He lost oxygen to the brain before he was pulled to the surface a few minutes later.
For example, many agricultural and industrial work environments can suddenly lose oxygen without that being detected by humans.
It's because you're losing oxygen and you're gasping for breath.
There is also the possibility of a suit breach, causing the space diver to lose oxygen.
The Europan atmosphere also does occasionally lose molecular oxygen (O) to space.
As doctors worked to revive him, he lost oxygen to his brain for half an hour, with devastating consequences.
Due to poor ventilation, diesel trains occasionally lose oxygen and fail to make it up the tunnel.
Every year, the city loses shade, oxygen and a bit of countryside.
On top of the longhouses they made holes to keep the smoke out so they didn't lose oxygen.
The coffee loses oxygen, and it becomes murky.