Effect of high altitude, acclimitization

1. Effects of High Altitude

3. Effects of High Altitude Area

4. The Static Atmosphere
 An envelope of atmosphere 100 km above
it.
 Three zones;
 11 km -‘Troposphere',
 The middle zone 20 km -- ‘Stratosphere'
 The outermost -- ‘Ionosphere'.

5. Effects 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

6. ALTITUDE Pressure Temperature Oxygen
Partial
pressure
(mm Hg)
Equivalent
Oxygen
percentage
Feet Meters (mm Hg) C Decrease C
0 0 760.0 15 0 159.2 20.96
1,000 305 733.0 13 -2 153.6 20.18
2,000 610 706.6 11 -4 148.1 19.46
3,000 914 681.0 9 -6 142.7 18.76
4,000 1,219 656.4 7 -8 137.5 18.07
5,000 1,524 632.4 5 -10 132.5 17.41
6,000 1,829 609.0 3 -12 127.6 16.77
7,000 2,134 586.4 1 -14 122.9 16.15
8,000 2,438 564.4 -1 -16 118.2 15.54
9,000 2,743 543.2 -3 -18 113.8 14.96
10,000 3,048 522.6 -5 -20 109.5 14.39
11,000 3,353 502.6 -7 -22 105.3 13.84
12,000 3,658 483.2 -9 -24 101.2 13.31
13,000 3,962 464.6 -11 -26 97.3 12.79
14,000 4,267 446.4 -13 -28 93.5 12.29
15,000 4,572 428.8 -15 -30 90.5 11.81
16,000 4,877 411.8 -17 -32 86.3 11.34
17,000 5,182 395.4 -19 -34 82.8 10.89
18,000 5,486 379.4 -21 -36 79.5 10.45
19,000 5,791 364.0 -23 -38 76.2 10.02
20,000 6,096 349.2 -25 -40 73.1 9.61

8. Physiological 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

9. Physiological Adaptation
 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

10. Physiology to Pathology
Depends on :-
 Rapidity of exposure to atmospheric low
pressure
 Severity & duration of O2 lack
 Physical condition of body
Beneficial adaptive response becomes
aberrant to cause disease process

11. Clinical Syndromes
 Acute Mountain sickness
 High Altitude Pulmonary Edema
 Chronic Pulmonary hypertension
 High Altitude Cerebral edema
 Coronary / cerebrovascular insufficiency
 Seroche- Monge’s disease
 Flare up of pre-contracted infection
 Psychological effects

12. 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

13. AMS – Symptomatic Treatment
 Headache
– Acetaminophen / ASA
– Avoid narcotics (decrease HVR)
 Nausea
– Prochlorperazine 10mg po / im
– Stimulates HVR

14. AMS – 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

15. High Altitude Pulmonary Oedema
Risk 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

16. Management 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 ?

17. HAPE - Treatment
 Stop Ascent!!!
 Descend at least 2000 ft unless close clinical
monitoring possible
 If monitoring possible
– Mild Cases
 Bed Rest (1-2 days)
– Moderate Cases
 Bed Rest
 Oxygen

18. HAPE – Treatment ( cont )
– Severe Cases
 Descent (1500 to 3000 feet, may
reattempt ascent
in 2-3 days)
 Oxygen 4-6 l / min
 Hyperbaric chamber
 pharmacological therapy

19. HAPE – Pharmacological Treatment
 Goals
1. Lower pulmonary artery pressure
2. Lower pulmonary blood volume
3. 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)

20. HAPE - HyprebaricTreatment
 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

21. HAPO Bag

26. High Altitude Cerebral Edema

27. High Altitude Cerebral Edema
(HACE/ HACO)
 Least common but most lethal altitude
illness
 Usually occurs above 12,000 feet
 Symptoms usually develop over 1-3
days
– reported range 12 hours to 9 days
 Represents end stage of AMS

28. High 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

29. High Altitude Cerebral Edema :
C/F
 Global encephalopathy
 Ataxia
 Altered mentation
 Seizures
 Occasional CN palsies (due to increased ICP)
 Papilledema
 Retinal hemorrhage
 Coma
 Death due to brain herniation

30. High Altitude Cerebral Edema
 Pathophysiology
– Hypoxia induces neurohumoral and hemodynamic
responses resulting in
1. over perfusion of microvascular beds
2. elevated hydrostatic pressure,
3. capillary leakage
4. edema

31. “Tight Fit” Hypothesis
 All brains swell at high altitude
 Degree of HACE related to ratio of CSF
to brain and thus ability to compensate
for acute edema
 Explains random nature of disease

32. MRI findings ….
Edema of splenium of
corpus callosum

33. High Altitude Cerebral Edema
 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

34. 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

35. Seroche- 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

36. Flare-up pre-contracted infections
 Viral, amoebic hepatitis
 Malaria
 Tuberculosis ?
 Diabetes mellitus

37. Psychological
 Disinterest, irritability, insubordination,
irrational reaction, lengthening reaction
time, ? Dementia (irreversible at low
altitude)
Others
 Dimness of vision, loosening of teeth,
loss of weight, flatulence, indigestion,
loose bowels, anemia

38. Acclimatization Schedule
(AO 110 / 80; DGAFMS Memorandum:140;
“Red Book” Para 167)
Stage 1 (2700 – 3600m) [9000’-12000’]
6days
 Days 1-2 : Rest, short walks, no climb
 Days 3-4 : Slow pace walk 1.5-3 km, no
steep climb
 Days 5-6 : 5 km walk, climb 300m

39. Stage 2 (3600- 4500 m) [12000’-15000’]
4 days
 Days 1-2 : slow walk 1.5-3 km, no steep
climb
 Day 3 : slow walk, climb 300m
 Day 4 : 300m climb with equipment
Stage 3 (> 4500m) [>15000’] 4days
 Same as Stage 2

40. Acclimatization Schedule
(AO 110 / 80; DGAFMS Memorandum:140;
Re-entry
“Red Book” Para 167)
 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