Third, in mechanically ventilated patients, especially those anesthetized or sedated, the abdominal contents restrict the dependent diaphragm, increasing the movement of the nondependent diaphragm and the nondependent portions of the lung.
C. Incorrect response: See explanation B.
D. Incorrect response: See explanation B.