During “strained” defecation it is not uncommon to hold the breath and compress

Question

During “strained” defecation it is not uncommon to hold the breath and compress the thoracic and abdominal muscles. This is called the Valsalva maneuver. It can cause fainting and is believed to be the reason why more falls and even deaths occur in the bathroom than any other part of the home. Explain why by answering the following questions.

a. The increased pressure in the thoracic cavity compresses the venae cavae. What would happen to venous blood pressure, venous return, stroke volume and cardiac output?

b. Why might a person faint?

c. What compensatory mechanisms are activated to correct the effects described above?

d. The increased pressure in the thoracic cavity also compresses the aortic arch. What compensatory mechanisms might be activated due to this compression?

Explanation / Answer

Venous blood pressure will reduce , venous return will be reduced, cardiac output is increased and stroke volume is also increased for few seconds and then come down

The man will get fainted because of lack of blood supply this is due to decrease in preload and thus there is very low amount of blood in the chambers of heart thus the ventricals can't provide enough blood to blood to compensate this para sympathetic system will get activated to increase all these measurements.

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