Operation Everest II

Charles S. Houston, M.D.

UNFORTUNATELY SOON AFTER they left the summit and began the climb to 30,000 feet, one of the doctors collapsed; though he was quickly revived, it seemed wise to discontinue the ascent and the group turned back. Six of the men settled in for another ten days at 25,000 feet while the remaining five continued on down to sea level …

This happened during the climactic “dash for the summit” in the last two weeks of Operation Everest II in November 1985. The sturdy six had entered the decompression chamber the first week in October and each day the pressure had been lowered slightly to simulate a gradual climb, similar to the ascent rate of many successful Himalayan expeditions. The doctors lived at sea level and each of the many times they entered the chamber they wore oxygen masks; if an oxygen tube were disconnected or kinked, unconsciousness came swiftly and with no warning.

Operation Everest II had been planned for almost five years, a repeat of a similar but more modest study in 1946, when four men were taken slowly to 29,000 feet over a period of 30 days while many tests were run. Not only had technology expanded enormously in the interim, but interest in altitude had attracted many scientists just as the Himalaya had drawn thousands of climbers and trekkers. Instruments were available to measure more things (and more accurately) than was possible in 1946, and scores of questions were crying out for answers that had not been and could not be found by scientific mountain expeditions due to the rigors of that environment.

Millions of people live and work at 17,000 feet, where the available oxygen in air is about half that at sea level. Hundreds of thousands are moderately active at sea level even though their bodies get inadequate oxygen because their lungs are damaged or their hearts incompetent. Though several hundred men and women have climbed Everest, most have done so using extra oxygen which means they are at a much lower altitude physiologically. An astonishing twenty have climbed Everest without any more oxygen than in the air about them. How can they do this? How can the millions who live at 17,000 feet survive and even thrive at altitudes that rapidly disable or even kill the sea level native taken there abruptly?

Operation Everest II, like its parent, was an attempt to dissect the marvellous changes the human body undergoes when exposed to lack of oxygen. We know a good deal about these changes and we know a good deal about what happens when acclimatization fails, or when we go from sea level to even a modest altitude too fast for our body to adjust. What we don’t know is which adjustments are due to lack of oxygen per se, and which are caused by the harsh environment at very high altitude. In fact, we aren’t completely sure which changes are beneficial and which are not. Operation Everest II would be a study of “pure” hypoxia, because the subjects would be living in a warm, comfortable room, with excellent and ample food and drink, plenty of recreation, opportunity to exercise at any level they wished, and protected from cold, exhaustion, anxiety and fear. There too researchers would have access to the most advanced instruments and technology.

The subjects were selected from more than 60 applicants, as carefully as one should choose members of a major expedition. All were very fit, all were interested in how their bodies functioned, most were climbers, and three had been to 20,000 feet or higher. Two were doctors, two were pre-medical students, and the rest had science backgrounds or interests. They were and are a fantastic group.

Twenty scientists were invited from among the leaders in physiology in the US and Canada; they were experts in special fields and all were very much interested in hypoxia; about half were also climbers. For Operation Everest I in 1946 Dick Riley and I had been joined by only a few other scientists still on active duty and had the support of some 30 naval and civilian personnel. The generous support of Captain Ashton Graybiel got that project underway in three months. OEII was more complicated: overall, about 70 persons were involved and it took five years to implement. John Sutton, my colleague on the Mount Logan studies, soon joined me and we enjoyed the enthusiastic help of John Maher, until his untimely death; Allen Cymerman, director of altitude research at ARIEM, took his place and John, Allen and I became the principals.

I had been looking for the right place and the choice soon became obvious: the US Army Research Institute of Environmental Medicine (ARIEM) in Natick, Massachusetts. The command agreed to let us use their large decompression chamber and excellent laboratory and equipment. Best of all, ARIEM generously provided staff to operate chamber and laboratory. Then came four years of frustrating effort to find money—a problem sadly familiar to mountaineers as well as to researchers. After three requests had been turned down by the National Institutes of Health, and my desperate appeals to many foundations had met only one favorable response, the chief of the Army Research and Development Command, General Gary Rapmund took the project in hand and gave us every consideration and his enthusiasm—which meant almost more.

