Positive-pressure breathing as a G-protection device: safety concerns

Positive-pressure breathing (PPB), a technique in which air is forced into a pilot by means of a face mask to raise intrathoracic pressure, is examined. It has been shown to lengthen subjects´ ability to endure +G_z acceleration epochs and has been proposed for operational use to increase G-tolerance. However, PPB can cause ear pain, ear and sinus blocks, pneumothorax, and air embolism. All these side-effects are potentially fatal to the pilot. The pressure proposed for operational use, at altitudes that occur in partially pressurized cockpits of operational aircraft, causes greater lung distension than pressure gradients known to cause pulmonary overpressurization in animals and man. Other means of increasing G-tolerance safely are also examined