Pulsus paradoxus - mechanism and causes
Core concept
- Not paradoxical - an exaggeration of the normal. Inspiratory SBP fall is normally <10 mmHg
- >10 mmHg = pulsus paradoxus
Tamponade mechanism
- Inspiration -> dec intrathoracic pressure -> inc systemic venous return -> inc RV filling
- Pericardial volume is fixed -> the RV can only expand into the LV
- -> septal shift leftward = ventricular interdependence
- Simultaneously inc pulmonary vascular capacitance -> blood pools in the lungs
- -> dec LV preload -> dec LV stroke volume -> SBP falls
Airflow obstruction mechanism
- Same endpoint by a different route: very large negative intrathoracic pressure swings
- inc RV filling + septal shift, plus inc LV transmural pressure = inc afterload
3 more sections, plus exam facts
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