What are the indications for home oxygen therapy in Interstitial Lung Disease (ILD)?

Indications for Home Oxygen Therapy in Interstitial Lung Disease

Home oxygen therapy should be prescribed for patients with interstitial lung disease (ILD) who have severe chronic hypoxemia (PaO₂ ≤7.3 kPa or ≤55 mmHg) when clinically stable, and for those with PaO₂ ≤8 kPa (≤60 mmHg) with evidence of peripheral edema, polycythemia, or pulmonary hypertension. 1

Primary Indications for Home Oxygen in ILD

Resting Hypoxemia

• Severe chronic hypoxemia: PaO₂ ≤7.3 kPa (≤55 mmHg) when clinically stable 1
• Moderate hypoxemia with complications: PaO₂ ≤8 kPa (≤60 mmHg) with:
  • Peripheral edema
  • Polycythemia (hematocrit ≥55%)
  • Evidence of pulmonary hypertension 1

Exertional Hypoxemia

• ILD patients with mild chronic hypoxemia who have either:
  • Dyspnea on exertion
  • Desaturation during exercise (SpO₂ <90%)
  • Desaturation during sleep 1

Assessment Protocol for Home Oxygen Therapy

1. Timing of assessment:

   • Must be performed when patient is clinically stable (at least 8 weeks after any exacerbation) 2
   • Requires two arterial blood gas measurements at least 3 weeks apart to confirm need 2

2. Initial screening:

   • Identify patients with SpO₂ ≤92% for formal blood gas assessment
   • Consider referral at SpO₂ ≤94% if peripheral edema, polycythemia, or pulmonary hypertension is present 2

3. Titration process:

   • Start at 1 L/min flow rate
   • Increase in 1 L/min increments until SpO₂ >90%
   • Confirm with ABG that target PaO₂ ≥8 kPa (≥60 mmHg) is achieved 1

Duration and Monitoring Requirements

• Minimum usage: At least 15 hours daily to achieve survival benefit 1, 2
• Follow-up assessment:
  • Home visit within 4 weeks by a specialist nurse or healthcare professional
  • Formal reassessment at 3 months with blood gas measurement to confirm continued need 2
  • Subsequent follow-up visits at 6-12 months 1

Special Considerations

Flow Rate Adjustments

• Non-hypercapnic patients should increase flow rate by 1 L/min during sleep 1
• Active patients should receive ambulatory oxygen assessment to determine if flow rate needs increasing during exercise 1
• Patients with cognitive or physical impairments may need to be maintained on a single flow rate for safety 1

Patient Education

• Formal education by a specialist home oxygen assessment team is essential for compliance 1
• Patients should understand that oxygen therapy may be discontinued if reassessment shows clinical improvement 1

Common Pitfalls to Avoid

• Premature prescription: Avoid initiating oxygen during or immediately after an exacerbation 2
• Inadequate monitoring: Failure to reassess after 3 months may result in unnecessary continuation 2
• Overlooking hypercapnia: Monitor for worsening CO₂ retention during oxygen titration 2
• Unrealistic expectations: Patients often expect oxygen to relieve dyspnea, but benefits may be more related to other physical symptoms 3

Evidence Quality and Limitations

It's important to note that recommendations for oxygen therapy in ILD are largely extrapolated from COPD studies, with limited high-quality evidence specific to ILD 1, 4. The single randomized controlled trial identified specifically for ILD patients with hypoxemia showed no significant survival benefit after 3 years 4. However, guidelines still strongly recommend home oxygen therapy for ILD patients with severe hypoxemia based on physiological principles and clinical experience.

Despite these limitations, the potential benefits of preventing complications associated with chronic hypoxemia (such as worsening pulmonary hypertension) outweigh the risks in patients meeting the criteria for home oxygen therapy 1.