RESPIRATORY ADJUSTMENTS AT HIGH ALTITUDEDEESHAN RAJ SIVASANKER 082013100017IMS BANGALORE

LEARNING OUTCOMESCHANGES OCCURING AT BODY IN HIGH ALTITUDE

EFFECTS DURING RAPID ASCENT : PULMONARY OEDDEMA

EFFECTS DURING SLOW ASCENT : MOTION SICKNESS

ACCLIMATIZATION

INTRODUCTION Height in excess of 10,000 feet (3000 meter) above the sea level is defined as HIGH ALTITUDE

Barometric Pressure -pressure decreases with increasing altitude-composition of air remains the same aa at the sea level -total pressure of air (P) will be equal to sum of partial pressure P=pO2 + pCO2 + pN2 + pH2O

Increase altitude causes :I. Decrease in Barometric Pressure ; hence total

pressure of air decreases II. pH2O and pCO2 remains constant III. Progressive decrease in pO2 & pN2

Decrease in pN2 produces no effects on the bodyTherefore effects of high altitude entirely depends

to decrease in pO2 ; effects of HYPOXIC HYPOXIA

Effects of hypoxic hypoxia at high altitude depends on :

I. Rate at which hypoxia develops i.e either Rapid Ascent or Slow Ascent

II. Duration of stay : Long term stay e.g permanent residents at high altitude (Acclimatization)

EFFECTS OF HIGH ALTITUDE DURING RAPID ASCENTRapid ascent more than 10,000 feet can produce PULMONARY OEDEMA

It is seen in individuals :I. Who engage in heavy physical work

during 1st 3 days after arrival (75 – 80 % of subjects )

II. Who are “acclimatized” to high altitudes ; spend 2 weeks or more at sea level and then reascend

CAUSES OF PULMONARY OEDEMA ARE :

(A) Hypoxia - gets aggravated by work -increases membrane permeability of pulmonary capillaries -Hence producing Pulmonary Oedema (B) At high altitude sympathetic activity increases due to : I. Hypoxic stimulation of Vasomotor CenterII. “Cold” (temperature falls by 2 degree for

every 1000 feet or 300 meter increase altitude )

III. Increase physical work

Increase Sympathetic Activity

vasoconstriction

Increase Pulmonary Capillary Pressure

Drives the fluid out of Pulmonary Capillaries

Pulmonary Oedema

EFFECTS OF HIGH ALTITUDE DURING SLOW ASCENT

At high altitude , individual suffers from MOUNTAIN SICKNESS

Starts approximately 8 -12 hours after arrival at high altitude

Last for about 4 - 8 days

Mountain sickness are closely associated with CEREBRAL OEDEMA or ALKALOSIS

It is characterised by :I. Nausea II. VomittingIII. HeadacheIV. InsomniaV. Dyspnoea

Signs and Symptoms of Mountain Sickness can be prevented if :

1) Cerebral oedema is reduced by administration of large doses of GLUCOCORTICOIDS

2) Respiratory Alkalosis that results from HYPERVENTILATION is prevented by treatment with Acetazolamide

ACCLIMATIZATIONDefinition -physiological readjustments and compensatory mechanism in the body that reduce the effects of hypoxia in permanent residents at high altitude

These process permit a normal and prolonged life in people living in high altitudes

Acclimation is possible by following process : 1) increase in Pulmanory Ventilation2) Decrease Affinity of the Hemoglobin for O2

under hypoxic conditions3) Rise in Hemoglobin Concentration4) Increased Vascularity of Hypoxic Tissues5) Increased Diffusion Capacity of lungs for O2 6) Changes at Tissue Level to Reduce the Effect

of Hypoxia

REFERENCEDIRECTOR PROFFESOR A.K.JAIN ,TEXT BOOK OF PHYSIOLOGY , PUBLISHED BY AVICHAL , 5TH EDITION , INDIA