How does the presence of pulsus paradoxus typically manifest in arterial blood pressure monitoring, and what condition is it most strongly associated with?

Pulsus paradoxus manifests in arterial blood pressure monitoring as an exaggerated decrease in systolic blood pressure during inspiration. Normally, systolic blood pressure decreases slightly (less than 10 mmHg) during inspiration due to increased venous return to the right side of the heart and a slight decrease in left ventricular stroke volume. Pulsus paradoxus is defined as a decrease in systolic blood pressure of greater than 10 mmHg during inspiration. On an arterial blood pressure waveform, this appears as a cyclic decrease in the peak systolic pressure with each inspiratory effort. The condition most strongly associated with pulsus paradoxus is cardiac tamponade. Cardiac tamponade is a life-threatening condition in which fluid accumulates in the pericardial sac (the space surrounding the heart), compressing the heart and impairing its ability to pump blood effectively. In cardiac tamponade, the increased pressure in the pericardial sac restricts right ventricular filling during inspiration. As the right ventricle expands, it pushes the interventricular septum towards the left ventricle, reducing left ventricular volume and output, leading to a significant drop in systolic blood pressure during inspiration. While cardiac tamponade is the classic association, pulsus paradoxus can also be seen in other conditions that cause increased intrathoracic pressure or impaired ventricular filling, such as severe asthma, chronic obstructive pulmonary disease (COPD), and constrictive pericarditis.