Valsalva's manoeuvre

A manœuvre first described by an Italian, A.M. Valsalva (1666-1723). It occurs when the breath is held while muscles in the abdomen and chest are contracted. The chest contents become compressed, increasing gas pressure in the cavity of the thorax and blood pressure in the blood vessels. When breathing is restarted, a reflex reaction causes the heart to slow down, sometimes resulting in dizziness and fainting. Weight-lifters may unintentionally perform a Valsalva's manoeuvre if they hold their breath during a lift. It can cause dizziness, blackouts, and inguinal hernias. This is why weight-lifters are instructed to breathe normally when performing their exercises and never to hold their breath. It is not unknown for children to perform the Valsalva manoeuvre intentionally in order to induce a fainting attack. They, and anyone else performing the manœuvre, should be strongly discouraged because the increase in intrathoracic pressure can provoke a heart attack in people with a weak heart.

A technique for increasing the intrathoracic and intra-abdominal pressure by trying to breathe out forcibly (using the diaphragm and abdominal muscles) when the glottis (the opening between the vocal cords) is closed. It was named after the Italian anatomist A. M. Valsalva (1666-1723). The manoeuvre is often performed during isometric exercises and weight-lifting. Air is trapped and pressurized in the lungs, causing blood pressure to rise. The great veins may collapse, reducing the flow of blood returning to the heart. Immediately after the manoeuvre, a reflex bradycardia can occur that may cause dizziness and fainting. Valsalva's manoeuvre is potentially dangerous. It can cause a heart attack in people with high blood pressure or cardiovascular disease.