What is the influence of quadriplegia on the vital capacity when the patient changes position from upright to supine?

A. No change in the vital capacity occurs.
B. The vital capacity increases.
C. The vital capacity decreases.
D. The change in vital capacity is unpredictable.

?ANS: B
A. Incorrect response: See explanation B.
B. Correct response: In patients who have quadriplegia, intact diaphragmatic function may significantly increase vital capacity by shifting from upright to supine. The effect results from the increased residual volume in the upright position created by the outward bulging of the abdominal contents and consequent drop in the diaphragm.
C. Incorrect response: See explanation B.
D. Incorrect response: See explanation B.