Development, feasibility and acceptability of a diaphragm focussed Inspiratory Muscle Training (IMT) intervention in difficult to wean, mechanically ventilated patients.

Background Diaphragm weakness is present in 63-80% of patients mechanically ventilated for over 48 hours and is associated with increased length of intensive care and hospital stay, greater cognitive and functional impairments and increased mortality risk. The diaphragm is responsible for 80% of work in normal breathing, therefore specific diaphragm strengthening may help patients wean from mechanical ventilation. 63% of intensive care physiotherapists worldwide use Inspiratory Muscle Training (IMT), which aims to improve diaphragm strength through the application of resistance during inspiration, using a device connected directly to the patient's tracheostomy. However, there are a number of issues with current IMT approaches in intensive care. There is no consensus on how to specifically train the diaphragm. High-intensity IMT will substantially recruit extra-diaphragmatic inspiratory muscles and type IIb (power) diaphragm muscle fibres; neither are useful for ventilator weaning. Current approaches to IMT in mechanically ventilated patients do not improve clinical outcomes, and can be unpleasant and distressing for patients. Research question Can a Diaphragm-focussed and patient-acceptable Inspiratory Muscle Training load (D-IMT) be identified and tested in difficult-to-wean, mechanically ventilated patients? Aims 1. Develop a diaphragm-focussed and patient-acceptable IMT load (D-IMT). 2. Test the feasibility of conducting a randomised controlled trial comparing the D-IMT load with usual care. Objectives Study 1 1. Measure diaphragmatic and extra-diaphragmatic inspiratory muscle activity during four IMT loads. 2. Explore the acceptability of these different IMT loads using qualitative methods in line with participants' communication ability. 3. Integrate quantitative and qualitative data to determine a diaphragm-focussed and patient acceptable IMT load (D-IMT) Study 2 Conduct a feasibility randomised controlled trial (RCT) to ascertain if it is possible to conduct a definitive RCT to test the clinical- and cost-effectiveness of D-IMT compared to usual care. Methods and timelines Study 1 (months 1-17). An observational, mixed methods study. Forty difficult-to-wean, mechanically ventilated participants will perform ten breaths of IMT at 15, 25, 35 and 45% of their maximal inspiratory strength on up to three occasions. During IMT, diaphragm activity will be measured using an oesophageal electromyography (EMG) catheter. Extra-diaphragmatic inspiratory muscle activity will be measured using surface EMG. Participant experience of each load will be explored qualitatively. These data will be integrated to inform a diaphragm-focussed, patient-acceptable IMT load (D-IMT). Study 2 (months 18-36). Feasibility RCT. Fifty difficult-to-wean, mechanically ventilated participants will be randomised to usual care or D-IMT and usual care. The D-IMT group will perform the IMT load defined in study 1 five days per week until they no longer require mechanical ventilation. Feasibility outcomes: eligible patients, recruitment rates, completeness of outcome measures, IMT fidelity, patient adherence to IMT, participant retention, adverse events. Semi-structured interviews will be conducted on physiotherapists who administered D-IMT to explore acceptability of the intervention. Anticipated impact and dissemination Findings will be disseminated via peer-reviewed publications, conference presentations and patient and public events in collaboration with the project's PPI group. Results of study 2 will inform a definitive RCT with the potential to improve clinical and patient-related outcomes and reduce NHS costs.