OBSERVATIONS ON PULSUS PARADOXUS (WITH SPECIAL REFERENCE TO PERICARDIAL EFFUSIONS): I. CLINICAL

The occasional occurrence of a marked respiratory variation in the amplitude of the pulse was first described in 1850,1and since that time many reports concerning its clinical significance have appeared. The opinions expressed in regard to the probable cause and significance of this phenomenon have been manifold, diverse, and often contradictory; so much so, perhaps, that modern writers seem inclined to look on the question of pulsus paradoxus as the remnant of an unfinished polemic. During the routine examination of a large number of patients coming into the hospital, we were impressed by the appearance of pulsus paradoxus in certain types of disease. Observations were therefore made on these patients; and animal experiments were devised to aid in the clinical interpretation of this interesting pulse phenomenon. The first critical exposition of pulsus paradoxus was presented by Kussmaul2in 1874. His polygraphic records were not complete, but his detailed descriptions