Patients under protective mechanical ventilation, an intervention that saves lives, may need sedation and paralyzing agents. However, sedation and paralyzing agents are associated with multiple complications, including diaphragm dysfunction.~Several strategies have been proposed to reduce diaphram dysfunction. A novel approach is to stimulate the phrenic nerve, either transvenously or transcutaneously. Transvenous stimulation requires a catheter, which eventually is associated with increased risk of infection and thrombosis. In this scenario, transcutaneous phrenic nerve pacing is attractive but may be more susceptible to patients' anthropometric measures.~The correlation between patients' anthropometric measures and the location of the phrenic has been poorly studied.
This will be a prospective observational study where the investigator will scan patients' necks with an ultrasound and look for anatomical landmarks that may help identify the phrenic nerve.