Evone® Flow-Controlled Ventilation During Upper Airway Surgery: A Clinical Feasibility Study and Safety Assessment

Abstract

Introduction: During upper airway surgery in a narrowed airway due to tumor or stenosis, safe ventilation, good laryngotracheal exposure, and preservation of an adequate surgical working space are of paramount importance. This can be achieved by small-lumen ventilation such as High Frequency Jet Ventilation (HFJV). However, this technique has major drawbacks, such as air-trapping and desaturation in patients with poor pulmonary reserve. Recently, an innovative ventilating system with flow-controlled ventilation (FCV) and a small-lumen endotracheal tube, the Evone® (Ventinova, Eindhoven, The Netherlands), was introduced, claiming to counter the drawbacks of HFJV. Objectives: To evaluate feasibility and safety of the Evone® FCV system in difficult upper airway surgery and to critically appraise this novel ventilation method. Patients and methods: Evone® is a FCV-device using a small-bore cuffed tube (Tritube®). This ventilator actively sucks air out of the lungs, rather than relying on the passive backflow of air like in HFJV. Data related to the medical history, surgery, and anesthesia of all consecutive patients undergoing upper airway surgery with Evone® FCV ventilation were included in a tertiary center retrospective observational study. Results: Fifteen Patients, with a median age of 54 years, were included. Surgical procedures and indications included laser-assisted endoscopic treatment of idiopathic subglottic stenosis (n = 3), tracheal stenosis (n = 1), and posterior glottic stenosis (n = 2), biopsy and/or Transoral Laser Microsurgery for laryngeal (pre)malignancy (n = 7) and resection of benign lesions with posterior (supra)glottic location (n = 2). Mean ventilation duration was 52.0 min (range 30-115 min, SD 19.6 min), mean surgery duration was 31.7 min (range 15-65 min, SD 13.2 min), mean minimal SaO2 was 96.3% (range 89-100%, SD 4.0%) and mean peak pCO2 was 41.4 mmHg (range 31-50 mmHg, SD = 5.5 mmHg). No anesthesia- or surgery-related complications, adverse events or intra-operative difficulties were reported during or after any of the 15 procedures. In all cases, compared to HFJV, Evone® FCV ventilation allowed a superior visualization and working space during the surgical procedure. Conclusion: The Evone® FCV ventilation system provides excellent conditions in patients undergoing upper airway surgery, as it combines excellent accessibility and visibility of the operation site with safe and stable ventilation.

Keywords: flow-controlled ventilation; high frequency jet ventilation; idiopathic subglottic stenosis; laryngeal cancer; laryngotracheal stenosis; transoral laser microsurgery.

Copyright © 2020 Meulemans, Jans, Vermeulen, Vandommele, Delaere and Vander Poorten.

Figures

Figure 1

The Tritube® small-bore tube.

Figure 2

Evone® ventilator connected to the Tribute® tube.

Figure 3

Peroperative view of the control screen of the Evone®.

Figure 4

Figure illustrating the difference in airway pressure (paw) curve of the conventional volume-controlled ventilation (VCV) vs. the flow-controlled ventilation (FCV) of the Evone®. In VCV, the paw decreases exponentially, giving a “bended” curve during expiration. In FCV, this part of the curve has been linearized, meaning that the flow is constant during the whole expiration.

Figure 5

Working mechanism of the Evone® (Bernoulli principle). During the inspiratory phase, tube B, which is simply an air outlet out of the ventilator, is blocked. Therefore, the air that is forced through tube A (air inlet) is insufflated into the lungs of the patient through tube C (the endotracheal small-bore tube). During the expiratory phase, tube B is automatically opened. Therefore, the high-speed air that is insufflated through tube A shoots through tube B. This generates a low pressure, actively suctioning air out of tube C. This phenomenon relies on the Bernoulli principle and is called jet entrainment.

Figure 6

Peroperative microscopic view of the glottis and subglottis after CO2 laser radial incisions in an idiopathic subglottic stenosis (Cotton-Myer grade III) have been performed. Hence the small bore tube (star) allowing minimal traumatic intubation and creating an ideal exposure and working space while maintaining stable ventilation.

Figure 7

Endoscopic view on an idiopathic subglottic stenosis (Cotton-Myer grade III). The small bore tube (star) allowed for intubation of this severe stenosis. In these severe cases, HFJV could be problematic due to obstruction of the passive air backflow. This problem is tackled in FCV, allowing for good and stable ventilation.

Figure 8

Endoscopic view on a cT2N0 infiltrating squamous cell carcinoma of the right vocal fold with submucosal extension in the sinus of Morgagni. Thanks to the small bore tube (star), margin assessment and achievement of a free posterior margin during TLM are not hindered.

Figure 9

Endoscopic view on a cT1N0 infiltrating squamous cell carcinoma of the right vocal fold. Thanks to the small bore tube (star), an adequate surgical workspace is created.

Figure 10

Microscopic view after right-sided posterior cordotomy in a patient with posterior glottic stenosis. The posteriorly located surgical field is not obstructed by the Tritube® (star), and allowed a quick and uncomplicated procedure.

Figure 11

Endoscopic view on a posterior glottic stenosis. The small bore tube (star) provides excellent view on the posterior glottis, without interfering with the evaluation of arytenoid mobility and performance of a posterior cordotomy.