Valsalva Manoeuvre

Key points

• Forced expiration against a closed glottis → ↑ intrathoracic pressure → ↑ venous/right atrial pressure → ↓ venous return (the initial physiological response).
• ↓ preload → fall in cardiac output (Frank-Starling); on release a further slight fall in output (↑ aortic volume) before normal output returns.
• Uses: terminating an episode of supraventricular tachycardia; normalising middle-ear pressures.
• HOCM is the classic condition whose murmur gets louder following Valsalva.