Diving Simulation: The standard dive simulation assumes sea level ambient pressure and, to avoid the possibility of the bends, is limited to a simulated maximum depth of 20 feet and a maximum "dive" duration of 1 hour. We make a first assumption that the diver rapidly descends to 5 feet at which point they attempt to equalize ME-ambient pressure and then proceed to the maximum depth of 20 feet within 5 minutes (These parameters can be modified depending on the diver's experience and the chamber pressure can be increased to simulate a dive to 30 feet). We also assume that the return to the surface is approximately 10 feet per minute. With the subject seated comfortably in the chamber, pressure is increased to 1500 daPa+ambient (gauge pressure =1500 daPa, approximately depth of 5 feet), the subjects middle-ear pressures are measured by tympanometry and any symptoms/signs evaluated. If these assessments are normal, the chamber pressure is increased to 6100 daPa+ambient (approximate depth of 20 feet for sea and fresh water), maintained at that pressure for 20 minutes and then decreased to ambient (ascent to surface). The rate of change in depth is set at 5 ft/minute. The subject reports symptoms throughout and middle-ear pressure is measured bilaterally by tympanometry periodically.