The aim of this study is to assess whether an auto-titrating oxygen system can maintain constant oxygen saturations (SpO2) in patients who are on long-term oxygen therapy (LTOT) during activities of daily living.

Currently LTOT is provided at a constant fixed-flow rate e.g. 2 litres per minute all the time after appropriate assessment. The flow rate is not changed during usual household activities but is increased for walking. A number of studies have investigated the SpO2 of patients on LTOT during the daytime in patients' homes. The results have shown that patients' SpO2 decreases intermittently whilst they are doing activities of daily living such as watching television, putting away the shopping, having a shower or bath and dressing and undressing. This is a problem as it can lead to breathlessness, increased stress on the heart and affect brain function. In order to correct the drop in SpO2 that patients experience during everyday activities, the investigators have developed an oxygen system, which can automatically change the amount of oxygen delivered depending on a patients' oxygen saturations - an auto-titrating oxygen system. In this study, patients on LTOT will be asked to simulate a series of activities of daily living twice: once whilst on their usual fixed-flow oxygen therapy and once on the auto-titrating oxygen system. The activities will be carried out in a hospital setting. During the activities, SpO2 will be recorded continuously. The main outcome of interest from the study will be the SpO2 throughout the study on fixed-flow oxygen and the auto-titrating oxygen system.

Long-term oxygen therapy (LTOT) is prescribed for patients with stable severe hypoxemic respiratory failure according to specific criteria set out in different guidelines from international respiratory societies. The aim of LTOT is to maintain the resting partial pressure of oxygen (PO2) >60 mmHg or oxygen saturation (SpO2) >90%.

A number of studies have demonstrated that whilst at home, patients on LTOT experience episodes of intermittent hypoxia (SpO2 <90%) and spend significant amounts of time with SpO2 <90%. These episodes of desaturation occur most frequently during activities of daily living and may be harmful as they could lead to pulmonary hypertension, arrhythmias and ischaemic heart disease. Simply increasing the LTOT flow rate by 1 or 2 litres in one option but this exposed the patients to hyperoxaemia and the risk of hypercapnia. An another method optimising LTOT is to utilise an auto-titrating oxygen system. These system allow close control of SpO2 by automatically adjusting the flow of oxygen to match a target SpO2. At the Royal Brompton Hospital and Imperial College London, the investigators have developed our own auto-titrating oxygen system - called intelligent oxygen therapy (iO2t).

This system has been tested in patients with chronic obstructive pulmonary disease (COPD) and LTOT during a 6 minute walk test with promising results (ERS 2015).

The aim of this study is to investigate whether the intelligent oxygen therapy system can reduce intermittent hypoxia in patients on LTOT during simulated activities of daily living. Patients will be asked to a series of activities of daily living over a period of 1 hour including: washing, dressing, putting away shopping and cleaning. The patients will do these activities twice: once on their usual LTOT and once on the auto-titrating oxygen system in a cross-over design.

Inclusion Criteria:

1. Age >18 years
2. Currently on or eligible for LTOT for respiratory failure

Exclusion Criteria:

1. LTOT flow rate ≥4 litres per minute
2. Exacerbation of underlying lung disease in the past 4 weeks
3. Inability to understand English
4. Significant co-morbidities
5. Patients who lack capacity to consent
6. Pregnancy