A. Incorrect response: See explanation B.
B. Correct response: Normally during inspiration, systolic arterial blood pressure can decrease up to 10 mm Hg, and pulse increases to compensate. A greater decrease in systolic blood pressure or weakening of the pulse during inspiration is considered pulsus paradoxus. It occurs commonly in cardiac tamponade and severe asthma. Systolic pressure decreases during inspiration with severe asthma particularly because negative intrathoracic pressure increases venous return. A number of studies have shown that the administration of heliox to patients experiencing an asthma attack results in decreased work of breathing, decreased dyspnea, and significantly lower pulsus paradoxus.
C. Incorrect response: See explanation B.
D. Incorrect response: See explanation B.