Home Oxygen Therapy

Indications

Indications for Long-Term Oxygen Therapy 

Long-term oxygen therapy (LTOT) is prescribed for patients with chronic hypoxemia to improve tissue oxygenation, reduce complications associated with hypoxemia, and, in selected populations, improve survival. The strongest evidence supporting LTOT exists for patients with chronic obstructive pulmonary disease (COPD). However, LTOT use has been extended to other chronic cardiopulmonary disorders based on physiologic rationale and expert consensus.

Chronic Obstructive Pulmonary Disease

LTOT is recommended for patients with COPD who have a resting arterial oxygen tension (PaO₂) less than 7.3 kPa (55 mm Hg) or an arterial oxygen saturation (SaO₂) less than 88% while breathing room air. LTOT is also indicated in patients with a resting PaO₂ less than or equal to 8.0 kPa (59 mm Hg) or SaO₂ less than or equal to 89% when accompanied by evidence of cor pulmonale, right-sided heart failure, or secondary polycythemia (hematocrit greater than 55%). Results from studies demonstrated that LTOT improves survival in patients with severe chronic hypoxemia due to COPD.[2][3] In addition to its mortality benefit, LTOT has been associated with improvements in quality of life, exercise tolerance, cognitive function, and mood, as well as reductions in hospitalizations.[3]

Interstitial Lung Disease

Patients with advanced interstitial lung disease (ILD) frequently develop chronic hypoxemia because of impaired gas exchange. Persistent hypoxemia may contribute to reduced tissue oxygen delivery, diminished functional capacity, pulmonary hypertension, and poorer overall prognosis. Although randomized controlled trials evaluating LTOT specifically in ILD are lacking, current recommendations are largely extrapolated from evidence obtained in COPD populations.[4]

Despite this weak evidence base, the American Thoracic Society issued a strong recommendation for LTOT for at least 15 hours per day in adults with ILD and severe chronic resting hypoxemia. The recommendation places high value on indirect evidence from patients with COPD and the potential for harm from untreated severe hypoxemia.[5] Notably, results from a 2025 Swedish population-based study (the DISCOVERY cohort) suggested that initiating LTOT in patients with ILD (n = 2507) was associated with reduced acute exacerbations and hospitalizations among patients with at least 12 months of follow-up, although the study was not randomized.[6]

Pulmonary Hypertension

Although oxygen administration reduces pulmonary vascular resistance and improves exercise tolerance in patients with pulmonary arterial hypertension, the 2022 European Society of Cardiology and European Respiratory Society Guidelines state that long-term oxygen therapy has no demonstrated sustained benefit on disease progression.[7] Results from the Long-Term Oxygen Therapy in Precapillary Pulmonary Hypertension study (n = 20) demonstrated that LTOT significantly improved the 6-minute walking distance by 42.2 m but did not demonstrate a survival benefit.[8] In the absence of robust data on the use of oxygen in pulmonary arterial hypertension, the European Society of Cardiology and European Respiratory Society Guidelines extrapolate their recommendations from evidence in patients with COPD and advise supplemental oxygen when PaO₂ is less than 60 mm Hg, or SaO₂ is less than 92% on at least 2 occasions.[7]

Cystic Fibrosis

Patients with advanced cystic fibrosis may develop chronic respiratory failure and sustained hypoxemia as lung disease progresses. Although direct evidence evaluating LTOT in cystic fibrosis is limited, no results from dedicated studies have established its effect on survival. Oxygen therapy is commonly used to improve oxygenation and reduce complications associated with chronic hypoxemia, and current recommendations are largely extrapolated from studies conducted in COPD populations.[4][9]

Advanced Cardiac Failure

No randomized trials have specifically evaluated LTOT in this population. Despite the lack of randomized evidence, current American Thoracic Society guidelines recommend LTOT for patients with severe chronic resting hypoxemia (PaO₂<55 mm Hg or SaO₂<88%), regardless of the underlying cause, including heart failure. Cor pulmonale serves as a qualifying criterion at the higher PaO₂ threshold of 56 to 59 mm Hg. The recommendations are primarily extrapolated from evidence from the Medical Research Council trial and the Nocturnal Oxygen Therapy Trial rather than from heart failure–specific data.[10]

