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One Lung Ventilation During Thoracic Surgery

  1. One lung ventilation is required for a number of thoracic procedures such as lung, esophageal, aortic or mediastinal surgeries. In one lung ventilation, one lung is collapsed intentionally and the other is ventilated. This offers the surgeon easier and better access within the designated hemithorax (on collapsed side).
  2. Most common method of one-lung ventilation is double lumen endobronchial tube. Other methods, not commonly used are:- Single - lumen tracheal tube with a bronchial blocker, and single lumen bronchial tube.

Components of double lumen tube

Double lumen endobronchial tube has two separate colour coded lumen each with its own bevel.
One lumen ends in the trachea and the other lumen ends in either the left or right main bronchus. Each lumen has its own cuff (tracheal and bronchial cuffs) and colour coded pilot balloon. The proximal end of these tubes is connected to a breathing system.

Mechanism of action

Because of the differing anatomy of the main bronchi and their branches, both right and left versions of any particular double lumen tube must exist. Once correctly positioned the anaesthetist can selectively ventilate one lung, so for operations requiring that the right lung is deflated, a left sided double lumen tube would be used that enables selective ventilation of the left lung alone and vice versa.

How to confirm the position of the double Lumen tube?

The position of the tubes should be checked by auscultation immediately after intubation and after positioning the patient for operation. The auscultatory method for checking the correct placement of tube is just a clinical method for ensuring correct placement of the tube and the confirmation of correct placement of the tube should be the done by flexible fiberoptic bronchoscopy.

What is the use of end tidal CO2 determination (EtCO2) in intubation?

The EtCO2 can be used to confirm the position of the endotracheal tube. (whether the tube is in oesophagus or trachea).
The persistent detection of CO2 by a capnograph is the best confirmation of tracheal placement of an endotracheal tube (EtCO2).


Note: Capnography can detect whether the tube is in trachea or oesophagus but cannot differentiate between tracheal intubation and endobronchial intubation because in both these cases there will be persistent detection of CO].

Other methods for ensuring correct position of DLT

  1. Auscultation
  2. Chest radiography
  3. Use of underwater seal
  4. Characteristic feeling of bag
  5. Fluoroscopy
  6. Selective capnograhy
  7. Chest inflation on positive pressure

Intrapulmonary shunt during one lung ventilation

During one-lung ventilation only one lung is ventilated, however both lungs are perfused because the collapsed lung continues to be perfused. Therefore, the patients develops a large right to left intrapulmonary shunt (20- 30%), i.e., the blood which comes from right side of heart (deoxygenated blood) cannot be oxygenated in nonventilated lung and get mixed with oxygenated blood which comes from ventilated lung Right to left shunt. Mixing of unoxygenated blood from the still ventilated dependent lung widens the PA.a (alveolar to arterial) O2 gradient and often results in hypoxemia.

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