Chief Master Sgt. Max Grindstaff, 12th Flying Training Wing command chief from Randolph Air Force Base, Texas listens as Senior Airman Ivan Wilson, an aerospace physiology technician with the 12th Medical Group goes through the operational procedures of an oxygen regulator inside the bases high altitude chamber. (U.S. Air Force photo/Steve Thurow)

Chief Master Sgt. Max Grindstaff, 12th Flying Training Wing command chief from Randolph Air Force Base, Texas watches the flow indicator on oxygen regulator inside the bases high altitude chamber during training with the 12th Medical Group Aerospace Physiology technicians. (U.S. Air Force photo/Steve Thurow)

Tech. Sgt. Mike Stegen, an aerospace physiology technician with the 12th Medical Group (right) signals Chief Master Sgt. Max Grindstaff 12th Flying Training Wing command chief from Randolph Air Force Base, Texas, with a 'thumbs up,' to confirm that all equipment is operational before taking the bases high altitude chamber to 25,000 feet. (U.S. Air Force photo/Steve Thurow)

Chief Master Sgt. Max Grindstaff 12th Flying Training Wing command chief from Randolph Air Force Base, Texas questions Tech. Sgt. Mike Stegen, an aerospace physiology technician with the 12th Medical Group about the equipment used for delivering oxygen during training in the bases high altitude chamber. (U.S. Air Force photo/Steve Thurow)

Chief Master Sgt. Max Grindstaff, 12th Flying Training Wing command chief from Randolph Air Force Base, Texas watches the effects of decreased atmospheric pressure on gases trapped inside the sinuses or middle ear, which expand 3x at an unpressurized altitude of 25,000 feet during a training mission in the 12th Medical Group's high altitude chamber. (U.S. Air Force photo/Steve Thurow)

Chief Master Sgt. Max Grindstaff, 12th Flying Training Wing command chief from Randolph Air Force Base, Texas, signals 12th Medical Group high altitude chamber operator with a 'thumbs up,' to confirm that all equipment is operational before proceeding to 25,000 feet. (U.S. Air Force photo/Steve Thurow)