Why is a small pneumothorax in the chest of a supine, mechanically ventilated patient sometimes difficult to detect via chest radiography?

Question

A. because most of the pulmonary perfusion accumulates in the bases
B. because the patient generally cannot take a deep breath in the supine position
C. because the air often accumulates over the anterior surface of the chest
D. because the air tends to collect in the apices of the lungs

Answer 1

?ANS: C
A. Incorrect response: When a patient is supine, the pulmonary perfusion gravitates toward the posterior surface of the lung.
B. Incorrect response: Taking a deep breath is not the issue. What becomes problematic is the manner in which the extra-alveolar air becomes distributed over the patient's anterior thorax when the patient is in the supine position.
C. Correct response: When the patient is erect, pleural air accumulates in the apex of the thorax. However, if the patient is supine when the radiograph is obtained, the highest part of the thorax is over the anterior surface of the lung. Therefore, a small pneumothorax may be difficult to detect.
D. Incorrect response: When a patient is supine, the pulmonary perfusion gravitates toward the posterior surface of the lung.