Clinical trial NCT02121808: EPO2-PV: Evaluation of Pre-Oxygenation Conditions in Morbidly Obese Volunteer: Effect of Position and Ventilation Mode
Official title: Evaluation of Different Pre-Oxygenation Conditions in Morbid Obesity: Position and Ventilation Mode, in a Respiratory Physiology Laboratory, on Voluntary Subjects
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Morbid Obesity
Bariatric Surgery Candidate
Keywords: Morbid Obesity
Bariatric Surgery Candidate
Pre-Oxygenation
Functional Residual Capacity
Lead sponsor: Laval University
Sponsor class: OTHER
First posted: 2014-04-24
Enrollment: 20
Sex: ALL
Minimum age (years): 21
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: PREVENTION

Brief summary: The risk of complications associated with airway management in obese patients is significant. The results of pre-oxygenation allow a prolonged non-hypoxic apnea time for the clinician. The increase in FRC and non-hypoxic apnea time is correlated. The best condition to accomplish the pre-oxygenation in morbidly obese patient is still undetermined in medical literature.

This study is designed to evaluate the effect of different positions combined with different ventilation modes during the pre-oxygenation phase of anesthesia's induction. EPO2: PV will evaluate the effect of different combinations of positions and ventilation modes on pulmonary volumes (mainly functional residual capacity) in a morbidly obese volunteer.

Detailed description: Complications related to airway management are the major contributing factor to morbidity in anesthesiology. This risk of complications markedly increases when faced with a difficult airway in an obese patient. Pre-oxygenation creates a safety margin by increasing the patient's oxygen stores, through a higher functional residual capacity (FRC). When pre-oxygenated, the clinician may proceed to intubation after a variable period of apnea, while maintaining oxygen saturation over 92%. In non-obese individuals, pre-oxygenation allows a non-hypoxic apnea time of eight minutes. In the obese population, however, this non-hypoxic apnea time decreases to two to three minutes.

Different methods of pre-oxygenation have been proposed in order to increase apnea time before significant oxygen desaturation. Amongst these methods, the following are of particular interest: pre-oxygenation to vital capacity, pre-oxygenation with spontaneous ventilation and positive pressure, and pre-oxygenation with elevated head positioning ("beach-chair"). These methods have been extensively studied in individuals of normal height and weight.

The main objective of pre-oxygenation is to raise oxygen levels available at the alveolar level in order to increase the non-hypoxic apnea time, before a significant desaturation occurs. This raised alveolar oxygen concentration can be done by maintaining a higher inspired oxygen fraction and by promoting a larger FRC which is the oxygen reserve build through the pre-oxygenation phase. In morbid obese patients, these parameters are affected by a lower expiratory flow, lower expiratory flow and closing of small radius airways. The final result probably come from a more cephalad position of the diaphragm induced by a larger intra-abdominal volume.

Actually, different studies demonstrate the advantage of a beach-chair position and non-invasive positive pressure ventilation for pre-oxygenation of obese patients. These advantages are shown by a shorter time of pre-oxygenation to obtain an end-tidal O2 \> 90 % and a longer non-hypoxic apnea time (Sat O2 \>90%). Up to date, there is no published data on the FRC as a result of different combinations of position and ventilation mode. This study will evaluate FRC by helium dilution technique.

We propose a crossover randomised trial on volunteers waiting for a bariatric surgery. We want to compare, in pre-oxygenation situation, without induction of general anesthesia, the effect of three positions and two ventilation modes on the FRC measure.

Eligibility criteria: Inclusion Criteria:

* BMI 40 - 80 kg / m2
* Waist circumference: Men: More than 130 cm
* Waist circumference: Women: More than 115 cm

Exclusion Criteria:

* Facial hair
* Cranio-facial abnormality
* Claustrophobia
* Asthma
* COPD (defined by FEV1 \< 80 %)
* Severe cardiovascular disease (defined by NYHA ≥3)
* Pregnancy
* Tobacco use
* NI-CPPV Intolerance documented by a respiratory specialist (pneumologist).

Primary outcomes:
measure: Functional Residual Capacity
timeFrame: After a 5 minutes pre-oxygenation period
Secondary outcomes:
measure: Diaphragmatic Amplitude.
timeFrame: After a 5 minutes pre-oxygenation period
measure: Respiratory Mechanics
timeFrame: At the end of a 5 minutes pre-oxygenation period
measure: Patient's Comfort
timeFrame: At the end of a 5 minutes pre-oxygenation period
Other outcomes:
measure: Vital Signs
timeFrame: At the end of a 5 minutes pre-oxygenation period
Locations:
city: Quebec city
country: Canada
facility: Institut universitaire de cardiologie et de pneumologie de Québec
state: Quebec
Study officials:
affiliation: Laval University
name: Etienne J Couture, MD
role: PRINCIPAL_INVESTIGATOR
affiliation: Laval University
name: Jean S Bussières, MD
role: PRINCIPAL_INVESTIGATOR
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