His familiar black medical bag will be left behind.

Instead, a lightweight, portable bag - that can be quickly transformed into a low-pressure hyperbaric chamber - will be toted by a Salt Lake internist when he ascends on of the world's most treacherous mountains next month.Dr. Robert Ross Greenlee will be studying and documenting the effectiveness of the Gamov Hyperbaric Bag, invented to treat altitude illness, when he travels with the Wyoming Centennial Everest Expedition to Mount Everest.

Greenlee, who's taking a three-month leave as medical director of Intermountain Health Care's Instacare in Rose Park, will be one of three doctors on the 34-member expedition, tagged "Cowboys on Everest."

His specific assignment: To treat the sick climbers - a colossal task considering the altitude to which they'll scale.

Although surveyors disagree on the exact height of Everest, the 1954 Indian government survey set the present official height at 29,028 feet.

Altitude illnesses can affect individuals at elevations of 8,000 feet. In fact, the medical clinic at Snowbird reports frequent cases of a mild altitude mountain sickness weekly.

Yet, according to Greenlee, treatments have traditionally been limited.

"The major intervention consists of taking the victim to a lower altitude as quickly as possible," the 31-year-old physician said. "Unfortunately, weather conditions, avalanche conditions or even the severity of the patient's illness occasionally make rapid descent impossible.

"This unavoidable delay can lead to disastrous, and in some cases, fatal consequences."

The physician/climbers on the Wyoming Centennial Everest climb have geared up to treat the inevitable injuries.

"It would be nice if we had a hospital, because people are going to get pretty sick," the Salt Lake doctor said. "But we are only taking what is feasible and necessary."

Thousands of dollars of "bare necessities," - most donated by Rose Park Instacare - will include four large boxes of medical supplies. Sutures, syringes, sponge trays, surgical scrubs, adhesive bandages will be taken along to treat cuts, burns, scrapes, broken bones, sunburns, snow-blindness and other injuries.

Another large box will carry some 50 different types of drugs - from antibiotics to pain killers to anti-nausea medication.

The hyperbaric bags are the highest-tech equipment they'll cart. Four bags will be taken as physicians expect to see at least 20 cases of acute mountain sickness, which causes weakness, nausea, vomiting, headaches, and confusion.

More disturbing to Greenlee is the possibility of high altitude pulmonary edema, marked by coughs, increased shortness of breath and respiratory rate.

The air-tight cylindrical bags, into which people can be placed, will likely undergo repeated, rigorous tests. The bags simulate descent.

According to Greenlee, each bag can be pressurized to 2 pounds per square inch, which is equivalent to descending to between 5,000 and 6,000 feet.

"If a person is so sick that he can't walk, you are looking at a difficult rescue," Greenlee said. "On the other hand, if a person can be treated overnight in a bag and can then walk down under his own powers, you may have saved his life."

The bags are pressurized with foot pumps. They have bleed-off type valves that release air once the desired pressure in the bag is reached. Attachment of a manometer ensures that the valves are functioning properly.

"There's a lot of technical aspects to the bags," Greenlee said. "You can't just stick a person in like you would something in a microwave, and take him out in a few minutes and expect him to be all better.

"Probably the most important thing is preventing the carbon dioxide from building up in the bags so you have to keep air circulating through."

Although there is limited data about the effectiveness of the bags, Greenlee said, what information is available is encouraging.

"Even climbers who were not thought to be ill reported feeling much better after use of the bag," he said. One climber with frostbite was placed in the bag and felt that he could feel an immediate improvement in sensation in the affected areas, Greenlee said.

Positive notes aside, the local doctor, who will be stationed at the advance base camp (21,000 feet), won't likely venture higher. There will, however, be a camp at 27,000 or 28,000 feet - the so-called "death zone."

"The problem is that I have read too much about the altitude illnesses and I am not convinced I want to go up that high," he said. "The truth of the matter is there just isn't enough oxygen up there to do yourself any good."