A few weeks back, I shared some information on the flight restrictions enacted due to 
concerns of hypoxia and hypoxia symptoms in pilots of the F-22 Raptor. Yesterday, it was reported that a potential cause of has been identified.
The flight restrictions, which limit flights within 30 minutes of a landing field, are still in place. According to Col. Kevin Robbins, a commander of the First Fighter Wing at Langley Air Force Base, 11 incidents of hypoxia have been reported in the last 10 months.
There have been and still are many speculated reasons for the hypoxia (which we review here and here). The latest release suggests that it is not the aircraft itself, but a piece of equipment worn by the pilots, a vest, that is to blame.
Due to the 9Gs the F-22 pilots may endure, an inflatable vest is worn. The vest provides counter-pressure during rapid decompression. While protecting the lungs, it also has the effect of restricting breathing, potentially being a hazard in terms of hypoxia.
The Environics Reduced Oxygen Breathing Device (ROBD2) is used in the training of pilots on hypoxia.
