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Hypoxia: Inadequate tissue oxygenation

Hypoxia: Inadequate tissue oxygenation. At the lung: hypoxic hypoxia At the blood: Anemia (reduced # RBCs or Hb) Carbon monoxide: left-shifted O 2 -Hb curve and decreased carrying capacity Hypoxemia due to hemoglobin mutation (thalassemia) Perfusion-related (stagnant hypoxia) Tissue level

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Hypoxia: Inadequate tissue oxygenation

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  1. Hypoxia: Inadequate tissue oxygenation • At the lung: hypoxic hypoxia • At the blood: • Anemia (reduced # RBCs or Hb) • Carbon monoxide: left-shifted O2-Hb curve and decreased carrying capacity • Hypoxemia due to hemoglobin mutation (thalassemia) • Perfusion-related (stagnant hypoxia) • Tissue level • Metabolic disorders • Poisons • Cyanide: inhibits oxidative phosphorylation • Dinitrophenol: uncouples oxidative phosphorylation • Carbon monoxide (cytochrome binding): prevents electron transfer to oxygen

  2. Transport Primary: bicarbonate Secondary: combined with proteins (eg: hemoglobin) and dissolved (PCO2) Carbon dioxide

  3. Carbamino 5% 30% Arterial Arterio-venous Blood difference 90% 60% HCO3 Dissolved 5% 10% CO2 Transport

  4. Transport Primary: bicarbonate Secondary: combined with proteins (carbamino; eg: hemoglobin) and dissolved (PCO2) Respiratory regulation of pH The total amount of CO2 in blood (TCO2) reflects an equilibrium between the bicarbonate, carbamino, and dissolved CO2 Carbon dioxide

  5. H2O + CO2 H2CO3 H+ + HCO3- CA pKa for CO2 H+ + HCO3- is 6.1 [HCO3-] pH = 6.1 + log PCO2 * 0.03 [HCO3-] pH REM: PCO2 Acid-Base Handling CO2 Transport Not a good buffer, but CO2 and HCO3- can be regulated independently

  6. Dissolved CO2 CO2 Dissolved CO2 CO2 CO2 + H2O H2CO3 Carbamino Hb HCO3 HCO3 H+ Cl Cl HHb @ Hb HbO2 @ O2 O2 O2 O2 H2O H2O Tissue Red Blood Cell CO2 Transport CA Plasma

  7. Transport Primary: bicarbonate Secondary: combined with proteins (carbamino; eg: hemoglobin) and dissolved (PCO2) Respiratory regulation of pH The total amount of CO2 in blood (TCO2) reflects an equilibrium between the bicarbonate, carbamino, and dissolved CO2 The influence of oxygen on carbamino CO2 helps minimize pH extremes Carbon dioxide

  8. v v 55 At Hb SO2=75% At Hb SO2=95% 50 CO2 Concentration (Vol%) a 45 50 55 40 45 PCO2 (mmHg) Haldane effect

  9. Transport Primary: bicarbonate Secondary: combined with proteins (carbamino; eg: hemoglobin) and dissolved (PCO2) Respiratory regulation of pH The total amount of CO2 in blood (TCO2) reflects an equilibrium between the bicarbonate, carbamino, and dissolved CO2 The influence of oxygen on carbamino CO2 helps minimize pH extremes Regulation of arterial PCO2 to 40 determines the quantification of ventilation Carbon dioxide

  10. 80 M 60 VCO2 = 400 ml/min Hypoventilation 40 Hyperventilation 20 M VCO2 = 200 ml/min 0 0 5 10 15 20 PACO2 (mmHg) Alveolar Ventilation (L/mm)

  11. 60 mmHg PCO2 40 40 mmHg 20 mmHg 30 B A [HCO3-] p (mmol/L) 20 D 10 7.3 7.4 7.5 7.6 7.7 7.1 7.2 pH CO2 Transport

  12. Metabolic Compensation for Respiratory Acidosis/Alkalosis 40 C 30 B A [HCO3-] p (mmol/L) 20 E D 10 7.3 7.4 7.5 7.6 7.7 7.1 7.2 pH CO2 Transport 60 mmHg PCO2 40 mmHg 20 mmHg

  13. Respiratory Compensation for Metabolic Acidosis/Alkalosis 40 H 30 A [HCO3-] p (mmol/L) 20 F G 10 7.3 7.4 7.5 7.6 7.7 7.1 7.2 pH CO2 Transport 60 mmHg PCO2 40 mmHg 20 mmHg

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