http://swissbaync5d7ykaz7dh7v4qjrb4gmen5aj3bogxrcgbb43ij34bjuyd.onion/pdf/Books/Survival/Medicine/sectionf.htm
This
is done by one of several maneuvers, including blowing against a closed mouth and nose,
swallowing, yawning, or the Valsalva or Frenzel maneuvers. (The Valsalva is a forced
exhalation with nose pinched, lips closed against mouthpiece, glottis open. The Frenzel is
accomplished with nose pinched and lips closed against the mouthpiece; the back of tongue
is thrust against soft palate, gently pushing air through the eustachian tubes.)