First there was the ascent of Mont Blanc in 1786; climbs followed in Asia and South America.

As explorers began to challenge the higher parts of the Earth, the high-altitude environment occasionally proved unexpectedly fatal.

Deaths in otherwise healthy young men were attributed to “heart failure”, “pneumonia” or “stroke”; a specific syndrome associated with rapid ascent was not suspected.

Thomas Ravenhill published the first detailed clinical description of high-altitude illnesses in 1913, based on his work with high-altitude miners in Chile.

In fact, high-altitude environment exposes travellers to the elements: cold, low humidity, increased ultraviolet radiation and decreased air pressure, all of which can cause problems.

However, the biggest concern is low oxygen level or “hypoxia”. At 3,000 metres for example, the inspired oxygen is only 69 per cent of sea-level value.

As mentioned in last week’s column, the magnitude of hypoxic stress depends on climbed altitude, rate of ascent and duration of exposure.

As discussed last week, acute mountain sickness is the most known form of high-altitude illnesses.

Two less common, but more serious conditions will be reviewed here: high-altitude pulmonary oedema and high-altitude cerebral oedema.

HAPE

A potentially fatal condition in which lung capillaries lose their integrity and start leaking fluid.

The fluid, made of blood products and water, accumulates in the lungs causing “oedema” and consequent distress.

It is a medical emergency. You should seek medical care and descend as soon as possible if you develop symptoms.

Waiting to descend can be disastrous as symptoms can worsen quickly and you may not be able to walk.

Symptoms: They include cough, breathlessness with activity and difficulty walking uphill.

These symptoms usually begin two to four days after arriving at altitude.

They could worsen, and you may feel more short of breath, even while resting. You may also begin to cough up pink, frothy sputum (spit).

Prevention: As with other high-altitude illnesses, the best way to prevent high-altitude pulmonary oedema is to ascend slowly.

Preventive medicines are not usually recommended unless you have a history of HAPE and/or you must ascend quickly to altitudes above 3000 metres. Preventive medicines may include Nifedipine (commonly used to treat high blood pressure), Dexamethasone (a steroid derivative), or Acetazolamide (a special diuretic).

Treatments:

• Supplemental oxygen is the most effective treatment and should be started as soon as possible. It should be continued until symptoms resolve.

• Hyperbaric treatment, if available, could be used and may be an alternative to descent. Here, you would spend several hours in an inflatable pressure bag that you are zipped into, and it is inflated with a foot pump. When inflated, the air inside the chamber is more like the air you breathe at lower altitudes.

This increases the amount of oxygen in your blood, quickly relieving symptoms of high-altitude illness. The total packed weight of bag and pump is about 14lb (6.5kg). Absolute contraindication to using the bag includes weak or absent spontaneous respiration; relative contraindications are middle-ear congestion (small risk of barotrauma) and claustrophobia. Hyperbaric stay could be combined with oxygen supplementation.

• Nifedipine and/or other medicines mentioned above may be helpful.

• Stay warm and avoid cold temperatures that might worsen hypoxia and affect blood circulation.

HACE

Another life-threatening altitude disease. It is caused by leaky capillaries in the brain, leading to cerebral swelling. Along with injuries, a 2008 medical study showed it as the leading cause of death at high altitudes.

It usually occurs within one to three days after travelling above 3,000 to 3,500 metres.

Symptoms:

• Exhaustion, severe weakness and lethargy

• Difficulty walking straight

• Confusion and irritability

Prevention and treatment is the same as with HAPE.

•Joe Yammine is a cardiologist at Bermuda Hospitals Board. He trained at the State University of New York, Brown University and Brigham and Women’s Hospital. He holds five American Board certifications. He was in academic practice between 2007 and 2014, when he joined BHB. During his career in the US, he was awarded multiple teaching and patients’ care recognition awards. The information herein is not intended as medical advice nor as a substitute for professional medical opinion. Always seek the advice of your physician. You should never delay seeking medical advice, disregard medical advice or discontinue treatment because of this article.