What are the guidelines for prescribing oxygen therapy?

Guidelines for Prescribing Oxygen Therapy

Oxygen therapy should be prescribed according to a target saturation range, with most acutely ill patients aiming for 94-98% saturation and those at risk of hypercapnic respiratory failure aiming for 88-92%. 1

Principles of Oxygen Prescription

• Oxygen is a treatment for hypoxemia, not breathlessness
• Oxygen does not treat underlying causes of hypoxemia, which must be diagnosed and treated urgently
• Oxygen should be prescribed and administered by trained staff

Step-by-Step Oxygen Prescription Process

1. Assessment and Initial Prescription

• Check oxygen saturation by pulse oximetry in all breathless and acutely ill patients
• Prescribe oxygen using a target saturation range:
  • 94-98% for most acutely ill patients
  • 88-92% for patients at risk of hypercapnic respiratory failure (COPD, obesity hypoventilation, chest wall deformities, neuromuscular disorders)

2. Device Selection and Flow Rate

• Choose appropriate delivery device based on clinical scenario:

Clinical Scenario	Initial Device	Initial Flow Rate	Target SpO₂
Mild hypoxemia	Nasal cannulae	1-2 L/min	94-98%
Moderate hypoxemia	Simple face mask	5-6 L/min	94-98%
COPD/hypercapnic risk	Venturi mask 24-28%	2-6 L/min	88-92%
Severe hypoxemia	Reservoir mask	15 L/min	94-98%

• For critically ill patients (cardiac arrest, shock, sepsis, major trauma), start with reservoir mask at 15 L/min pending reliable oximetry readings 1, 2

3. Documentation Requirements

• Document oxygen prescription on drug chart or electronic prescribing system
• Record:
  • Target saturation range
  • Delivery device
  • Flow rate
  • Duration of therapy (if applicable)
• Sign the drug chart on each drug round

4. Monitoring and Adjustment

• Record oxygen saturation and delivery system on monitoring chart
• Adjust oxygen delivery devices and flow rates to maintain target saturation range
• Perform clinical assessment if:
  • Saturation falls by ≥3%
  • Saturation falls below target range
  • Oxygen therapy needs to be initiated or increased due to falling saturation

5. Blood Gas Analysis

• Perform arterial blood gas analysis in:
  • Severe hypoxemia
  • Suspected hypercapnia
  • Poor response to oxygen therapy
  • Deteriorating clinical status
• For patients at risk of hypercapnic respiratory failure, repeat blood gas assessment 30-60 minutes after increasing oxygen therapy 1

6. Weaning and Discontinuation

• Reduce oxygen in stable patients with satisfactory oxygen saturation
• Discontinue once patient can maintain saturation within or above target range on room air
• Keep prescription for target range in place in case of future deterioration 1

Special Considerations

Patients with COPD or at Risk of Hypercapnic Respiratory Failure

• Target saturation range: 88-92%
• Use controlled oxygen therapy (Venturi mask 24-28%)
• Monitor closely for hypercapnia with blood gas analysis
• Consider non-invasive ventilation if respiratory acidosis develops despite controlled oxygen therapy 1, 3

Critical Illness

• Initially use high-concentration oxygen (reservoir mask at 15 L/min)
• Adjust to maintain target saturation once reliable oximetry readings are available
• For patients with COPD who develop critical illness, use same initial high oxygen approach but monitor closely with blood gases 1, 2

Common Pitfalls to Avoid

• Inadequate monitoring: Failure to regularly check oxygen saturation can lead to undetected deterioration 4
• Incorrect flow rates: Ensure oxygen is flowing at prescribed rate - studies show up to 35% of patients receive lower than prescribed flow rates 4
• Equipment issues: Check for leaks in tubes and connections 4
• Inappropriate targets: Setting different target saturations based on carbon dioxide levels is not justified - evidence shows mortality is lowest with saturations of 88-92% even in normocapnic COPD patients 3
• Overuse of oxygen: Hyperoxemia can be harmful, particularly in COPD patients 3

By following these guidelines, you can ensure safe and effective oxygen therapy for your patients while avoiding common pitfalls that may lead to adverse outcomes.