Individualized vs Low PEEP in One Lung Ventilation

During surgery on the lung, ventilation of one lung at a time is often necessary. During
thoracic surgery requiring one-lung ventilation (OLV), hypoxemia (reduced oxygen tension in
blood) can present a clinical challenge. Due to multiple factors, the likelihood of hypoxemia
during OLV in obese patients is increased. Atelectasis (collapse of the lung airspaces)
contributes to hypoxemia and can be mitigated by application of recruitment maneuvers and
positive end-expiratory pressure (PEEP). A recruitment maneuver is a breath given in a
mechanically ventilated patient that helps to open up collapsed air spaces, and PEEP is
application of a continuous amount of positive pressure that helps keep the air spaces open
at the end of an exhaled breath. Adjusting the level of PEEP to each individual patient's
optimal lung compliance (individualized PEEP) improves blood oxygen levels compared to
application of standard low PEEP (5 cmH2O); however, higher levels of PEEP required to
achieve optimal lung compliance could increase intrathoracic pressures to a level that
impedes normal circulation. This could negatively affect blood flow (cardiac output) and
delivery of oxgyen to vital organs.

Evidence addressing OLV in obese patients is lacking. The purpose of this study is to compare
brain oxygen levels (cerebral oxygen saturation) and measures of blood flow and gas exchange
during OLV with individualized PEEP vs low standard PEEP in obese patients undergoing
thoracic surgery. To our knowledge, there is no previous study that compares oxygen delivery
to vital organs (such as the brain) during OLV using individualized PEEP versus standard low
PEEP, in an obese patient population.

In this study, subjects undergoing OLV during surgery to remove a portion of the lung
(lobectomy) will undergo a process to determine their individualized PEEP and then two
20-minute experimental periods-- one period with OLV with low PEEP and one period with OLV
with individualized PEEP. Measurements of cerebral oxygen saturation, blood oxygen levels,
cardiac output, and blood pressure medication dose will be measuring before and after these
experimental periods during surgery.

Inclusion Criteria:

1. Subject undergoing elective pulmonary lobectomy requiring one-lung ventilation

2. Body-mass index ≥ 30 kg/m2

3. Age ≥ 18 years and ≤ 80 years

Exclusion Criteria:

1. Age ≤ 18 year or ≥ 80 years

2. Moderate or severe cardiac valvular disease

3. Left ventricular ejection fraction < 30%

4. Moderate or severe right ventricular systolic dysfunction

5. Severe pulmonary hypertension

6. Presence of pulmonary bullae or blebs on preoperative chest imaging studies (e.g.,
radiograph, computed tomograph)

7. Emergency surgery

8. Previous history of lung surgery on the non-operative lung

9. Pregnancy

10. Incarceration

11. Mental incapacitation

12. Patient refusal

13. Non-English speaking