One-lung ventilation and methods of improving oxygenation

Published on 07/02/2015 by admin

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Last modified 07/02/2015

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One-lung ventilation and methods of improving oxygenation

Michael J. Murray, MD, PhD and Sarang S. Koushik, MD

One-lung ventilation (OLV) is achieved through a double-lumen tracheal tube, through a single-lumen tracheal tube advanced into either the right or left mainstem bronchus, or by advancing a bronchial blocker though a single-lumen tracheal tube into one of the mainstem bronchi. Multiple indications for OLV are noted in Table 158-1.

Table 158-1

Indications for One-Lung Ventilation

Absolute Relative
Video-assisted thoracoscopy
Protective isolation (infection, hemorrhage)
Differential ventilation (bronchopleural fistula)
Pulmonary alveolar lavage		 Surgery on thoracic aorta or esophagus
Pneumonectomy or lobar resection*

*If one-lung ventilation is used, the surgical incision can be smaller because the deflation of the nondependent lung enables the surgeon to have better surgical access without a large thoracotomy incision.

Mechanism of hypoxia

The lateral decubitus position is often necessary to perform various thoracic operations and for some cardiac surgical procedures. When patients are in the lateral position, their dependent lung is often underventilated because it is compressed by the abdominal contents and by the mediastinum. The nondependent lung is relatively overventilated because its compliance is increased, particularly when the corresponding hemithorax is opened. Conversely, because of gravity, the dependent lung is well perfused, whereas the nondependent lung is underperfused. Because of the mismatch of perfusion to ventilation, hypoxemia is common in patients operated upon in the lateral decubitus position. Once ventilation to the nondependent lung ceases and the dependent lung is the only lung being ventilated (as occurs with OLV), the nondependent lung becomes atelectatic and the ventilation-perfusion ratio approaches 0, creating a transpulmonary shunt through the upper lung. The degree of hypoxemia correlates with the degree of the shunt. Because CO2 is 20 times more diffusible than O2 in the lung, ventilation through the dependent lung removes sufficient CO2 so that hypercarbia is rarely seen.

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