3. Physiology
        3.2. Cardiovascular
            3.2.6. Special circumstances Valsalva manoeuvre

Valsalva manoeuvre

[Ref: PK1: p157-158; WG21:p611; KB2: p53-55]



Phase 1

(Straining starts)

BP increases, because

HR decreased due to increased BP


Phase 2

(Continued straining)

BP drops initially because of decreased cardiac output secondary to decreased venous return.

--> Stimulation of baroreceptors

--> Reflex compensation via sympathetic stimulation


--> BP later restored (or even exceed baseline level)



Phase 3

(Release of straining)

BP decreases because (essentially reverse of phase 1)

HR increased further [PK1:p157]

HR unchanged because the phase is very brief [KB2:p53]


Phase 4

(Continued relief)

Return of normal venous return to heart

--> Cardiac output returns to near normal

BP overshoots above the baseline initially because of vasoconstriction

--> Baroreceptor inhibited

--> Reflex vagal stimulation


--> BP later restored to normal


Abnormal responses

Diminished baroreceptor reflex

e.g. quadriplegia, diabetic autonomic neuropathy, elderly

Also in hyperaldosteronism, for unknow reason [WG21:p611]

Congestive cardiac failure

Square-wave response seen

May be due to increased pulmonary blood volume
--> LV filling maintained for extended periods


Less vasoconstriction/BP effect

Much smaller BP overshoot in phase 4

HR not changed much


Lower BP during phase 2

Increased BP overshoot during phase 4


Use of Valsalva manoeuvre


Valsalva ratio



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