MEDICAL PROBLEMS AT HIGH ALTITUDES‘HEIGHT DOES MATTER’

Manu ChopraMD, DNB, MNAMSPulmonologist

10 Heroes perished at Siachen

Siachen

Deployment of Army at high altitudes

HOW HIGH IS HIGH-ALTITUDE ?

High altitude: 1500-3500m above sea level Very high altitude: 3500-5500m Extreme altitude: above 5500m

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• Hackett PH, Roach RC. High altitude medicine. Widerness medicine 2007

Tibetan plateau & Himalayan valleys (8848m)

Andes (6962m

)

Ethiopian highlands (4620m)

CATEGORISATION FOR DESCRIPTIVE CONVENIENCE:

ALTITUDE TYPE FROM SEA-LEVEL (In feet)

HIGH 8,000 – 12,000

VERY HIGH 12,000 – 18,000

EXTREMELY HIGH

Above 18,000

Why do we go to high altitudes?

Tourism

Manali 2050m

Nainital 2084m Shimla 2205m

Srinagar 1585m

Mussoorie 2006m

Mountaineering

Mt K2 8611mKanqchenjunga- 8,586 M

Mt Everest 8848m

Nanga Parbat 8126m Dhaulagiri 1 8167m

Habituation and religion

Thiksey monastery Leh 3650m

Ladakhi

Kedarnath3553m

Korzok Village Ladakh 4600m

Kibber Village4270m

Tabo Monastery Spiti 3280m

Military purposes

High altitude areas of indian army map

The Road…..

Long way to go..

The end of world or road !!!

First view

Company Post

Accomodation of Lucky few

Peculiarities of high altitude

PECULIARITIES OF HA

BAROMETRIC PRESSURE HEAVY SNOW WINDY CLIMATE FREEZING TEMPERATURES DANGERS RADIATION

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Barometric pressure versus altitude

Altitude (m) Altitude (feet)Barometric Pressure (mm Hg)

Inspired PO2 (mm Hg)

0 0 760.0 159.1

1,000 3,280 674.4 141.2

2,000 6,560 596.3 124.9

3,000 9,840 525.8 110.1

4,000 13,120 462.8 96.9

5,000 16,400 405.0 84.8

6,000 19,680 354.0 79.1

8,000 26,240 267.8 56.1

8,848 29,028 253.0 43.1

HEAVY SNOW

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WINDY CLIMATE

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Wind chill Factor

A combination of air temperature and wind speed that affects the freezing rate of exposed skin.

Wind Chill/Frostbite Chart

As this chart indicates, if the actual temperature is -200 F and the wind is blowing 15 mph, the cold effect on your bared skin is -450 F. At this temperature, frostbite can begin in as little as 10 minutes.

FREEZING TEMPERATURES

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 −16 °C to -60 °C

Avalanches and land slides

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Radiation exposure

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5% increase in UV rays/ 300m gain + snow reflection

Physiological changes at high altitudes

ACCLIMATIZATION AT HIGH ALTITUDE:

Air Lungs

Blood

Tissue

•Delivery of atmospheric O2 to the tissues normally involve 3 stages---with a drop in PO2 at each stage.•When the starting PO2 is lower than normal, body undergoes acclimatization so as to—(i)↓ pressure drop during transfer(ii)↑ oxygen carrying capacity of blood(iii) ↑ ability of tissues to utilize O2

Hypoxic ventilatory response

• Starts within 10- 15 min of exposure 1500m• Mechanism

VENTILATORY ACCLIMATIZATION

Ascent to altitude

Hypoxia

Carotid body stimulation

Respiratory centres stimulation

Increased ventilation

Improved hypoxia

Decreased PCO2

CO2 + H2O  H2CO3  HCO3- + H+

Gas exchange

1. Ventilation & perfusion matching Increased Ventilation = Increased cardiac

outputIncreased Pulmonary

Perfusion Alveolar hypoxia triggers Hypoxic

Pulmonary vasoconstriction-redistribution of blood flow to areas

less perfused at sea level - improved gas exchange

2. Lung DiffusionLUNG DIFFUSION

Major rate limiting step• High altitude O2 diffusion, because of

– a lower driving pressure for O2 from the air to the blood ( low Po2)

– and inadequate time for equilibration ( decreased transit Time)

