PSV on Ventilation Inhomogeneity and Lung Function in Patients Under SB Across LMA

Study Overview
=================
Brief Summary
-----------------
General anesthesia has been demonstrated to have a negative impact on lung function. Both surgery and patient position influence the perioperative lung function. Laryngeal mask airway (LMA) has been proved to be safe and efficient to maintain the airways patent during general anesthesia. Pressure support ventilation (PSV) with LMA is routinely used in clinical practice. The aim of the present trial is to characterize perioperative changes in lung volume, ventilation inhomogeneity and respiratory mechanics in patients in the lithotomy position and spontaneously breathing through LMA with and without PSV.

Detailed Description
-----------------
This study is a randomized controlled trial. Participants for this study will be recruited from the Gynecological department of the University Hospitals of Geneva, scheduled for gynecological procedures in the lithotomy position under general anesthesia. A total of 40 patients will be enrolled and randomly assigned into 2 groups: Group SB (spontaneously breathing without PSV) and Group PSV (spontaneously breathing with PSV). Measurements of end-expiratory lung volume (EELV) and ventilation inhomogeneity will be performed in all patients with a nitrogen multiple breath washout method, before and 1 hour after surgery. Similarly, airway resistance (Rrs) and reactance (Xrs) will be measured at the same time by using the Forced Oscillation Technique. The primary endpoint: Perioperative changes in ventilation inhomogeneity (LCI) and respiratory mechanics (Rrs and Xrs) of patients, positioned in lithotomy and undergoing general anesthesia while breathing spontaneously through LMA with or without PSV. The secondary endpoints: Presence of respiratory complications, oxygen need in the recovery room, length of stay in the recovery room and in the hospital. Correlation between duration of positioning and surgery with lung function and volume measurements. Relevance: There are no studies that addressed the value of pressure support ventilation to overcome the potential changes in lung function following spontaneous ventilation across a LMA in the lithotomy position.

Official Title
-----------------
The Value of Pressure Support on Ventilation Inhomogeneity and Lung Function in Patients Under Spontaneous Breathing (SB)Across Laryngeal Mask Airway

Conditions
-----------------
Respiratory Function Tests, Anesthesia, General, Patient Positioning, Ventilation

Intervention / Treatment
-----------------
* Procedure: general anesthesia across LMA
* Procedure: Spontaneous breathing(SB)
* Procedure: Pressure Support Ventilation


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: - American Society of Anesthesiologists physical status (ASA) Ⅰ and Ⅱ grade, adult female patients, aged between 18 and 50 years scheduled for elective gynecological surgery in the lithotomy position. Exclusion Criteria: Age<18 years and >50 years old ASA score of III-V Patients with a potentially difficult airway (cervical spine disease, Mallampati classification III or IV or mouth opening of <2.5 cm) Risk of regurgitation/aspiration(previous upper gastrointestinal tract surgery, known or symptomatic hiatus hernia, oesophageal reflux, peptic ulceration or not fasted) Respiratory diseases(bronchial asthma requiring therapy) Patient refusal Malignant hyperthermia history Sore throat within 10 days Body mass index (BMI) >30 kg/m2 Cardiac disease associated with dyspnea more than New York Heart Association II Severe psychiatric disorder.

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
-----------------
Female

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Group SB<br>Patient is scheduled for elective conisation or hysteroscopy under general anesthesia. The ventilation mode for this group is spontaneous breathing(SB) without pressure support ventilation (PSV) under laryngeal mask airway (LMA). General anesthesia across LMA under SB without PSV | Procedure: general anesthesia across LMA<br>* general anesthesia across LMA<br>Procedure: Spontaneous breathing(SB)<br>* general anesthesia across LMA under SB without PSV<br>|
| Active Comparator: Group PSV<br>General anesthesia across LMA under SB with PSV Patient is scheduled for elective conisation or hysteroscopy under general anesthesia. The ventilation mode for this group is SB with PSV under LMA. | Procedure: general anesthesia across LMA<br>* general anesthesia across LMA<br>Procedure: Spontaneous breathing(SB)<br>* general anesthesia across LMA under SB without PSV<br>Procedure: Pressure Support Ventilation<br>* general anesthesia across LMA under SB with PSV<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Perioperative changes in ventilation inhomogeneity (LCI) | LCI will be derived from the nitrogen multiple breath washout technique that will be applied before and after general anesthesia for gynecology in the lithotomy position with patients breathing spontaneously through a LMA with and without pressure support. | Through study completion, an average of 12 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Alterations in end expiratory lung volume in ml/kg (EELV) | EELV will be measured from the nitrogen multiple breath washout technique that will be applied before and after general anesthesia for gynecology in the lithotomy position with patients breathing spontaneously through a LMA with and without pressure support. | Through study completion, an average of 12 hours | 
| Changes in respiratory system compliance (Crs) | Crs will be measured by the forced oscillation technique | Through study completion, an average of 12 hours | 
| Changes in airway resistance (Raw) | Raw will be measured by the forced oscillation technique | Through study completion, an average of 12 hours | 
| Perioperative respiratory complications | any respiratory complications (apnoea/ bradypnoea, bronchospasm, laryngospasm, oxygen desaturation <90%/ hypoxemia, hypoventilation/ atelectasis, pulmonary embolism, cough and /or airway obstruction | Through study completion, an average of 12 hours | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
anesthesia, Respiratory Function, Patient Positioning