Effect of Inverse Ratio Ventilation During Induction of General Anesthesia on Safe Apnea Time in Obese Patients

Study Overview
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Brief Summary
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The purpose of this study is to investigate the clinical application value of inverse ratio ventilation in obese patients during induction of general anesthesia by studying the effect of inverse ratio ventilation on the safe apnea time.

Detailed Description
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Inverse ratio ventilation(IRV) can produce mean airway pressure(Pmean)similar to external positive end expiratory pressure(Peep) by increasing inspiratory time. Moreover, the increase of Pmean was not accompanied by the further increase of peak airway pressure (Ppeak) and airway plateau pressure (Pplat), while the application of external peep accompanied with the increase of Pplat increased the risk of barotrauma . High level of Peep increased cardiac load and decreased cardiac output. A number of studies have found that the hemodynamic stability of patients can be achieved when IRV regulates the inspiratory / expiratory ratio in an appropriate range (I: E < 2:1). Therefore, the inverse ratio is considered to be superior to Peep in terms of gas exchange and respiratory mechanics.

Official Title
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Effect of Inverse Ratio Ventilation During Induction of General Anesthesia on Safe Apnea Time in Obese Patients:A Randomized Controlled Trial

Conditions
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Obesity

Intervention / Treatment
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* Other: Inspiratory-to-expiratory (I : E) ratio of 1:2
* Other: Inspiratory-to-expiratory (I : E) ratio of 2:1


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Obese patients, aged 18-65 years, of either gender, ASA grade II-III, body mass index (BMI) > 30 kg / m2, scheduled for general anesthesia under tracheal intubation, signed informed consent. Exclusion Criteria: Patients who need rapid sequence induction (RSI); patients with expected difficult airway; severe chronic respiratory diseases, such as tuberculosis, bronchitis, bronchial asthma and COPD; patients with severe cardiovascular diseases, such as severe ischemic heart disease and pulmonary hypertension; patients with severe cerebrovascular diseases, such as cerebral hemorrhage and cerebral infarction; patients with abnormal basal metabolic rate, such as pregnancy, thyrotoxicosis, pheochromocytoma; and severe stomach reflux disease; patients with abnormal hemoglobin and hematocrit.

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


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Group 1:2<br>Patients in the control group had noninvasive positive pressure ventilation with inspiratory-to-expiratory (I : E) ratio of 1:2. | Other: Inspiratory-to-expiratory (I : E) ratio of 1:2<br>* After preoxygenation and induction of anesthesia, noninvasive positive pressure ventilation with inspiratory-to-expiratory (I : E) ratio of 1:2 for 5 min before endotracheal intubation.<br>|
| Other: Group 2:1<br>Patients in the IRV group had noninvasive positive pressure ventilation with inspiratory-to-expiratory (I : E) ratio of 2:1. | Other: Inspiratory-to-expiratory (I : E) ratio of 2:1<br>* After preoxygenation and induction of anesthesian, noninvasive positive pressure ventilation with inspiratory-to-expiratory (I : E) ratio of 2:1 for 5 min before endotracheal intubation.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Safe Apnea Time | The safe apnea time was defined as that period of time during which the arterial saturation as measured by pulse oximetry remained at or above 93% . | The arterial saturation as measured by pulse oximetry remained at or above 93% after endotracheal intubation immediately. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| EtO2 | Fractional concentration of oxygen in end-tidal gas | After 3 minutes of preoxygenation After 5 minutes of noninvasive positive pressure ventilation | 
| EtO2 | Fractional concentration of oxygen in end-tidal gas | After 3 minutes of noninvasive positive pressure ventilation | 
| EtO2 | Fractional concentration of oxygen in end-tidal gas | After 5 minutes of noninvasive positive pressure ventilation | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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inverse ratio ventilation, safe apnea time