Transnasal Humidified Rapid Insufflation Ventilatory Exchange in Morbidly Obese

Study Overview
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Brief Summary
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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
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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.

Official Title
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Increasing Duration of Apnea Without Desaturation at Induction of Anesthesia in Morbidly Obese Patients Using Transnasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE)

Conditions
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Anesthesia Intubation Complication, Anesthesia

Intervention / Treatment
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* Procedure: low flow passive oxygenation
* Procedure: high flow passive oxygenation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Adult patients American Society of Anesthesiologists physical status classification class 2-3 BMI > 40 elective surgery under general anesthesia Exclusion Criteria: expected difficult airway (El Ganzouri Risk Index > 6) oxygen saturation of less than 98% despite adequate preoxygenation, nasal obstruction smoker, more than 10 cigarettes per day chronic respiratory disease FEV1 (forced expiratory volume in one second) < 70% elevated intracranial pressure unable to give informed consent Pregnant or breast feeding

Ages Eligible for Study
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Minimum Age: 19 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Prospective, single center, randomized, observer blinded, controlled
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Low flow Oxygen Group<br>low flow passive oxygenation during laryngoscopy with 10l/min oxygen via standard nasal prongs | Procedure: low flow passive oxygenation<br>* low flow passive oxygenation during laryngoscopy with 10l/min oxygen via standard nasal prongs<br>|
| Experimental: THRIVE Group<br>high flow passive oxygenation during laryngoscopy with 120l/min oxygen via THRIVE system | Procedure: high flow passive oxygenation<br>* high flow passive oxygenation during laryngoscopy with 120l/min oxygen via THRIVE system<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Duration of safe apnea | The duration until oxygen saturation drops to 95% during laryngoscopy | duration from the application of rocuronium until the oxygen saturation drops to 95% during laryngoscopy or a maximum of 15 minutes if the oxygen saturation does not drop to this level. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| blood gas analysis | arterial blood samples will be taken every 2 minutes after rocuronium was given until 2 minutes after intubation | every 2 minutes after rocuronium was given until 2 minutes after intubation |