Bi-PAP vs Sham Bi-PAP on Pulmonary Function in Morbidly Obese Patients After Bariatric Surgery

The Effect of Bi-PAP at Individualized Pressures on the Postoperative Pulmonary Recovery of Morbidly Obese Patients (MOP) Undergoing Open Bariatric Surgery (OBS) and Possible Placebo Device-related Effects (Sham-Bi-PAP)

The effect of biphasic positive airway pressure (Bi-PAP) at individualized pressures on the postoperative pulmonary recovery of morbidly obese patients (MOP) undergoing open bariatric surgery (OBS) and possible placebo device-related effects (sham-Bi-PAP) were investigated.

In the present study the effect of Bi-PAP on the postoperative respiratory function and related complications of MOP undergoing OBS through a randomized sham-controlled design was investigated. Bi-PAP was applied at individualized pressures in order to optimize respiratory support and sham Bi-PAP was also used in order to neutralize possible placebo device related effect and researcher related bias. The investigators hypothesized that the use of Bi-PAP at individualized pressures in MOP undergoing OBS, ameliorates postoperative respiratory function as well as diminishes related pulmonary complications, postoperative pain and duration of hospitalization. Primary endpoints were the difference in pre- and postoperative measurements of certain pulmonary function parameters (forced expiratory volume at one second (FEV1), forced vital capacity (FVC), peak expiratory flow rate (PEFR) and oxygen saturation by pulse oximetry (SpO2) and the incidence of certain pulmonary complications postoperatively (hypoxemia, atelectasis, lower respiratory tract infections). Secondary endpoints were postoperative pain and days of hospitalization.

Atelectasis, Pulmonary Infection, Chronic Obstructive Pulmonary Disease (COPD), Pulmonary Disease, Hypoxemic Respiratory Failure, Hypoxemia, Morbid Obesity

Bi-PAP, BiPAP, morbid obesity, anesthesia, bariatric surgery, sham Bi-PAP, sham BiPAP, postoperative complications

Patients were assigned into the following two study groups postoperatively: Sham Bi-PAP (control group) group in which sham Bi-PAP was applied through nasal mask for 3 days postoperatively. Bi-PAP group in which Bi-PAP through nasal mask, at individualized IPAP/EPAP pressures, was applied for 3 days postoperatively. 1 patient was initially enrolled in the protocol but was excluded from the participant flow design because of recent onset of cardiovascular disease (CAD).

Sham Bi-PAP was applied through nasal mask for 3 days postoperatively. Sham Bi-PAP was created by introducing a "hole" at the connection of the mask with the spiral tube of Bi-PAP. With this modality, also used on previous studies, the applied pressure by sham Bi-PAP was constant and equal to 2 centimeter of water (cm H2O).

Bi-PAP through nasal mask, at individualized IPAP/EPAP pressures, was applied for 3 days postoperatively. IPAP and EPAP in the Bi-PAP system were individualized for each patient in accordance with accepted values of SpO2, PaCO2, and patient synchronization and tolerability with the device.Individualized setting of pressures in patient group was applied gradually starting with 12/4 cm H2O (IPAP/EPAP) and up to 18/10 (IPAP/EPAP) with consecutive increases of 2 cm H2O.

The Bi-PAP system combines inspiratory support-IPAP (inspiratory positive airway pressure) with expiratory support-EPAP (expiratory positive airway pressure) and has been used, with good results, in a number of different clinical conditions such as COPD, respiratory failure due to neuromuscular disease, cardiogenic pulmonary edema and immediately post-operatively with pro-phylactic purpose.

Sham Bi-PAP was created by introducing a "hole" at the connection of the mask with the spiral tube of the conventional Bi-PAP system. By doing so, the applied pressure by sham Bi-PAP was constant and equal to 2 cm H2O.

occurrence of atelectasis as defined by chest X-ray (CXR) post-operatively with CXR before surgery as baseline

Intensity of pain was assessed post-operatively by Numerical Rating Scale (NRS) (0-10, 0=no pain, 10=worst pain imaginable)

Inclusion Criteria: All patients have been Morbidly Obese (BMI> 40kg/m2) for at least 10 years All patients had unsuccessfully tried to lose weight by other non-invasive means. All patients enrolled were continuous positive airway pressure (CPAP) and Bi-PAP naïve and had no knowledge about the Bi-PAP apparatus prior to enrollment All patients underwent OBS (gastroplasty by Mason or gastric bypass) by the same operating team All patients were treated with the same standard anesthetic protocol Exclusion Criteria: Cardiovascular and pulmonary disease not related to obesity status Chronic renal disease Patients who were initially enrolled but did not use the allocated device (Bi-PAP or Sham Bi-PAP) for at least 12 h daily were also excluded at a later point.

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