A continuous loss of moisture and heat occurs during mechanical ventilation and prediposes patients to airway damage. Vaporizing humidifier has known to be advantages of improvement of oxygenation and protection of airway damage. However, there is a lack of study about the effect of humidified ventilation on oxygenation and respiratory mechanics during one-lung ventilation. We therefore invesgate that the effect of humidified ventilation on oxygenation and respiratory mechanics during one-lung ventilation .

Inclusion Criteria:

• ASA physical status class I,II
• Unilateral lung lobectomy
• Use of one-lung ventilation

Exclusion Criteria:

• COPD
• CAOD
• Unstable cardiovascular status
• Peak inspiratory pressure > 30 mmHg