Wednesday, August 14, 2013

Supplemental Oxygen

At Cho Oyu BC. encircled is my team's
stock of O2 bottles
  (A technical narrative about supplemental O2 and comparison with scuba dive tanks).
Curious people often asked about oxygen use and how the set was different from scuba diving tanks. The keen interest in this topic amazed me. Fortunately, I was a professional diver so I usually offered a long, technical explanation on the subject until the one asking fell asleep. Haha!

Generally, scuba divers used air tanks to breathe underwater. Humans don’t have gills. High-altitude mountaineers sometimes used supplemental oxygen tanks because the air was so thin beyond 26,000 feet. The extra oxygen was a supplement or an addition.

Typical scuba dive tanks contained compressed air, not oxygen. Compressed air was normal air, a mix of nitrogen and oxygen. Technical diving tanks may use different gas “flavors.” Normally, it was a mix of light gas (hydrogen or helium) and oxygen or different percentages of nitrogen and oxygen called ‘nitrox’ (e.g., 33 percent oxygen). Mixed gas tanks like those with helium or hydrogen are mainly used beyond the usual recreational dive limit of below 130 feet. Nitrox is mainly used in shallow water with a longer bottom time underwater.

In diving, most recreational divers use a demand-type breathing apparatus where you only consumed the gas when you breathed. The more efficiently you breathed, the longer the air supply lasted. The bad effect of compressed air bubbles was known as decompression sickness (DCS). Too much nitrogen in the brain caused nitrogen narcosis, a feeling of temporary insanity. It was possible to get high while diving below. :)

Too much air bubbles in one’s joints caused “bends” or pain in the joints similar to tetanus that led to paralysis. Too much oxygen in the blood caused convulsions. This happened when one went deeper than 205 feet while using compressed air. Oxygen in the blood increased six times more than normal, resulting in convulsions, drowning and death. Ascending too fast underwater could cause air embolism and lung rupture given the sudden loss of pressure. Scuba diving was totally different from high-altitude mountaineering that required supplemental oxygen. Or, in bad-ass slang, a totally different kind of shit!

An oxygen tank contained pure oxygen. Most devices like what I used had continuous flow type of delivery, not the demand-type version. This meant you lost precious molecules even if you weren’t breathing. This system automatically mixed the oxygen with the air inside the face mask. In the end, the user wasn’t breathing pure oxygen.

The oxygen tank’s supply depended on the tank size and regulator flow rating (e.g. liters per minute). The regulator could be set from very low (e.g., 0.5 for sleeping at very high camps) to low (minus 1) or just right (2-3) or high (4 or 5). One oxygen tank could last from four to 10 hours of continuous use, depending on the regulator setting. It weighed less than 4 kgs, an extra weight but extremely necessary.

As for the physiological effects of air pressure in a high-altitude environment, too much oxygen in the blood was bad though few high-altitude climbers ever experienced this. Too little oxygen could cause AMS and hypoxic hypoxia that led to disorientation, accidents, breathlessness and other not-so-nice things. Severe AMS caused deadly cerebral or pulmonary edema. DCS or air embolism (too much air in the blood and system) could kill scuba divers. AMS was the killer in high-altitude climbing.
Wanna be safe? Stay home! Hehe :) 

Supplemental oxygen use simulated an altitude of less than 3,000 feet of the actual height. If I was climbing at 27,000 feet and using oxygen with a normal setting, that put me at only 24,000 feet. This was why it was safe to remove the mask for a few minutes without becoming unconscious. Unlike the portable hyperbaric chamber called Gamow bag, the air, sometimes with supplemental oxygen, was enclosed and pressurized. It could simulate an altitude of as low as 7,000 feet, depending on the model. I’ve heard of people dying because of playing with it. The sudden release of pressure simulated a fatal jump of altitude of 7,000 feet from the climber’s current altitude of 20,000 feet, for example

Oxygen use at high altitudes didn’t start with mountaineering. Hot air ballooning made progress first before high-altitude climbing.The poor balloonists suffered AMS before science pinpointed what it was. When high-altitude mountaineering came about, there was already sufficient knowledge about thin air and better technology on supplemental oxygen use.

Why were airplanes flying at 37,000 feet pressurized? Planes are like flying Gamow bags. Emergency oxygen breathing bags are dropped when the air pressure in the plane dips to a dangerous level. The sudden thinning of air (or less pressure) can knock you unconscious within a few seconds. You can die if the situation doesn’t improve.

In our Everest climb, my team made sure that we didn’t run out of oxygen. We brought around six bottles per climber. We started using oxygen at 7,000 meters from Camps 3 to 4. On summit day, we used fresh tanks from Camp 4, then changed to another set of fresh tanks at the Balcony (6-10 hours to summit) before the final push. We also carried extra oxygen bottles for the descent. This was normal practice when one climbed Everest on Nepal’s side. Oxygen was used in the Death Zone (above 26,000 feet), but with the schedule to push for the summit coinciding with the same day we arrived at Camp 4, climbers started using oxygen from Camp 3. Oxygen use lessened fatigue and expedited recovery needed by the climber to go for an immediate assault. Despite that, not many made it to the top.

In history books, mountaineers have used oxygen since Mallory’s time (1924). Hillary’s team used bottled oxygen during their first ascent in 1953. My 4-kg oxygen equipment could last longer compared to their 12-kg, four-canister model. Other mountaineers after Hillary used supplemental oxygen until elite climbers Messner and Peter Habeler successfully climbed Everest without bottled oxygen in 1978. After proving that human survival science could be partly wrong, the elite made their non-oxygen-aided marks on every 8,000-meter peaks. Messner was the first to summit all 14 peaks in the Death Zone without using supplemental oxygen.

Why have I used oxygen?
Although the purist, extreme and elite mountaineers have different views on this, I prefer to summit, then go down safely. The ones who don’t use oxygen double their chances of failure, frostbite, even death. A teammate in Cho Oyu decided not to use extra oxygen and ended up delirious for eight hours. He couldn’t recall I was climbing with him the whole time.

My Cho Oyu guide pulled that hombre down a few hundred meters, then smacked a mask of oxygen on his face for a few minutes so he could be conscious enough to climb down a little until he collapsed again. He survived, thanks to the guide. This climber and I exchanged emails, and he told me about his frostbite-related problems that lasted for a year. It was eventually treated. My personal objective became clear: Safety first.
  But will I ever climb an 8,000-meter peak without supplemental oxygen? Possibly in the future.

1 comment:

Mosh Montalban said...

Hi Sir Romi, Napaka Informative naman po nito nyong Blog nyo. Buti nakita ko to :) mas Informative pa dun sa blog ni sir Gid. anyways, i will continue reading your Blogs way back sa una niyong post :)

i really didn't know na may pagkakaiba pala yung tanks ng Diver sa Tanks ng Mountaineer.

Thanks po for Nourishing my mind.