Effectiveness of the endotracheal tube cuff on the trachea: physical and mechanical aspects

Pre-hospital emergency cricothyrotomy in dogs part 2: Airway sealing and ventilation using cricothyrotomy tubes

Cricothyrotomy (CTT) has been recommended for use in the pre-hospital setting for military working dogs and Operational K9s during airway emergencies. Although the CTT can establish a patent airway for spontaneous ventilation, the ability to seal the airway and provide positive pressure ventilation (PPV) using tubes designed for humans has not been determined. Using various CTT tubes placed in cadaver dog airways, this study aimed to determine: (1) Whether the tube cuff could create a functional airway seal with safe intra-cuff pressures; (2) The magnitude of delivered tidal volume (TV) loss during a standard breath to assess the possibility of delivering an adequate tidal volume with a bag-valve device (BVM); (3) The best performing tubes for either test; (4) The reasons behind the findings using observations from upper airway endoscopy, dissection, and measurements. Cadaver dogs of similar weights to MWD and Operational K9 breeds had various CTT tubes placed including three from commercial kits, a standard endotracheal tube, and a tracheostomy tube. The minimum occlusive volume technique was used to inflate the tube cuff and a pressure ≤ 48 cm H₂O with an adequate seal was considered successful. Individual TVs were calculated for each dog and added to the volume lost during delivery of a standard breath from an ICU ventilator. Endoscopy and airway dissection were performed to assess the relationship between tubes cuffs and the airway. The tubes from the CTT kits performed poorly with regards to producing an airway seal with the H&H tube failing to seal the airway all tests. Tracheal dimensions were significantly associated with successful airway sealing (P = 0.0004). Tidal volume loss could be compensated using a BVM in 34/35 tests with the H&H tube in cadaver 8 the only to fail. Tracheal airway sealing is influenced by airway anatomy when tube cuffs are inflated to a target pressure and larger tubes do not always provide a better seal. The CTT tubes tested have the potential to facilitate ventilation with a BVM under the conditions set in this study. The 8.0 mm endotracheal tube performed the best and the H&H the worst in both tests.

Evaluation of audible leak versus pressure volume loop closure for polyvinyl chloride cuff and polyurethane microcuff in endotracheal tube inflated with air: a prospective randomized study

Cuff pressure of endotracheal tube (ETT) must be high enough to seal the trachea, and must be low enough to allow adequate perfusion of tracheal mucosa. Compared with polyvinyl chloride (PVC) cuffed tubes, polyurethane cuffed tubes protect more efficiently. Different methods of ETT cuff pressure maintenance in practice have been reported. We planned to compare ETT cuff pressure using different techniques in PVC and polyurethane microcuff tubes in a prospective randomized study. Eighty surgical patients between 16-65 years belonging to American Society of Anesthesiologists physical status I-III, scheduled for orotracheal intubation under general anaesthesia, were included. All enrolled patients were randomized into four groups (n = 20 per group), followed by corresponding treatments, including intubation by PVC ETT or polyurethane microcuff ETT and cuff inflation by auscultation of audible leak or pressure volume loop. Amount of air required to inflate cuff was more in polyurethrane tube as compared to polyvinyl tube. While comparing the two methods of cuff inflation, less volume of air was required in pressure volume loop method. We concluded that PVC cuff tube and polyurethane microcuff tube both are safe tubes used in adult patients. However, when inflated using same technique polyurethane microcuff tubes required larger volume to inflate cuff. Further, pressure generated in polyurethane microcuff tubes in much lower than PVC tubes. The study was approved by the Institutional Ethics Committee of Pt B D Sharma, PGIMS, Rohtak (No. IEC/Th/18/Anst15) on January 20, 2018 and registered with Clinical Trials Registry-India (registration No. CTRI/2019/01/017170) on January 18, 2019.

Evaluation of the Efficiency of the Atraumatic Endotracheal Tube in the Pulmonary-Gas Exchange: an Experimental Study

OBJECTIVE

Mechanical ventilation is frequently necessary, in which case the use of an endotracheal tube is mandatory. The tube has an inflatable balloon in its distal extremity, whose aim is, among other functions, an efficient arterialization. However, serious injuries in the place of contact of the balloon with the trachea can be frequent. Some studies point out that balloons with permanent pressure may reduce this complication. Nevertheless, air scape, expressed by the inspiratory (IV) and expiratory volume (EV) variation (Δ IV-EV), may occur, possibly leading to hypoxemia. Thus, the goal of this study was to verify the efficiency of a modified endotracheal tube on arterializations compared to the traditional endotracheal tube.

METHODS

The modified endotracheal tube presents intermittent insufflation, with three drillings in the internal region of the cuff, allowing for insufflation in the inspiratory phase of the mechanical ventilation. Three animals were used for the control group, with a cuff pressure of 30 cmH₂O, and seven pigs had the modified endotracheal tube. Each animal was kept under mechanical ventilation (FIO₂=0.21) for 6 hours. Arterial and venous gases were measured every three hours (T₀; T₃; T₆).

RESULTS

The gases confirmed the lack of hypoxia between the Groups, with a difference in the ΔIV-EV at T0 (P=0.0486).

CONCLUSIONS

In this study, the lack of hypoxia showed the efficiency of the modified endotracheal tube. However, new studies are necessary, particularly in diseased lungs, in order to evaluate the real efficiency of the mentioned device on the pulmonary gas exchange.

Failed intubation of an unanticipated postintubation tracheal stenosis: a case report

Encountering a patient with unanticipated laryngotracheal stenosis (LTS) during anesthetic induction is challenging for an anesthesiologist. Because routine history taking and pre-anesthetic evaluation cannot rule out the possibility of LTS, other measures should be taken. Perioperative airway maintenance is considered crucial for avoiding complications such as airway edema, bleeding, obstruction, collapse, and ultimately respiratory failure and arrest. We report an unanticipated tracheal stenosis discovered during anesthetic induction that hindered endotracheal intubation. Because airway maintenance was difficult, we postponed surgery until determining the cause of the difficult entry, considered possible therapeutic approaches (both anesthetic and surgical), and provided successful surgery with a continuous epidural block.