Background There are no ILD specific guidelines on the use of ambulatory oxygen. The AmbOx trial is a multicenter, randomised, cross-over controlled trial (NCT02286063), to assess quality of life during two weeks on ambulatory oxygen compared to two weeks off oxygen, in patients with fibrotic ILD.

Methods Individuals with fibrotic ILD whose oxygen saturation was normal at rest, but dropped to ≤88% on a 6MWT, with stable symptoms during a two week run-in period, were recruited and randomised. Primary outcome: health status assessed by King’s Brief ILD questionnaire (KBILD). A simple question on whether breathlessness had changed (better, same, worse) over the previous two weeks was a key secondary outcome. Patients‘ experiences with portable oxygen were explored through interviews in a subgroup. At the end of the four week trial period, patients were asked if they wished to continue with the ambulatory oxygen.

Results Out of 84 randomised patients, 76 completed the trial. Mean age 64.5±1.1 years, 58 males, 53 ever smokers, FVC 73.3%±19.1%, DLCO 38.7%±12.8%. 43 patients had possible/definite IPF. Ambulatory oxygen, compared to no oxygen, was associated with improvements in total KBILD score (p<0.0001). At the end of the two weeks on oxygen, the majority of patients reported improved breathlessness (better:52/76 – same:23/76 – worse:1/76), compared to the two weeks on no oxygen (better 1/76 – same:57/76 – worse:18/76). On trial completion, 51/76 (67%) of patients chose to continue on ambulatory oxygen. On multivariate analysis, factors independently predictive of the patient’s decision to continue, included younger age (64.8 vs 72.8 years, p=0.002), more severe disease (CPI 55.5 vs 49.1, p=0.003) and patient’s global assessment of improvement in breathlessness (OR 3.2, p=0.018). Despite symptomatic improvements in the majority, ambulatory oxygen was also associated with a number of patient-reported challenges, explored in the patient interviews.