Fibrotic lung disease is a group of severe scarring lung diseases with a dismal prognosis, often leading to respiratory failure and need for oxygen treatment. The symptom burden is often extremely high with dyspnea at rest and increasing dyspnea with exertion. Patients will often need more oxygen during activity thus repeatedly adjustments of oxygen flow rates are required to target an acceptable saturation at rest and during activities. This is impractical and can lead to an undesirable focus on oxygen levels as well as reduced use of the oxygen treatment in everyday life.

There is an urgent need for oxygen equipment that is easy to use to help patients live a life with fever symptom-related restrictions. Closed Loop Oxygen Titration (CLOT) is a new type of optimized oxygen treatment, which automatically adjusts the oxygen flow rate to the exact amount needed for the patient. The CLOT has already been tested and found useful in patients with other lung diseases, however it has not yet been tested in an isolated group of patients with fibrotic lung disease.

The goal of this clinical trial is therefore to study if automatically adjusted oxygen delivery can be useful for patients with fibrotic lung disease who needs oxygen treatment during activity.

The main questions aimed to be answered are: Will participants experience less breathlessness during walking, when the oxygen supply is individually adjusted to maintain an acceptable level of oxygen saturation?

Our hypotheses are that automatically adjusted oxygen dose during walking will results in less breathlessness compared to the usual fixed dose of oxygen. Furthermore, that participants will walk longer and maintain a better oxygen saturation during a walking test when offered automatically adjusted oxygen dose.

Participants will perform two walking tests with both automatically adjusted and fixed dose oxygen in random order, and the difference in sensation of breathlessness will be compared between the two tests.

Recruitment of participants

Participants with fibrotic lung disease will be recruited by a pulmonary specialist from the Centre for Rare Lung Diseases, Department of Respiratory Diseases and Allergy, Aarhus University Hospital during a routine outpatient visit. If exertional oxygen desaturation is suspected or has been documented by a six-minute walking test the investigator, a pulmonary specialist will inform the patient about the study and ask for study participation.

The patient will be asked to sign the informed consent. The information given to the patient specifies that the informed consent gives access for study personnel to access the medical record for relevant information necessary to complete the study. The written informed consent form will be signed and personally dated by the subject and the person conducting the informed consent conversation.

Ethical considerations

No risk for the patients is considered to be related to participation in the study. The walking tests are conducted by an experienced physiotherapist with solid knowledge about patients with fibrotic lung disease and when to terminate walking tests due to clinical symptoms. Furthermore, patients are enquired to stop the test if they experience discomfort. Walking tests with or without oxygen supply is a part of standard clinical practice for patients with fibrotic lung disease at the Centre of Rare Lung Diseases and the O2matic has been approved for clinical use.

Patients can benefit individually by gaining knowledge about their oxygen need at exercise, and as a group contribute to increased knowledge about the effect of automated oxygen treatment on dyspnea during exercise and on exercise endurance. International guidelines have restricted recommendations for ambulatory oxygen therapy due to limited evidence. This study may contribute to stronger recommendations for the prescription of ambulatory oxygen therapy in the future.

Inclusion Criteria:

• Verified diagnosis of fibrotic interstitial lung disease
• Desaturation during a recent (6 months) 6-minute walk test below 88% on atmospheric air or during an incremental shuttle walking test
• Able to walk at least 50 meters
• Self-reported stable respiratory symptoms in the previous 2 weeks
• Age ≥ 18 years
• Cognitively able to understand and participate in the study
• Written informed consent

Exclusion Criteria:

• Long term oxygen treatment
• A pulmonary or cardiac condition other than fibrotic interstitial lung disease limiting exercise performance
• Unstable heart condition or symptomatic stenotic valve disease
• Any physical condition limiting exercise performance.
• Smoking the previous 24 hours
• Pregnancy
• Anaemia, haemoglobin < 7.3 mmol/l (women) or < 8.3 mmol/l (men)

The participant will wear a high flow nasal canula for oxygen treatment during both endurance shuttle walk tests, which will mask the mode of oxygen delivery and dose for both the participant and the assessor (investigator). A health care professional not involved in the data collection or outcome assessment will set up the equipment before each test to secure masking of the O2matic device and oxygen delivery mode.