Defining a diaphragm-focused and patient-acceptable inspiratory muscle training (IMT) load in difficult to wean, mechanically ventilated patients: a protocol for a prospective, mixed methods study

Abstract

Introduction: Diaphragm dysfunction is associated with failure to wean from mechanical ventilation. Inspiratory muscle training (IMT) may help improve outcomes for difficult-to-wean patients, yet the optimal approach remains unknown. High load IMT causes a training effect on the extra-diaphragmatic inspiratory muscles, but does not improve weaning success, questioning the utility of frequently cited high intensity IMT loads. Additionally, patients may find IMT unpleasant and distressing due to dyspnoea experienced during IMT. The aim of this study is to define a diaphragm-focused IMT load which is acceptable to patients.

Methods: This study is designed as a prospective, mixed methods study. Forty difficult to wean, tracheostomised patients on mechanical ventilation will perform IMT at 15, 30, 45 and 60% of their maximal inspiratory pressure (PImax) in a randomised order using a tapered flow resistive loading device (POWERBreathe KH2, POWERBreathe, UK). Electrical activity of the diaphragm will be measured using an oesophageal multipair catheter (NAVA, Getinge, Sweden); extra-diaphragmatic (parasternal, scalene and sternocleidomastoid) muscle activity will be measured using surface electromyography. Patient experience of each load will be explored by measuring perceived breathing difficulty and unpleasantness using 0–10 numeric rating scales, verbal or written communication techniques in line with the participants' communication ability, and/or bespoke communication boards co-designed with the study patient and public involvement (PPI) group. Quantitative and qualitative data will be integrated to inform a diaphragm-focused, patient-acceptable IMT load.

Ethics and dissemination: Ethical approval was obtained from Wales Research Ethics Committee 4 (Reference 25/WA/0242) on 30 October 2025. Results from this study will be presented at scientific meetings and published in peer-reviewed journals.

Trial registration number: NCT07256821.