This is an observational clinical research study investigating patients with fibrotic interstitial lung disease (fILD), also known as pulmonary fibrosis.

It is not known why some patients with fILD clinically deteriorate. This study will investigate whether measuring oxygen levels during sleep or exercise can help identify patients who are at increased risk of clinical deterioration.

This work will build upon the FIBRINOX study, previous clinical research conducted by the Guy's and St Thomas' ILD research team. The FIBRINOX study showed that patients with fILD and normal oxygen saturations at rest, but who desaturate whilst asleep or during exercise, have a significantly increased mortality and greater reduction in quality of life compared to patients who do not desaturate at night or during exercise.

The reasons for these differences in mortality and health related quality of life are not known. Data suggests that worsening fILD and the development of pulmonary hypertension, a condition characterised by increased pressure in the pulmonary arteries that is associated with poorer outcomes, may be playing a role.

This clinical research study will recruit approximately 160 patients with a tertiary ILD centre diagnosis of fibrotic interstitial lung disease (fILD). Data from routinely performed investigations as part of tertiary ILD assessment will be systematically recorded.

Investigations will include lung function tests, echocardiography, blood tests, a 6-minute walk test and overnight oximetry. Participants will also complete several quality-of-life questionnaires. These investigations will be performed at baseline, and again at 12 months, with all tests also repeated at 6 months except for an echocardiogram. After the initial 1 year study period, a 3 year post-recruitment mortality and right heart catheter check will be performed using the participants' medical records. Data will be collected from CT scans and right heart catheters if performed during the study period as part of the participants usual clinical care.

This study is designed to establish whether patients with fILD who desaturate during sleep or exercise are more likely to experience functional decline, as well as confirm previous findings of increased mortality and worsening quality of life as demonstrated in the FIBRINOX study. The data generated by this observational study will help generate future hypotheses, research questions and clinical study.

Inclusion Criteria:

1. Patients aged 18 year and over
2. Tertiary MDT diagnosis of FILD with >10% fibrosis on CT chest as determined by the investigator. Underlying diagnoses to include but not limited to: idiopathic pulmonary fibrosis (IPF), non-specific interstitial pneumonitis (NSIP), chronic hypersensitivity pneumonitis (CHP), connective tissue disease-related interstitial lung disease (CTD-ILD), fibrotic organising pneumonia (FOP) and pulmonary sarcoidosis.
3. Able to provide informed written consent

Exclusion Criteria:

1. The use of or any indication for long-term oxygen therapy (LTOT)
2. Known moderate or severe obstructive sleep apnoea with an apnoea/hypopnoea index (AHI) or oxygen desaturation index (ODI) over 15 events per hour
3. Radiological predominance of emphysema compared with fibrosis on CT chest
4. Inability to complete all health status questionnaires as set out in this protocol, with appropriate support
5. A confirmed diagnosis of pulmonary hypertension
6. Significant cardiovascular comorbidity including severe, uncontrolled hypertension, uncontrolled arrhythmia, recent acute coronary syndrome within 30 days prior to study enrolment, that could mean exercise testing poses a risk to patient health, in the opinion of the investigator
7. Musculoskeletal comorbidity that will preclude the participant's ability to reliably complete the complete 6-minute walk test (6MWT)
8. Participation in another research project which may confound this study's research findings

Patients with a tertiary ILD centre diagnosis of fibrotic interstitial lung disease

No individual participant data will be shared or made available to researchers outside of the site research team where the patient is based, and GSTT ILD research team.