small lumen 

Conventional small lumen ventilation: A lifesaver with drawbacks

Ventilation through small lumen is clinically valuable in emergency “Cannot Intubate, Cannot Oxygenate” (CICO) situations, (anticipated) difficult airways and laryngeal surgery. Conventional ventilation fails in cases of severe airway obstruction, as the thick tube that is needed to enable effective ventilation cannot be advanced through the airways.

Needle cricothyroidotomy in conjunction with Transtracheal Jet Ventilation (TTJV) has been used as a last option to avoid death in CICO situations ^1-3. In TTJV, oxygen is injected percutaneously under high pressure (e.g. 1.5 bar or higher) via a narrow-bore cannula, typically with an internal diameter of 2 mm. Because of the high resistance of this cannula, the expiration then relies on passive egress of gas via mouth or nose. Thus, to avoid a dangerous pressure buildup in the airways during repeated injections of oxygen, the airway should remain well open. As a consequence, in situations of partial or even complete airway obstruction, TTJV can lead to barotrauma-related lung damage such as pneumothorax or subcutaneous emphysema. As the high pressure buildup in the chest also affects blood circulation, this series of events is often followed by hemodynamic deterioration or even full cardiac arrest. Thus, despite the fact that TTJV can save lives in emergency CICO scenarios, it has clear safety drawbacks. A systematic review including 44 studies revealed that TTJV in CICO is associated with a high risk of barotrauma (32%), device failure (42%) or any other complication (51%) ⁴. 

During upper airway surgery, jet ventilation through a small lumen allows intubation of difficult airways and provides surgical space. As described above, airway patency is required to allow passive backflow of gases, which in turn causes movements of tissue (vocal cords) and secretions/debris, hampering the surgeon’s working conditions. To avoid these movements, periods of apnea may be applied. However, during apnea the surgeon has a limited amount of time to perform the required handling, which is considered stressful, and sequential periods of apnea will significantly add to the surgical time. Alternatively, the use of a cuffed micro-laryngeal tube with a smaller inner diameter (ID) than conventional tubes (5–6 vs. 7–8 mm) allows passive expiration in most cases and prevents the undesirable movement of anatomical and physiological structures. Moreover, the cuff seals the airway and protects the patient from aspiration. However, the 5 mm ID tubes in particular may cause ventilation issues as the pressure in the lungs cannot be reduced fast enough.

Use of a small lumen tube is not only beneficial during surgery, but also in the postoperative period: First, it reduces the risk of intubation-related complications such as sore throat, which can cause substantial discomfort, or tracheal stenosis caused by damage during intubation ^14,15. Second, guidelines and handbooks on the management of tracheal extubation state that small-bore tubes make extubation safer in high-risk patients, as these tubes should be left in situ until it is likely that reintubation will not be required ^12,13.

Figure 1. Comparison of ultrathin Tritube with conventional tubes. The small outer diameter of Tritube is beneficial during intubation, ventilation and extubation.

 EVA^®/FCV^® uniquely provides safe small lumen ventilation with full respiratory control

Due to the unique concept of controlling the full ventilation cycle by generating a constant and continuous flow, EVA^®/FCV^® enables safe and efficient ventilation through high-resistant small lumen tubes and catheters (ID 1.6 – 3 mm). EVA^®/FCV^® provides inspiration and active expiration through the same ventilation tube. It thereby allows the management of difficult airways and can save lives in CICO situations. Several research groups have consistently shown rapid reoxygenation using Ventrain (EVA^® technology) in animal models for CICO situations, where EVA^® was shown to be superior to conventional ventilation strategies ^16-19. Furthermore, numerous clinicians have reportedly saved the lives of babies and adults with this technology ^20-23. As such, EVA^® ventilation has been acknowledged as a real life-saving technology by key opinion leaders in handbooks and articles ^13,24,25.

EVA^®/FCV^® in conjunction with small lumen tubes and catheters has proven to be beneficial during various upper airway surgical procedures, avoiding the risk of barotrauma related to jet ventilation, or the need for an alternative tracheotomy ^26-30.

EVA^®/FCV^® allows the use of Tritube, an ultrathin cuffed endotracheal tube with an ID of only 2.4 mm, offering several new possibilities during laryngeal surgery. Tritube provides a large surgical exposure due to the OD of only 4.4 mm. Due to its cuff, it also offers a clear and hygienic sight for the surgeon, as undesired movement of vocal cords or debris is prevented (Figure 1). Dr. Kristensen published on the use of Tritube in combination with Ventrain in seven patients undergoing laryngeal surgery ³¹ (Figure 2). He noted that this arrangement provided an “unprecedented view of the intubated airway during oral, pharyngeal, laryngeal or tracheal procedures” and stated that the technique has the “potential to replace temporary tracheostomy, jet-ventilation or extra-corporeal membrane oxygenation in selected patients.” In this series of cases, two very complicated airway patients at high risk of losing the airway during intubation under anesthesia were intubated while awake. The described technique was slightly adapted and used by others ³². For safety reasons, one patient was transported to the PACU with a Tritube in place (with the cuff deflated) to ensure airway access in case of any postoperative swelling or bleeding. This patient was subsequently uneventfully extubated one hour after surgery ³².

Figure 2. Comparison of conventional MLT-6 tube (left) with Tritube (right) for management of difficult airway. Tritube provides improved view of the intubated airway. Adapted from Kristensen et al., Acta Anaesthesiol Scand 2017 ³¹.

Furthermore, the first observational multicenter study using Evone in combination with Tritube for patients undergoing ENT surgery shows stable ventilatory parameters throughout the procedures ³³. Videos illustrate good visibility of the laryngeal structures during and after placement of Tritube. With Tritube’s cuff deflated, patients could comfortably breathe spontaneously after emergence from anesthesia. The authors state that “FCV in combination with Tritube contributes to the armamentarium for airway management” ³³. Two randomized controlled trials additionally highlight the benefits of Tritube during ENT surgery: A study by Schmidt et al., comparing Tritube with a conventional MLT-6 tube, revealed a significantly reduced concealment of laryngeal structures (7±2 vs. 22±8 %, P<0.001) and improved surgical conditions as judged by residents in training (P=0.006) ³⁴. Preliminary data from a second study by Kristensen and colleagues, comparing Tritube with MLT-6 in patients with predicted difficult airways, revealed clearly improved intubation and surgical conditions in the Tritube patients versus the control group ³⁵. Additionally, this study showed that, with a deflated cuff, Tritube was equally well tolerated as compared to a standard tube exchanger when left in situ postoperatively, allowing patients to freely breathe and talk ³⁵.