Long-term oxygen therapy is a fundamental treatment modality for patients with chronic hypoxaemic lung disease. Typically, oxygen is administered at a constant flow rate. However, due to fluctuating activity levels, patients' oxygenation status can vary, potentially leading to oxygen desaturation and increased dyspnoea.

Emerging evidence suggests that automatic oxygen titration - a method of adjusting oxygen flow in response to current oxygen saturation - may have acute advantages over constant oxygen flow.

The primary objective of this study is to investigate the effect of automatic oxygen titration compared to prescribed constant oxygen flow rates on patients' perceived dyspnoea during exercise endurance training.

Rationale:

Hypoxaemia is common in people with chronic lung disease and can affect exercise tolerance. Oxygen therapy is then recommended.

Oxygen supplementation is usually delivered at constant oxygen flow rates. Only a few studies have investigated the short-term effects of automated oxygen delivery compared to a constant oxygen flow rate during exercise tests (e.g. 6-minute walk test, shuttle walk tests). These studies have shown that automatic oxygen delivery can lead to an acute increase in exercise capacity, including an improvement in the perception of breathlessness. The use of automated oxygen delivery during endurance exercise has not been studied. The most common reason for stopping prolonged exercise in patients with chronic lung disease is dyspnoea. Therefore, the use of automatic oxygen delivery in a pulmonary rehabilitation clinic could be beneficial in the context of personalised therapy for patients requiring oxygen if it further reduces dyspnoea, potentially enabling the patient to train their endurance even better.

Therefore, the primary aim of this study was to investigate whether the use of automatic oxygen supplementation versus constant oxygen supplementation has a different effect on the perception of dyspnoea in patients with hypoxaemia during endurance exercise.

Design:

This study is designed as a randomised, double-blind, controlled cross-over trial. Participants will first undergo a cycle-based peak work rate test to determine their individual maximal peak work rate. They then take part in two sets of five endurance training sessions. One set is performed with a constant oxygen flow prescribed for each participant, while the other uses automatic oxygen titration. The order in which these two sessions are performed is randomised.

Inclusion Criteria:

• Chronic lung disease
• Hypoxemia (pO2< 55mmHg) under room air conditions (rest or during exercise) or SpO2<88% during exercise
• established Long-term oxygen therapy or given indication for a Long-term oxygen therapy/ supplemental oxygen therapy for exercise
• Age: 18 to 80 years
• Participation in an inpatient pulmonary rehabilitation program (Schoen Klinik BGL, Germany)
• Written informed consent

Exclusion Criteria:

- Acute exacerbation of underlying pulmonary disease requiring cessation of exercise training.

The participant and investigator is blinded to the type of oxygen supply (constant flow or automatic titrating flow).