Rationale: Delivery dry gas during anesthesia is associated with post-operative sore throat (POST). Oxygen nebulizer therapy increases humidity to the airway, especially post-extubation.

Objective: To investigate the effect and complications of oxygen nebulizer therapy on POST.

Inclusion Criteria:

• Age 18-75 years
• Pre-operative Hb >10 g% or Hct > 30%
• American Society of Anesthesiologist (ASA) class I-III
• Elective surgery
• General anesthesia with oroendotracheal tube using Macintosh laryngoscope
• Not exposed to intraoperative nitrous oxide
• Oxygen saturation at room air > 95% before induction and at arrival the PACU

Exclusion Criteria:

• Cases needing ICU admission immediately post-operative
• Conditioning requiring post-operative oxygen therapy e.g. heart disease, pregnancy, morbid obesity, cardiac and thoracic surgery
• Patients' conditioning affecting to complication of nebulizer oxygen therapy e.g. pulmonary disease, bleomycin treatment
• Patient's conditioning affecting POST assessment e.g. pre-operative using ventilator, recent upper respiratory tract infection (URI), recent lower respiratory tract infection and history of difficult airway
• Surgical conditioning affecting POST e.g. airway surgery, oral surgery, esophageal and neck surgery