1. Respiration

2. High altitude Changes
Atmosph. Pressure at sea level=760mmHg and PO2=160mmHg
As one ascends – Atmosph pressure keeps on decreasing
Composition or percentage of constituent gases remains same
At 10,000 feet = 523 mmHg PO2=110mmHg
At 50,000 feet = 87 mmHg PO2=18mmHg
Acclimatization – try to be normal at high altitude.

3. BAROMETRIC PRESSURE CHANGES IN HIGH ALTITUDE
As the altitude increases above the sea level, the corresponding atmospheric pressure decreases.
The partial pressure of Oxygen also decreases.
The arterial Oxygen saturation levels also decrease with increase in the altitude.

4. PARTIAL PRESSURES OF OXYGEN

6. ACCLIMATIZATION “Getting used to…”
People remaining at high altitudes for days, weeks or years become more and more acclimatized to low PO2.
This causes the hypoxia to cause fewer deleterious effects on their bodies.
They can thus work harder at higher altitudes without hypoxic effects.

7. Acclimatization
At 10,000 feet, atmosph pressure = 523 and alveolar PO2 = 110mmHg
The changes in response to hypoxia if somebody stays at high altitude for sometime by
Great increase in pulmonary ventilation
Increases RBCs no
Increased diffusion capacity of lung
Increased vascularity of the tissue
Increased ability of tissue cells to use oxygen despite low PO2

8. Increased Pulmonary Ventilation
Hypoxic stimulation of resp. center by periph. Chemoreceptors
Immediate compensation to ↓PO2 by ↑ alveolar ventilation to →↑ CO2 exhaling →↑ PCO2 → inhibitory effect as resp. center opposes ↓ PO2 stimulatory effect
After a few days stimulatory effect overwhelms inhibitory effect b/c ↓ HCO3 ions in brain

9. Increased RBCs Count Hypoxia → erythropoietin →↑ RBC production
Hct from normal (40-45) to 60-65
Hb from normal (15mg/dl) to 20-22G/dl

10. Increased Diffusing Capacity
↑ Pulmonary capillary blood vol. → capillaries expanding → ↑ surface area
Also inc in air vol → ↑ surface area
Inc in pulm art blood pressure– more perfusion
So diffusing capacity for O2 from normal (21 ml/mmHg/mint) to 65 ml/mmHg/mint

11. Increased Vascularity of Tissue (Circulatory Changes)
Initially ↑ cardiac out by 30% approx.
As Hct ↑ - C.O. becomes normal
↑ in capillaries in non-pulmonary areas – called increased capillarity (angiogenesis)
Hypoxia → pulmonary vasoconstriction → Retrograde pressure on Rt heart → Rt ventricular hypertrophy
Pulmonary vasoconstriction → pulmonary hypertension

12. Cellular Acclimatization
More capillary formation in tissue → ↑ vascularity
Also ↑ Mitochondria, ↑ Myoglobin & Cytochromes oxidase enzyme

14. Acute Mountain Sickness
May be nausea, vomitting, headache, Irritability, Dyspnoea, at 1200ft
At ft - twitching, seizures
At ft – coma leading to death
Cerebral vasodilatation in response to hypoxia →fluid leakage into cerebral tissue → cerebral edema → Disorientation & other cerebral dysfunction
Pulmonary edema – exact cause not known

15. Vasocosntriction in pulmonary capillaries leads to increased blood pressure in open capillaries leading to edema
Breathing oxygen, especially under pressure, can reverse symptoms

16. Chronic Mountain Sickness
RBC count ↑ - so Hct ↑
Pulmonary arterial pressure ↑
Rt heart – hypertrophy
↑ Hct → ↑ blood viscosity → sluggish circulation → ↑ O2 supply
Natives at high altitude –
Chest barrel shaped – chest longer
Aortic & carotid bodies of bigger size
Pulmonary hypertension & Rt ventricular hypertrophy
↑ RBC count with ↑ Hct

17. Seen in people who reside for long at high altitudes.
Red cell number and mass increases exceptionally.
Pulmonary arterial pressure becomes very high.
The heart becomes enlarged in the right side.
The peripheral arterial pressure begins to fall
Congestive Cardiac failure & death follows
They need to be taken to low altitudes as soon as possible.
They recover in low altitudes within days or weeks.