Oxygen Therapy in Critical Illness

Precise Control of Arterial Oxygenation and Permissive Hypoxemia

Daniel Stuart Martin, BSc, MBChB, PhD, FRCA, FFICM; Michael Patrick William Grocott, MBBS, MD, FRCA, FRCP, FFICM


Crit Care Med. 2013;41(2):423-432. 

In This Article


The selection of optimum arterial oxygenation goals is essential if cellular hypoxia and unnecessarily excessive oxygenation (and ventilation) are to be avoided. It is imperative that balancing the risks associated with hypoxemia and hyperoxemia forms part of the daily assessment of critically ill patients. Oxygen administration should be considered in the same way as other drugs, being titrated to a measured end point to avoid excessive and inadequate dosage. While the signs of excessive oxygen administration are often difficult to tease apart from a patient's underlying lung injury, limiting the dose administered and the mechanical means to achieve oxygenation may reduce harm in some individuals. There are no generally acceptable thresholds for the lower limit of oxygenation that can be tolerated and individual evaluation is crucial when determining prescribed targets. The development of new technologies and biomarkers may aid patient selection, and provide an umbrella of safety with regards to tissue oxygenation.

At present, any immediate change in clinical practice toward PH is not justified in the absence of experimental data in critically ill patients. However, greater attention to both the concentration of oxygen received by patients and the arterial oxygenation achieved is likely to be beneficial. Implementation of the PCAO method of oxygen prescription may assist in this process, providing a safe oxygenation range for the patient.

The weight of clinical experimental data coupled with observational and basic science studies suggest that a comprehensive evaluation of PH in critically ill patients should be a high research priority.