Acute exacerbations of COPD contribute to significant morbidity and mortality in the United Kingdom (UK). The ability to assess response to treatment during exacerbations that require hospitalisation would allow clinicians to better risk stratify patients for higher or lower level in-patient or out-patient care. Current methods of detecting clinical deterioration are validated in general medical populations and may lack sensitivity and specificity in patients with respiratory morbidity. The use of respiratory muscle EMG to assess neural respiratory drive (NRD) has been demonstrated to be a predictor of readmission in patients admitted to hospital with COPD. The technique has been applied on 'spot' readings of limited duration due to the need for hand analysis of the data. It has been performed by a trained clinical physiologist who removed any interference data and standardised the data gathered. New automated software allows for longer periods of observation, mostly unsupervised, and as a result, the NRD measurements are more likely to be affected by various sources of variability. The influence of clinical and physiological factors as they occur during routine clinical management, such as administration of bronchodilator medication, time of day of readings or proximity to chest physiotherapy, are not yet understood. This trial is designed to gather data to better understand these relationships with NRD.

Introduction Patients admitted to hospital with acute exacerbations of COPD are at risk of significant in-hospital morbidity and mortality. Current markers of treatment success involve the integration of basic physiological variables (respiratory rate, heart rate, oxygen saturations), clinical examination and patient reported symptoms changes. Whilst the use of these physiological parameters are gold standard there remains concern that patient deterioration is often not detected and escalated effectively. This has led to the development and implementation of a range of clinical physiological composite scores such as the medical early warning score or the National Health Service (NHS) early warning scores. However, these scores have been validated in general rather than specific populations and there are concerns regarding their use in respiratory patient groups.The use of the parasternal intercostal muscle EMG (EMGpara) has been reported to track clinical change and identify treatment failure during hospital admissions with acute exacerbations of COPD (AECOPD) in selected and unselected cohorts. In these pilot works measurements were taken on research equipment and data analysed individually by a trained physiologist. The clinical physiologist ensured standardisation of recording conditions such as proximity to medication, patient position, time of day and recent activity. The effect of such clinical and physiological factors on EMGpara was minimised by the operator with preventive measures, such as the control for the measurement time, the limitation of the recording duration and the exclusion of any artefactual changes in EMGpara. The development of automated software allows for frequent sampling and continuous monitoring, which will potentially permit earlier detection of clinical deterioration. With an automated system however, clinical and physiological factors need to be carefully considered, in particular when the measurement is performed in an unsupervised or less closely supervised environment. This feasibility study is therefore designed to investigate repeatability of EMGpara in hospital-based AECOPD management (i.e. EMGpara changes reflect changes in clinical status). It will give us insight into potential control/mitigation measures and their implementation, in order to ultimately minimise false readings.

Study objectives To investigate the clinical and physiological factors that may affect the measurement of EMGpara in acute setting so as to enhance the clinical effectiveness of EMGpara in identifying treatment failure and clinical deterioration.

Inclusion Criteria:

• COPD (as defined by GOLD criteria
• Acute exacerbation of COPD necessitating hospital admission
• Expected to remain an inpatient for ≥ 24 hours
• Able to give informed consent to participation in the study

Exclusion Criteria:

• Decompensated respiratory failure (pH < 7.35)
• Significant physical, social or psychiatric factors that would prevent compliance with trial protocol
• Aged < 35 years or aged > 85 years
• Pregnancy
• BMI > 30kg/m2
• Presence of another acute pathology (such as pulmonary embolism or pulmonary oedema) to explain the acute presentation

Patients admitted to St Thomas' Hospital with a primary diagnosis of an acute exacerbation of COPD.