Airway Pressure Changes Using Esophageal Balloon Catheter (OBC) in Laparoscopic Surgery
Condition: Ventilator Lung
Study type: Interventional

Summary: 
      This is a single centre study. The investigators intend to recruit 20 subjects over 4 months.
      Patients undergoing laparoscopic abdominal surgery for cholecystectomy, laparoscopic
      gynaecological surgery and laparoscopic urologic procedures either as day surgery, same day
      admission or in patients, will be included in the study. Patients will be identified at the
      time of listing for surgery and referred to study team, which in turn will recruit the
      patients. Informed consent will be obtained at the time of recruitment and a copy of consent
      with details of principal investigator would be provided to subjects. All data collection
      will be done intraoperative. Patient would be followed up once at day 3 post op period. If
      patients have any complications related to the study, they will be followed up weekly until
      the complication is resolved.
    

Detailed description: 
      General anaesthesia: Patients will be induced and intubated as per the choice of consultant
      anaesthetist. Anaesthesia will be maintained with inhalational agent and paralysis maintained
      with atracurium infusion or bolus so as to keep train of four counts <2 twitches using
      peripheral nerve stimulator throughout surgery. Conventional ventilation was standardised
      with mode as pressure control ventilation, pressure inspired targeted to either tidal
      ventilation of 6-8 ml/kg or end tidal carbon di oxide concentration of 40-50 mmHg and
      positive end expiratory pressure limited to 5 cm of water. Fraction of inspiratory oxygen was
      adjusted to keep oxygen saturation > 95%. No recruitment manoeuvres were permitted unless,
      patient is desaturating actively, and in which case patient will be excluded from the study.
      Abdominal cavity was insufflated with carbon dioxide with initial high flow and pressure, but
      later the pressure was maintained at 15cm water.

      Esophageal balloon catheter insertion, placement and removal: After applying topical
      anaesthetic (10% lidocaine spray) to patient's nasopharynx and water-soluble lubricant jelly
      to distal end of esophageal catheter, it is inserted into patient's esophagus via nasal
      cavity or oropharyngeal cavity. Estimated depth of catheter insertion is calculated as:
      patient's height (in cm) X 0.288. Once the esophageal balloon catheter is inserted to
      estimated depth, balloon is inflated with 4 ml of air and pressure on the stomach is applied
      to look for positive deflection of oesophageal pressure reading. Once convinced, 2 ml air was
      taken out and catheter was slowly withdrawn till cardiac oscillations are visible. Occlusion
      test is performed to confirm the placement of catheter in lower thoracic region. In occlusion
      test, patient is briefly disconnected from ventilator, endotracheal tube is blocked and
      pressure is applied on to chest wall. Simultaneous increase in oesophageal balloon pressure
      and airway pressure is noted. (Change is oesophageal pressure/ change in airway pressure on
      application of external pressure should be close to 1). Stylet is removed and Oesophageal
      balloon catheter is secured at this position on nostril or angle of mouth similar to
      nasogastric tube and connected to pressure transducer to do necessary measurements. Catheter
      is removed at the end of surgery before extubation after complete deflation of cuff.

      Measurements: Soon after confirmation of position, patient is subjected to end inspiratory
      hold to record the end inspiratory pleural pressure and plateau airway pressure. Patient is
      then subjected to end expiratory hold to record end expiratory pleural pressure and positive
      end expiratory pressure. Similar steps are repeated once pneumoperitoneum is achieved and
      patient is placed in trendelenburg or reverse trendelenburg position and once
      pneumoperitoneum deflated. Problems encountered during insertion and measurement of
      esophageal balloon catheter will be resolved using manufacturer's recommendation.
    

Intervention name(s): Adult esophageal balloon catheter (obc)
Intervention type(s): Device
Intervention description(s): Using OBC to determine airway pressure changes in patients undergoing general anaesthesia for laparoscopic surgery
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: Airway pressure; Oesophageal pressure; transpulmonary pressure; laparoscopic surgery