X3.1 Controlled oxygen delivery

Controlled oxygen delivery (28%, or 0.5–2.0 L/min) is indicated for hypoxaemia (Young et al., 1998)

Correction of hypoxaemia to achieve a Pao₂ of at least 55 mmHg (7.3 kPa) and an oxygen saturation of 88%–92% is the immediate priority. (NHLBI/WHO Workshop Report, April 2001) 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 (NIPPV) may reduce the need for endotracheal intubation (see below for more detail).

Administering oxygen at an inspired oxygen concentration (fraction of inspired oxygen; Fio₂) of 24%–28% by means of a venturi mask is usually sufficient to improve oxygenation in most patients. Nasal cannulas, although more comforta­ble, deliver a variable concentration of oxygen, but a flow of 0.5–2.0 L per minute is usually sufficient. Gas flow provided through Hudson-type masks is inadequate when patients are tachypnoeic, so these should not be used. Careful monitor­ing with oximetry and, where hypercapnia is a potential concern, arterial blood gas measurement is required. There is no benefit in trying to obtain Spo₂ levels over 92%.

High flow oxygen should be avoided, as it is rarely necessary and may lead to hypoventilation and worsening respiratory acidosis. Patients should be weaned off supple­mentary oxygen as soon as possible, with none for 24–48 hours before discharge, unless home oxygen is prescribed.

There is currently insufficient evidence to treat acute exacerbations of COPD with Heliox mixture.