Comparison of the impact of three inspiratory muscle training programs on diaphragm strength and endurance in intubated and mechanically ventilated patients with difficult weaning : a multicentric randomized controlled trial

Background: Inspiratory muscle training (IMT) consists of a resistive inspiratory maneuver through a pressure device comprising a unidirectional valve that hinders inspiration. IMT was found to significantly increase inspiratory muscle strength in adults undergoing invasive Mechanical ventilation (MV). Despite, it exists an important heterogeneity of IMT protocols, and it is unclear if it reduces MV duration. Furthermore, inspiratory muscles endurance is scantly evaluated while the assessment of this function may be fundamental for a successful weaning. In this multicentric controlled randomized parallel trial, we compared the effects of three different IMT protocols (low, high and mixed intensity ) on inspiratory muscle strength and endurance in difficult to wean patients in two intensive care units (ICU). Methods: : 92 subjects presenting difficult weaning were randomized in 3 groups to perform one IMT protocol twice daily. The primary outcome was the Maximal Inspiratory Pressure (MIP) increase in each group after successful extubation or 30-days. Secondary outcomes were Pressure peak increase (Ppk), as endurance marker, weaning duration, and safety. Results: : During the weaning process, the observed increase of MIP was 12.2 ±11.2 cmH 2 O in the mixed intensity group (EDRIC), 5.3 ±15.5 cmH 2 O in the low intensity group (CADER), and 6.8 ±15.1 cmH 2 O in the high intensity group (MARTIN). There was a non-statistically significant difference between EDRIC group and CADER group (mean adjusted difference: -6.65, 97.5%CI [-14.35; 1.04], p=0.052), neither between EDRIC group nor MARTIN group (mean adjusted difference: -3.67, 97.5%CI [-11.52; 4.18], p=0.289). No significant difference in Ppk increase were observed between the three groups. Over 358 IMT sessions, only 3 serious adverse events (spontaneously reversible bradycardia) were considered possibly related to the study. Conclusion: Independently of IMT protocol applied, MIP and Ppk seemed to improve in our cohort of difficult to wean patients. Ppk could be a helpful tool to assess diaphragm function exhaustively. EDRIC group showed a slightly higher efficacity.