ValsalvaWhat is the Valsalva manoeuvre? Forced expiration against a closed glottis Clinically, this is achieved by producing a pressure of 40 mmHg and holding it for 10

seconds

Can you describe the changes in MAP and HR in a normal person performing the Valsalva?

These changes can be described in four phases: Phase I:

o The increased intrathoracic pressure is transmitted onto the aortao This produces a transient increase in BP and a reflex bradycardia

Phase II:o The sustained positive intrathoracic pressure causes a decrease in venous

return, causing a fall in BPo Reflex sympathetic stimulation causes a reflex tachycardia and vasoconstriction,

restoring the BP Phase III:

o The positive airway pressure is released and the transmitted raised intrathoracic pressure on the aorta is lost

o This produces a transient fall in BP with further reflex tachycardia and vasoconstriction

Phase IV:o Venous return is restored, producing an overshoot in BPo Reflex vagal stimulation causes a reflex bradycardia before both parameters

return to normal

What happens with a square waveform?

With a square waveform, the BP remains high throughout the manoeuvre and returns to its previous level at the end

This occurs when the CVP is markedly raisedo CCFo Constrictive pericarditiso Cardiac tamponadeo Valvular heart disease

What happens in autonomic dysfunction?

The BP falls and remains low until the intrathoracic pressure is released HR changes and overshoot are absent E.g. autonomic neuropathy, elderly

What happens in hypovolaemia or IPPV? There is an exaggerated fall in BP

What is the Valsalva ratio? Longest RR interval in phase IV divided by the shortest RR interval in phase II Normally >1.5, but can be less in autonomic dysfunction

What are the clinical uses of the Valsalva manoeuvre? Expelling pus from the middle ear! Bedside test of autonomic function, volume status Termination of SVT (due to increased vagal tone in phase IV) Evaluating heart murmurs (HOCM louder)