Valsalva
Valsalva
Forced expiration against a closed glottis (straining, defecation, coughing)
- A test of physiological autonomic function
- Therapeutic role in termination of paroxysms of SVTs (increased vagal activity during phase IV)
Physiological changes
- Phase I
- Rise in intrathoracic pressure
- Transmitted to thoracic aorta - increase in BP
- Phase II
- Reduced venous return - fall in SV and CO
- Fall in CO produced reflex tachycardia
- Phase III
- Opening glottis, sudden drop in intrathoracic pressure
- Intra-arterial pressure falls as direct pressure on thoracic aorta relieved
- Phase IV
- Fall in thoracic pressure leads to improved venous return
