Effects of High Altitude

Effects of High Altitude Area

The Static AtmosphereThe Static Atmosphere

An envelope of atmosphere 100 km above it.

Three zones; 11 km -‘Troposphere', The middle zone 20 km -- ‘Stratosphere' The outermost -- ‘Ionosphere'.  

Effects of High Altitude AreaEffects of High Altitude Area

Areas located above 9000’ (2700 m) High altitude aviation & troops deployed at

high altitude – Indian troops at locations highest in the world

Environment– Low atmospheric pressure & pO2

– Low temp & humidity– Intense sunshine & cosmic radiation– Isolation in monotonous mountainous area– Enemy fire

ALTITUDEALTITUDE Pressure TemperaturePressure Temperature Oxygen Oxygen Partial Partial pressure pressure (mm Hg)(mm Hg)

Equivalent Equivalent Oxygen Oxygen percentagepercentage

FeetFeet MetersMeters (mm Hg)(mm Hg) C DecreaseC Decrease CC      

  00   00   760.0760.0   1515   00   159.2159.2   20.9620.96

1,0001,000 305305 733.0733.0 1313 -2-2 153.6153.6 20.1820.18

2,0002,000 610610 706.6706.6 1111 -4-4 148.1148.1 19.4619.46

3,0003,000 914914 681.0681.0 99 -6-6 142.7142.7 18.7618.76

4,0004,000 1,2191,219 656.4656.4 77 -8-8 137.5137.5 18.0718.07

5,0005,000 1,5241,524 632.4632.4 55 -10-10 132.5132.5 17.4117.41

6,0006,000 1,8291,829 609.0609.0 33 -12-12 127.6127.6 16.7716.77

7,0007,000 2,1342,134 586.4586.4 11 -14-14 122.9122.9 16.1516.15

8,0008,000 2,4382,438 564.4564.4 -1-1 -16-16 118.2118.2 15.5415.54

9,0009,000 2,7432,743 543.2543.2 -3-3 -18-18 113.8113.8 14.9614.96

10,00010,000 3,0483,048 522.6522.6 -5-5 -20-20 109.5109.5 14.3914.39

11,00011,000 3,3533,353 502.6502.6 -7-7 -22-22 105.3105.3 13.8413.84

12,00012,000 3,6583,658 483.2483.2 -9-9 -24-24 101.2101.2 13.3113.31

13,00013,000 3,9623,962 464.6464.6 -11-11 -26-26 97.397.3 12.7912.79

14,00014,000 4,2674,267 446.4446.4 -13-13 -28-28 93.593.5 12.2912.29

15,00015,000 4,5724,572 428.8428.8 -15-15 -30-30 90.590.5 11.8111.81

16,00016,000 4,8774,877 411.8411.8 -17-17 -32-32 86.386.3 11.3411.34

17,00017,000 5,1825,182 395.4395.4 -19-19 -34-34 82.882.8 10.8910.89

18,00018,000 5,4865,486 379.4379.4 -21-21 -36-36 79.579.5 10.4510.45

19,00019,000 5,7915,791 364.0364.0 -23-23 -38-38 76.276.2 10.0210.02

20,00020,000 6,0966,096 349.2349.2 -25-25 -40-40 73.173.1 9.619.61

Physiological AdaptationPhysiological Adaptation Low pO2 >> alveolar & arterial hypoxia >> tissue

hypoxia Higher tissue O2 demand met by rise in cardiac

output & pulmonary ventilation Tachypnoea & tachycardia – hypoxic drive

With time, the higher “frequency”- replaced by “amplitude” rise

Erythropoietin from kidney – RBC count, volume, Hb increases

Glucocorticoid & vasopressin to counteract hypoxic stress

Haemopoeietic, CVS, Resp & CNS systemic changes

Indians – changes usually > 2500 m (30% decrease in atm pressure)

