Effect of Boussignac CPAP Ventilation on PaO2 and PaO2/FiO2 Ratio in Morbidly Obese Patients Undergoing Bariatric Surgery
Condition: Morbid Obesity
MeSH terms: Obesity, Morbid
Study type: Interventional

Summary: 
      The purpose of this study is to determine if the application of Boussignac continuous
      positive airway pressure (CPAP) immediately after extubation improves PaO2 and PaO2/FiO2
      ratio in morbidly obese patients undergoing gastric bypass surgery .
    

Detailed description: 
      Background: In 2010, the prevalence of obesity in individuals above 15 years old in Portugal
      was 15.5% for males and 17.7% for females. .In this country bariatric surgery has increased
      significantly playing an important role in the treatment of individuals with BMI ≥ 40 kg/m2
      or less than 35 kg/m2 in the presence of comorbidities.

      Morbid obesity has a negative impact in the respiratory physiology and is associated with a
      decreased compliance of the lung and chest wall, increased airway resistance, decreased
      respiratory muscle strength, increased work of breathing, worsening of ventilation /
      perfusion ratio and postoperative hypoxemia. General anesthesia and surgery in these patients
      will maximize these physiologic alterations.

      Ahmad et al. (2008) found that morbid obesity per se, regardless of the presence of
      obstructive sleep apnea was associated with increased risk of desaturation in the first 24h
      of the postoperative period.

      Gaszynski et al. (2007) found that the use of Boussignac CPAP in the postoperative period of
      patients undergoing bariatric surgery improved oxygenation. However, it was used capillary
      blood gas analysis not arterial blood and the FiO2 was different between groups.

      More recently, in 2011, Wong et al. investigated the effect of Boussignac CPAP versus Venturi
      mask in the first one hour after bariatric surgery, measuring the PaO2 / FiO2 ratio at 1 hour
      and 2 hours of the postoperative period. The group maintained with CPAP showed better
      results. There were no differences between the two groups for FEV1 and FVC. The study does
      not reveal, however, the analgesic protocol used postoperatively or the patient's position
      during the spirometric measurements. These variables could be possible confounders. The PaO2
      absolute value was not evaluated because of the different FiO2 between patients.

      Objectives: We aim to assess the impact of the application of Boussignac CPAP ventilation
      immediately after extubation for improving PaO2 and PaO2/FiO2 ratio in morbidly obese
      patients submitted to gastric bypass surgery. As a secondary objective we intend to evaluate
      if there are differences in spirometry parameters.

      Methods: A randomized controlled study on 24 patients undergoing gastric bypass surgery.
      Control group receives a Ventury mask immediately after extubation and the intervention group
      gets the Boussignac CPAP immediately after extubation. Both groups have the same anesthetic
      protocol during the intraoperative period and receive a 50% FiO2 after extubation. Venturi
      mask and Boussignac CPAP are maintained for two hours. A blood sample is collected from
      radial artery to measure PaO2 and calculate PaO2/FiO2 ratio before surgery and at 1, 2 and 24
      hours after extubation in both groups. Evaluation of forced expiraroty volume in 1 second
      (FEV1) and forced vital capacity (FVC) with a portable spirometer is also performed at the
      same intervals. Patients are monitored for oxygen saturation, arterial pressure and cardiac
      rhythm while using the devices. Tolerance to the device, analgesic requirements and sedation
      level are also monitored and registered.
    

Intervention name(s): Boussignac CPAP; Venturi face mask
Intervention type(s): Device; Device
Intervention description(s): Boussignac CPAP with a 50% FiO2 (adjusted in a piece adapted to the system) and a pressure of 5cmH2O (measured with a manometer) is applied immediately after extubation and mantained for two hours after extubation in the post anesthesia care unit (PACU).; Venturi mask with a 50% FiO2 is used immediately after extubation and mantained for two hours in the post anesthesia care unit (PACU).
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment