Prescribing oxygen therapy

• oxygen should be prescribed to achieve a target saturation of 94-98% for most acutely unwell patients or 88 -92% for those at risk of hypercapnic respiratory failure
• Normal Oxygen Saturations
  • in adults less than 70 years of age when awake at rest and at sea level: 96% - 98%
  • aged 70 and above when awake at rest and at sea level: greater than 94%.
  • NB: Patients of all ages may have transient dips of saturation to 84% during sleep
    
    
• Contraindications to Oxygen therapy
• are no absolute contraindications to oxygen therapy if indications are judged to be present. The goal of oxygen therapy is to achieve adequate tissue oxygenation using the lowest possible FiO2
• supplemental Oxygen should be administered with caution in patients suffering from paraquat poisoning and with acid inhalation (seek specialist advice from the UK National Poisons Information Service) or previous bleomycin lung injury
  
  
• Oxygen administration and carbon dioxide retention
  • in patients with chronic carbon dioxide (CO2) retention, oxygen administration may cause further increases in carbon dioxide and respiratory acidosis. This may occur in patients with COPD, neuromuscular disorders, morbid obesity or musculoskeletal disorders
  • There are several factors, which lead to the rise in CO2 with oxygen therapy in patients with hypercapnic respiratory failure, and details are in the BTS guideline available at:
    • http://www.brit-thoracic.org.uk/ClinicalInformation/EmergencyOxygen
  • patients at risk of hypercapnic respiratory failure e.g. severe COPD should not be given high concentrations of oxygen. 24-28% oxygen should be administered
    
• Emergency situations
  • In the emergency situation oxygen prescription is not required. Oxygen should be given to the patient immediately without a formal prescription or drug order but documented later in the patient's record
  • all peri-arrest and critically ill patients should be given 100% oxygen (15 l/min reservoir mask) whilst awaiting immediate medical review. Patients with COPD and other risk factors for hypercapnia who develop critical illness should have the same initial target saturations as other critically ill patients pending the results of urgent blood gas results after which these patients may need controlled oxygen therapy or supported ventilation if there is severe hypoxaemia and/or hypercapnia with respiratory acidosis
  • all patients who have had a cardiac or respiratory arrest should have 100% oxygen provided along with basic/advanced life support.

Notes:

• percentage oxygen prescribed
  • for therapeutic uses, the range of percentage tends to be between 24% and 60%. Oxygen may also be measured and prescribed as a measure of litres per minute (l/min), in this case the percentage delivered will vary depending upon the mask/delivery system used
    • patients at risk of hypercapnic respiratory failure e.g. severe COPD should not be given high concentrations of oxygen. 24-28% oxygen should be administered
• it may be prescribed as a regular drug for long-term oxygen therapy or as an 'as required' drug when used e.g. for short-burst oxygen therapy. If oxygen is being delivered from cylinders, the usual flow rates are 'medium', 2 litres per minute and 'high', 4 litres per minute
  

Reference:

• Portsmouth Hospitals NHS Trust (2010). Policy for the prescription and administration of Oxygen in Adults
• South Staffordshire and Shropshire Healthcare NHS Foundation Trust (2009). Administration of Oxygen policy.