Contraindications

Smoking and fire risk represent one of the most recognized safety concerns associated with home oxygen therapy because oxygen accelerates combustion near open flames, and smoking is a leading cause of burn incidents. However, active smoking is not universally classified as an absolute contraindication. The 2020 American Thoracic Society Clinical Practice Guideline does not designate smoking as an absolute contraindication but recommends safety education and treatment of tobacco dependence for current smokers.[5] A 2024 Swedish Respiratory Society task force similarly recommended an individualized risk-benefit assessment rather than a blanket prohibition.[11] Additional safety precautions, such as keeping oxygen supplies away from open flames, electrical circuits, and oil-based nasal products, are universally recommended.[5]

Equipment

Oxygen Delivery Systems and Interfaces

Several oxygen delivery systems are available for home use, including oxygen concentrators, liquid oxygen systems, compressed gas cylinders, and portable oxygen generators. Selection of the most appropriate system depends on the patient's clinical condition, prescribed oxygen requirements, mobility needs, desired inspired oxygen concentration, and tolerance of the delivery device. A low-flow nasal cannula, the most commonly used interface for home oxygen therapy, delivers oxygen at flow rates of 1 to 6 L/min. For each 1 L/min increase in oxygen flow, the inspired oxygen concentration increases by approximately 3% to 4%. Because oxygen delivered through a nasal cannula mixes with ambient air in the nasopharynx, the actual inspired oxygen concentration varies with respiratory rate, tidal volume, oxygen flow rate, and the degree of mouth breathing.[12]

Simple oxygen masks provide oxygen flow rates of 6 to 10 L/min and can achieve inspired oxygen concentrations of approximately 35% to 50%, depending on mask fit and the patient's ventilatory pattern.[13] Oxygen is delivered through a small-bore tube connected to the mask, and exhaled gas exits through side ports that also permit room air entrainment. To avoid carbon dioxide rebreathing, oxygen flow rates should generally exceed 5 L/min when using a simple face mask.[14]

Venturi masks provide a fixed, predictable inspired oxygen concentration and are available in configurations delivering 24% to 40% oxygen. Because they allow precise oxygen titration, Venturi masks may be particularly useful for patients with chronic hypercapnic respiratory failure who require long-term oxygen therapy.[14] Additional oxygen delivery interfaces are available for selected patients and may improve comfort by reducing head contact or avoiding direct facial contact. Alternative interfaces can be useful for individuals who are unable to tolerate conventional nasal cannulas or face masks.

Preparation

Patient Screening for LTOT Requirement

Pulse oximetry is widely available and can help screen patients who may require LTOT.[9] Results from studies showed that an SpO₂ threshold of 92% had 100% sensitivity but only 69% specificity for identifying patients with a PaO₂ less than 7.3 kPa. Stable individuals with an SpO₂ of 92% at rest should be referred for blood gas analysis and assessment of the need for LTOT. Those stable with an SpO₂ of 94% at rest and clinical evidence of peripheral edema, a hematocrit of 55%, or pulmonary hypertension should be referred for blood gas analysis and assessment of the need for LTOT.[9][15]

Technique or Treatment

LTOT should be used for at least 15 hours per day, because results from a 2024 New England Journal of Medicine trial by Ekström et al demonstrated that 24-hour use did not reduce hospitalization or death compared with 15 hours per day (hazard ratio, 1.08; 95% CI, 0.78–1.50), supporting the less burdensome regimen as equally effective.[5] Oxygen should be titrated to a target SpO₂ of at least 90% or, in patients at risk for hypercapnia, 88% to 92% to avoid suppressing hypoxic ventilatory drive.[5][11] Periodic reassessment is critical and has been identified as a top 5 Choosing Wisely priority in adult respiratory medicine.

When LTOT is initiated after an acute exacerbation, reassessment within 30 to 90 days is recommended because up to 50% of patients may no longer qualify. The 2026 Global Initiative for Chronic Obstructive Lung Disease Report recommends reassessment 1 to 4 weeks after discharge and again at 12 to 16 weeks.[5][11] For stable individuals, reassessment at least every 6 months is advised to confirm continued need, prescription accuracy, and equipment adequacy, with SpO₂ or arterial blood gas measurements obtained at rest and during exertion.[11] Clinicians generally should not discontinue oxygen therapy in patients with chronic stable hypoxemia who met LTOT criteria before hospitalization because the safety of discontinuation in this population is unknown and discontinuation may worsen hypoxemia.

