Pulsus Paradoxus

IT is well known that arterial pressure may fluctuate with the respiratory cycle, falling with inspiration and rising with expiration. This fluctuation occurs to a slight degree during normal breathing and may be more marked with forced respiratory effort, heart failure or pericardial tamponade.Ever since the phenomenon was first observed, suggested explanations have abounded. However, with the slow accumulation of knowledge on the relation between cardiac function and pleural pressure, it has now become possible to propose unifying concepts that account for the phenomenon both in normal and pathologic situations.Only two mechanisms seem to be involved. The first . . .