Which laryngeal mask for fiberoptic-aided wire-guided catheter exchange tracheal intubation? The Classic-LMATM or the Proseal-LMATM: a mannequin study
A Joffe, E Liew
adults, airway management, critical care, difficult airway, simulation, wire-guided catheter exchange
A Joffe, E Liew. Which laryngeal mask for fiberoptic-aided wire-guided catheter exchange tracheal intubation? The Classic-LMATM or the Proseal-LMATM: a mannequin study. The Internet Journal of Anesthesiology. 2009 Volume 23 Number 1.
Grants, sponsors, and funding sources
The AirSim TM airway trainer used in this study was supported by intramural departmental funds
Use of a laryngeal mask (LMA) as a conduit for fiberoptic-aided tracheal intubation when unanticipated airway difficulty is encountered has been previously reported. One such technique, which utilizes a pre-packaged, commercially available, wire-guided airway exchange catheter set (Arndt Airway Exchange Catheter Set, Cook Critical Care, Bloomington, Indiana) and an LMA Classic TM (
Therefore, the primary aim of our study was to compare ease of use, operator preference, time to completion, and failure rates while performing a fiberoptic-aided wire-guided airway exchange tracheal intubation through the
Materials and Methods
The University of Wisconsin Health Sciences Minimal Risk Institutional Review Board approved the study. Written informed consent was obtained from all participants. Twenty-five physicians were invited and agreed to participate in the study (5 senior staff, 5 fellows, 5 third-year anesthesia trainees, 5 second-year anesthesia trainees, and 5 first-year anesthesia trainees). The 5 anesthesia staff were chosen for their considerable experience in this technique and served as the reference standard for intergroup comparisons. The least experienced anesthesia trainee had performed > 25 fiberoptic intubations in the operating room prior to participation. Each participant performed 4 intubations, 2 with each LMA.
All intubations were performed on an AirsimTM airway management trainer (Trucorp, Belfast, Ireland) through a #3
After preliminary use of the mannequin by the investigators to pilot the study protocol, the #3 LMA, rather than a #4 LMA was chosen as it was felt to increase the chances of a high-grade laryngeal view after LMA insertion by the participant. Repeated flipping of a coin randomized the order in which each LMA was used. Both the mannequin, the airway tubes of the LMA and the components of the airway exchange catheter set were pretreated with surgical grade silicone spray. Prior to LMA insertion, the posterior LMA cuff was treated with lubricant jelly as recommended by the manufacturer. All participants were similarly briefed regarding the procedure and performed the procedure without any assistance. After placement of the LMA, a 15mm bronchoscope adapter was connected to the LMA. With the FOS at the airway tube orifice, the position of the LMA was graded by one of the authors (AMJ, ECL) as viewed through the eyepiece of the FOS: 1=full view of the vocal cords, 2=partial view of the cords including arytenoids, 3=epiglottis only, or 4=other (LMA, cuff, pharynx, other). Timing was started when the FOS was handed to the participant. The operator passed the FOS via the LMA through the vocal cords and into the trachea. A 160 cm, unmarked, polytetraflouroethylene (PTFE) coated, 0.038 inch (0.96 mm) diameter Amplatz guide wire was then passed through the injection port of the FOS and advanced through the working channel until it could be visualized within the trachea beyond the tip of the scope. The scope was gradually removed with the guide wire under direct visualization using the FOS to assure that the wire remained in position. After the FOS was removed, a 70 cm, 14Fr (4.7mm OD) airway exchange catheter with guide markings every centimeter, was passed over the guide wire through the adapter into the trachea. The airway exchange catheter has a through-lumen design with distal side ports that allows continued ventilation during airway exchange procedures when an airway adapter is attached to the proximal end. The LMA was deflated and removed keeping both the guide wire and airway exchange catheter in the same relative position. A tracheal tube was then passed over the wire and exchange catheter; the airway exchange catheter and the guide wire were then removed, leaving the tracheal tube in place. Timing was stopped after two breaths were given. LMA reinsertion was not allowed once the FOS had been placed in the LMA. Operators were allowed to reposition the LMA over the FOS to improve their view of the vocal cords so long as the FOS stayed inside the airway tube of the LMA. Inability to manipulate the FOS or any other component of the exchange kit through the LMA was considered a failure of the technique. After each intubation attempt, the participant was asked to rate separately the interaction of the FOS and the LMA and the components of the catheter exchange set and the LMA: 1=easy, no resistance 2=slightly difficult, minor resistance 3=moderately difficult, moderate resistance 4=severe difficulty, severe resistance. Additionally, participants were asked to identify which LMA they preferred. No specific questions were asked other than those already recorded for the ease of intubation, only the overall subjective impression of the participant based on the entirety of their experience for each LMA.
For each experience grade, intubation times between each LMA were compared with Mann-Whitney U. The time from insertion of the FOS to tracheal intubation, between operators and LMA, was compared by one-way analysis of variance (ANOVA) with Bartlett’s test for equal variances and Dunnet’s multiple comparison test using staff and
Overall, the median rating for passing a FOS into the trachea was 1 (1-2 [1-3]) through the
The time to complete the wire-guided catheter exchange intubation is shown in table 1.
Staff intubated faster through the
There were 8 failures, 4 with each LMA. No anesthesia staff encountered intubation failure. Two failures were encountered in each of the other experience grades, but no single participant experienced more than 1 failure of their 4 attempts. In 4 cases, the esophagus was intubated. In another 4 cases, the tracheal tube could not be passed after the LMA was removed because of inadvertent dislodgement of the airway exchange catheter and wire from the trachea (2 cases) or airway exchange catheter only resulting in kinking of the wire in the posterior pharynx (2 cases).
The main findings of our study are that performing fiberoptic-aided tracheal intubation using the Arndt Airway Exchange Catheter Set was subjectively easier through a
The only effect of operator experience was between our reference standard, the experienced anesthesia staff, and first-year anesthesia trainees and fellows when intubating through the
Use of a LMA as a conduit for a fiberoptic-aided tracheal tube placement by a modified Seldinger technique is not new. Clinical reports have described a similar technique to ours. Rajan described the use of a 5Fr 60 cm tracheal tube introducer modified by perforating the distal tip with a 16-guage needle and cutting away the proximal 1 cm and a 140 cm 0.35 mm diameter guide wire used in a manner similar to what we described (7). Warrilow reported using a Corpak Nasointestinal feeding tube and guide wire (VIASYS Healthcare Medsystems Division, Wheeling, Il.) in place of an airway exchange catheter and guide wire (8). As with the technique reported by Rajan, modification of the equipment by cutting off the terminating connector and side port so that the tracheal tube could fit over it was required. Additionally, the tracheal tube was finally placed using direct laryngoscopy with Magill’s forceps to guide the feeding tube/tracheal tube apparatus over the wire. Neither technique utilized equipment specifically designed for the task. Most distinguishable from our procedure, the techniques of Rajan and Warilow require equipment not readily available in an emergency situation. Most recently, the pre-packaged, wire-guided airway exchange kit we describe has been used successfully in a series of critically ill adults who could not be intubated by direct laryngoscopy (1).
We acknowledge that studies performed on airway mannequins gives limited insight into actual clinical practice. However, the mannequin used in our study is reported to be a high fidelity model for LMA insertion (9) and has accurate airway anatomy. In addition, we studied the two LMA devices most commonly used for airway rescue, the
In summary, operators with varying degrees of experience are able to perform tracheal intubation by wire-guided catheter exchange with little difficulty through both the