A single institutional cross-over study design to compare between high flow humidified oxygen (HFHO) device versus conventional CPAP for non-ventilated lung during thoracic surgery.

The investigators hypothesize that HFHO may be an alternative tool to supply oxygen to non-ventilated lung during one lung ventilation. CPAP can improve oxygenation at a cost of lung hyperinflation which is an unwanted condition during thoracic surgery especially the video-assisted one.

Recruiting adult patients who undergo lung surgeries that requires one-lung ventilation. Exclusion criteria include the followings:-

1. Emergency case.
2. Patients with severe COPD(Chronic Obstructive Pulmonary Diseases).
3. Patients with moderate baseline hypoxemia (SpO2 < 90% on room air).
4. Patients with severe hemoptysis.
5. Patients with upper or lower airway abnormalities.
6. Patients undergo pulmonary lavage.
7. Patients with known pulmonary hypertension.
8. Patients with known pulmonary/tracheobronchial infections.
9. Patients with suspected difficult airway.
10. Patients with BMI over 35.
11. Pregnant patients.

Following a standard anesthetic practice. All participants will receive an intravenous based anesthetic with or without regional blocks. The appropriate sized double lumen endobronchial tube will be placed and fiberoptic bronchoscope is used to verify a proper position. Patient will also get an arterial line for frequent ABG (Arterial Blood Gases) samplings.

Computer generated randomization will divide patients into 2 groups. Baseline ABG will be drawn. After one lung ventilation commenced for 20 minutes, the 2nd ABG will be drawn, the surgeon who was blinded to the intervention will evaluate the quality of lung collapse using 5-point Likert scale. Then, patients will either receive a CPAP or HFHO (depends on randomization) for 20 minutes. Up on 1st intervention completion, the 3rd ABG and lung collapse evaluation will be performed.

Following the first intervention, the non-ventilated lung will be suctioned out and wait for 20 minutes. Another ABG will be sampled at this point.

The patient will receive the 2nd alternative intervention (CPAP or HFHO- depend on their randomization) for 20 minutes. The final ABG and lung collapse evaluation will be performed.

If any severe hypoxemia/ hypercarbia and marked violation of protocol occurs. Patients will be excluded.

Inclusion Criteria:

• All adult > 18 years of age undergoes lung surgeries that required one-lung ventilation

Exclusion Criteria:

• emergency case
• severe COPD
• moderate baseline hypoxemia
• pulmonary hypertension
• difficult upper/lower airway
• BMI > 35
• severe pneumonia
• bronchial lavage
• massive hemoptysis

Not yet decided