Mechanical ventilation is a life-saving treatment frequently applied in intensive care unit (ICU). Nonetheless, by putting at rest the respiratory muscles, it can lead to respiratory muscle weakness and atrophy, which are accompanied by prolonged duration of mechanical ventilation, difficult weaning and increased ICU mortality. Despite a strong theoretical rationale and some evidence supporting the use of inspiratory muscle training (IMT) to address respiratory muscle weakness and atrophy, the optimal approach to IMT remains largely uncertain. In fact, mechanistic studies evaluating physiological adaptations that occur in respiratory muscles of mechanically ventilated patients in response to different training regimens have not been conducted so far.
The aim of this study is to comprehensively investigate changes in respiratory muscle function in response to three different conditions that patients will be exposed to during their period of weaning from mechanical ventilation.
Difficult and prolonged weaning patients
Adequate oxygenation
Febrile temperature < 38ºC
Hemodynamic stability
Pre-existing neuromuscular disease
Agitation
Hemodynamically instable (arrhythmia, decompensated heart failure, coronary insufficiency)
Hemoptysis
Parallel
Procedure: Usual Care (UC)
Other interventionIntermittent spontaneous breathing periods
Procedure: UC + HI-IMT
Other interventionUC + Supervised daily sessions of training including 4 sets of 6-10 full vital capacity breaths against an external load using a tapered flow resistive device (POWERbreathe KH2, HaB International, UK). The maximum tolerable resistance allowing patients to inhale at least 70% of their inspiratory vital capacity will be chosen and progressively increased throughout the training period.
Procedure: UC + LI-IMT (sham IMT)
Other interventionUC + superrvised daily sessions of training including 4 sets of 6-10 breaths at the lowest external imposable load with the tapered flow resistive device (POWERbreathe KH2, HaB International, UK) (i.e. 3 cmH2O).
Maximal Inspiratory Pressure (PImax)
Using a unidirectional valve which will be connected to the patient's tracheostomy tube or endotracheal tube for an uninterrupted period of 25 seconds.
Diaphragm mobility, thickness and thickening fraction by ultrasounds
Assessment by diaphragm ultrasounds
Change in contractile material and structural alteration of sternocleidomastoid muscle
By analyzing muscle microbiopsies using Hematoxylin \& Eosin (H\&E) staining.
Change in fiber proportion of sternocleidomastoid muscle fibers
By analyzing muscle microbiopsies with immunostaining of the myosin heavy chain.
Change in size of sternocleidomastoid muscle fibers
By analyzing muscle microbiopsies with immunostaining of the myosin heavy chain.
