Valsalva maneuver
The Valsalva maneuver is performed by a forceful attempt of exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut while expelling air, as if blowing up a balloon. Variations of the maneuver may be used either in medical examination as a test of cardiac function and autonomic nervous control of the heart (because the maneuver raises the pressure in the lungs), or to clear the ears and sinuses (that is, to equalize pressure between them) when ambient pressure changes, as in scuba diving, hyperbaric oxygen therapy, or air travel.