Preoxygenation With Positive Inspiratory Pressure During Induction of Anesthesia

Study Overview
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Brief Summary
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Adults patients scheduled for elective surgery were randomly allocated to receive preoxygenation with spontaneous breathing, positive pressure ventilation (positive inspiratory pressure: 12 cmH2O) without PEEP, and with PEEP (positive inspiratory pressure: 12 cmH2O, PEEP: 6 cmH2O). Preoxygenation time was measured from face mask positioning to FEO2=90% (FEO2 : expired fraction of O2). After endotracheal tube placement the time until SpO2=93% (SpO2 : peripheral oxygen saturation) was measured during monitored apnoea. Patient's discomfort was recorded (visual analogue scale).

Detailed Description
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Inclusion criteria : age older 18 years, American Society of Anesthesiologists physical status I and II, and scheduled surgery with general anaesthesia and oro-tracheal intubation. Exclusion criteria : rapid sequence induction, anticipated difficult mask ventilation (2 or more factors among age > 55 years, body mass index > 26 kg m-2, beard, history of snoring, lack of teeth), anticipated difficult intubation (history of difficult intubation, Mallampati class 3 and 4, thyromental distance < 60 mm, interincisor distance < 35 mm, limited cervical spine movement), and refusal to participate to the study and to sign informed consent. Preoperative data recorded : age, height, weight, ASA physical status, and history of asthma, current smoking (ex-smokers were considered after a 3 month period without smoking), number of pack-years, sign inform consent The day of surgery, randomly allocation (random number table, block sizes of 15) to one of the 3 preoxygenation methods: spontaneous breathing, noninvasive positive inspiratory pressure ventilation (PPV) at 12 centimeters of water (cmH2O) without PEEP or with PEEP at 6 cmH2O (PEEP). Intravenous line placement and standard monitoring. Preoxygenated through a face mask firmly applied and connected to the anaesthesia machine delivering a fresh gas flow of 12 l min-1. The circle breathing system was previously flushed with the O2 bypass during 30 s before mask placement. The inspired O2 concentration was set at 100%, the inspiratory trigger sensitivity was set at -2 l min-1, the adjustable pressure limiting valve was opened, and maximal airway pressure was limited at 18 cmH2O. Inspired and expired fraction of O2 and carbon dioxide (CO2) were continuously measured. End of the preoxygenation defined by FEO2=90%, intravenous anaesthesia was performed with propofol (2.5 mg kg-1 followed by a continuous administration at 8 mg kg-1 h-1 continuous infusion of propofol to target a bispectral index between 40 and 50), alfentanil 40 microg kg-1, and succinylcholine 1 mg kg-1. No face mask ventilation was provided before orotracheal intubation which was performed at the end of muscles fasciculation. The correct position of the tube (tracheal position above carina) was immediately checked using fiberoptic visualisation and was mandatory before atracurium 0.5 mg kg-1 administration. If tube misplacement occurred, the patient was excluded from the study in order to perform standard care. The time until SpO2 reached 93% was measured. The SpO2 and FEO2 were recorded every 10 s during the preoxygenation phase. The SpO2 was recorded every 10 s during the apnea phase. Just before leaving the post-anaesthesia care unit, the patient was asked to evaluate the preoxygenation method with the following questions: How do you evaluate the preoxygenation phase on the scale (cursor placed on a 100 mm visual analogue scale) between very comfortable (0 mm) to very uncomfortable (100 mm)? Do you want to have the same preoxygenation method for further anaesthesia (yes/no)? Primary endpoint : time for preoxygenation (average 180 s) calculated from face mask positioning to FEO2=90%. Secondary endpoints: duration of apnoea from tracheal tube positioning to SpO2 = 93% (average 5 to 10 min), and patient's comfort evaluated on a 0 to 100 mm visual analogue scale.

Official Title
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Randomized Controlled Trial on Preoxygenation Through Spontaneous Breathing or Non Invasive Positive Pressure Ventilation With and Without Positive End Expiratory Pressure

Conditions
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Anesthesia

Intervention / Treatment
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* Other: PPV : positive pressure ventilation
* Other: PEEP : PPV + PEEP


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: American Society of Anesthesiologists (ASA) physical status I and II Scheduled surgery with general anaesthesia and oro-tracheal intubation Exclusion Criteria: rapid sequence induction anticipated difficult mask ventilation anticipated difficult intubation refusal to participate to the study and to sign informed consent

Ages Eligible for Study
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Minimum Age: 18 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: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: spontaneous breathing (SB)<br>preoxygenation through a face mask firmly applied and connected to the anaesthesia machine delivering a fresh gas flow of 12 l min-1. The inspired O2 concentration was set at 100%. End of preoxygenation FEO2=90% | |
| Experimental: positive pressure ventilation (PPV)<br>PPV : positive pressure ventilation : preoxygenation with noninvasive positive inspiratory pressure ventilation (12 cmH2O) without PEEP. Preoxygenation through a face mask firmly applied and connected to the anaesthesia machine - non invasive inspiratory ventilation mode - inspiratory trigger sensitivity was set at -2 l min-1, the adjustable pressure limiting valve was opened, and maximal airway pressure was limited at 18 cmH2O - PEEP=0 cmH2O End of preoxygenation FEO2=90% | Other: PPV : positive pressure ventilation<br>* Inspiratory pressure support ventilation (12 cmH2O) without PEEP<br>|
| Experimental: PPV + PEEP<br>PEEP : PPV + PEEP : preoxygenation with noninvasive positive inspiratory pressure ventilation (12 cmH2O) with PEEP at 6 cmH2O. Preoxygenation through a face mask firmly applied and connected to the anaesthesia machine - non invasive inspiratory ventilation mode - inspiratory trigger sensitivity was set at -2 l min-1, the adjustable pressure limiting valve was opened, and maximal airway pressure was limited at 18 cmH2O - PEEP=6 cmH2O End of preoxygenation FEO2=90% | Other: PEEP : PPV + PEEP<br>* Inspiratory pressure support ventilation (12 cmH2O) with PEEP (6 cmH2O)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time for Preoxygenationfrom Face Mask Positioning to FEO2=90% | Time measured form face mask positioning until FEO2 reached 90% on the gas monitor | up to 5 min | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time Until SpO2=93% | time until SpO2=93% after endotracheal tube placement has been confirmed | up to 10 min | 
| Discomfort of the Preoxygenation Phase Self Reported by the Patient | discomfort of the preoxygenation phase evaluated on a visual analogue scale (0 no discomfort - 100 maximal discomfort) just before PACU leaving | Before PACU leaving |