What is the definition of pulsus paradoxus?

Pulsus paradoxus is defined as a decrease in systolic blood pressure of more than 10 mmHg during inspiration. This phenomenon is primarily observed in conditions such as cardiac tamponade, severe asthma exacerbations, and other conditions that cause significant respiratory distress or heart compromise. During inspiration, negative intrathoracic pressure increases venous return to the right side of the heart, which can transiently decrease left ventricular filling and stroke volume due to the interplay of the pericardial space or structural changes in the thoracic cavity. This results in a notable drop in systolic blood pressure during inhalation.

Thus, the definition aligns specifically with the cardiovascular changes associated with the respiratory cycle, and option C accurately captures this unique physiological response.