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Acid-Base Balance. Lectures on respiratory physiology. Some definitions. An acid is a molecule that releases hydrogen ions in solution A base is a molecule that can accept a hydrogen ion A buffer is a substance that can reversibly bind hydrogen ions.
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Acid-Base Balance Lectures on respiratory physiology
Some definitions • An acid is a molecule that releases hydrogen ions in solution • A base is a molecule that can accept a hydrogen ion • A buffer is a substance that can reversibly bind hydrogen ions
Law of Mass Action CA CO2 + H2O H2CO3 H+ + HCO3- AT EQUILIBRIUM, [H+] x [HCO3-] K = [H2CO3] [H+] x [HCO3-] = SOLUBILITY x PCO2
[H+] x [HCO3-] K = 0.03 x PCO2 WHICH, AFTER TAKING LOGS, BECOMES: [HCO3-] pH = pK + Log( ) 0.03 x PCO2 - THE HENDERSON - HASSELBALCH EQUATION
[HCO3-] pH = 6.1 + Log( ) 1.2 PCO2 = 40 24 PLASMA [HCO3-], meq/l NORMAL 7.40 pH
100 80 PCO2: 60 40 30 PLASMA [HCO3-], meq/l 20 10 pH
[HCO3-] pH = pK + Log( ) 0.03 x PCO2 80 BUFFER LINE 40 20 N PLASMA [HCO3-], meq/l pH
ACID - BASE DISTURBANCES: * RESPIRATORY ACIDOSIS * RESPIRATORY ALKALOSIS * METABOLIC ACIDOSIS * METABOLIC ALKALOSIS
RESPIRATORY ACIDOSIS: H+ + HCO3- CO2 + H2O 80 BUFFER LINE 40 20 N PLASMA [HCO3-], meq/l pH
RESPIRATORY ACIDOSIS: H+ + HCO3- CO2 + H2O 80 BUFFER LINE 40 20 N PLASMA [HCO3-], meq/l pH
RESPIRATORY ACIDOSIS: H+ + HCO3- CO2 + H2O 80 BUFFER LINE 40 20 N PLASMA [HCO3-], meq/l pH
RESPIRATORY ALKALOSIS: H+ + HCO3- CO2 + H2O 80 BUFFER LINE 40 20 N PLASMA [HCO3-], meq/l pH
RESPIRATORY ALKALOSIS: H+ + HCO3- CO2 + H2O 80 BUFFER LINE 40 20 N PLASMA [HCO3-], meq/l pH
METABOLIC ACIDOSIS: H+ + HCO3- CO2 + H2O 80 BUFFER LINE 40 20 N PLASMA [HCO3-], meq/l pH
METABOLIC ACIDOSIS: H+ + HCO3- CO2 + H2O 80 BUFFER LINE 40 20 N PLASMA [HCO3-], meq/l pH
METABOLIC ALKALOSIS H+ + HCO3- CO2 + H2O 80 BUFFER LINE 40 20 PLASMA [HCO3-], meq/l pH
METABOLIC ALKALOSIS H+ + HCO3- CO2 + H2O 80 BUFFER LINE 40 20 PLASMA [HCO3-], meq/l pH
COMPENSATED RESPIRATORY ACIDOSIS COMPENSATED METABOLIC ALKALOSIS 80 BUFFER LINE 40 20 PLASMA [HCO3-], meq/l pH
VENTILATION LUNGS DIFFUSION CAPILLARIES HEART AND CIRCULATION PERFUSION CAPILLARIES DIFFUSION TISSUE THE OXYGEN TRANSPORT SYSTEM
Classification of tissue hypoxia: * Hypoxic hypoxia * Anemic hypoxia * Circulatory hypoxia * Histotoxic hypoxia