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  • Cited by 2
  • Print publication year: 2008
  • Online publication date: October 2009

6 - Oxygenation


Oxygenation is one of the primary gas exchange functions of the lung. This chapter reviews how to assess the adequacy of oxygen uptake and, in the context of the mechanisms of arterial hypoxaemia, examines how this can be improved in the mechanically ventilated patient. The oxygenation assessment has two facets, one pulmonary, and one extra-pulmonary. Oxygen moves from the alveolar gas to the pulmonary capillary blood by diffusion. Currently in the UK, as with high-frequency oscillatory ventilation (HFOV), airway pressure release ventilation (APRV) is typically used as a rescue technique for those failing to achieve adequate oxygenation with conventional ventilation. The diffusion coefficient for a gas is proportional to the gas's solubility in the medium through which the gas has to diffuse, and is inversely proportional to the square root of the gas's relative molecular mass. Imbalance between pulmonary ventilation and pulmonary perfusion is the most common cause of hypoxaemia.