In light of the rising number of minimally invasive thoracic procedures, intraoperative one-lung ventilation is being used more frequently 1. In addition to improving surgical access, one-lung ventilation is critical for its ability to 1) control the ventilation distribution pattern, 2) minimize damage or contamination to the healthy lung, and 3) enable single lung lavage 1.
In most patients, single lung ventilation is achieved with special airway devices such as double-lumen endotracheal tubes which selectively direct the airflow to one lung. To this end, the double-lumen tube needs to be well selected to match a patient’s tracheal diameter 2. Single-lumen tubes may also be used, though they are rarely implemented 1. For pediatric patients and other patients for whom double-lumen tubes would be too large, bronchial blockers can be utilized 3. These are inserted down a tracheal tube following intubation to block off either the right or left main bronchus, resulting in the collapse of the lung tissue distal to the obstruction. One study found that the Rusch Bifid EZ bronchial blocker was equally efficacious as double-lumen tubes, and also caused less tracheal and bronchial mucosa injury and fewer sore throats 4. Intraoperatively, a fiberoptic bronchoscope is generally used in parallel to guide placement, confirm positioning, and troubleshoot any problems.
One-lung ventilation requires a number of preoperative considerations and may lead to intraoperative and/or postoperative complications. First, one-lung ventilation requires a specific skillset tailored to airway management, gas exchange sustenance, and injury prevention. This is particularly challenging since maintaining adequate gas exchange may sometimes preclude the effective avoidance of acute lung injury. The most efficacious one-lung ventilation titration parameters have yet to be pinpointed, but a multimodal approach – based on end-expiratory pressure application, alveolar recruitment strategies, and low tidal volume is ideal to maintain effective ventilation and reduce lung damage 5.
Second, while the ventilation to one of the lungs is interrupted, perfusion in the non-ventilated lung remains – generating an intrapulmonary shunt characterized by wasted perfusion to the non-ventilated lung. Hypoxic pulmonary vasoconstriction and other protective mechanisms may counteract hypoxia to a certain extent. However, anesthesiologists must be acutely prepared to handle hypoxemia that may result from such one-lung ventilation scenarios 6; a slew of targeted clinical approaches to this end have been specifically developed 7. In addition, the double-lumen tubes used for the one-lung ventilation can rupture the airways in rare cases 8; the surgical team must also be prepared to respond in this situation.
Finally, patients having undergone one-lung ventilation end up at an increased risk of developing acute lung injury postoperatively, either due to their underlying pathology or to the surgical procedure itself 1. Specific lung protective strategies have been honed to mitigate the extent of lung damage 9.
Today, in the context of the current COVID-19 pandemic, it is important to note that establishing one-lung ventilation in patients with COVID-19 places anesthesia personnel at high risk for infection given the requisite gas exchange between a patient’s lungs and the operating room environment 10. Careful procedures must be strictly followed to minimize COVID-19 infectivity to staff accordingly 11.
One-lung ventilation is clinically critical and will continue to be implemented across an increasingly large range of patients. Each technique for one-lung ventilation presents its own set of advantages and disadvantages, and should be selected appropriately based on patient age, lung morphology, disease history, and clinical context.
References
1. Ashok V, Francis J. A practical approach to adult one-lung ventilation. BJA Educ. 2018. doi:10.1016/j.bjae.2017.11.007
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3. Brodsky JB. Lung separation and the difficult airway. Br J Anaesth. 2009. doi:10.1093/bja/aep262
4. Mourisse J, Liesveld J, Verhagen A, et al. Efficiency, efficacy, and safety of EZ-blocker compared with left-sided double-lumen tube for one-lung ventilation. Anesthesiology. 2013. doi:10.1097/ALN.0b013e3182834f2d
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10. Kostroglou A, Alevizou A, Sidiropoulou T. One-Lung Ventilation: A Simple Technique to Reduce Air Contamination During the Coronavirus Disease 2019 (COVID-19) Pandemic. J Cardiothorac Vasc Anesth. 2020. doi:10.1053/j.jvca.2020.05.007
11. Tryphonopoulos P, McFaul C, Gagne S, Moffett S, Byford L, Thompson C. COVID-19 and One-Lung Ventilation. Anesth Analg. 2020. doi:10.1213/ANE.0000000000004915