Prospective Clinical Study of PCV and PCV-VG in Patients Undergoing Bariatric Surgery

With the development of economy and changing of life style, obesity is becoming a common phenomenon. More and more obese patients are undergoing bariatric surgery every year.

Obesity results in a series of physiological changes particularly the respiratory system. The decrease of lung compliance and the limited total lung capacity, vital capacity, functional residual capacity are all contributed to intraoperative hypoxemia and postoperative lung complications. Presently study mainly discuss lung protective ventilation strategies from four aspects: tidal volume,ventilation modes,positive end-expiratory pressures and lung recruitment maneuvers.

This prospective study will compare two ventilation modes in obese patients undergoing bariatric surgery:pressure-controlled ventilation(PCV) and pressure-controlled ventilation volume-guaranteed（PCV-VG).

The total of 100 patients will be divided into two groups randomly. The patients will be ventilated with PCV or PCV-VG modes plus positive end expiratory pressure (PEEP) of 5cmH2O throughout the whole operation.

The respiratory and hemodynamic parameters in six time points will be recorded, and the postoperative chest computerized tomography (CT) will be checked to identify the postoperative lung complications.

• PCV-VG, PEEP5cmH₂O (Device): This is an innovative ventilation mode developed in recent years. The preset tidal volume help the machine modify inspiratory pressures and compensate the decrease of lung compliance.
• PCV, PEEP5cmH₂O (Device): This is a traditional ventilation mode used in obese patients in the past.

Primary outcomes

• Dynamic lung compliance measure [three hours]: Dynamic lung compliance can be calculated based on tidal volume,peak inspiratory pressure and PEEP. 10minutes after induction,10minutes after pneumoperitoneum,60minutes after pneumoperitoneum and 10minutes after pneumoperitoneum release will be recorded.

Secondary outcomes

• Postoperative lung complications [five days]: Lung complications mainly contains pneumonia,atelectasis,pleural fluid. The investigator compare the preoperative chest CT with the postoperative chest CT and follow-up participants until participants leave hospital.
• the risk factors of postoperative lung complications [five days]: risk factors may include age, gender, BMI, ventilation duration, etc

Sex: All, ages: 18 Years to 65 Years

Inclusion Criteria:

* BMI≥30kg/m²
* ASA classification II-III
* Bariatric surgery

Exclusion Criteria:

* Patients combined restrictive or obstructive lung diseases,pneumonia, bullae of lung ; patients after pneumonectomy
* Patients combined with other severe internal medicine diseases
* duration of pregnancy or suckling

• Results publication: Dion JM, McKee C, Tobias JD, Sohner P, Herz D, Teich S, Rice J, Barry ND, Michalsky M. Ventilation during laparoscopic-assisted bariatric surgery: volume-controlled, pressure-controlled or volume-guaranteed pressure-regulated modes. Int J Clin Exp Med. 2014 Aug 15;7(8):2242-7. eCollection 2014. PMID 25232415
• Results publication: Aldenkortt M, Lysakowski C, Elia N, Brochard L, Tramer MR. Ventilation strategies in obese patients undergoing surgery: a quantitative systematic review and meta-analysis. Br J Anaesth. 2012 Oct;109(4):493-502. doi: 10.1093/bja/aes338. PMID 22976857

• Weimin Liang, doctor, Study director, Huashan Hospital