It’s three in the morning and I’ve woken up, unable to breathe.
Ordinarily, you’d think this predicament would provide some cause for concern, but at an altitude of over 5000 metres (approximately 17,000 feet) I’ve been reassured this “periodic breathing” is a normal physiological response for someone like me who usually lives at sea level. So a little unnerving, yes, but typical nonetheless. After a few moments and a deep, forced inhale, I’m breathing quietly again and able to drift back to sleep.
We are staying in a place called Gorak Shep, at the head of the Khumbu Valley in Nepal. It may as well be the moon – we are surrounded by dust and rock, our lodgings aside a frozen lake. Everest Base Camp is less than two kilometres away, and later (but still before dawn) our troop of twenty three hikers, mostly physiology students who are doubling as researchers and study participants, will climb to Kala Patthar (5643 metres, 18,514 feet), a landmark overlooking Base Camp with views of the Everest summit. Before we depart, however, we are all required to have our weight, blood pressure, resting heart rate, oxygen saturation, respiratory rate and end tidal CO2 measured and recorded.