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Audit of oxygen prescribing

Editor—The results of the audit of oxygen prescribing by Dodd et al raise numerous issues.1 The audit focused solely on the prescribed input rather than a measure of outcome. No reference was made to adjusting treatment with regard to the patient's oxygen saturation.2 Realistic goals for desired saturation would reduce the risks of either continued hypoxia or excessive treatment in severe chronic obstructive pulmonary disease. 
 
The spectre of carbon dioxide narcosis was again raised. Intensivists repeatedly find that seriously hypoxic and exhausted patients have had their oxygen treatment reduced because of a raised arterial concentration of carbon dioxide.3 Guidelines issued by the British Thoracic Society for the management of chronic obstructive pulmonary disease state that the aim of initial treatment is to raise the arterial oxygen concentrations (to ⩾6.6 kPa) and that a fall in arterial pH to less than 7.26 (equivalent to a hydrogen ion concentration of 54 nmol/l) gives cause for concern.4 The main focus is not on concentrations of carbon dioxide. 
 
A few patients require careful titration of oxygen treatment, but the current widespread assumption that everyone with a diagnosis of chronic obstructive pulmonary disease should therefore have their oxygen treatment drastically restricted is dangerous. Where there is a suspicion of a retention of carbon dioxide, further history should be sought to avoid increasing hypoxia in an already exhausted patient.