– Long term adaptation – diffusing capacity increases

Cardiac response

Cardiac output increases

Tachycardia:Increased catecholamine release &

sensitivityAlso d/t peripheral chemo. Response

CO oxygen delivery to the tissues

Stroke Vol decreases

Hematological adaptation

Erythropoietc response

Increase in Hb conc in 1-2 days initially – hemoconcentration

( diuresis) later – increased RBC production due

to increased erythropoietin Hypoxia is the primary stimulus for

erythropoietin secretion Se erythropoietin levels increase in 24-

48 hrs decline within 3 weeks

O2 Hb affinity

Tissue adaptation

Plasma to cytoplasm – 10mmHg Cytoplasm to mitochondria – 1-

2mmHgDiminished ms fibre Increased myoglobin conc Increased levels of enzymes involved

in oxidative phosphorylation

CNS adaptation

Cerebral Blood flow Cerebral bld flow increases

initially due to hypoxia Hypocapnia cerebral

vasoconstriction bld flow decreases

13% greater than sea level Improved O2 delivery

Cerebral function

Motor, sensory & cognitive abilities impair

New tasks are learned with difficulty at 3048m

Short term memory impaired Arterial So2 85% - impair concentration

and fine motor coordination Arterial So2 75% - poor judgement and

irritability

Fluid Balance Acclimatisation Diuresis & natriuresis Peripheral venous constriction →

increased central volume → decreased ADH and aldosterone → diuresis → decreased plasma volume and

hyperosmolality.

Respiration & sleep Cheyne-Stokes Respirations

Above 10,000 ft (3,000 m) most people experience a periodic breathing during sleep. The pattern begins with a few shallow breaths increases to deep sighing respirations falls off rapidly.

During period of breathing-arrest, person often becomes restless & may wake with a sudden feeling of suffocation.

Can disturb sleeping patterns exhausting the climber.

O2 & acetazolamide help

TO SUMMARIZE………. At high altitude air is thin. To make up for

it, the blood gets thick, respiration ↑ & circulation improves, provided adequate time is given & body functions properly still some limitations remain as implied!!!

• Process by which people gradually adjust to high altitude• Determines survival and performance at high altitude• Series of physiological changes

O2 deliveryhypoxic tolerance +++

• Acclimatization depends on• severity of the high-altitude hypoxic stress• rate of onset of the hypoxia• individual’s physiological response to hypoxia

Acclimatisation

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ACCLIMATIZATION PROTOCOL

FIRST STAGE ACCLIMAZATION(Above 2700 m and up to 3600 m): The acclimatization period will be for 6 days as under:

(i) First and second day: Rest except for short walks in the unit lines only, not involving any climbs.

(ii) Third and fourth day: walk at slow pace for 1.5 -3Km avoid steep climbs.

(iii) Fifth and sixth day: walk upto 5 Km and climb upto 300 m at a slow pace.

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ACCLIMATIZATION PROTOCOL SECOND STAGE ACCLIMATIZATION(Above

3600 m and up to 4500 m): This is carried out for 4 days as under: (i ) First & Second day: Slow walk for a

distance for 1.5 -3 Km avoid steep climbs.

(ii) Third day: slow walk and climb upto 300 m.

(iii) Fourth day: Climb 300 m without equipment.

THIRD STAGE ACCLIMATIZATION:(Above 4500 m): This also lasts for 4 days and is on the same lines as second stage acclimatization.

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Medical problems at high altitude

maladaptation

ACUTE

Acute Mountain Sickness

High Altitude Pulmonary Oedema

High Altitude Cerebral Oedema

CHRONIC

Chronic Mountain Sickness

Pulmonary Arterial Hypertension of HA

HA ILLNESSES UNRELATED TO ACCLIMATIZATION

High altitude retinopathy UV keratitis Thrombotic episodes Hypothermia Local cold injury

(A) Chilblains(B) Trench foot(C) Frost bite

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Relationships of the Different Forms of Altitude Illness

Altitude illness may be an interrelated spectrum :

AMS HAPE

HACE

Acute Mountain Sickness :Etiology22-50% travellersTypically occurs at altitude > 8000 feetRarely occurs at altitude 6000 to 8000 feetNo predeliction based on genderMore likely if :

•Rapid ascent• Lack of acclimatization• Exertion soon after arrival• Alcohol intake• Sedatives (sleeping pills)• Narcotics

Acute Mountain Sickness : Pathophysiology

Much individual variation in susceptibilityLikely mild cerebral oedema develops “Tight fit hypothesis”

Acute Mountain Sickness (AMS)

Symptoms:▪ Headache +▪ Fatigue▪ Nausea & Vomiting▪ Impaired night vision▪ Anorexia▪ Dizziness▪ Sleep Disturbance

Signs: no characteristic finding

▪ Mild tachycardia▪ Peripheral oedema▪ Crackles

Acute Mountain Sickness : Differential Diagnosis

DehydrationHypothermiaExhaustionAlcohol hangoverRespiratory/ CNS infectionPsychiatric disordersCarbon monoxide poisoning