Physiological changes in early adaptation Interstitial fluid into vascular compartment >>

hypervolemia >>overload of pulmonary circulation Hyperventilation >> tissue CO2 washout >>

hypocapnia & alkalosis >> left shift of O2

dissociation curve >> fall in cerebral/ coronary flow

Increase in 2,3 DPG in RBC >> restores O2

delivery to tissues; increase sensitivity of resp centre to lower CO2 tension

Physiological AdaptationPhysiological Adaptation

Physiology to PathologyPhysiology to Pathology

Depends on :-Rapidity of exposure to atmospheric low

pressureSeverity & duration of O2 lackPhysical condition of body

Beneficial adaptive response becomes aberrant to cause disease process

Clinical SyndromesClinical Syndromes

Acute Mountain sicknessHigh Altitude Pulmonary EdemaChronic Pulmonary hypertensionHigh Altitude Cerebral edemaCoronary / cerebrovascular insufficiencySeroche- Monge’s diseaseFlare up of pre-contracted infectionPsychological effects

Acute Mountain Sickness Severity of symptoms as per altitude Headache, insomnia, disturbed sleep Nausea, vomiting, giddiness Palpitations Fatigue, breathlessness Disinterest in work, lack of concentration, depression,

muscular weakness, drowsinesss – “hangover” Prevention

– Acclimatization– Proper fluid intake– Avoid smoking, alcohol, late dinner– Aspirin– Duty as “buddy system”- report sick earliest– Evacuate to lower altitude

AMS – Symptomatic TreatmentAMS – Symptomatic Treatment

Headache– Acetaminophen / ASA– Avoid narcotics (decrease HVR)

Nausea– Prochlorperazine 10mg po / im– Stimulates HVR

AMS – Specific TreatmentAMS – Specific Treatment

Acetazolamide– Prophylactic and curative– Carbonic anhydrase inhibitor– Causes bicarbonate diuresis and metabolic acidosis– Increased ventilation and arterial oxygenation– Dose 250 mg po tid

Dexamethasone– Reduces cerebral edema – Useful if acetazolamide not tolerated– Dose 8mg im/po followed by 4mg im/po q6h

Ginkobiloba

High Altitude Pulmonary OedemaRisk factors Rapid Ascent above 3000 m Physical exertion H/O AMS or HAPO Re-inductees

Clinical features Usually < 3 days; rarely up to 10 days Dyspnoea, cough, palpitation, nausea

vomiting, chest discomfort, blood stained sputum

Cyanosis, tachycardia, hypertension, pulmonary rales

Management of HAPOManagement of HAPO Evacuation to lower altitude Oxygen Recompression in chamber – 1 atm X 16hrs All cases of HAPO/ HACO in portable one man

recompression bag; 150 mm Hg (reduce altitude by 6000’); reduce to 50mm Hg every 5 min; recompress 150mm Hg(ensures air circulation)

Bring patient out of bag 2 hourly for 15-20 min - monitoring/ nursing

Diuretics Anti-hypertensives Antibiotics ?

HAPE - TreatmentHAPE - Treatment

Stop Ascent!!!Descend at least 2000 ft unless close clinical

monitoring possibleIf monitoring possible

– Mild Cases Bed Rest (1-2 days)

– Moderate Cases Bed Rest Oxygen

HAPEHAPE – Treatment – Treatment ( cont )( cont )

– Severe CasesDescent (1500 to 3000 feet, may

reattempt ascent

in 2-3 days)Oxygen 4-6 l / minHyperbaric chamberpharmacological therapy

HAPEHAPE – – Pharmacological TreatmentPharmacological Treatment

Goals1. Lower pulmonary artery pressure2. Lower pulmonary blood volume3. Lower pulmonary vascular resistance

Nifedipine :10mg sl then 30mg SR bid Sildenafil : 25-50 mg Nitric oxide : inhalation of 40 ppm of NO

produces decrease in syst pulm arterial pressure in those prone to HAPE

Lasix : 40-80 mg orally or IV Beta agonist inhaler (salmetrol)

HAPEHAPE - - HyprebaricTreatmentHyprebaricTreatment

Portable Hyperbaric Chambers– Lightweight (14.9 lb)– Manually pressurized– Generate 103mm Hg (2 psi) above ambient pressure

Simulates descent of 4000-5000 feet at moderate altitudes Simulates descent of 9000 feet at top of Mt. Everest

