John Zeckendorf, who in 2017 became the first Tasmanian to reach the Mount Everest summit, said the rescue mission would have been difficult and Mr Lee was extremely lucky to be alive.

"Very few people could of pulled off that rescue," Mr Zeckendorf said.

Mr Lee, tweeting from his hospital bed in Kathmandu with his mother at his side, wrote on Thursday "I am alive...Body wrecked with liver problems ... vision damage. Piecing what happened. Rest."

The climber, who attended Prospect High School and the University of Tasmania, has documented his dreams of reaching the Mount Everest summit - without oxygen - on his blog.

His latest Mount Everest summit attempt ended when climbers found him unconscious last week on the Northern slopes and safely brought him down from an altitude of 7500 metres.

Mr Zeckendorf said the fact that Mr Lee made it down alive is nothing short of a miracle.

"Such a good rescue is so unlikely that I am rather gobsmacked," Mr Zeckendorf said.

"Any rescue above 6000 feet is hard, and it gets exponentially harder the higher you go. Even body retrieval is virtually impossible so it is an extraordinary effort to get back down," he said.

"He was lucky he happened upon a team that was strong enough to bring him down, who were in the right place at the right time, and also happened to have a rope ... I don't know of many teams who would carry a spare rope up there just for the sake of it."

After viewing media coverage of the rescue, Mr Zeckendorf said the rescuers appeared to place Mr Lee in a sleeping mat, which would of acted like a sled, and tied rope around his body to keep him secure.

"The rescuers would of worked in a star pattern around him. The strongest ones are behind [Mr Lee] lowering him down, and the ones up the front are stopping him from skidding off the ridge.

"It would be really hard work, with an extra 20 kilos pulling you down the mountain, when you can barely balance. Don't forget you would be struggling yourself, so you have to get the strength to carry that extra weight."

Mr Zeckondorf said weather conditions for this year's climbing season have been unusual, caused by a hurricane off the coast of India, making Mr Lee's survival even more amazing.

"Everest is right on the edge of the atmosphere and when the air pressure drops because of the cyclone, it can change everything on the mountain, how much oxygen there is, and air pressure," he said.

"It was a tough year. It was colder, it was windier, there was a shorter weather window of three days, and there was a lot more precipitation about, which means softer snow which means harder work."

Given that Mr Lee was attempting to climb without oxygen, his statistical chance of survival was even less.

"Doing it without oxygen is probably a bit like playing Russian roulette. You put one bullet in a revolver and you have a one in six chance of dying, but when you climb Everest without oxygen the chances are probably much higher ... you are stacking up probability against you.

"It is exceptionally dangerous, and unusual. [With rough figures] about 5000 people have summited, and about 200 go without oxygen."

Eleven climbers have died in the 2019 Mount Everest climbing season.