Effect of Positive End Expiratory Pressure at the Time of Induction in Morbidly Obese Patients

Background: Positive end expiratory pressure (PEEP) at the time of induction increases oxygenation by preventing lung atelectasis. However, PEEP may not prove beneficial in all cases. Factors affecting the action of PEEP have not been elucidated well and remain controversial. Pulmonary vasculature has direct bearing on the action of PEEP as has been proven in previous studies. Thus this study was planned to evaluate the action of PEEP on the basis of pulmonary artery systolic pressure (PASP) which is non invasive and easily measured by trans-thoracic echocardiography.

Methodology: This Randomized prospective study comprised of 70 morbidly obese patients, ASA grade II or III, aged 20-65 years with BMI \> 40kg/m2, scheduled for elective laparoscopic bariatric surgery. Ten patients had to be excluded. Thus a total of 60 patients participated in the study. Thirty patients received no PEEP at the time of induction while other 30 patients were given a PEEP of 10cm of H2O. Serial ABG samples were taken pre operatively, at the time of intubation, 5 min after intubation and 10 min after intubation. Patients were then divided into four groups on the basis of PASP value of ≤ 30 mm Hg with and without PEEP or \> 30 mm Hg

This prospective study was conducted in the Department Of Anaesthesiology\& Critical Care, Sri Aurobindo Institute of Medical Sciences \& P.G. Institute and Mohak Hospitals, Indore, over a period of one year. Seventy morbidly obese patients, ASA grade II or III, aged 20-65 years with BMI \> 40kg/m2, scheduled for elective laparoscopic bariatric surgery were selected and a written informed consent was obtained. All the recruited patients underwent 2D-trans-thoracic echocardiography and PASP was recorded. Echocardiography was performed by same cardiologist as this measurement is operator dependent. Patients who denied consent, those undergoing Emergency and/or open surgery and those requiring more than 2 attempts for intubation were excluded.

Arterial line was inserted pre operatively and ABG sample was taken and hemodynamic parameter recording done while the patient was breathing room air. Both groups were pre-oxygenated for 3 minutes with 100% Oxygen. Standard procedure was used for induction of anesthesia in all the patients. No premedication was given. All the patients were induced with i.v. Glycopyrolate (0.005-0.01 mg/kg), i.v. Fentanyl (2µg/kg) and i.v. Propofol. Once the patient became unresponsive to verbal commands, Succinylcholine was then administered in a dose of 1- 1.5 mg/ kg. Mechanical ventilation was started with 100% oxygen. A PEEP of 10 cm H2O was applied using four hand technique in Study group while the control group received no PEEP. After one minute endotracheal intubation was done. PEEP was continued in study group after intubation.

Arterial blood gas (ABG) analysis and hemodynamic parameters were recorded at following stages:

1. Just after inflation of cuff of endotracheal tube
2. 5 minutes post intubation
3. 10 minutes post intubation

Patients were then again divided into four groups on the basis of PASP:

Group 1: Patients with PASP ≤ 30 mmHg receiving no PEEP (n= 11) Group 2: PASP ≤ 30 mm Hg receiving PEEP of 10 cm H2O (n= 11) Group 3: PASP \> 30 mm Hg receiving no PEEP (n= 19) Group 4: PASP \> 30 mm Hg receiving PEEP of 10 cm H2O (n=19)

Eligibility Criteria:
Inclusion Criteria: Patients recruited were

* Anesthesia society of Anesthesiologist (ASA) physical status l, II or III,
* Aged 20-65 years
* BMI \> 40kg/m2
* scheduled for elective laparoscopic bariatric surgery

Exclusion Criteria:

* Patients who denied consent
* Did not fulfill the inclusion criteria,
* patients undergoing Emergency and/or open surgery
* Patients requiring more than 2 attempts for intubation