Hypo and Hypercapnoea

Explain the physiological effects of hyperoxia, hypoxaemia, hypercapnia, hypocapnia, and carbon monoxide poisoning

Carbon dioxide is lipid soluble and can rapidly cross membranes, allowing it affect acid-base status in any compartment.

Hypercapnoea

  • Respiratory Effects

    • Increased respiratory drive via chemoreceptor stimulation
  • CVS effects

    • Peripheral vasodilation
      • May cause tachycardia from sympathetic stimulation
    • Pulmonary vasoconstriction
    • Myocardial depression
      Intracellular acidosis.
    • Arrythmogenic
  • CNS effects
    • Increased CBF
    • Increased ICP secondary to increased CBF
    • SNS activation
    • CNS depression
      When PaCO2 > 100mmHg

Hypocapnoea

  • Respiratory Effects
    • Left-shift of oxyhaemoglobin dissociation curve
    • Respiratory depression
  • CVS effects
    • Myocardial depression
      Intracellular alkalosis.
  • CNS effects

    • Decreased cerebral blood flow
  • Electrolyte effects

    • Decreased serum K+
    • Decreased serum Ca2+
      Leads to paresthesias and twitches.
      • Ca2+ binds to H+ binding site on albumin

References

  1. Brandis K. The Physiology Viva: Questions & Answers. 2003.
Last updated 2017-09-17

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