Valsalva Maneuver

Question 1

What happens to BP during phase 1?

Answer 1

In phase 1, the intrathoracic pressure is suddenly positive, and so the blood is expelled from pulmonary vessels, increasing ventricular preload, and briefly increasing BP.

Question 2

What happens to BP during phase 2?

Answer 2

The maintenance of the raised intrathoracic pressure means that venous return is decreased, and so BP decreases. This is detected by the baroreceptors of the aortic arch and carotid sinus, which cause a tachycardia and an improvement of BP back to near-normal levels.

Question 3

What happens to BP in phase 3?

Answer 3

In phase 3, the patient relaxes and the pressure is released, causing the intrathoracic pressure to fall, which draws blood into the thoracic vessels. This means a reduction in venous return, and a fall in BP.

Question 4

How does a patient perform a Valsalva Maneuver?

Answer 4

After a full inspiration, the patient forcefully exhales against a closed glottis. A pressure of 40mmHg should be maintained for 10 seconds.

Question 5

What happens to BP in phase 4?

Answer 5

In phase 4, the reduced BP is detected by the baroreceptors , which act to cause tachycardia and vasoconstriction, and an increase in BP. There is an overshoot as the venous return begins to increase, before the BP settles to normal levels.