individualized vs low peep in one lung ventilation

Conditions: One-Lung Ventilation; Obesity; Lung Diseases

Summary: the aim of the prospective crossover study is to investigate the effect of individualized positive end-expiratory pressure (peep) on measures of tissue oxygenation, compared with low peep.

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.

Eligibility criteria:
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