Long-term oxygen therapy (LTOT) improves survival in patients with chronic obstructive pulmonary disease (COPD) and chronic hypoxaemia with international guidelines recommending LTOT for patients with chronic hypoxaemia secondary to respiratory failure. LTOT is prescribed at a fixed-flow rate aiming to maintain the partial pressure of oxygen ≥8 kilopascals or oxygen saturations (SpO2) >90% at rest.
However, many patients on domiciliary LTOT continue to experience episodes of intermittent hypoxia (SpO2 <90%) during rest, exercise, activities of daily living (ADL) and sleep with the potentially harmful consequences of arrhythmias, ischaemic heart disease, transient increases in pulmonary pressures and reduced cerebral oxygenation. The aim of this thesis was to explore whether a novel smartphone based auto-titrating oxygen system (the intelligent oxygen therapy system [iO2Ts]), could reduce intermittent hypoxia by delivering variable flow oxygen to maintain a pre-set SpO2 target during various activities which typically take place over a period of 24 hours.
In the first study, the iO2Ts significantly reduced intermittent hypoxia compared to ambulatory oxygen in patients with COPD on LTOT during a 6-minute walk test (6MWT). The second study showed that the iO2Ts is equivalent to ambulatory oxygen in reducing intermittent hypoxia during a 6MWT in patients with interstitial lung disease (a group of patients who rapidly desaturate on exercise). The third study showed that the iO2Ts reduced intermittent hypoxia during ADL in patients on LTOT compared to usual LTOT. In a fourth pilot study, the iO2Ts maintained oxygenation as well as usual LTOT and did not change transcutaneous carbon dioxide levels compared to LTOT during sleep.
In summary, this thesis has shown that the iO2Ts can reduced intermittent hypoxia in patients on LTOT during various activities which typically take place over 24 hours. The reduction in intermittent hypoxia could optimise domiciliary and ambulatory oxygen for patients on LTOT.