Transnasal Humidified Rapid Insufflation Ventilatory Exchange in Morbidly Obese
Condition: Anesthesia Intubation Complication; Anesthesia
Study type: Interventional

Summary: 
      This project will investigate the duration of apnea without desaturation when using
      transnasal humidified rapid insufflation ventilatory exchange (THRIVE) vs. low flow nasal
      oxygen at anesthesia induction in obese patients.
    

Detailed description: 
      Background Providing safe anesthesia for surgery in obese patients requires specific
      consideration of the pathophysiological changes and respiratory complications are frequent.
      Anesthesia induction needs special attention in this patient population. A decrease in
      functional residual capacity (FRC) after induction of anesthesia dramatically shortens the
      duration of apnea without desaturation (DAWD) during which the airway can be secured.

      Several measures such as positioning in a semi sitting position, preoxygenation with PEEP and
      passive insufflation of oxygen during laryngoscopy have been shown to prolong the DAWD. None
      of these measures is able to produce positive endexpiratory pressure (PEEP) during
      laryngoscopy which would counteract the loss of FRC and therefore prolong the DAWD further.

      Transnasal humidified rapid insufflation ventilator exchange (THRIVE, also knowns as "high
      flow nasal oxygen therapy" and "heated and humidified nasal oxygen") devices have been used
      for several years in intensive care and are available from numerous vendors. With THRIVE,
      heated and humidified oxygen is insufflated via nasal prongs at a rate up to 120 l/minute and
      it has been shown that this creates levels of PEEP, proportional to the amount of gas flow.
      Using THRIVE during the apneic phase of anesthesia induction in obese patients might be
      superior compared to low flow oxygen techniques as THRIVE generates PEEP during laryngoscopy,
      which might counteract the loss of FRC and consequently might prolong the DAWD.

      Aim of the project This project will investigate the DAWD when using THRIVE vs. low flow
      nasal oxygen at anesthesia induction in obese patients.

      Hypothesis The duration of apnea without desaturation is longer in the "THRIVE" group
      compared to the "low flow oxygen" group.

      Methods The study will be conducted as a single center, prospective, randomized, controlled
      trial at the Medical University of Vienna, Austria.

      Forty adult patients of the ASA classification 2 and 3 with a BMI >40 undergoing elective
      surgery under general anesthesia will be included. Patients with expected difficult airway,
      patients with an oxygen saturation <98% despite preoxygenation, patients with nasal
      obstruction, smokers (>10 cigarettes/day), patients with chronic respiratory disease,
      patients unable to give consent, and pregnant or breastfeeding patients will be excluded.

      Patients will be randomly assigned to one of two groups ("low flow oxygen" or "THRIVE" group)
      and anesthesia will be induced in a standardized fashion in both groups. During laryngoscopy,
      patients in the low flow group will receive nasal oxygen insufflation at a rate of 10 l/min
      and patients in the THRIVE group will receive oxygen at a rate of 120 l/min via a THRIVE
      system. Difficult laryngoscopy will be simulated and intubation will be performed as soon as
      oxygen saturation drops to 95%. The time from anesthesia induction until oxygen saturation
      drops to 95% (DAWD) will be measured.
    

Intervention name(s): low flow passive oxygenation; high flow passive oxygenation
Intervention type(s): Procedure; Procedure
Intervention description(s): low flow passive oxygenation during laryngoscopy with 10l/min oxygen via standard nasal prongs; high flow passive oxygenation during laryngoscopy with 120l/min oxygen via THRIVE system
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: Prospective, single center, randomized, observer blinded, controlled
Masking: Single (Investigator)
Primary purpose: Treatment