X3.1 Controlled oxygen delivery

Controlled oxygen delivery (0.5–2.0 L/min) is indicated for hypoxaemia (Beasley 2015)

In the emergency setting, supplemental oxygen may be required to relieve hypoxaemia. Oxygen flow should be carefully titrated to achieve a target SpO2<sup/) arterial oxygen saturations between 88 and 92%. Nasal cannulas deliver a variable concentration of oxygen, but a flow of 0.5–2.0 L per minute is usually sufficient.

High flow oxygen via a Hudson mask or non-rebreather mask should be avoided, as it is rarely necessary and may lead to hypoventilation and worsening respiratory acidosis and increased mortality. A randomised study has demonstrated that in the pre-hospital emergency setting titrated oxygen via nasal cannula compared with high flow oxygen reduced mortality by 78% in COPD patients (NNH=14) (Austin 2010) [evidence level II]. Nonetheless, a recent retrospective study of patients with exacerbations of COPD admitted to a New South Wales hospital between 2011 and 2013 found that oxygen concentrations of greater than 28% were still delivered to the majority of patients, both in the ambulance and the emergency department (Susanto 2015). Similarly, in a Victorian retrospective case file emergency department audit of patients admitted to hospital with exacerbation of COPD between Jan 2012 and March 2013, 84.4% had a final ambulance oxygen saturation reading of > 93% (95% CI 79.5-88.3%) (Chow 2016). In Wellington, New Zealand, an audit of patients with an exacerbation of COPD transferred by ambulance to hospital was undertaken, before and after an education program to reduce high concentration oxygen delivery was undertaken (Pilcher 2015). Significantly fewer patients received high concentrations of oxygen in 2010; however, concern was voiced by the authors about the continued use of high concentration oxygen to drive nebulisers. Education may be the key to changing practice.

Where there is evidence of acute respiratory acidosis (or a rise in PaCO2), together with signs of increasing respiratory fatigue and/or obtunded conscious state, assisted ventilation should be considered. Early non-invasive positive pressure ventilation (NIV) may reduce the need for endotracheal intubation (see below for more detail).