Patients at risk of hypercapnia
Before starting oxygen therapy, identify patients at increased risk of developing hypercapnia related to oxygen therapy, including fatal hypercapnic respiratory failure. Conditions and situations that increase the risk of developing hypercapnia with oxygen therapy include (but are not limited to):
- previous hypercapnic respiratory failure
- chronic obstructive lung disease, including chronic obstructive pulmonary disease (COPD), bronchiectasis and cystic fibrosis
- history of heavy smoking
- obstructive sleep apnoea
- morbid obesity
- severe kyphoscoliosis or ankylosing spondylitis
- neuromuscular disorders with respiratory muscle weakness
- use of respiratory depressant drugs (eg opioids, benzodiazepines)
- patients with acute asthma who are tiring.
To reduce the risk of hypercapnia in patients with any risk factor for hypercapnia, use a lower target oxygen saturation with appropriate monitoring; a target oxygen saturation measured by pulse oximetry (SpO2) of 88 to 92% is recommended. However, in critically ill patients, the standard target (SpO2 92 to 96%) may be used initially, pending results of arterial blood gas analysis. See Pulse oximetry to monitor acute oxygen therapy for more information on target oxygen saturation levels.
Perform arterial blood gas analysis in patients at risk of hypercapnia receiving oxygen therapy1.
Consider hypercapnia if a patient on acute oxygen therapy develops a reduced level of consciousness (eg drowsiness, confusion), or other signs of hypercapnia (eg bounding pulse, flushed skin). Hypercapnia can be life-threatening—seek specialist advice for management. Reducing fraction of inspired oxygen (FiO2) is central to management, and additional ventilatory support may be required (eg noninvasive ventilation, intubation).
Recognise that adequate oxygenation is not the same as adequate ventilation, and that pulse oximetry does not detect hypercapnia; see Pulse oximetry to monitor acute oxygen therapy.
If hypercapnia develops during oxygen therapy, document this in the patient’s medical record and advise the patient to wear a medical alert bracelet or necklace.