There is increasing interest in how thoracic (chest) ultrasound might enhance the management of patients with respiratory failure and breathlessness, particularly in the emergency admissions or intensive care setting. Thoracic ultrasound is already used in a number of clinical settings. It is recognised that a number of lung abnormalities can be identified using thoracic ultrasound, such as consolidation (in pneumonia) or peripheral soft tissue lesions (in lung cancer). Furthermore, thoracic ultrasound offers clinicians a non-invasive diagnostic tool that provides immediate feedback and results.

Patients with breathlessness and respiratory failure represent a significant proportion of emergency admissions to hospital and commonly require urgent treatment with limited information available to guide the clinician. The range of diseases that present with breathing difficulties is broad (e.g. pneumonia, heart failure, pulmonary embolus) and difficult to differentiate in patients who often have multiple medical problems. This leads to non-specific treatment in the face of diagnostic uncertainty with the associated risks of treatment complications, increased morbidity and mortality, and distress for patients and relatives. It is in the assessment of these patients with acute respiratory failure where thoracic ultrasound might be of greatest benefit and which this research is designed to address.

This is a single centre study (Churchill Hospital, Oxford) recruiting 125 participants over an eight month period. The study will test the reliability of a thoracic ultrasound protocol at identifying lung abnormalities in a stable outpatient population with respiratory disease (chronic obstructive pulmonary disease; interstitial lung disease; patients on haemodialysis to replicate acute pulmonary oedema / heart failure). It is hoped the results of this study will inform further research in acutely unwell patients with respiratory failure and breathlessness to see whether thoracic ultrasound can improve diagnostic and therapeutic decisions.

This is a prospective cohort study and forms part of educational research intended to ultimately contribute towards a higher degree (MD or DPhil). The study is being co-ordinated through the Oxford Respiratory Trials Unit, Churchill Hospital, Oxford and has been developed by the study co-ordinator (Dr Corcoran) and Chief Investigator (Dr Rahman) with support from Professor Gleeson.

This study will assess the efficacy of TUS in identifying extravascular lung water (EVLW) through the presence or absence of B-lines (also known as "comet tails") on ultrasound; whilst also determining whether TUS can distinguish between other pulmonary pathologies that may cause both a similar ultrasonographic appearance and respiratory compromise. A TUS protocol will be tested and validated in a stable patient population, concurrently assessing patient and operator satisfaction with the tool. It is intended that the results of this study will inform a larger second-phase study of a modified TUS protocol in the acute clinical setting (medical admissions unit +/- emergency department).

Potential participants in this study will be screened from normal clinical care in the relevant departments at the Churchill Hospital, Oxford - i.e. specialist COPD and ILD clinics in the respiratory department; outpatient haemodialysis units in the renal department. Healthy volunteers will also be sought using advertisements placed on noticeboards in the Oxford University Hospitals NHS Trust and selected Oxford University departments.

All participants enrolled in the study will undergo CT and thoracic ultrasound scanning as per the study protocol. These are low-risk interventions with no harm expected as a direct consequence of participation in the study.

Participants will also undergo baseline spirometry (if not done in the last month) and blood tests for the purposes of the study; these are also considered low-risk interventions with no harm expected as a direct consequence of participation in the study.

The study involves only a single visit and therefore it should impose a minimal burden on participants, and for the majority of participants their study visit will be arranged to coincide with a pre-arranged trip to the hospital for normal clinical care (e.g. a regular haemodialysis or outpatient clinic visit).

Inclusion Criteria:

• Haemodialysis (n=50) - patients with end-stage renal failure (ESRF) requiring long-term regular haemodialysis.
• Chronic Obstructive Pulmonary Disease (COPD) (n=25) - patients with a confirmed diagnosis of COPD based on clinical history, obstructive spirometry (FEV1/VC ratio <70%) and radiology (e.g. hyperexpansion on plain chest radiograph; evidence of small airways disease or emphysema on cross-sectional imaging).
• Interstitial Lung Disease (ILD) (n=25) - patients with a confirmed diagnosis of ILD based on clinical history and radiology (evidence of ILD on cross-sectional imaging).
• Control (n=25) - age-matched healthy volunteers with no history of cardiac, respiratory or renal disease.

Exclusion Criteria:

• Age < 18 years
• Inability to provide informed consent to participate in the study
• Pregnant or breastfeeding
• Known diagnosis of heart failure or chronic renal failure in participants recruited to the COPD or ILD arms of the study.
• Known diagnosis of COPD or ILD in participants recruited to the haemodialysis arm of the study.
• Known history of cardiac, respiratory or renal disease in participants recruited to the control arm of the study.

Participants will be screened from normal clinical care in the outpatient haemodialysis unit and specialist respiratory clinics (COPD and ILD) at the Churchill Hospital, Oxford. Age-matched volunteers will also be sought for the control arm of the study.