Ultrasonograpahic Evaluation of Diaphragmatic Functions in Obese Patients Undergoing Laparoscopic Sleeve Gastrectomy
Condition: Bariatric Surgery Candidate
Study type: Interventional

Summary: 
      Major laparoscopic sleeve gastrectomy surgery requires steep Trendelenburg position with
      pneumoperitoneum for a long time leading to decrease pulmonary compliance and lung volumes
      due to cephalic displacement and decrease excursion of the diaphragm, consequently leading to
      the possibility of atelectasis formation. Different strategies have been proposed to reduce
      atelectasis and other pulmonary complications in obese patients as induction of anesthesia in
      the head up position with or without CPAP, protective intraoperative mechanical ventilation
      with high or low levels of PEEP and implementation of Recruitment Maneuvers. Up to
      investigators' knowledge, there is no study done to evaluate the effect of intraoperative use
      of PEEP and alveolar recruitment maneuver on diaphragmatic function and incidence of
      atelectasis via ultrasonography in obese patients undergoing laparoscopic sleeve gastrectomy.
    

Detailed description: 
      Bariatric surgery is one of the fastest-growing areas of surgery. It is the most effective
      treatment for morbid obesity and its secondary co-morbidities. Although there is no gold
      standard surgical procedure for obesity management, laparoscopic sleeve gastrectomy (LSG) is
      considered to be the first choice procedure and recently it becomes the most common bariatric
      surgical procedure performed worldwide. LSG is preferred to open techniques because it is
      associated with less incisional pain, shorter operative time, fewer pulmonary complications,
      and earlier hospital discharge.

      However, laparoscopic procedures are operated under general anesthesia that decreases
      functional residual capacity (FRC) and enhances atelectasis. Also, it is performed in
      conjunction with intra-abdominal CO2 insufflation and subsequent increase in the
      intra-abdominal pressure, this CO2 pneumoperitoneum together with the steep Trendelenburg
      position which is maintained for long period in LSG, result in cephalic displacement of the
      diaphragm leading to several respiratory changes as decreased FRC and vital capacity (VC),
      decrease pulmonary compliance, consequently resulting in atelectasis formation in the
      dependent lung regions. Moreover, obese patients are more prone to develop peri-operative
      atelectasis and postoperative pulmonary complications that are almost twice the risk among
      healthy subjects.

      This alteration in FRC and lung volumes are more clinically relevant as it can result in
      small airway closure and further ventilation-perfusion mismatch that may lead to
      postoperative hypoxemia and respiratory complications. Several studies revealed that these
      lung volumes decrease and its ensuing complications are not only due to cephalic displacement
      of the diaphragm but also due to decreased diaphragmatic excursion.

      Several strategies have been proposed to reduce the incidence of atelectasis and other
      pulmonary complications such as induction of anesthesia in the head-up position with or
      without a continuous positive airway pressure (CPAP), use of intraoperative PEEP and
      implementation of alveolar recruitment maneuver (RM) but it seems that the latter may be an
      effective method according to several studies conducted on morbidly obese patients undergoing
      laparoscopic surgery and demonstrated that intraoperative recruitment of lung volume improves
      the respiratory mechanics and oxygenation. While other studies showed that the application of
      PEEP intraoperatively during laparoscopic colorectal surgery is helpful for preserving
      diaphragmatic excursion and consequently reduce the incidence of atelectasis.

      It is worth mentioning that ultrasonography (US) can play an important role in evaluating the
      diaphragmatic structure by measuring diaphragmatic thickness as well as diaphragmatic
      function by measuring diaphragmatic excursion/displacement (DD). It is a promising bedside
      test to evaluate the structure and dynamic function of diaphragm peri-operatively and in
      critically ill patients to predict the expected outcome.

      The investigators hypothesize that performing RM in addition to PEEP may have an impact on
      improving diaphragmatic function in terms of diaphragmatic excursion evaluated by
      ultrasonography in obese patients undergoing LSG. Therefore; it may decrease the incidence of
      postoperative pulmonary complications.
    

Intervention name(s): addition of positive end expiratory pressure in ventilated patients; addition of positive end expiratory pressure and recruitment maneuver in ventilated patients
Intervention type(s): Procedure; Procedure
Intervention description(s): patients will be intraoperatively mechanically ventilated with PEEP of 5 cmH2O.; patients will be intraoperatively mechanically ventilated with PEEP of 5 cmH2O and intermittent four times of RM consisting of maintaining airway pressure 40 cmH2O for 40 sec.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment