"Forced expiration against a closed glottis after a full inspiration.
Standardised form 40 mmHg held for 10 seconds
Previously used to expel pus from the middle ear.
[Antonio Valsava (1666-1723), Italian anatomist].
Phase I
Blood is expelled from the thoracic vessels by the increase in intrathoracic pressure.
Phase II
The increase in intrathoracic pressure causes a reduction of venous return, lowering the preload and BP
The baroreceptor reflex is activated, causing vasoconstriction and a tachycardia, raising BP towards normal.
Phase III
As intrathoracic pressure suddenly drops there is pooling of blood in the pulmonary vessels, causing a further drop in BP.
Phase IV
With venous return restored there is an overshoot, as compensatory mechanisms continue to operate.
The increased BP causes a baroreceptor mediated bradycardia.
The Valsalva manoeuvre is a useful bedside test of autonomic function. With autonomic dysfunction (e.g. autonomic neuropathy and drugs), the BP falls and remains low until the intrathoracic pressure is released. The changes in pulse rate and overshoot are absent. For reasons that are still obscure, patients with primary hyperaldosteronism also fail to show the heart rate changes and the blood pressure rise when the intrathoracic pressure returns to normal. Their response to the Valsalva manoeuvre returns to normal after removal of the aldosterone-secreting tumour.
Other abnormal responses
Square wave response
Seen in cardiac failure, constrictive pericarditis, cardiac tamponade and valvular heart disease. Blood pressure rises, remains high throughout the manoeuvre, and returns to its previous level at the end
Figure 2. Arterial blood pressure response and Korotkoff's sounds during Valsalva's manoeuvre.
(A) Sinusoidal response in normal patient.
(B) Absent overshoot in patient with autonomic dysfunction.
(C) Square wave response in patient with heart failure"
from AnesthesiaUK
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