Sat27November0445PM 25

The Valsalva manoeuvre is the forced expiration of air against a closed upper airway. It results in a series of cardiovascular changes mediated by the autonomic nervous system which are divided into four phases (I, II, III and IV).

Which one of the following options best describes the cardiovascular changes in phase III in a normal patient?

(Please select 1 option)

Raised intrathoracic pressure, increase in blood pressure, and increase in heart rate

Increased intrathoracic pressure, decrease in blood pressure, and increase in heart rate

Normal intrathoracic pressure, decrease in blood pressure, and increase in heart rate This is the correct answer

Normal intrathoracic pressure, increase in blood pressure, and decrease in heart rate

Increased intrathoracic pressure, increase in blood pressure, and decrease in heart rate Incorrect answer selected

Explanation

The Valsalva manoeuvre involves forced expiration against a closed glottis to generate an intrathoracic pressure of 40 mmHg for 10 seconds. The effects on the heart rate (HR) and blood pressure (BP) are then monitored and divided into four phases.

Phase I - An initial increase in venous return from intrathoracic vessels causes a transient decrease in HR and increase in BP.

Phase II - As the high intrathoracic pressure in maintained there is a decrease in the venous return which is sensed by baroreceptors. This causes an increase in HR and decrease in BP. The BP tends to return to normal by the end of phase II.

Phase III - Sudden release of forced expiration and/or glottal opening results in a return of the intrathoracic pressure to normal. This causes pooling of blood into intrathoracic vessels resulting in a decrease in BP, whilst the HR remains elevated.

Phase IV - During phase IV the intrathoracic pressure remains normal and the continued increase return of systemic venous blood produces a reflex bradycardia associated with an increase in BP to normal.

Reference:

Clifton B, Armstrong S, Davis L. Primary FRCA in a Box. London: Royal Society of Medicine Press; 2009.

Yentis SM, Hirsch NP, Smith GB. Anaesthesia and Intensive Care A-Z. 4th edn. Edinburgh: Churchill Livingstone; 2009.

Answer Statistics

1

7%

2

19%

3

31%

4

22%

5

24%

Times answered: 240