Home Oxygen Therapy

Indications

Indications for Long-Term Oxygen Therapy (LTOT)

1. Chronic Obstructive Pulmonary Disease (COPD)
   • LTOT is indicated for patients with chronic obstructive pulmonary disease (COPD) when:
     • A resting PaO2 = 7.3 kPa (55 mm Hg) or SaO2 88% or less while being at rest in a stable clinical condition
     • A resting PaO2 = 8.0 kPa (59 mm Hg) or SaO2 89% or less if there is evidence of cor pulmonale, right heart failure or polycythemia (hematocrit greater than 55%) while being  in a stable clinical condition[2]
     • Many previous studies showed a survival benefit of LTOT in COPD patients with chronic hypoxemia.[3][4] Also, with COPD, LTOT may improve patient outcome measures other than survival benefits, including quality of life, depression, cognitive function, exercise capacity, and hospital admission rate.[4]
2. Interstitial Lung Disease (ILD)
   • Patients with severe ILD may develop chronic hypoxemia, which may lead to reduced tissue oxygenation with many subsequent complications and worsen prognosis. The use of LTOT in patients with ILD may improve survival and prevent complications. There are no randomized controlled trials (RCTs) reporting the LTOT effects in ILD, and so, recommendations for LTOT are extrapolated from evidence in COPD patients.[2]
3. Pulmonary Hypertension
   • There is no evidence of LTOT survival benefits in patients with pulmonary hypertension, except pulmonary hypertension due to COPD. But LTOT in pulmonary hypertension may improve tissue oxygenation and prevent complications due to chronic hypoxemia.[2]
4. Cystic Fibrosis (CF)
   • Severe CF patients may develop chronic hypoxemia. LTOT in patients with CF may lead to survival improvement and prevent complications caused by chronic hypoxemia, but no studies examined the use of LTOT in CF patients. Recommendations for LTOT in these patients are extrapolated from evidence in COPD patients.[5][2]
5. Advanced Cardiac Failure
   • There are no studies on the effects of LTOT in patients with chronic heart failure. Using LTOT in patients with advanced cardiac failure and resting hypoxemia may lead to an improvement in tissue oxygenation and preventing complications due to hypoxemia.[5]

Contraindications

There is only one absolute contraindication to home oxygen therapy. Home oxygen therapy is not indicated in patients who continue smoking cigarettes because of the significant risk of fire.[6] Similarly, oxygen cylinders or supplies should be kept away from the flames or electrical circuits.

Equipment

 Many types of devices are available for home oxygen use. These include concentrators, liquid systems, cylinders, and generators. The choice of an oxygen delivery system depends on the clinical status of the patient and the needed concentration of inspired oxygen and patient tolerance to the device used.

Typical routes for home oxygen therapy include:

• The low-flow nasal cannula is one option, which supplies a low flow of oxygen (1 to 6 liter per minute). For each liter per minute of oxygen flow, about 3% to 4% is added to the oxygen concentration. Oxygen delivered by nasal cannula to the nasopharynx mixes with room air. Consequently, the concentration of oxygen by nasal cannula varies depending upon the patient's respiratory rate, tidal volume, oxygen flow rate, and extent of mouth breathing.[7]
• Simple oxygen masks used to supply a flow of oxygen rates between 6 and 10 L per minute with oxygen concentrations between 35% and 50%, and this depends on the patient's respiratory rate and the mask fit.[8] In a simple mask, oxygen delivery is through a small-bore tube connected at the base of the mask. Exhaled gas escapes through holes on each side of the mask. Room air enters through these holes and mixes with oxygen, an oxygen flow rate greater than 5 L per minute is needed to prevent CO2 rebreathing.[9]
• Venturi masks, which allow for a fixed O2%, are available for delivery of controlled oxygen concentrations of 24% to 40%. May benefit patients with hypercapnic respiratory failure requiring LTOT.[9]
• Other interfaces exist that allow minimal head contact but no facial contact.[7]

Preparation

Patient Screening for LTOT Requirement

A pulse oximeter is widely available and can be useful for screening patients who might be indicated for LTOT.[5] Studies showed that using the SpO2 level equal to 92% has 100% sensitivity and specificity of only 69% for identifying patients with a PaO2 less than 7.3 kPa. Stable patients with oxygen saturation (SpO2) equal to 92% at rest should be referred for a blood gas evaluation, and assessment for LTOT need. Stable patients with clinical evidence of peripheral edema, hematocrit equal to 55% or pulmonary hypertension with oxygen saturation (SpO2) equal to 94% at rest should be referred for a blood gas evaluation, and assessment for LTOT need.[10][5]

Follow-up of LTOT Patients

• Follow-up should occur at three months after initiating LTOT, to ensure LTOT is still necessary.
• Patients receiving LTOT should have follow-up at 6 to 12 months after the first 3-month follow-up.[1]

Complications

There are potential toxicities in patients administered oxygen in high concentrations (above 50%) for long periods like atelectasis, oxidative stress, and peripheral vasoconstriction, but the benefits outweigh the risks. Uncontrolled oxygen delivery may lead to a worsening of hypercapnia in patients with chronic obstructive pulmonary disease. It is advised to target the SpO2 to 90% to 92% to prevent tissue hypoxia while minimizing any side effects, which might be associated with excessive oxygen supplementation.

• Patients should be made aware of the dangers of using home oxygen in the presence of any naked flame, such as cookers and candles. Oxygen cylinders should be at least 5 feet away from naked flames, a heat source, or electrical devices.
• There is a significant risk of fire associated with smoking while using home oxygen therapy. Smoking cessation should be advocated. And a written education plan should be given to patients before ordering home oxygen.[11]
• The skin around the facemask or nasal cannula can get irritated or bruised if the mask fits tightly.
• The nasal mucosa might become dry, and nosebleeds can occur.
• Morning headache or tiredness can occur with oxygen therapy.

Enhancing Healthcare Team Outcomes

A respiratory therapist can evaluate and assist patients with their home oxygen needs. The respiratory therapist can provide expertise in the various types of home oxygen delivery devices and provide ongoing assessment of the patient. Patient compliance can be maximized by selecting the appropriate device.[10] Before, referring patients to home oxygen evaluation services, patients should receive both written and verbal information.[1] [Level 4]