As Siachen survivor Hanamanthappa battles for life, this is what he has to face.

The Telegraph reports that a search-and-rescue team found Hanamanthappa conscious but drowsy and disoriented, dehydrated, suffering from poor oxygen supply and dangerously low blood sugar level. Doctors at the rescue site, a mountain top at 19,600 feet, resuscitated him, treated him with warm intravenous fluids, humidified warm oxygen, and passive external rewarming and sent him via helicopter to a base camp at 10,000 feet, then on an aircraft to Delhi.

"When someone is buried in snow, the cold and lack of oxygen are the biggest threats," said William Selvamurthy, a specialist in high-altitude physiology.

"It is possible Hanamanthappa was trapped in a space with air-carrying conduits, air from the surface leaked into that space. It would have also helped if he refrained from significant activity - lack of activity would have helped reduce the body's metabolic needs," he said.

Physiologists say the human body when exposed to extreme cold responds involuntarily with vasoconstriction - a narrowing of blood vessels - to minimise heat loss from the body to the surroundings. Vasoconstriction helps delay hypothermia, or loss of body heat, a doctor said.

The normal body temperature is about 37C, and persistent hypothermia can progress to a severe, irreversible and life-threatening condition. Any hypothermia leading to a temperature drop up to 28C can lead to impaired consciousness, a drop below 24C leads to unconsciousness.

Physiologists say the bulletin from the Army Hospital suggests the life-saving measures that Hanamanthappa requires themselves pose a challenge. "The rewarming can lead to vasodilation, or expansion of the blood vessels, which can contribute to a drop in blood pressure," Selvamurthy said.

"Someone who is in a dehydrated condition is already likely to have low blood pressure, so the rewarming can exacerbate the fall in blood pressure."

Hanamanthappa has been administered antibiotics, a medication to increase his blood pressure, and is receiving intravenous fluids. He is under care of a team of critical care specialists, surgeons, a neurologist, a nephrologist, and an endocrinologist.