Experiments on humans can only be done after each subject has been thoroughly briefed and understands what is to be done, including the risks and benefits, and has signed a Consent Form. Before this, every procedure must be approved by a Human Use Review Committee (HURC), a group of medical eagles who look at every aspect not only to protect the subjects, but also to determine what will be learned. We would be doing some rather daring and painful experiments and getting HURC approval took many months.

We would be using some very sophisticated electronic equipment—and every piece had to be inspected for safety in the chamber. Penetrations had to be drilled through the steel walls for the passage of dozens of shielded wires and tubes. Banks of oxygen cylinders had to be manifolded and fed to many outlets inside the chamber. A proper toilet and shower had to be prepared, a good diet kitchen made available, and special food obtained. The vacuum pumps and air conditioners would run steadily for six weeks: we had to be certain of fall-back equipment. These and many other details were attended to by Jim Devine, chief of the chamber crew. For Operation Everest I two auxiliary generators were specially installed because we would be operating during the hurricane season. We certainly did not anticipate Hurricane Gloria when she hit Natick—but ARIEM had the backup ready.

Our goal was to examine all stages of the “oxygen transport system” during acclimatization to lack of oxygen. That phrase includes acquisition of air by breathing in, passage of oxygen from lung to blood by diffusion, carriage of oxygen from lung to tissues by hemoglobin, passage of oxygen from blood to cells by diffusion, and utilization of oxygen by mitochondria (the tiny factories in each cell). We would also look at the reverse process—the carbon dioxide transport system, but in less detail. We would examine breathing and what drives it while awake and while asleep and during maximum work. We would look at the relationship between the ventilation of the lungs and the passage of blood past the lung sacs (alveoli)—called the ventilation/perfusion ratio. We would ‘look’ at the heart by echocardiography, a non-invasive procedure which bounces sound waves off the heart to draw a moving picture of its action. Many tests would be run on blood, and bits of muscle would be taken by needle biopsy to measure how muscle uses oxygen at rest and during strenuous work. We wanted to determine whether a man could maintain his normal weight despite hypoxia if given plenty of good food and comfortable surroundings. We particularly wanted to see how much work a well acclimatized man could do on the top of Everest, measurements never actually made before.

The most ambitious study required passing a small tube (Swan-Ganz catheter) into an arm vein, to the heart, past the valves, and into the lung. This enabled us to measure blood pressure in the pulmonary artery, pressures in various chambers of the heart, output of the heart, and (very important) the amount of oxygen remaining in venous blood returning to the heart from all over the body. By injecting a solution of several inert gases into a vein and measuring their appearance in the exhaled air, we could determine the diffusing capacity of the lung—that is, the ease or difficulty with which oxygen moves from lung to blood. The most painful test was biting out a small sample of a big thigh muscle at rest and after exercising to exhaustion.

The chamber was not exactly spacious. The men would live in the main chamber (20 by 9 feet) which was connected to a small lock (8 by 8) which in turn was attached to a small chamber (9 by 12) where most tests would be done. When we wished to “go up”, we entered the lock at sea level, closed the heavy steel door, and the air was drawn out until pressure in the lock equalled that in the chambers, when those doors would open. Lock trips took 5-15 minutes each way. The chambers were very well ventilated and monitored constantly for carbon dioxide and oxygen levels. In the lock, accessible to the subjects most of the time, were a toilet and shower. Food and small items could be “sent up” through small pass-through locks in each chamber. Double decker bunks, a treadmill, two exercise cycles and a climbing simulater (Versaclimber, generously loaned to us by the company) crowded the main chamber and lock, while the small chamber was crammed with instruments of every sort.

The amount of data obtained and now in computer programs is awesome and will take months to sort out and analyze, even longer to put into some 20 scientific papers, and longer still to fully understand. Here are some highlights of what we found.

