Valsalva maneuver
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In medicine, the Valsalva maneuver is performed by forcibly exhaling against closed lips and pinched nose, forcing air into the middle ear if the Eustachian tube is open. This maneuver with slight modifications can be used as a test of cardiac function and autonomic nervous control of the heart or to ‘clear’ the ears (equalize pressure) when ambient pressure changes, as in diving or aviation.
The technique is named for Antonio Maria Valsalva, the 17th Century physician and anatomist from Bologna, whose principal scientific interest was the human ear. He described the Eustachian tube and the maneuver to test its patency.
[edit] Physiological response
The normal physiological response consists of 4 phases, which are marked on the figure at right:
- Initial pressure rise: On application of expiratory force, pressure rises inside the chest forcing blood out of the pulmonary circulation into the left atrium. This causes a mild rise in blood pressure.
- Reduced venous return and compensation: Return of blood to the heart is impeded by the pressure inside the chest. The output of the heart is reduced, the blood pressure falls. This occurs from 5 to about 14 seconds in the illustration. The fall in blood pressure reflexly causes blood vessels to constrict with some rise in pressure (15 to 20 seconds). This compensation can be quite marked with pressure returning to near or even above normal, but the cardiac output and blood flow to the body remains low. During this time the pulse rate increases.
- Pressure release: The pressure on the chest is released, allowing the pulmonary vessels and the aorta to re-expand causing a further initial slight fall in pressure (20 to 23 seconds) due to decreased left ventricular return and increased aortic volume, respectively. Venous blood can once more enter the chest and the heart, cardiac output begins to increase.
- Return of cardiac output: Blood return to the heart is enhanced by the effect of entry of blood which had been dammed back, causing a rapid increase in cardiac output and of blood pressure (24 seconds on). The pressure usually rises above normal before returning to a normal level. With return of blood pressure, the pulse rate returns towards normal.
Deviation from this response pattern signifies either abnormal heart function or abnormal autonomic nervous control of the heart.
[edit] Practical applications
When rapid ambient pressure increase occurs as in diving or aircraft descent, this pressure tends to hold the Eustachian tubes closed, preventing pressure equalization across the ear drum, with painful results. To prevent this, divers, caisson workers and pilots ‘equalize’ pressure by swallowing, which tends to open the tubes. If this fails, then by blowing hard against closed lips and nose while swallowing. This is another application of the Valsalva maneuver. A helpful hint is to use this when traveling (in a car for instance) at high altitudes. Sound will be dulled, but by using this your ears will 'pop' and you can hear with more clarity. If you don't want to use this, then try swallowing a few times, or yawning.
Note that normally the Valsalva maneuver will be done against a closed soft palate, so the raised pressure will not reach the eustachian tubes.
Straining, blowing against resistance as in blowing up balloons has a Valsalva effect and the fall in blood pressure can result in dizziness and even fainting.
