One-lung Ventilation Techniques to Facilitate Thoracoscopic Surgery: Time for Some Different Studies?

To the Editor: Huang et al. recently presented a new one-lung ventilation open-closed airway technique that facilitates collapse of the non-ventilated lung for thoracoscopic surgery. 1 Their study protocol ensures that the non-ventilated lung is: 1) likely free of slowly diffusing nitrogen; 2) able to undergo passive elastic recoil collapse via an open airway for one minute after the pleural cavity is opened; and 3) able to collapse optimally because with its airway occluded, all the ongoing oxygen uptake inevitably reduces its size. Many other randomized controlled trials have been published on this topic and differing strategies have been proposed. 2 However, all have practical or theoretical shortcomings: ceasing mechanical ventilation temporarily for a varying length of time to allow elastic recoil reduction in lung volume 2 has a limited benefit unless the pleural cavity is already open; occlusion of the non-ventilated lung's airway before the chest is opened 3,4 requires time for it to be beneficial (estimated between 6 and 15 minutes); 3,4 and while connecting the non-ventilated lung to an oxygen source 5 effectively ensures ongoing apneic oxygenation, 6,7 there will be no accompanying obligatory reduction of volume as will occur in an occluded lung. The open-closed airway technique 1 overcomes these shortcomings. The one theoretical risk of the open-closed airway technique would be its use for a prolonged period in the presence of extensive pleural adhesions. 5 Oxygen uptake will continue as the airway-occluded non-ventilated lung is freed from the chest wall 5 and will result in a time-dependent reduction in pressure in the lung, 8 generated from the alveoli and measurable throughout the hemithorax (unlike airway suctioning where the lung itself is likely largely protected by small airways closure). Thus, if pleural adhesions delay lung collapse, or airway occlusion is planned before pleurotomy, 3,4 airway, alveolar, and interstitial pressures will fall before the chest is opened 5 or before the lung can collapse due to the adhesions. Since pulmonary arterial and venous pressures are negligibly affected, there is a theoretical risk of unilateral pulmonary edema under these circumstances. Whether this new open-closed airway technique will provide ideal operating conditions or improve patient outcomes in patients undergoing thoracoscopic surgery compared with other one-lung ventilation methods remains to be established. However, comparing different one-lung ventilation practices is complicated by the fact that thoracic surgical patients often have varying degrees of underlying chronic obstructive pulmonary disease and emphysema. Perhaps 'within-patient' studies conducted prior to a planned surgical procedure should be considered. Although time-consuming, 9 such studies would enable two different one-lung ventilation techniques to be undertaken in the same patient, with a 'return to baseline' performed between them. The information gained from visual assessments made five and ten minutes after the start of one-lung ventilation could potentially help with decision-making about optimal surgical conditions for delicate procedures such as intersegmental plane identification prior to segmentectomy. Randomized controlled trials, on the other hand, do not accommodate the differences in patient pathophysiology, 10 and are unlikely to be helpful. 1.Huang R, Wang N, Lin X, et al. Facilitating lung collapse for thoracoscopic surgery utilizing endobronchial airway occlusion preceded by pleurotomy and one-minute suspension of two-lung ventilation. J Cardiothorac Vasc Anesth 2024; 38:475-81.2.Li Y-L, Hang L-H. Recommendations and considerations for speeding the collapse of the non-ventilated lung during single-lung ventilation in thoracoscopic surgery: a literature review. Minerva Anestesiol 2023; 89:792-803.3.Zhang Y, Yan W, Fan Z, et al. Preemptive one lung ventilation enhances lung collapse during thoracoscopic surgery: A randomized controlled trial. Thorac Cancer 2019; 10:1448-52.4.Somma J, Couture ÉJ, Pelletier S, et al. Non-ventilated lung deflation during one-lung ventilation with a double-lumen endotracheal tube: a randomized-controlled trial of occluding the non-ventilated endobronchial lumen before pleural opening. Can J Anaesth 2021; 68:801-11.5.Pfitzner J, Peacock MJ, Daniels BW. Ambient pressure oxygen reservoir apparatus for use during one-lung anaesthesia. Anaesthesia 1999; 54:454-8.6.Pfitzner J, Pfitzner L. The theoretical basis for using apnoeic oxygenation via the non-ventilated lung during one-lung ventilation to delay the onset of arterial hypoxaemia.[erratum appears in Anaesth Intensive Care 2006; 34:114]. Anaesth Intensive Care 2005; 33:794-800.7.Jung DM, Ahn HJ, Jung SH, et al. Apneic oxygen insufflation decreases the incidence of hypoxemia during one-lung ventilation in open and thoracoscopic pulmonary lobectomy: A randomized controlled trial. J Thorac Cardiovasc Surg 2017; 154:360-6.8.Moreault O, Couture EJ, Provencher S, et al. Double-lumen endotracheal tubes and bronchial blockers exhibit similar lung collapse physiology during lung isolation. Can J Anaesth 2021; 68:791-800.9.Pfitzner J, Peacock MJ, Harris RJ. Speed of collapse of the non-ventilated lung during single-lung ventilation for thoracoscopic surgery: the effect of transient increases in pleural pressure on the venting of gas from the non-ventilated lung. Anaesthesia 2001; 56:940-6.10.Pfitzner J. Evidence-based medicine: time to upend the pyramid for some clinical situations? Br J Anaesth 2018; 120:1134-5. John Pfitzner: Writing – review & editing, Writing – original draft, Conceptualization. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.