Six of the subjects lived for ten days at 25,000 feet and made several trips to 29,000 feet, staying there for as long as four hours. Two subjects were taken out earlier, one at 18,000 and one at 25,000 feet because of brief collapse blamed on the altitude. Both recovered within minutes. Just as had happened during Operation Everest I all subjects had headaches beginning about 17-18,000 feet, but subsiding above 22-23,000 feet. All had trouble sleeping, partly due to headache, partly because they had very dry sore throats which nothing seemed to help—much as on high mountains, and partly because periodic breathing, which began about 10,000 feet, kept rousing them.

Above 20,000 feet headache and restless sleep led us to lower the chamber 1000 to 1500 feet from six in the evening to six the next day, heeding the mountaineers’ doctrine of working high but sleeping low. The ascent profile is shown in Figure 1, and is quite similar to that of Operation Everest I. We faced a dilemma: if the ascent were too fast our subjects were less likely to acclimatize fully, but if too slow, the time in the chamber would be unbearably long. By the fortieth day both subjects and scientists felt we could not continue much longer.

All of the subjects lost weight though all were fit and trim to start with. This was a surprise and disappointment because we went to great lengths to give them the best food we could and catered to every wish (including Ben and Jerry’s ice cream—their favorite). They simply lost appetite and consumed fewer calories.

All had been accustomed to lots of exercise, and they continued, running for 2 to 3 hours on the treadmill or cycling against a heavy load, or working out on the Versaclimber (an ingenious device which exercises both arms and legs). But above 23,000 feet they became more lethargic, exercised less (though they always felt better when they did so), and took less interest in reading or in anything except lying in the sack—just as during the final week of Operation Everest I.

Yet at 25,000 feet they did run on the treadmill and they were able to work up to a third their capacity at sea level during the maximum exercise test at 25,000 feet and only slightly less at 29,000 feet. When called on, they did have strength—for short bursts of maximum effort. As altitude increased they breathed larger and larger volumes of air during work, and moving air did not seem to be a limiting factor. On the other hand the amount of blood pumped at rest and during work decreased as altitude increased, suggesting that the ability to move blood may have limited what they could do—that and muscle fatigue.

Alveolar gas samples were taken to measure the amount of oxygen and carbon dioxide deep in the lungs for comparison with the amount in arterial and mixed venous blood. All were slightly more favorable than predicted by scientific mountain expeditions, suggesting that 29,000 feet may not be the absolute limit to how high a man could climb—if there were a higher mountain.

Could these men have climbed the Hillary step? Could they have summited and still had some reserve? Only a few others have done so without oxygen. How did these subjects compare with the few who have summited Everest breathing only the air about them? Even more interesting—are the Everest sum- miters different from you and me, and if so—how?

In answering this one must remember that we were watching and studying these acclimatizing men with our normal sea level eyes and brains; no one who is unaffected by hypoxia is there to watch those who summit Everest without extra oxygen. We know from what they have written that even the best are close to the limits of survival. They hallucinate, they stagger, they gasp for breath, every step is described as a tremendous effort, the world seems unreal. Our subjects, seen from sea level, were not so badly affected. Though they were certainly not as well as at sea level nor as fully acclimatized as many climbers on an expedition which has spent months on a mountain, they weren’t bad.

None of our measurements indicated that our subjects were supermen—just as tests done on elite summiters show that they are little different from other athletes but excel mainly in determination and ability to endure pain and to press on and up. It seems to be will and spirit and courage rather than physical differences which differentiate the man who climbs Everest without oxygen from other mortals.

Did we learn to predict who will and who will not acclimatize? Did we find any new yardsticks by which to measure acclimatization? Can we predict who is more likely to get altitude sickness and who will not? As I write this we are not far enough along with number crunching and analysis to answer these really important questions. Maybe later.

When all the data have been analyzed and hashed over we may have some suggestions for mountaineers. Perhaps of more benefit to more people, we may be able to shine new light on problems faced by the hundreds of thousands of patients short of oxygen at sea level because of heart or lung disease.

For the scientists and the subjects Operation Everest II was and remains an unforgettable experience—stimulating, exhausting, overwhelming at times, but very rewarding to all. Asked whether he would do it again, one subject said “No way … no, never … at least not for a while”. That’s how we all felt, then.