An auxiliary surface EMG will be recorded via ordinary skin electrodes at the diaphragm, and intercostal and rectus abdominis muscles. The degree of neuromuscular blockade is continuously measured by accelerometry of the adductor pollicis muscle with ulnar nerve stimulation (TOF-watch SX®). Anesthesia is induced with propofol and remifentanil. Manually assisted ventilation with an air/oxygen mixture of 40% oxygen is started as soon as patients are becoming apnoeic. Train-of-four (TOF) monitoring starts after the induction of anesthesia (before rocuronium administration) and continues until awakening. The investigators will insert a 16 Fr. nasogastric catheter which allows electrical activity of the diaphragm (Edi) registration (NAVA, Maquet, Solna, Sweden). After baseline measurements, 0.6 mg/kg rocuronium is injected. After tracheal intubation, subjects will be ventilated by a standard ventilation mode (tidal volume 7 ml/kg, frequency of 12 breaths per minute, inspired oxygen fraction of 30%), with end-tidal PCO2 targets of 30-35 mmHg and a PEEP of 5 cmH2O. SpO2 values will be maintained at ≥98%. Spontaneous recovery is allowed to progress until the re-appearance of the second twitch of the TOF. The volunteers will then receive either sugammadex 2mg/kg or neostigmine 50µg/kg + glycopyrrolate 10µg/kg (using the commercially available 5:1 co-formulation) or neostigmine 50µg/kg followed 3 minutes later by administration of sugammadex 2mg/kg. At the onset of spontaneous respiration, an arterial blood gas sample will be drawn. NAVA catheter positioning will be confirmed using the 'Edi catheter positioning' tool as soon as a signal is received. A second arterial blood gas sample will be drawn at the moment of awakening.