What are the indications and contraindications for long-term oxygen (O2) therapy?

Indications and Contraindications of Long-Term Oxygen Therapy

Long-term oxygen therapy (LTOT) is primarily indicated for patients with severe resting hypoxemia (PaO₂ ≤7.3 kPa/55 mmHg) or moderate hypoxemia (PaO₂ 7.3-8.0 kPa/55-60 mmHg) with evidence of end-organ damage such as pulmonary hypertension, cor pulmonale, or polycythemia. 1

Indications for LTOT

Primary Indications

• Severe resting hypoxemia:

  • PaO₂ ≤7.3 kPa (55 mmHg) or SaO₂ ≤88% in stable condition 1, 2
  • Measurements must be confirmed twice over a 3-week period during clinical stability 1

• Moderate hypoxemia with evidence of end-organ damage:

  • PaO₂ between 7.3-8.0 kPa (55-60 mmHg) with one or more of the following: 1
    • Peripheral edema suggesting congestive heart failure
    • Pulmonary hypertension
    • Polycythemia (hematocrit >55%)
    • Cor pulmonale on ECG or echocardiograph

Disease-Specific Indications

LTOT should be prescribed for patients with the following conditions when they meet the above hypoxemia criteria:

1. Chronic Obstructive Pulmonary Disease (COPD) 1

   • Strongest evidence base for mortality benefit
   • Must be in stable condition (not during exacerbation)

2. Interstitial Lung Disease (ILD) 1

   • Same criteria as COPD apply
   • Consider palliative oxygen therapy for severe breathlessness

3. Cystic Fibrosis 1

   • Same criteria as COPD apply

4. Pulmonary Hypertension 1

   • Including idiopathic pulmonary hypertension
   • When PaO₂ ≤8 kPa (60 mmHg)

5. Advanced Cardiac Failure 1

   • Same criteria as COPD apply

6. Neuromuscular or Chest Wall Disorders 1

   • Non-invasive ventilation should be first-line treatment
   • LTOT may be added if hypoxemia persists despite NIV

Administration Requirements

• Duration: Minimum of 15 hours per day, including sleep periods 1, 2
• Target: Flow should be adjusted to achieve PaO₂ >8.0 kPa (60 mmHg) or SaO₂ >90% 1, 2
• Typical flow rate: 1.5-2.5 L/min via nasal cannula 1, 2
• Annual reassessment: Flow rates should be assessed at least once yearly 1

Contraindications and Precautions

Absolute Contraindications

• Current smoking: LTOT is generally not prescribed for patients who continue to smoke due to fire hazard and safety concerns 1, 2

Relative Contraindications/Precautions

• Hypercapnia risk: Excessive oxygen administration can worsen CO₂ retention in susceptible patients 2

  • Start with low-dose oxygen (24% by Venturi mask or 1-2 L/min by nasal cannula)
  • Monitor arterial blood gases after 30-60 minutes of oxygen therapy
  • Target SpO₂ of 88-92% to prevent worsening hypercapnia

• Unstable respiratory status: Oxygen requirements should be assessed during clinical stability, not during acute exacerbations 1, 3

Common Pitfalls to Avoid

1. Inadequate duration of therapy: Less than 15 hours/day provides reduced survival benefit. Continuous administration has been shown to have greater survival benefit than intermittent administration 1, 2

2. Inappropriate prescription: Prescribing LTOT for patients with only moderate hypoxemia (PaO₂ >55 mmHg) without evidence of end-organ damage has not been shown to improve survival 3, 4

3. Failure to reassess: Oxygen requirements can change over time. Annual assessment of flow rates is recommended 1

4. Overlooking hypercapnia risk: Excessive oxygen can worsen hypercapnia in some patients with COPD. Close monitoring is essential 2

5. Inadequate patient education: Patients need proper instruction on equipment use, safety precautions, and the importance of adherence to prescribed duration 2

Delivery Systems

• Nasal cannulae: Most commonly used for LTOT 1, 2
• Venturi masks: Provide more accurate oxygen concentration 1, 2
• Transtracheal oxygen: Option for patients with high oxygen demands or cosmetic concerns 1, 2
• Oxygen sources: Concentrators (easiest for home use), liquid oxygen (advantage for portability), or cylinders (less practical for LTOT) 2

LTOT remains one of the few interventions proven to improve survival in patients with severe hypoxemia, particularly those with COPD. When properly prescribed and administered according to established guidelines, it can significantly improve mortality outcomes and quality of life for eligible patients.