It is the lack of oxygen rather than the reduced air pressure that actually limits the height at which we can breathe. An elevation of about 20,000 feet above sea level is the maximum height at which sufficient oxygen exists in the air to sustain us.
And at 10,000 feet (Breckenridge, CO), there is approximately 33% less effective oxygen.
Above about 8,000 meters (26,000 feet), the human body cannot survive at all, and starts to shut down. Mountaineers call this altitude the "death zone." To prevent severe altitude sickness, mountaineers bring supplemental (extra) supplies of oxygen and limit their time in the "death zone."
It refers to altitudes above a certain point where the amount of oxygen is insufficient to sustain human life for an extended time span. This point is generally tagged as 8,000 m (26,000 ft, less than 356 millibars of atmospheric pressure).
Above about 8,000 meters (26,000 feet), the human body cannot survive at all, and starts to shut down. Mountaineers call this altitude the "death zone." To prevent severe altitude sickness, mountaineers bring supplemental (extra) supplies of oxygen and limit their time in the "death zone."
By a curious coincidence, the highest point on earth, that is Mt. Everest at 8,848 m, appears to be right at the limit of human tolerance to hypoxia. The altitude of the highest permanent human habitation, that is a town, is 5,100 m.
By 7,000 meters (22,966 feet), survival times plummet and lucid thought becomes difficult. By 8,000 meters—the so-called “death zone”—even the strongest climbers can survive for a few days at best.
As the body acclimates to higher altitude (for most this means an altitude greater then 8,200 feet), one urinates more often as the body works to avoid respiratory alkalosis (elevated blood PH) by your kidneys excretion of bicarbonate.
Today's fighter pilots therefore operate in cabins pressurized according to a pressurization schedule,15 they breathe up to 100% oxygen,15 and they wear and use pressure breathing equipment.
Pulmonary effects can present as early as within 24 hours of breathing pure oxygen. Symptoms include pleuritic chest pain, substernal heaviness, coughing, and dyspnea secondary to tracheobronchitis and absorptive atelectasis which can lead to pulmonary edema.
Breathing air containing 21% oxygen risks acute oxygen toxicity at depths greater than 66 m; breathing 100% oxygen there is a risk of convulsion at only 6 m.
The concentration of oxygen in normal air is only 21%. The high concentration of oxygen can help to provide enough oxygen for all of the organs in the body. Unfortunately, breathing 100% oxygen for long periods of time can cause changes in the lungs, which are potentially harmful.
At oxygen levels of 10 to 14 percent, faulty judgment, intermittent respiration, and exhaustion can be expected even with minimal exertion (Exs. 25-4 and 150). Breathing air containing 6 to 10 percent oxygen results in nausea, vomiting, lethargic movements, and perhaps unconsciousness.
When the altitude of an airplane is less than 12,500 feet, there is no supplemental oxygen required for anyone in a private plane. From 12,500 feet to 14,000 feet, supplemental oxygen must be used by the required flight crew for any portion of the flight that is more than 30 minutes.
It occurs even in healthy persons at altitudes above 6000 ft. It may lead to sleep disturbances with frequent awakenings and a feeling of lack of air [29]. De Aquino Lemos et al. found that hypoxia reduced total sleep time, sleep efficiency, slow-wave sleep, and rapid eye movement.
“As the atmospheric pressure reduces, the gas that's dissolved in the liquid will come out of that liquid. So essentially in the bowels, you'll have more gas that will diffuse across into the gut and expand, obviously causing flatus.”
There is lower atmospheric pressure at higher altitudes. Something known as the ideal gas law explains why the same mass of gas expands and takes up more space in your bowels. The greater the volume of gas building up in your belly, the more likely you are to pass it.
Because you are prone to dehydration and constipation at altitude, drink lots of water and don't overeat.
At 10,000 feet msl, there will be a standard temperature of -4.8° C or 23.3° F. Keep in mind at sea level, the standard temperature is 15° C or 59° F.
Somewhere between 30,000 and 40,000 feet the pressure around you becomes far too low to push those oxygen molecules across the membranes in your lungs, and you get hypoxic (altitude sickness). If you try to breathe 100 percent oxygen above 40,000 feet for very long without a special type of mask, you'll die.
Air has a density of about 1.2 g /litre, and water has a density of about 1 kg /litre. Air is therefore about 830 times less dense than water. The height of a column of water in a water barometer is about 10 m.
The mountain has claimed over 300 climbers in recent history, and about two-thirds of that number remain on the mountain. The current estimate of remains left behind on Everest total around 200.
This adds to the technical challenge of climbing K2. The altitude presents yet another obstacle. Some of the most challenging climbing is done in the death zone, or the part of the mountain located above 8,000 metres (26,000 feet) where the body is deprived of oxygen.
To answer the question simply, yes, a helicopter can fly to the top of Mount Everest. A helicopter-based summit to the top of Everest has been successful as well. In 2005, Didier DelSalle flew to the top of Mount Everest.