THE DANGERS OF HIGH ALTITUDE CLIMBING. Vicki Evans WFNN: Vice President Sydney, Australia.

Mt Kosciuszko

Barometric Pressure o Low elevations: the pressure is greater, since the molecules of air are compressed from the weight of the air above them. BUT… o Higher elevations: there's less pressure and the molecules are more dispersed. = a measurement of the air’s force against a surface. o The % of oxygen at sea level is the same as at high altitudes - 21%. But because the air molecules are more dispersed, each breath delivers less oxygen to the body. o A breath at 12,000 feet (3,657.6 m), is 40% less oxygen than at sea level. At 18,000, feet it’s 50% less.

Physiology As O2 pressure decreases, breathing & heart rate increase, as does the hearts’ contractility & force of contraction. RBCs increase in size & production. Increased urination & sweating = Dehydration Polycythemia + dehydration maybe risk factors for sludging of blood in small vessels  TIAs. Cerebral damage is due to disruption to the BBB.

Above 7,000m – Hallucinations MRI changes Memory retrieval impaired Loss of consciousness Learning & spatial memory impaired Dizziness & tingling Exertional dyspnoea Psychomotor impairment Reaction time slows Altered sleeping patterns & frequent waking at night Altered night vision Commercial aircraft are pressurised to an equivalent of m Extreme Altitude Very High Altitude High Altitude Altitude(m)P02mm/Hg Altitude

What causes altitude sickness?  Ascending faster than 300m per day … and …  Vigorous exercise… * Physically fit individuals & athletes also get altitude sickness.

Acute Mountain Sickness (AMS) = the body’s response to low oxygen pressure (“thinner air”) at high altitudes. Mild symptoms, m above sea level - ski resorts. Symptoms vary & is related to the rate of ascent (> 300m/day) & how long the person is at that height. Like a hangover - headache, nausea & fatigue. Can happen regardless of how fit or experienced the climber is. Can lead to life threatening HAPE & HACE.

High Altitude Pulmonary Edema (HAPE) Excess fluid on the lungs causing dyspnoea. It is never normal to feel breathless at rest - even on the summit of Everest!

High Altitude Cerebral Edema (HACE) Potentially fatal metabolic encephalopathy associated with a time-dependent exposure to hypoxia at altitude. A form of vasogenic edema Neurological manifestations – persistent severe headache, confusion, clumsiness, ataxic, fatigue, irritability, vague, visual disturbances, photophobia, seizures, CN III & VI palsies, extreme emotion, loss of consciousness ….. death. DESCENT is the most successful treatment.

AMS occurs by going too high, too quickly. Need to acclimatise – give the body time to adjust to altitude. Sleep at an altitude LOWER than the altitude you were at during the day. Drink plenty of water (avoid alcohol). Acetazolamide (Diamox). ? High carbohydrate diet ?gingko biloba. Prevention of AMS

MRI - Cerebral Edema 33yr old male after evacuation from Mt Denali. NB: leaked fluid - at high altitude from capillaries, rather than swollen cells.

Treatment of HACE & HAPE Immediate descent! Only one drug is currently known to prevent AMS and to be safe for this purpose: Acetazolamide (diamox). It causes some minor side effects - tingling fingers and a funny taste. ? Dexamethasone Pressure bags (Gamow) and oxygen can buy time

Abhijeet Gorhe Clinical Research Coordinator, UC Davis Medical Center. Introducing…