What are the indications for Long-term Oxygen Therapy (LTOT)?

Indications for Long-Term Oxygen Therapy (LTOT)

Long-term oxygen therapy (LTOT) is primarily indicated for patients with chronic hypoxemia with a resting PaO2 ≤7.3 kPa (55 mmHg) or ≤8 kPa (60 mmHg) with specific complications such as peripheral edema, polycythemia, or pulmonary hypertension. 1

Primary Indications by Condition

COPD

• PaO2 ≤7.3 kPa (55 mmHg) at rest when clinically stable (Grade A evidence) 1
• PaO2 ≤8 kPa (60 mmHg) with evidence of:
  • Peripheral edema
  • Polycythemia (hematocrit ≥55%)
  • Pulmonary hypertension (Grade A evidence) 1
• Patients with resting hypercapnia who meet other LTOT criteria (Grade B evidence) 1

Interstitial Lung Disease (ILD)

• PaO2 ≤7.3 kPa (55 mmHg) at rest (Grade D evidence) 1
• PaO2 ≤8 kPa (60 mmHg) with evidence of:
  • Peripheral edema
  • Polycythemia (hematocrit ≥55%)
  • Pulmonary hypertension (Grade D evidence) 1

Cystic Fibrosis (CF)

• PaO2 ≤7.3 kPa (55 mmHg) at rest (Grade D evidence) 1
• PaO2 ≤8 kPa (60 mmHg) with evidence of:
  • Peripheral edema
  • Polycythemia (hematocrit ≥55%)
  • Pulmonary hypertension (Grade D evidence) 1

Pulmonary Hypertension

• PaO2 ≤8 kPa (60 mmHg) (Grade D evidence) 1
• Supplemental oxygen should maintain oxygen saturations >90% at all times 2

Advanced Cardiac Failure

• PaO2 ≤7.3 kPa (55 mmHg) at rest (Grade D evidence) 1
• PaO2 ≤8 kPa (60 mmHg) with evidence of:
  • Peripheral edema
  • Polycythemia (hematocrit ≥55%)
  • Pulmonary hypertension on ECG or echocardiograph (Grade D evidence) 1

Neuromuscular or Chest Wall Disorders

• Non-invasive ventilation (NIV) is first-line treatment for type 2 respiratory failure
• Additional LTOT may be required if hypoxemia persists despite NIV 1

Assessment Process

1. Initial Screening:

   • Patients with resting SpO2 ≤92% should be referred for arterial blood gas assessment 1
   • Patients with clinical evidence of complications may be considered for assessment at SpO2 levels ≤94% 2

2. Timing of Assessment:

   • Patients should be clinically stable for at least 8 weeks after last exacerbation 2
   • Measurements should be repeated at least 3 weeks apart to confirm chronic hypoxemia 3

3. Prescription Requirements:

   • LTOT should be used for at least 15 hours per day to achieve survival benefits 2
   • Optimal use is 24 hours per day (with breaks as needed for practical reasons) 2
   • The greater the daily use (>15 hours), the greater the survival benefit 1

Important Considerations and Pitfalls

• Smoking Status: If LTOT is prescribed for patients who continue to smoke, they should be informed that clinical benefits may be limited 1

• Controversial Indications (not currently recommended):

  • Moderate hypoxemia (PaO2 >60 mmHg) without complications 4
  • Exercise-induced hypoxemia alone 4, 5
  • Sleep hypoxemia alone 4, 5
  • Breathlessness without hypoxemia 6

• Common Prescription Errors:

  • Premature assessment (before clinical stability)
  • Inadequate duration of therapy (<15 hours/day)
  • Inappropriate indications (e.g., normoxemia with dyspnea) 2

Monitoring Requirements

• Arterial blood gases should be measured at rest 5
• During exercise, effort testing should ensure adequate SaO2 5
• During sleep, continuous monitoring of SaO2 and PaCO2 should confirm correction of overnight hypoxemia 5
• Morning arterial blood gas should assess PaCO2 to prevent hypoventilation from oxygen therapy 5

Delivery Methods

• Nasal cannula is the most common delivery method 6
• Portable oxygen (liquid oxygen) should be considered to improve compliance and quality of life, especially for ambulatory patients 3

By following these evidence-based indications and prescription guidelines, LTOT can significantly improve survival, reduce pulmonary hypertension, and enhance quality of life in patients with chronic hypoxemia.