Risk of Gastric Insufflation Related to Facemask Ventilation Technique During Anaesthetic Induction, With or Without PEEP
Condition: Air Insufflation; Regurgitation
Study type: Interventional

Summary: 
      Continuous positive pressure during anesthetic induction is today not routinely used partly a
      to the risk of gastric insufflation because of higher ventilatory pressures. However there
      are conflicting data with improvement of GERD symptoms in CPAP treated OSA patients. The
      investigators aim to compare the risk of gastric insufflation regarding mask ventilation
      technique, with or without positive end expiratory pressure. For measurements a High
      Resolution Impedance Manometry Catheter is used.
    

Detailed description: 
      Anesthetic induction agents cause a number of physiological changes within the respiratory
      system. Almost every induction agent causes apnoea. There is a reduction of FRC and an
      increase in airway resistance. Combined with preoxygenation with a high fraction of oxygen
      there is a significant risk of pulmonary atelectasis. Adding a continuous positive pressure
      during ventilation of the apnoeic patient improves many of the respiratory effects caused by
      induction agents. However the added continuous pressure will increase the total inspiratory
      pressure and a high inspiratory pressure is associated with an increased risk of gastric
      insufflation during mask ventilation. On the other hand there are data suggesting that
      continuous positive pressure is beneficial in treatment of GERD-symptoms.

      The investigators hypothesis is, if performed correctly, that the continuous positive
      pressure will not increase the risk of gastric insufflation. In order to investigate this
      matter 30 healthy human subjects will undergo anesthetic induction, 15 with no PEEP added and
      15 with a PEEP of 10 cm H2O during mask ventilation.

      Protocol:

        1. Preoxygenation, 100 % oxygen via Face mask for 3 minutes with 0 PEEP or 10 cm H2O PEEP.

        2. Start of Remifentanil Target Controlled Infusion, target concentration 6 ng/ml.

        3. Propofol 2-2.5mg/kg to adequate depth of anesthesia.

        4. 30 seconds after apnea mask ventilation with Dräger ZEUS IE starting with an inspiratory
           pressure of 3cm H2O that is gradually increased to a maximum of 30 cm H20 or to signs of
           air insufflation in the esophagus. Group 1 with 0 PEEP and group 2 with 10 cm H2O PEEP.

        5. End of Remifentanil- and Propofol infusion.

      Pressures and passage of air or liquid from pharynx to stomach will be continuously
      registered during the procedure. For measurements a High Resolution Impedance Manometry
      Catheter with the ability to measure pressures and impedance simultaneously will be used.

      The esophagus and the stomach is divided into four functional units for analysis.

        1. The upper esophageal sphincter

        2. The esophageal body (3 cm below upper esophageal sphincter to 3 cm over the lower
           esophageal sphincter)

        3. The lower esophageal sphincter

        4. The stomach (3 cm below the lower esophageal sphincter)

      The different units are detected in pressure plots where the levels of pressure reflects the
      anatomical units. Manometric values is specified in mmHg. For detection of passage of air and
      flow of liquid an impedance baseline is set before measurements start. Passage of air is
      defined as a sudden rise in impedance of 1 kΩ in anterograde direction. Detection of fluid is
      defined as a 50% decline in impedance. For analysis of data Mano View analysis software is
      used.

      Pressures and impedance will be continuously recorded during the time frame from
      preoxygenation to maximum inspiratory pressures are reached. Data will be analysed at each
      level of pressure 3, 5, 10, 15, 20, 25 and 30 cm H2O. Contained data will be statistically
      compared between groups.
    

Intervention name(s): Mask ventilation with PEEP via a face mask device
Intervention type(s): Procedure
Intervention description(s): 15 subjects will undergo anesthetic induction with an application of PEEP of 10 cm H2O during mask ventilation via a face mask.
15 subjects will undergo anesthetic induction without PEEP during mask ventilation via a face mask.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: PEEP; Air insufflation; Mask ventilation; Esophageal manometry; Esophageal impedance