A Comparison of the Face Mask and Oral Mask Ventilation After Nasal Surgery.

American Society of Anesthesiologists (ASA) physical class I or II, adult patients aging 19-45 yr, scheduled for nasal surgery will be recruited.

Patient characteristics will be recorded; age, gender ASA physical status, height, weight. Simple randomization will be accomplished with a computer-generated sequence of numbers and sealed envelopes will be used to allocate patients into 2 treatment sequences, Sequence O: oral mask ventilation followed by face mask ventilation and Sequence FM: face mask ventilation followed by oral mask ventilation.

Patients will be premedicated with midazolam. Ringer's lactate infusion at 15 mL•kg-1•h-1 will be initiated. Standard monitors will be established including neuromuscular monitorization and the Bispectral index monitor (BIS).

The patients head will be placed in the neutral position on a positioning pad Anesthesia will be induced with propofol 2 ml kg and fentanyl 50 mcg. Anesthesia will be maintained with oxygen in nitrous oxide and sevoflurane. The patient was ventilated trough an face mask. The appropriate size mask with the best fit will be selected and the mask size will be noted. Gas flow will be 4 L min. During the induction period the mask ventilation grade of the patients will be determined (Grade 0: ventilation by mask not attempted, Grade 1: ventilated by mask, Grade 2: ventilated by mask with oral airway or other adjuvant, Grade 3: difficult mask ventilation (inadequate, unstable, or requiring two practitioners), Grade 4: unable to mask ventilate (Han's grading scale)) and patients with Grade ≥ 2 will be excluded from the study. Muscle relaxation and intubation will be facilitated with rocuronium 0.6 mg kg-1. At the end of surgery trachea will be extubated when TOF 0.9 is obtained and the patient is spontaneous breathing, meanwhile inhalation anesthesia will be continued (BIS 50-70). After extubation, spontaneous ventilation will be assisted with mask ventilation. Mask ventilation will be applied according to sequence allocation and the mask ventilation grades with each mask technique will be determined with the same grading system. Spontaneous ventilation will be assisted with mask ventilation.

The face mask will be applied with the one handed EC-clamp technique. The mask will be placed over the bridge of the nose and mouth and a chin-lift, head tilt maneuver will be used. The oral mask; size 1 or 2 child's mask will be placed only over the mouth and the one handed EC-clamp technique with the chin-lift, head tilt maneuver will be used again. The masks will be changed after three consecutive measurements for each mask technique and the crossover time will be short.