Because changes in pulse volume are independent of changes in pulse rate. This paradox goes back to the
original patients described by Kussmaul in 1873, who had such an inspiratory decrease in systolic pressure to
completely lose their peripheral pulse, even though they still maintained consciousness and an apical beat.
This was a paradox to Kussmaul; hence, his choice of the Latin term pulsus respiratione intermittens (i.e.,
“intermittent pulse as a result of respiration”). Pulsus paradoxus had actually already been described in 1669
by the Cornish physician Richard Lower, who reported a case of constrictive pericarditis in his treatise on the
heart. Subsequently, the British physician Floyer (the same who recommended measuring the arterial pulse
with a portable clock) made a similar observation in asthma, and so did William in 1850. Since none of
these (Kussmaul included) had a sphygmomanometer (it had not been invented yet), they had to exclusively
rely on the peripheral pulse; hence, Kussmaul’s choice of the term “pulsus.” This, however, has become
outdated, not only because it describes an exaggerated physiologic (and not paradoxical) phenomenon, but
also because nowadays these respiratory changes are not detected by arterial pulse, but by blood pressure.
original patients described by Kussmaul in 1873, who had such an inspiratory decrease in systolic pressure to
completely lose their peripheral pulse, even though they still maintained consciousness and an apical beat.
This was a paradox to Kussmaul; hence, his choice of the Latin term pulsus respiratione intermittens (i.e.,
“intermittent pulse as a result of respiration”). Pulsus paradoxus had actually already been described in 1669
by the Cornish physician Richard Lower, who reported a case of constrictive pericarditis in his treatise on the
heart. Subsequently, the British physician Floyer (the same who recommended measuring the arterial pulse
with a portable clock) made a similar observation in asthma, and so did William in 1850. Since none of
these (Kussmaul included) had a sphygmomanometer (it had not been invented yet), they had to exclusively
rely on the peripheral pulse; hence, Kussmaul’s choice of the term “pulsus.” This, however, has become
outdated, not only because it describes an exaggerated physiologic (and not paradoxical) phenomenon, but
also because nowadays these respiratory changes are not detected by arterial pulse, but by blood pressure.
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