Complications

Prolonged exposure to high oxygen concentrations (fraction of inspired oxygen greater than 50%) can cause absorptive atelectasis, oxidative stress, and peripheral vasoconstriction, although the benefits of correcting chronic hypoxemia generally outweigh these risks when oxygen is appropriately titrated.[16] Uncontrolled oxygen delivery may worsen hypercapnia in patients with COPD by suppressing hypoxic ventilatory drive, increasing ventilation-perfusion mismatch, and amplifying the Haldane effect, necessitating careful titration to an SpO₂ target of 88% to 92% in at-risk individuals.[10][17] Home oxygen therapy poses a significant fire hazard, particularly in patients who smoke or use e-cigarettes.

Oxygen equipment should be kept at least 5 feet from open flames, heat sources, or electrical devices, and clinicians should provide a written safety education plan before initiation.[5] Common local adverse effects include dry mouth (69.5%), dry nose (53.0%), nasal congestion, skin irritation from masks or cannulas, epistaxis, and increased tiredness (57.0%). Most of these adverse effects remain unreported and untreated, highlighting the importance of structured follow-up assessment.

Clinical Significance

Home oxygen therapy holds substantial clinical significance, primarily due to the demonstrated survival benefit of LTOT in patients with COPD and severe chronic resting hypoxemia, with additional benefits including improved exercise capacity, prevention of organ dysfunction, and symptom relief across multiple chronic lung diseases. The foundational evidence for LTOT derives from 2 landmark trials, the Nocturnal Oxygen Therapy Trial (NOTT) and the British Medical Research Council (MRC) trial. Results from these trials demonstrated that LTOT administered for at least 15 hours per day significantly reduces mortality in patients with COPD and severe resting hypoxemia (PaO₂<55 mm Hg).

Results from the NOTT demonstrated a 55% reduction in 2-year mortality risk with continuous oxygen compared with nocturnal oxygen alone, whereas results from the MRC trial demonstrated a 59% reduction in 5-year mortality risk compared with no oxygen (33% versus 55% mortality, P < .05).[5] Importantly, LTOT has not demonstrated a survival benefit in patients with moderate hypoxemia. Results from a systematic review and meta-analysis of 6 trials involving 1002 patients found little or no effect on survival, exacerbations, hospitalizations, or quality of life in this population.

Pulmonary Hemodynamics 

LTOT attenuates and sometimes reverses the progression of pulmonary hypertension in patients with COPD by reducing pulmonary artery pressure and pulmonary vascular resistance.[18][19] The 2026 Global Initiative for Chronic Obstructive Lung Disease Guidelines recognize pulmonary hypertension, peripheral edema, and polycythemia (hematocrit greater than 55%) as indications for initiating LTOT. These qualifying conditions permit initiation at the higher PaO₂ threshold of 55 to 60 mm Hg.

Hospitalization and Exacerbation Burden

The 2025 Swedish DISCOVERY cohort included 13,491 patients. Results from the study demonstrated that initiating LTOT was associated with significant reductions in acute exacerbations and all-cause hospitalizations among patients with COPD. Similar benefits were observed among patients with interstitial lung disease and pulmonary hypertension who had at least 12 months of follow-up.[6]

Symptom Relief and Functional Capacity

In the short term, oxygen administration can improve oxygen saturation by approximately 9 percentage points and improve physical performance on the 6-minute walking test by a clinically meaningful 37 m (P < .001).[20] The 2020 American Thoracic Society Clinical Practice Guideline strongly recommends LTOT for adults with COPD or interstitial lung disease who have severe chronic resting hypoxemia and conditionally recommends ambulatory oxygen for patients with severe exertional hypoxemia.[5] However, study results did not demonstrate sustained improvements in daily breathlessness or health-related quality of life among patients with moderate hypoxemia who received LTOT.[5]

Enhancing Healthcare Team Outcomes

A respiratory therapist can evaluate patients’ home oxygen requirements and assist with therapy. Device selection and ongoing assessment benefit from the respiratory therapist’s expertise in various types of home oxygen delivery devices. Selecting the appropriate device can improve treatment adherence.[15] Before referral to home oxygen evaluation services, patients should receive written and verbal education.[1]