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Blood gas analysis and acid-basic disorder

This article discusses the clinical significance of blood gas analysis and its role in evaluating respiratory failure and acid-base disorders. It covers parameters such as PaO2, PaCO2, SaO2, ODC, pH, HCO3-, SB, AB, BB, BE, T-CO2, and AG. The article also explains the classification of respiratory failure and acid-base disorders, as well as the regulation of acid-base balance in the body.

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Blood gas analysis and acid-basic disorder

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  1. Blood gas analysis and acid-basic disorder

  2. Blood Gas Analysis • Arterial blood • Sea level (101.3kPa, 760mmHg) • Quiet • Anti-coagulate blood • Inspire air (Whether O2 supply)

  3. Clinical Significance • To evaluate respiratory failure type Ⅰ or type Ⅱ • To evaluate acid-basic disorder

  4. How to evaluate respiratory failure? PaO2: Arterial blood oxygenic partial pressure. Normal: 95-100mmHg (12.6-13.3kPa) Estimate formula of age: PaO2=100mmHg-(age×0.33) ±5mmHg

  5. Hypoxia • Mild: 80-60mmHg • Mediate: 60-40mmHg • Severe: <40mmHg

  6. Respiratory Failure PaO2<60mmHg respiratory failure Notice: sea level, quiet, inspire air rule off other causes ( heart disease)

  7. Classification of Respiratory Failure PaCO2: The carbon dioxide partial pressure of arterial blood Normal: 35-45mmHg (4.7-6.0kPa) mean: 40mmHg

  8. Classification of Respiratory Failure Type Ⅰ TypeⅡ PaO2 (mmHg) <60 <60 PaCO2 (mmHg) ≤50 >50

  9. Other Parameters SaO2: Saturation of arterial blood oxygen Normal: 0.95-0.98 Significance: a parameter to evaluate hypoxia, but not sensitive ODC ( Dissociation curve of oxygenated hemoglobin): “S” shape

  10. SaO2% PO2 Oxygen dissociation curve

  11. PH 2,3DPG temperature CO2 ODC to right deviation Oxygenated hemoglobin release oxygen to tissue, prevent hypoxia of the tissue. But absorbed oxygen of hemoglobin is decreased from the alveoli. Bohr effect: movement of ODC place is induced by PH.

  12. PA-aO2: Difference of alveoli-arterial blood oxygenic partial pressure. Normal: 15-20mmHg (<30mmHg in the old) Significance: a sensitive parameter in gas exchange

  13. PvO2: Oxygenic partial pressure of mixed venous blood. Normal: 35-45mmHg mean: 40mmHg Significance: Pa-vO2 is to reflect the tissue absorbing oxygen.

  14. CaO2:The content of the oxygen of the arterial blood. Normal: 19-21mmol/L Significance: a comprehensive parameter to evaluate arterial oxygen.

  15. Parameters in acid-basic disorder evaluation PH: negative logarithm of Hydrogen ion concentration. Normal: 7.35-7.45 mean: 7.4 〔HCO3- 〕 PH=Pka+log 0.03PaCO2 20 ＝6.1+log 1

  16. HCO3- (bicarbonate): SB (standard bicarbonate) AB (actual bicarbonate) SB: the contents of HCO3- of serum of arterial blood in 38℃, PaCO2 40mmHg, SaO2 100%. Normal: 22-27mmol/L mean: 24mmol/L AB: The contents of HCO3- in actual condition. In normal person: AB=SB

  17. AB and SB are parameters to reflect metabolism, regulated by kidney. • Difference of AB-SB can reflect the respiratory affection on serum HCO3- . Respiratory acidosis: AB>SB Respiratory alkalosis: AB<SB Metabolic acidosis: AB＝SB<Normal Metabolic alkalosis: AB=SB>Normal

  18. Buffer bases（BB)： is the total of buffer negative ion of blood. BB: HCO3- hemoglobin plasma proteins HPO42- (phosphate) Normal: 45-55mmol/L mean: 50mmol/L Significance: Metabolic acidosis: BB Metabolic alkalosis: BB

  19. Bases excess （BE): the acid or bases used to regulate blood PH 7.4 . ( in 38℃，PaCO2 40mmHg, SaO2 100%) Normal: 0±2.3 mmol/L Significance: add acid: BE(+), BB add base: BE(-), BB

  20. Total plasma CO2 (T-CO2)： total content of the CO2 . Normal: HCO3- >95%

  21. Anion gap (AG): the difference of undetermined anion and undetermined cation in serum. AG=Na+－(Cl-+ HCO3- ) Normal: 8-16mmol/L Significance: AG acidosis: ketoacidosis, kidney failure AG normal acidosis: Cl , diarrhea, fixed acid decrease to evaluate mix acid-basic disorder

  22. Regulation of Acid-basic Balance • Chemical buffer • Dielectric changes of incells and excells H+---K+, HCO3----Cl- • Physiology regulation of the lung and kidney

  23. Classification of Acid-basic Disorder • Complementary: PH is normal • Dis-complementary: PH is abnormal. • PH, PaCO2, HCO3- are three important parameters in acid-basic disorder evaluation.

  24. Classification of Acid-basic Disorder PH PaCO2 HCO3- Resp. acidosis Resp. alkalosis Meta. acidosis Meta. alkalosis

  25. Classification of Acid-basic Disorder • Mixed acid-basic disorder • Complementary formula example: original disorder: chronic respiratory acidosis ⊿ HCO3- =⊿PaCO2 ×0.35±5.58 complementary limit: 45mmol/L

  26. Classification of Acid-basic Disorder • Respiratory acidosis with metabolic acidosis • Respiratory acidosis with metabolic alkalosis • Respiratory alkalosis with metabolic acidosis • Respiratory alkalosis with metabolic alkalosis

  27. Respiratory acidosis with metabolic acidosis PaCO2: HCO3- : , normal, (slight) AB, SB, BB: , normal, (slight) PH: BE: negative value

  28. Respiratory acidosis with metabolic alkalosis PaCO2: AB: PH: , N,

  29. Mixed by three types of disorder • Respiratory acidosis + metabolic acidosis +metabolic alkalosis • Respiratory alkalosis + metabolic acidosis +metabolic alkalosis

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