Pulmonary gas exchange disturbance is a common anesthetic problem during one-lung ventilation (OLV) for thoracic surgery. The inverse-ratio ventilation (IRV), which prolongs the inspiratory time greater than expiratory time, can be applied for adult respiratory distress syndrome. The effect of IRV is to improve gas-exchange status by increasing mean airway pressure and alveolar recruitment. We tried to evaluate the effect of IRV during OLV with lung protective strategy.

Pulmonary gas exchange disturbance is a common anesthetic problem during one-lung ventilation (OLV) for thoracic surgery. Continuous positive airway pressure or positive end-expiratory pressure are usually applied to improve this disorder including hypoxia, but these methods are not enough. The inverse-ratio ventilation (IRV), which prolongs the inspiratory time greater than expiratory time, can be applied for adult respiratory distress syndrome. The effect of IRV is to improve gas-exchange status by increasing mean airway pressure and alveolar recruitment. The application of IRV during OLV has not been performed to our knowledge, and there is a possibility of IRV to improve oxygenation during OLV. There is a possibility of increase of auto-PEEP, or air trapping in subjects with chronic obstructive pulmonary disease, but this kind of auto-PEEP can be overcome by external PEEP. Therefore, we tried to evaluate the effect of IRV during OLV with lung protective strategy.

Inclusion Criteria:

• patients undergoing elective lung lobectomy surgery.
• the duration of one-lung ventilation is more than one hour.
• subjects with more than twenty years old.

Exclusion Criteria:

• subjects with past history of pneumothorax, asthma
• Age under 20, more than 70 years.
• Patients with ischemic heart disease, valvular heart disease
• patients with hemodynamic unstability