In order to standardize the anesthetic technique, no premedication will be administered to any patient candidate to undergo to microlaryngoscopy procedure. Besides each individual enrolled will receive neuromuscular monitoring with ulnar nerve stimulation with TOF Watch® (Organon, Oss, Netherlands). The device will be calibrated pre-operatively and parameters set using standard train of four (TOF) methodology after administration of hypnotic drug prior to muscle relaxation. Standard induction of general anesthesia will be performed using intravenous (iv) fentanyl (2 mcg kg-1), propofol (2 mg kg-1), and rocuronium (0.6 mg kg-1). Tracheal intubation will be performed when the patient fails to register signals with TOF. Rocuronium (0.15 mg kg-1) will be re-administered when PTC elicits more than 5 twitches in order to maintain a dNMB. Sevoflurane will be administered at1.0 MAC in an air/oxygen mixture. Fentanyl will be titrated with a bolus of 0.5 mcg kg-1 every 30 minutes to maintain analgesia. Prior to induction of anesthesia, ultrasonography diaphragm evaluation will be performed using an ESAOTE ultrasound machine (ESAOTE MyLab, Genova, Italy) by assessing the TF and amplitude of excursion. With the spontaneously breathing patient in semi-recumbent position, the amplitude of excursion will be evaluated following the method of Kim et al (7) using a 3.5-MHz ultrasound probe placed over the intercostal space above the 10th rib in the right mid-axillary line for the right diaphragm and the left mid-axillary line for the left diaphragm. The liver or spleen will be used as a window for each hemi-diaphragm. A two-dimensional mode will be used to find the best approach and to select the exploration line of each hemi-diaphragm. With the probe fixed on the chest wall during respiration, the ultrasound beam will be directed to the hemi-diaphragmatic domes at an angle of not less than 70°. During inspiration, the normal diaphragm contracts and moves caudally toward the transducer; this will be recorded as an upward motion of the M-mode tracing. The amplitude of excursion will be measured on the vertical axis of the tracing from the baseline to the point of maximum height of inspiration on the graph. Three measurements will be performed for each patient and averaged for each side at each time point of the protocol (7). Moreover, TF will be assessed following the method of Vivier et al (6) with a linear high frequency probe set at 12 Mhz. The diaphragm will be located with same method described above and the zone of apposition will assessed at 0.5-2 cm below the costophrenic sinus. The inferior border of the costophrenic sinus will be identified at end-inspiration as the zone of transition from the artifact representation of normal lung (the lung sliding) to the visualization of diaphragm and liver.