Respiratory muscle training and neurostimulation in critical illness: evidence and future directions

PURPOSE OF REVIEW: In recent years, respiratory muscle training and neurostimulation have emerged as strategies to prevent or reverse respiratory muscle weakness. This review evaluates the latest evidence for respiratory muscle training and neurostimulation as targeted interventions. RECENT FINDINGS: Inspiratory muscle training (IMT) improves physiological parameters including maximal inspiratory and expiratory pressures, peak expiratory flow, and diaphragm thickness, though clinical trials have not consistently shown benefits in weaning success, ventilator duration, or survival. Evidence for expiratory muscle training (EMT) in ICU patients is scarce, but combined IMT and EMT may improve outcomes. Neurostimulation of the diaphragm and expiratory muscles has advanced from feasibility to early clinical trials. Diaphragm neurostimulation has been demonstrated to improve diaphragm strength and weaning success. Preliminary experimental evidence suggests that diaphragm neurostimulation may also influence lung mechanics, haemodynamics, and brain function. SUMMARY: Respiratory muscle training and neurostimulation may attenuate critical illness-associated respiratory muscle weakness. While IMT improves physiological parameters, consistent clinical benefits have not yet been demonstrated. Neurostimulation represents a promising intervention, but further research is required to establish its impact on clinically relevant outcomes and to exclude potential harms when applied in the early phase of critical illness.