Muscle Recruitment During Neck Flexion and Inspiratory Muscle Training

The investigators will conduct a prospective longitudinal pilot study in patients receiving mechanical ventilation via endotracheal tube or tracheostomy. The investigators will perform a set of baseline measurements (as early as possible after the patient reaches the ability to spontaneously trigger the ventilator).These measurements include: I) ultrasound measurements (thickness and thickening fraction) of the diaphragm, parasternal intercostals, sternocleidomastoid and of the abdominal muscles; II) surface electromyography (sEMG) of the diaphragm, sternocleidomastoid, scalene, and of the abdominal muscles. Ultrasound and sEMG measurements will be performed during the current level of ventilation (decided by the clinical team), during minimal level of ventilatory support and/or during unassisted breathing; III) maximal inspiratory pressure (MIP); IV) maximal voluntary contraction (MVC) of neck flexion. As soon as patients can be disconnected from the ventilator I) IMT maneuvers and II) neck flexion maneuvers, will be started and performed once a week (each time in a randomized order), until patients are successfully weaned or for a maximum of 4 weeks. The investigators will also perform: III) ultrasound measurements; IV) surface electromyography of the muscles above specified during each IMT and neck flexion maneuver; V) MIP and MVC; these latter measurements will be repeated weekly and inspiratory muscle training and neck flexion intensity level targeted accordingly.