blood gas analyse

• acid: donate hydrogen ion

  base: receive hydrogen ion

  buffer: dissolved substance that stabilise pH
• carbonic acid bicarbonate buffer system in ECF

  protein buffer system in ECF & ICF

  phosphate buffer system (urinary buffer system)
• regulation mechanism that eliminate H+

  • respiratory system
  • metabolic system
• normal range:

  blood acidity: 7.35-7.45

  PaCO2 (respiratory acidosis/respiratory alkalosis): 4.7-6 kPa

  PaO2(hypoxaemia/normoxemia): 10.7-13.3 kPa

  HCO3(metabolic acidosis/metabolic alkalosis): 22-26 mmol/L

  Base excess(metabolic acidosis/ metabolic alkalosis): -2 to +2
• respiratory acidosis=alveolar hypoventilation

  • pneumothorax
  • weakened respiratory muscle

  respiratory alkalosis=alveolar hyperventilation

  • acute asthma/pneumonia/pulmonary embolism 肺栓塞

  metabolic acidosis

  • loss of bicarbonate

  metabolic alkalosis

  • excess bicarbonate
• uncompensated:

  pH: abnormal

  CO2 & HCO3: either one abnormal

  partially compensated:

  pH: abnormal

  CO2 & HCO3: both abnormal

  compensated:

  pH: normal

  CO2 & HCO3: both abnormal
• PaO2: (low oxygen) hypoxaemia / (high oxygen) normoxemia

  PaCO2: respiratory acidosis / respiratory alkalosis

  HCO3: metabolic acidosis / metabolic alkalosis