The main goal of this study is to establish the effectiveness of palliative oxygen in the context within which it is usually provided--relief of the sensation of breathlessness and improvement in quality of life for people with maximally-treated life-limiting illness.

When further medical management will not relieve intractable breathlessness, palliative oxygen is often prescribed regardless of whether the person meets the common oxygen funding criteria of severely low blood oxygen levels. The results of this study will inform best practice in the care of people with advanced life-limiting illness and intractable breathlessness, aid in the development of rational funding guidelines, and answer an international debate on the role of palliative oxygen.

This study is a definitive international multi-center randomized double-blind controlled trial of oxygen versus medical air for the relief of breathlessness in participants with intractable dyspnea and PaO2>55mmHg (a measure of blood oxygen levels). Specific aims include demonstration of the effectiveness of oxygen versus medical air in relieving breathlessness in the palliative setting (Specific Aim 1) and improving QOL (Specific Aim 2). Additionally, we will seek to establish which patients derive the greatest benefit (Specific Aim 3), the risks of therapy (Specific Aim 4), and the costs of therapy (Specific Aim 5). The primary hypothesis is that oxygen therapy is superior to air in relieving the sensation of breathlessness for patients with intractable dyspnea due to life-limiting illness in the setting of PaO2>55mmHg.

All participants are enrolled as outpatients. The "eligibility visit" occurs about 5-7 days before starting the study and will include review of the consent form, a short interview, physical exam, and blood tests. The visit can occur in the home or clinic. The blood tests include regular venipuncture and also an arterial blood gas, if these studies have not been done in the preceding month. The "randomization visit" occurs 2 days before the study starts (Day -2) and includes a short interview and quality of life (QOL) questionnaire; this visit is usually done in the home but can also occur in the clinic. The oxygen or air concentrators are delivered to the home on Day 0 by a trained person from the oxygen company. On the same day there is also a brief home visit from the study nurse that includes a short interview and QOL questionnaire. The participant uses the oxygen or medical air gas each of 7 days (Days 0-6) for at least 15 hours each day. While using the oxygen/air the participant fills out a short diary form in the morning and evening, within 30 minutes of waking up or retiring. The diary focuses on the breathlessness, how the participant is feeling, and potential side effects of the gas. The study nurse conducts a "check-in" telephone call on Day 3 to make sure the participant is doing OK. On the last day (Day 6) the nurse visits the home to conduct a brief interview with a short QOL questionnaire. The oxygen company will pick up the concentrator, usually on Day 7.

Inclusion Criteria:

• Adult patients with intractable dyspnea and PaO2>55mmHg in the setting of terminal illness where the underlying cause has been maximally treated; a medical specialist must document that all identified reversible causes of the dyspnea have been treated; PaO2 measurement must be in the last month
• Dyspnea at rest or with minimal exertion, as measured by a score of ≥ 3 on the Medical Research Council categorical dyspnea exertion scale
• On stable medications over the prior week except routine "as needed" medications.
• Survival of at least 1 month in the opinion of the treating physician

Exclusion Criteria:

• Meets international guidelines for long-term oxygen therapy with PaO2 56-59mmHg, i.e. symptomatic pulmonary hypertension with cor pulmonale
• Hemoglobin<10.0g/dL as measured within one month of baseline evaluation
• PaCO2 >50 mm Hg.
• Confusion as measured by Folstein Mini-mental Status Exam <24/30
• Current oxygen therapy or continuous oxygen therapy in previous week
• Actively smoking
• Active respiratory or cardiac event in the previous 2 weeks, not including upper respiratory tract infections; illness must be resolved for at least 2 weeks prior to baseline evaluation, as judged by a doctor involved in the care of the patient
• Previous respiratory failure induced by oxygen
• Unable to give informed consent or complete diary entries