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of the Week:
Pulsus Paradoxus (reversed due to mechanical ventilation). This patient was hypovolemic.
Pulsus paradoxus is an exaggeration of this normal blood pressure variation with breathing. It is defined as a fall in systolic pressure by more than 15 mmHg during spontaneousinspiration. Kussmaul first described this phenomena by noting the paradoxical disappearance of the arterial pulse during inspiration in the presence of a normal heart beat.
Causes for pulsus paradoxus includes severe cardiac decompensation and cardiac tamponade. Approximately 50% of patients with constrictive pericarditis, obstructive airway disease or asthma will have pulsus paradoxus. It can also occur in hypovolemic shock, pulmonary embolism, alveolar hyperinflation or tension pneumothorax.
In a mechanically ventilated patient, a reversal of this pressure variation occurs. Positive pressure ventilation displaces the ventricle wall inward during systole to assist in ventricular emptying. This causes a slight rise in the systolic pressure during mechanical inspiration.
Reversed Pulsus Paradoxus is defined as an exaggeration of the rise in systolic BP during mechanical inspiration. A rise in peak systolic pressure on mechanical inspiration by more than 15 mmHg is considered significant.
A reverse pulsus paradoxus in a mechanically ventilated patient is sensitive indicator of hypovolemia. It can also be present in cardiac tamponade, obstructive airway disease, severe cardiac deterioration, pneumothorax, asthma or pulmonary hyperinflation.
January 7, 2000
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