(Straining starts)
BP increases, because
HR decreased due to increased BP
(Continued straining)
BP drops initially because of decreased cardiac output secondary to decreased venous return.
--> Stimulation of baroreceptors
--> Reflex compensation via sympathetic stimulation
Thus,
--> BP later restored (or even exceed baseline level)
Also,
(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]
(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
Thus,
--> BP later restored to normal
e.g. quadriplegia, diabetic autonomic neuropathy, elderly
Also in hyperaldosteronism, for unknow reason [WG21:p611]
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
@@Why??
About | |
Created | 20050607 |
Reviewed | 20050816 |