– After short course of treatment patient often able to descend on their own

HAPO BagHAPO Bag

High Altitude Cerebral Edema

High Altitude Cerebral Edema High Altitude Cerebral Edema (HACE/ HACO)(HACE/ HACO)

Least common but most lethal altitude illness

Usually occurs above 12,000 feetSymptoms usually develop over 1-3

days– reported range 12 hours to 9 days

Represents end stage of AMS

High Altitude Cerebral EdemaHigh Altitude Cerebral Edema

Diagnostic criteria presence of change in mental status

and /or ataxia in a person with AMS

Or presence of both ie change in mental status

and ataxia in a person without AMS

Global encephalopathy Ataxia Altered mentation Seizures Occasional CN palsies (due to increased ICP) Papilledema Retinal hemorrhage Coma Death due to brain herniation

High Altitude Cerebral Edema : High Altitude Cerebral Edema : C/FC/F

Pathophysiology– Hypoxia induces neurohumoral and hemodynamic

responses resulting in

1. over perfusion of microvascular beds

2. elevated hydrostatic pressure,

3. capillary leakage

4. edema

High Altitude Cerebral EdemaHigh Altitude Cerebral Edema

““Tight Fit” HypothesisTight Fit” Hypothesis

All brains swell at high altitudeDegree of HACE related to ratio of CSF

to brain and thus ability to compensate for acute edema

Explains random nature of disease

MRI findings ….MRI findings ….

Edema of splenium of corpus callosum

Treatment– Descend 2000 feet and keep descending

until symptoms resolved– Supplemental O2 (4-6 l /minute)– Dexamethasone 8mg iv then 4mg q6h

iv – Hyperbaric chambers

High Altitude Cerebral EdemaHigh Altitude Cerebral Edema

Chronic Pulmonary Hypertension

> 3600 m for 6 months or more Etiology unsure Reverses with return to low altitude

Coronary/ cerebrovascular insufficiency Stress of hypoxia/ cold Atherosclerosis

Seroche- Monge’s diseaseSeroche- Monge’s disease

Alveolar hypoventilation syndrome at MSL Affects middle aged men Headache, dizziness, depression, drowsiness,

coma Polycythaemia, cyanosis, clubbing, pulmonary

htn, right ventricular hypertrophy Cured on return to lower altitude

Flare-up pre-contracted infectionsViral, amoebic hepatitisMalariaTuberculosis ?Diabetes mellitus

PsychologicalPsychological

Disinterest, irritability, insubordination, irrational reaction, lengthening reaction time, ? Dementia (irreversible at low altitude)

OthersDimness of vision, loosening of teeth,

loss of weight, flatulence, indigestion, loose bowels, anemia

Acclimatization ScheduleAcclimatization Schedule (AO 110 / 80; DGAFMS Memorandum:140;(AO 110 / 80; DGAFMS Memorandum:140;

“Red Book” Para 167) “Red Book” Para 167)

Stage 1 (2700 – 3600m) [9000’-12000’] 6days

Days 1-2 : Rest, short walks, no climbDays 3-4 : Slow pace walk 1.5-3 km, no

steep climbDays 5-6 : 5 km walk, climb 300m

Stage 2Stage 2 (3600- 4500 m) (3600- 4500 m) [12000’-15000’][12000’-15000’] 4 days4 days

Days 1-2 : slow walk 1.5-3 km, no steep climb

Day 3 : slow walk, climb 300mDay 4 : 300m climb with equipment

Stage 3 (> 4500m) [>15000’] 4daysSame as Stage 2

Re-entry Absence from high altitude > 4weeks : Full

acclimatization Absence < 10 days : No acclimatization Absence 10 days to 4 weeks - 4days

acclimatization at each stage as follows: – Day 1-2 : rest, short walk– Day 3 : slow walk 1-2 km, no climb– Day 4 : walk 1-2 km, climb up to 300m

Acclimatization ScheduleAcclimatization Schedule (AO 110 / 80; DGAFMS Memorandum:140;(AO 110 / 80; DGAFMS Memorandum:140;

“Red Book” Para 167) “Red Book” Para 167)