A prospective interventional study to detect the efficacy of bronchial cuff pressuremonitoring to detect the displacement of lung isolation device during elective thoracic surgeries.

Introduction

Dislodgement of lung isolation devices (double lumen tube and bronchial blocker) is known to occur during change of position of patient (from supine to lateral) and also during the surgery. Dislodgement of lung isolation device leads to loss of lung isolation, contamination of non-operative lung, raised peak airway pressures and at times complete loss of ventilation, thus compromising the safety of the patient significantly. Double lumen tubes (DLTs) are less likely to get dislodged than the bronchial blockers (BBs). However, the incidence of displacement of DLTs during positioning of patient has been reported to vary from 32% to as high as 74%. Seymour et al. carried out an audit of displacements of DLT during OLV with 506 consecutive double lumen Robertshaw tubes, they found 50 cases of tube displacement with 16 cases in which isolation failure was reported. The incidence was more with right sided tubes than left sided tubes, also proximal migration to be more common. For an anesthesiologist, close monitoring of ventilation parameters (assessment of inspiratory peak airway pressures, capnography, pressure-volume graph assessment) is an important tool to detect displacement of lung isolation device. Surgeons may find sudden loss of lung isolation due to displacement of lung isolation device. Direct visualization of displacement by means of pediatric fibreoptic bronchoscope (FOB) remains gold standard for confirmation of displacement.

During proximal migration of lung isolation device, bronchial cuff moves into wider portion of bronchus or sometimes in trachea. It leads to drop in cuff pressure. A study by Araki et.al. suggested that drop in bronchial cuff pressure occurred even before any change in pressure-volume loop or capnograph when DLT was displaced proximally. In that study, bronchial cuff pressure was measured intermittently using aneroid manometer [1].

In this study, we hypothesize that continuous measurement of bronchial cuff pressure using pressure transducer would give an early idea about dislodgement of lung isolation device. Primary outcome would be accuracy of bronchial cuff pressure monitoring in detection of displacement of lung isolation device. Secondary outcome would be the incidence of intraoperative displacement of lung isolation device.

Methodology

In the operation theatre, we would use standard intubation protocol practiced at TATA Memorial Hospital and under routine anesthesia monitoring (continuous ECG monitoring, etCO2, NIBP and oxygen saturation monitoring). Left bronchus would be intubated with either a left-sided DLT or a bronchial blocker. The choice between DLT and Bronchial blocker would be left to decision of OR anesthesiologist. Size of the DLT would be chosen as per prevalent practice of height based criteria. Intraoperative anesthesia maintenance would continue as per discretion of OR anesthesiologist. Use of nitrous oxide would be completely avoided during the study.

With the aid of a pediatric fibreoptic bronchoscope (FOB), lung isolation device would be adjusted so that the bronchial cuff of the device would be positioned just beyond the carina. Fine adjustment in position of lung isolation device would be done by a consultant OR anesthesiologist. Further all bronchoscopic examinations in that case would be done by the same consultant. Final desired position of lung isolation device would be considered as ‘zero position’. Bronchial cuff of the device would now be connected to a pressure transducer via a three-way device. Cuff would be inflated so as to block any air leak across the cuff. Under water seal or reservoir bag deflation would be monitored to confirm air tight seal. Volume of air used to inflate the cuff would be noted. Bronchial cuff pressure reading would be noted at this point.

Part 1:

Before starting the surgery, with patient in supine position,under bronchoscopy guidance, device would be moved proximally and distally in stepwise manner, based on bronchoscopic view as described below. Bronchial cuff pressure would be noted at each step.Change in bronchial pressure during proximal (step 1) and distal movement of lung isolation device would be noted as ‘delta pressure change’.

 

Distal movement

|Step 1 (D1)

Lung isolation device is pushed distally or inside the bronchus by 1 cm or till resistance is encountered till any further movement, whichever is earlier.

|Proximal movement

|Step 1 (P1)

Superior surface of bronchial cuff is at the carina

|Step 2 (P2)

Superior surface of bronchial cuff is above carina but major portion of cuff is still beyond carina

|Step 3 (P3)

Cuff is entirely above carina.

 Part 2:

Bronchial cuff pressure would be monitored throughout the surgery continuously. In event of change (decrease or increase in bronchial cuff pressure equal to delta pressure change, noted in part 1), or in case of a critical event (defined below) surgical manipulation would be stopped and the OR consultant anesthesiologist would do FOB examination to confirm position of the lung isolation device. Critical event is defined as-

a. A drop in oxygen saturation by 4% or <90%, whichever is earlier, or

b. Loss of lung isolation, or

c. An increase in peak airway pressure >35 cm of water, or

d. Loss or alteration in capnographsuggestive of obstruction of airway or leak across the cuff, wherever applicable.

 Any change from ‘zero position’ would be noted and graded as ‘positive’ for distal migration of device and ‘negative’ for proximal migration.

 Part 3:

At the end of the surgery, bronchoscopy would be performed to note any displacement of lung isolation device. After this, bronchial cuff would be deflated and lung isolation device would be removed from patient’s trachea by consultant anesthesiologist.

 Patient population:

We would include 100 adult patients or eligible patients over duration of 1 year.

·         Inclusion criteria- All adult (>18 years) patients undergoing thoracic surgeries requiring lung isolation.

 Â·         Exclusion Criteria –

1.      Pediatric patients

2.      Emergency surgeries

3.      Patients with known anatomical anomaly (known anatomical variation/ endobronchial mass/ Broncho pleural fistula) in trachea and bronchus.

4.      Patients with risk of contamination (blood/ secretions/pus) across the lungs. E.g. Patients with hemoptysis, infective lung conditions communicating with bronchus etc.

5.      Patients with lung isolation devicesplaced in right main bronchus.