I Used a Hypoxic Tent for 23 Nights to Prepare for a Climbing Trip. Things Didn’t Go As Planned.

I lay in a tent in the Canadian Rockies, drifting in and out of fitful sleep. Suddenly, I couldn’t breathe. I gasped for air but the tent’s slack walls had covered my mouth.

“Arghhh!” I screamed. I flipped the small plastic tent off my head and watched it crash into my bedroom wall. Breathing heavily, I flicked on my bedside light and remembered where I was: not on some Himalayan peak—as I’d hoped to be in a few days—but at home, where I was intentionally sucking the oxygen out of the air.