Does Pulmonary Compliance Optimization Through PEEP Manipulations Reduces the Incidence of Postoperative Hypoxaemia in Bariatric Surgery?
Condition: Bariatric Surgery
MeSH terms: Hypoxia
Study type: Interventional

Summary: 
      General anesthesia, even in patients in good health, impairs gas exchanges and ventilatory
      mechanics. These effects result primarily from atelectasis formation. They occur in 85-90% of
      healthy patients in the minutes following the induction when a positive end expiratory
      pressure (PEEP) is not used.

      The functional residual capacity (FRC) of obese patients during general anesthesia is even
      smaller than the one of healthy patients. There is a direct relationship between the body
      mass index and the decrease of the functional residual capacity. Obese patients have
      therefore more atelectasis. The increased abdominal pressure during the pneumoperitoneum will
      increase the decrease of the CRF, and thus aggravate the formation of these atelectasis.

      Atelectasis affect the peroperative gas exchanges and are likely to be involved in the
      worsening of postoperative hypoxemia episodes. In addition, atelectasis alter the clearance
      of secretions and the lymph flow, which predispose to lung infections.Taking all these
      factors into account, it is logical to think that the atelectasis presence can lead to an
      increase of the postsurgical morbidity (respiratory distress, infections). That is why
      actively fighting against the formation of these atelectasis is important.

      There is a lack of scientific evidence to say that the strategies against atelectasis as PEEP
      have a significant impact on the patient's postoperative status. The expected clinical
      benefits balance (reduction of respiratory distress episodes, infections and mortality)
      versus the risks linked to the maneuvers done to reduce the development of atelectasis
      (barotraumas, cardiac complications) remains to be determined.

      The primary goal of this study is to evaluate the impact of two different alveolar
      recruitment strategies on the incidence of postoperative hypoxemia in obese patients after
      bariatric surgery.

      The secondary objectives of this study are to compare the number of recruitment maneuvers,
      the Pa02 / FI02 ratio (ratio of arterial oxygen partial pressure to fractional inspired
      oxygen), the dynamic compliance, the anatomic dead space and intraoperative PaCO2-EtCO2
      gradient (arterial and end tidal gradient) between two alveolar recruitment strategies
      applied in obese patients during laparoscopic bariatric surgery (gastric bypass or sleeve
      gastrectomy).

      The tertiary objectives of this study are to report the number of respiratory complications
      and postoperative wound infections at the 30th postoperative day.
    

Detailed description: 
      General anesthesia, even in patients in good health, impairs gas exchanges and ventilatory
      mechanics. These effects result primarily from atelectasis formation. They occur in 85-90% of
      healthy patients in the minutes following the induction when a positive end expiratory
      pressure (PEEP) is not used.

      These atelectasis are formed on one hand by the reduction of the functional residual capacity
      (FRC) following a compression mechanism (loss of the inspiratory muscle tone, which is
      accompanied by a chest wall configuration change and a diaphragm cephalic movement) and on
      the other hand by a denitrogenation absorption process (ventilation at high Fi02 (oxygen
      inspired fraction) causing complete absorption of O2 with lack of support for the alveolus,
      which then collapses).

      The FRC of obese patients during general anesthesia is even smaller than the one of healthy
      patients. There is a direct relationship between the body mass index and the decrease of the
      functional residual capacity. Obese patients have therefore more atelectasis. The increased
      abdominal pressure during the pneumoperitoneum will increase the decrease of the CRF, and
      thus aggravate the formation of these atelectasis.

      Atelectasis affect the peroperative gas exchanges and are likely to be involved in the
      worsening of postoperative hypoxemia episodes. In addition, atelectasis alter the clearance
      of secretions and the lymph flow, which predispose to lung infections.Taking all these
      factors into account, it is logical to think that the atelectasis presence can lead to an
      increase of the postsurgical morbidity (respiratory distress, infections). That is why
      actively fighting against the formation of these atelectasis is important.

      Several strategies have been studied in order to improve respiratory mechanics and reduce
      impaired gas exchange during laparoscopic surgery in obese patients. The position called
      "chair", mechanical ventilation with PEEP, recruitment maneuvers followed by the PEEP, and
      spontaneous ventilation with CPAP before extubation, are all strategies that have proven
      effective to decrease development these atelectasis.

      Currently, the scientific community agrees on the fact that PEEP improves intraoperative
      respiratory function (improved compliance, oxygenation) especially in conjunction with
      recruitment maneuvers.

      But there is a lack of scientific evidence to say that the strategies against atelectasis as
      PEEP have a significant impact on the patient's postoperative status. The expected clinical
      benefits balance (reduction of respiratory distress episodes, infections and mortality)
      versus the risks linked to the maneuvers done to reduce the development of atelectasis
      (barotraumas, cardiac complications) remains to be determined.

      The primary goal of this study is to evaluate the impact of two different alveolar
      recruitment strategies on the incidence of postoperative hypoxemia in obese patients after
      bariatric surgery.

      The secondary objectives of this study are to compare the number of recruitment maneuvers,
      the Pa02 / FI02 ratio, the dynamic compliance, the anatomic dead space and intraoperative
      PaCO2-EtCO2 gradient between two alveolar recruitment strategies applied in obese patients
      during laparoscopic bariatric surgery (gastric bypass or sleeve gastrectomy).

      The tertiary objectives of this study are to report the number of respiratory complications
      and postoperative wound infections at the 30th postoperative day.
    

Intervention name(s): PEEP (positive end-expiratory pressure)
Intervention type(s): Device
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Prevention
Keywords: Bariatric surgery; Post-surgery hypoxemia; Obesity