Oxygen therapy: device, titration and hazards

Oxygen is a prescribed drug with a dose, a delivery device and a target, so the nurse matches the device to the concentration the patient needs and to how precisely it must be controlled — a nasal cannula for low concentrations that the patient's own breathing pattern will vary, a simple or partial-rebreather mask for moderate ones, a non-rebreather mask with its reservoir kept inflated for the highest concentration short of a ventilator, and a Venturi mask where the concentration must be fixed regardless of how the patient breathes — titrates the flow up or down against the prescribed saturation range rather than towards the highest reading the meter can show, gives the acutely hypoxaemic patient oxygen at once and never withholds it for fear of its hazards, and treats those hazards as things to prevent and watch for rather than reasons to under-treat: the patient with chronic hypercapnia, who is prescribed a lower target range and a controlled-concentration device and is watched for the drowsiness, headache and slowing breathing that mean the oxygen is being over-delivered and must be turned down and reported rather than switched off; oxygen toxicity and absorption atelectasis from a high concentration continued longer than the patient needs it; the drying of the airway that humidification prevents at higher flows; and the fire that any flame, spark or oil near oxygen invites, which is the first thing the patient going home on oxygen is taught.