Arterial blood gasses

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Sa O2 MUST be on room air (FiO2 = 0.21)

Hypoxemia - look @ pO2[edit]

  • 60-75 mild hypoxemia
  • 45-59 moderate hypoxemia
  • < 45 severe hypoxemia

pH[edit]

  • Acidic pH < 7.35
  • Basic pH > 7.45
  • If the pH is not in the direction of the pCO2 then this is a metabolic disorder with respiratory compensation
  • If the pH is NORMAL and the pCO2 is abdnormal, then this is a fully compensated respiratory disorder
  • If pH is in the direction predicted by the paCO2 and the BE=0 (BE = base excess) then this is an uncompensated respiratory disorder
  • If pH is in the direction predicted by PaCO2 and BE is + or - then partially compensated respiratory disorder

pCO2[edit]

  • Acidic > 45
    • indicates hypoventillation
  • Basic < 35
    • indicated hyperventillation

HCO3[edit]

  • Acidic < 24
  • Basic > 26

Count the number of acid (A) vs. base (B)[edit]

  • if pCO2 A/B matched pH A/B - respiratory
  • if HCO3 A/B matches pH A/B - metabolic

Compensation[edit]

If the change in PCO2

  • increases by 10 - HCO3 increases by 1 - acute respiratory acidosis
  • increases by 10 - HCO3 increases by 3-5 - chronic respiratory acidosis
  • decreases by 10 - HCO3 decreases by 2 - acute respiratory alkalosis
  • decreases by 10 - HCO3 decreases by 5 - chronic respiratory alkalosis

Other OSCE modules[edit]