Vicki Evans WFNN Vice President Sydney Australia Vicki

Vicki Evans WFNN: Vice President Sydney, Australia. Vicki. Evans@health. nsw. gov. au THE DANGERS OF HIGH ALTITUDE CLIMBING.

Mt Kosciuszko

Barometric Pressure = a measurement of the air’s force against a surface. 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. 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 O 2 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.

P 02 mm/Hg 40 Altitude(m) 9000 8000 50 7000 Extreme Altitude Above 7, 000 m – • Hallucinations • MRI changes • Memory retrieval impaired • Loss of consciousness 100 4000 3000 2000 150 1000 0 High Altitude 5000 Very High Altitude 6000 • • 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 1500 -2500 m

What causes altitude sickness? Ascending faster than 300 m 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, 2200 -2500 m above sea level - ski resorts. • Symptoms vary & is related to the rate of ascent (> 300 m/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.

Prevention of AMS • 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.

MRI - Cerebral Edema 33 yr 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

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