Using the Ventrain With a Small-Bore Catheter: Ventilation or Just Oxygenation?

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The recent case report by Evers et al1 outlining the use of the Ventrain (Ventinova Medical, Eindhoven, the Netherlands) device for 1-lung ventilation through a 65-cm, 7-F Arndt Endobronchial Blocker (Cook Medical, Bloomington, IN) to facilitate the repair of an iatrogenic injury to the left main stem bronchus offered a potential solution to a very challenging clinical situation. In their patient, the posterior membranous aspect of the proximal left main bronchus had been inadvertently disrupted intraoperatively by a double-lumen endotracheal tube, thus requiring a right thoracotomy to facilitate the left bronchial injury site. To ventilate the left lung distal to this bronchial injury, the authors passed the blocker through the left lumen of the double-lumen endotracheal tube, advancing it beyond the bronchial breach. After inflating the blocker balloon, they attached the Ventrain ventilator device to the blocker’s proximal end and were then able to use the Ventrain to alternatively inflate and actively deflate the left lung, thus providing some “ventilation” for the 20 minutes taken to repair the bronchus. Accordingly, they reported that the partial pressure of carbon dioxide (PaCO2) rose to 87 mmHg by the end of the 20-minute repair. Although the partial pressure of oxygen measured at the same time (94 mmHg) indicated that the patient had been adequately oxygenated, the significant hypercapnia suggested that the patient was grossly underventilated (and arguably might not have been ventilated at all).
Use of the Ventrain device has been reported in a number of different situations,2,3 including a report where emergency ventilation using the device was achieved in a porcine model of complete upper airway obstruction.3 In that animal study, the Ventrain was operated via a 3-mm internal diameter, 100-cm long Airway Exchange Catheter (Cook Medical Inc) which allowed for adequate ventilation (ie, normal blood gases). In contrast, the narrow 7-F lumen blocker that Evers et al1 used had an internal diameter of only 1 mm, making it likely very difficult to provide adequate actively assisted expiration (a fundamental feature of Ventrain ventilation). As the PaCO2 in anesthetized and apneic patients has previously been reported to rise at a rate of 3.4 mmHg·CO2·minute−1,4 the 20 minutes required to repair the bronchus would have expected to lead to an approximate 60 mmHg increase in PaCO2 from the pre-Ventrain baseline, even if the patient was apneic. Importantly, this increase would have resulted in a PaCO2 close to the final value that they actually reported. As for the partial pressure of oxygen, the adequate oxygenation may simply have been a result of providing some small amount of oxygen insufflation into the distal bronchus to match the metabolic demands and alveolar oxygen uptake (ie, approximately 250 mL·minute−1 oxygen consumption5).
So although using the Ventrain through a 7F blocker may have allowed the oxygenation needed to safely complete a 20-minute surgical procedure, this might similarly have been accomplished if free flow of oxygen had been provided to the bronchus without any ventilation at all.3 Although the authors should rightly be enthusiastic about the potential for this combined Ventrain and Arndt blocker technique, it should perhaps be tempered pending more investigation of the adequacy of its ventilation capability in clinical practice.
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