effects of high altitude
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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)