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Respiration

Learn about the impact of high altitude on respiration, acclimatization, and physiological changes such as increased pulmonary ventilation, RBC count, and vascularity of tissues. Understand conditions like acute and chronic mountain sickness and the importance of oxygen therapy.

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Respiration

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  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

  5. 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.

  6. 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

  7. 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

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

  9. 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

  10. 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

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

  12. Acute Mountain Sickness • May be nausea, vomitting, headache, Irritability, Dyspnoea, at 1200ft • At 18000 ft - twitching, seizures • At 23000 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

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

  14. 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

  15. 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.

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