Inclusion Criteria:  Persons aged > 18 years Applicable for Group 2: planned for elective surgery No relevant pre-existing conditions - corresponding to American Society of Anesthesiologists (ASA) level of I-II. Written informed consent by the patient for participation in the study given  Exclusion Criteria:  chronic lung diseases (bronchial asthma, COPD) known diaphragmatic weakness known neurological conditions with motor muscle weakness known paralysis of the phrenic nerve conditions that limit the mobility of the diaphragm (high intra-abdominal pressure, ascites, BMI >30) not able to read and understand the national language German skin lesions, infections or strictures in the neck area persons with Implanted cardiac support systems (pacemaker, implanted defibrillator) persons with implanted medical pumps pregnant women persons deprived of liberty by administrative or judicial decision or under legal guardianship. Participation in another clinical trial  Applicable for group 2 (intubated and mechanically ventilated) patients: Exclusion criteria at the time of stimulation:  Unstable patient after induction of anesthesia and intubation