Effects of 1:1 Inspiratory to Expiratory Ratios on Oxygenation and Intrapulmonary Shunt Fraction During One Lung Ventilation in the Obese Patients

Study Overview
=================
Brief Summary
-----------------
One-lung ventilation, even in patients with healthy weight, causes an impairment in gas-exchange and respiratory mechanics. We hypothesized that oxygenation during the one-lung ventilation in obese patients would be improved by applying inverse-ratio ventilation, reducing atelectasis in the dependent lung and resulting in reduced shunt. Because of the restrictive ventilatory effects of obesity, these patients often show a decreased functional residual capacity and decreased expiratory reserve volume, leading to an overall decreased tidal volume. These reduction leads to arterial hypoxemia, V-Q mismatch and Rt to Lt shunting. There are few studies on the one lung ventilation in obese patients about this prolonged inspiratory time ventilatory method. We plan to investigate the effect of this ventilation method in obese patients during one lung ventilation.

Official Title
-----------------
Effects of 1:1 Inspiratory to Expiratory Ratios on Oxygenation and Intrapulmonary Shunt Fraction During One Lung Ventilation in the Obese Patients

Conditions
-----------------
Obese Patients, One Lung Ventilation

Intervention / Treatment
-----------------
* Procedure: I:E ratio 1:2
* Procedure: I:E ratio 1:1


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Above 40 years of age. American Society of Anesthesiologists (ASA) Physical Status I, II, III. Obesity (BMI >25 kg/ m2 ) thoracic surgical procedure Exclusion Criteria: severe functional liver or kidney disease diagnosed HF ( NYHA class >3) reduced pulmonary diffusion capacity < 80%

Ages Eligible for Study
-----------------
Minimum Age: 40 Years
Maximum Age: 80 Years

Sexes Eligible for Study
-----------------
All

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

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

Design Details

Primary Purpose: Other
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: I:E ratio 1:2<br>We plan to evaluate the improvement on respiratory function with different ventilation I:E ratios (1:2 vs. 1:1) during the one-lung ventilation in an obese patients. | Procedure: I:E ratio 1:2<br>* We plan to evaluate the improvement on respiratory function with different ventilation I:E ratios (1:2 vs. 1:1) during the one-lung ventilation in an obese patients.<br>|
| Active Comparator: I:E ratio 1:1<br>The purpose of our study is to compare the effects of minimal prolonged 1:1 IE ratioventilation on respiratory mechanics and oxygenation with conventional 1:2 IE ratio ventilation during OLV in obese patients. | Procedure: I:E ratio 1:1<br>* The purpose of our study is to compare the effects of minimal prolonged 1:1 IE ratioventilation on respiratory mechanics and oxygenation with conventional 1:2 IE ratio ventilation during OLV in obese patients.<br>|

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

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes of the intrapulmonary shunt fraction and respiratory dynamic parameter | shunt fraction Qs/Qt = (CcO2- CaO2)/(CcO2- CvO2), CcO2 = Hgb x 1.34 x ScO2 + PcO2 x 0.003, lung compliance : Compliance= Vt / Pplat, physiologic dead space : Vd/Vt = 1.14 x (PaCO2 - PETCO2)/PaCO2- 0.005 | T1 (10min before one lung ventibation) T2 (30min after one lung ventilation started)T3 (60min after one lung ventilation started) T4 (10min after two lung ventilation) |