Arterial blood gasses

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

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

• 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 abnormal, 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

• Acidic > 45
  • indicates hypoventillation

• Basic < 35
  • indicated hyperventillation

• Acidic < 24
• Basic > 26

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

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