AMS - Treatment Mild

Rest and stop ascent

Descend if not improved after 24 hours

Drink fluids Simple analgesics

Resolves 1-3 days

Moderate/Severe Descend ≥ 100m Acetazolamide Dexamethasone Hyperbaric O2

Prevention Following

acclimatization protocols

Medications

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Progression of Acute Mountain Sickness

If ascent is continued or accelerated by a patient with untreated AMS, HAPE or HACE may occur and death may result

High Altitude Cerebral Oedema (HACE) Usually get AMS before HACE Mental status changes +/ ataxia Confusion, ataxia, stupor focal neurologic signs May lead to coma, irreversible

neurological damage or death Incidence 0.53% - 1.25%

HACE d/d

Other causes of encephalopathy CO poisoningHypertensive crisisHypoxia Meningitis HypoglycemiaHypothermia

HACE: signsAtaxia (e.g. poor heel – toe

walking)Focal neurological signs

Papilloedema & retinal haemorrhages

HACE: treatmentIMMEDIATE DESCENT Do NOT wait until morning if HACE

occurs at night Oxygen Hyperbaric bag (to facilitate descent

if necessary NOT replace it) Dexamethasone

High Altitude Pulmonary Edema (HAPE)

High Altitude Pulmonary Edema (HAPE)

Commonest cause (54%)of Hospital admission due to HAA related illnesses

Most common cause of death from high altitude illness.

• Until 1960 – Pneumonia• 1960 - Pulmonary edema

(Houston)

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Non cardiogenic pulmonary edema Manifests within 2-4 days of ascent

>2400m (8000 feet) 2nd night

Pathophysiology

Pulmonary hypertension Exaggerated Hypoxic Pulmonary

vasoconstriction High levels of ET1 Increased sympathetic tone Lower levels of NO

Uneven hypoxic vasoconstriction Pulmonary Endothelium Fragility Abnormal alveolar fluid resorption

High Altitude Pulmonary Oedema (HAPE)

Symptoms: AMS Reduced exercise

tolerance Dry cough

Dyspnea at rest Blood stained

sputum Mental changes

Signs: better than expected Tachycardia Tachypnoea Low grade fever Pallor Cyanosis Crackles Signs of RV strain

▪ RV heave, Loud P2

D/Ds of HAPE

Pneumonia Pulm embolism MI Asthma Pulm Infarction

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HAPE - Management

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General Specific

DescentRest – carry the patientHydration

Hyperbaric chamberOxygen - CPAPDrug therapy

Nifedipine Tadalafil/ sildenafil

Prevention

Acclamatisation Drugs

NifedipineSalmetrolTadalafilDexamethasone

SIACHIN HOSPITAL

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Miscellaneous Altitude Related Problems

Avalanche

50 to 100 miles per hourCan be as fast as 200 miles per hourCan generate impact pressures > 150 lbs/square inch (can destroy even concrete structures)

Occur with greatest frequency on slopes of 30 to 45 degrees

Causes of death in avalanche

Direct impact trauma of snow blocks or ice

Indirect trauma of hitting against objects such as trees or rocks

Hypoxia from encasement in snow

HypothermiaRestrictive chest compression

Radiation Exposure

High altitude retinopathy UV keratitis

pain, photophobia, tearing, erythema, chemosis, eyelid swelling

24 h to heal, analgesics and cold comp.

Wear sunglasses UV dermatitis

Miscellaneous Altitude Related Medical Problems

Immune suppression–probably related to tissue hypoxia–wounds slower to heal & more likely to get infected–wound infections can show antibiotic resistance

Prothrombotic state leading to various ThrombosisHigh altitude peripheral edema

High Altitude Pharyngitis/Bronchitis Khumbu cough

Purulent bronchitis and painful throat near universal at very high altitude

respiratory heat loss, bronchospasm and mucosal cracking (dry and cold effects)

coughing can lead to rib #s Antibiotics no use wear your balaclava – there are face

masks that act as HME

Medical problems of high altitude residents 1. Chronic mountain sickness- due to

excessive erythrocytosis Described in 1928 Monge’s disease Young and middle aged men Low Landers who ascend to HA High Landers with / without respiratory disease Increased blood volume, PAH, haematocrit >60% CNS symptoms dominate Plethoric florid faces, dark red conjunctiva, haemorrage below nail

2. High altitude pulmonary hypertension Without polycythemia

Local Cold Weather Injuries

Non Freezing ChilblainTrench foot

FreezingFrost bite

Chilblains

Trench Foot

Frost bite