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* From the Departments of Anaesthesia and Intensive Care and Neonatology,
University Children's Hospital, Zurich, Switzerland.
Address Correspondence to : Dr. Markus Weiss, Department of Anaesthesia, University Children's Hospital, Steinwiesstrase 75, Zurich, Switzerland. Phone: +41 1 266 71 11; Fax +41 1 266 71 68; E-mail: markus.weiss{at}kispi.unizh.ch
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Abstract |
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Methods: In 50 pediatric patients (mean age 12.8 ± 3.1 yr, range 6–16 yr) a grade 3 direct laryngoscopic view was simulated. Eight certified registered nurse anesthetists without experience in endoscopic intubation performed tracheal intubation on five or more patients using the video-optical intubation stylet. Time from insertion of the tube into the oral cavity until the tip had passed the vocal cords was recorded. Failed intubation was defined as intubation >60 sec, arterial oxygen saturation <92% or esophageal intubation. Subjective degree of difficulty was asked from the operators using a Likert-scale.
Results: Forty-six of the 50 patients were successfully intubated within 60 sec and without arterial oxygen desaturation. In four patients, video-assisted tracheal intubation failed due to prolonged intubation time. Intubation times ranged from 10–40 sec (median 15 sec). Mean intubation time in the first patient (24.5 ± 17.3 sec) appeared longer than for the fifth patient (20.8 ± 10.9 sec), but the difference was not statistically significant (P=0.87). Mean estimated degree of difficulty was 3.9 ± 2.1. Subjective estimates of difficulty increased with intubation times (P=0.001).
Conclusion: The video-optical intubation stylet can be considered a valuable aid for tracheal intubation in pediatric patients with a difficult airway.
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Introduction |
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Recently, we reported on the use of a video-endoscopic system within the tracheal tube for supervising tracheal intubation in pediatric patients.13 The video-display allowed the supervisor to instantly recognize malpositioned endotracheal tubes (ETT). It also provided a simple and rapid assistance to endoscopic intubation during impaired direct laryngoscopic view of the cords.
The aim of the present study was to evaluate systematically the efficacy of video-intuboscopic assisted tracheal intubation using a malleable video-optical intubation stylet (VOIS) in a setting simulating difficult intubating conditions.
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Methods |
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). An antifog agent was applied to the lens tip using a sterile gauze. The viewfinder is attached to a conventional video-endoscope camera and the standard Storz light adapter is connected to a light source by means of a light cable.
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). After passing the vocal cords, the VOIS was transiently drawn back, before advancing the ETT further down the trachea. Finally, tracheal ETT position was confirmed or adjusted by means of the monitor display. After removing the VOIS from the ETT, correct placement was confirmed by auscultation and capnography.
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The time requirement from insertion of the ETT into the oral cavity until the tube tip had passed the vocal cords, as indicated on the video-monitor, was recorded. Failed intubation was defined as intubation time exceeding 60 sec (potentially leading to hypoxemia in the insufficiently pre-oxygenated patient or critically ill patient with limited respiratory reserves), esophageal intubation or if arterial oxygen saturation fell below 92% during intubation. Visibility of the subglottic airway anatomy after passing the cords and of the tracheal carina on the monitor was recorded. Difficulties with, and attributed to, the fibre-optic stylet during intubation were recorded. After completing the procedure, participants had to estimate the subjective degree of difficulty with regard to intubation on a ten-point Likert-scale ranging from 1 (=very simple) to 10 (=very difficult).
We evaluated, by means of Cox proportional hazard analysis, whether any of the following variables was associated with the time required for successful intubation: experience of the intubating nurse anesthetist in direct laryngoscopy (in years), estimated difficulty, sequence of intubation attempt; patient gender, age, weight or length and best direct laryngoscopic view. Simple regression analysis was conducted to explore associations between estimated difficulty and any of the aforementioned variables. A significance level of P <0.05 was employed.
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Results |
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Although the glottic opening was visualized very rapidly in all patients, insertion of the tube into the trachea was delayed by compromised saggital manoeuvring within the hypopharynx (requiring manual adjusting of the angled ETT tip) and due to the narrow airway in children.
While subglottic airway structures were visible in all successful intubations, visualisation of the tracheal carina was achieved only in 26 patients (52%) because of the angled tip and small viewing angle of the scope.
Mean estimated degree of difficulty was 3.9 ± 2.1 (median 3). Again, estimated degree of difficulty was strongly associated with intubation time (P=0.001, the latter explaining 76% of the observed variance in estimated difficulty). Experience in laryngoscopy and number of attempts retained a weak, but significant association.
No problems were reported in relation to the ETT being connected to the bedside monitoring system by way of an endoscopic cable or to the removal of the intubation stylet from the ETT. Fogging of the distal lens occurred in six patients, but the view was still sufficient to conduct the intubation procedure. In two patients improper initial placement of the ETT tip into the vallecula resulted in soiling of the lens by secretions and required subsequent cleaning.
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Discussion |
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If difficulties with intubation are expected, the use of sophisticated approaches such as fibre-optic intubation in the awake or carefully sedated patient can be performed with skilled assistance and extensive preparation. However, difficulties with intubation are not always predictable and not all anesthesiologists are familiar with the bronchoscopic technique. In the emergency situation, fibre-optic intubation is likely to take too long, especially in inexperienced hands.
The video-assisted intubation technique combines the advantages of guiding the intubation stylet during conventional laryngoscopy and of fibre-optic endotracheal intubation.
Our results demonstrate that nurse anesthetists, representing operators not experienced with bronchoscopic intubation, were able to intubate the trachea in a grade 3 situation using the view obtained from the tip of the ETT. The ease of video-assisted intubation was reflected by the high success rate and rapidity of intubation after only a few attempts, and the low subjective degree of difficulty. These results confirm our earlier data obtained in mannequin studies.15,16 The technique, if performed strictly and exactly as described, may be considered a useful alternative for managing unexpected difficult laryngoscopy.
Because the endoscopic intubation technique does not jeopardize patient safety, it can be taught daily, during conventional laryngoscopy, allowing the anesthesiologist to be prepared for patients with unexpected difficult laryngoscopy. The device, not containing steering mechanics or a suction channel, is less expensive approximately (2000 US$) and more robust, and therefore less susceptible to damage during handling, cleaning and preparing, than a regular (more sophisticated) fibre-optic bronchoscope.
If the VOIS is inserted into the ETT before starting anesthesia (standby mode), it can be used immediately without modification of the intubation procedure and without additional assistance, when endoscopic intubation is required. This can be useful for intubation with a rapid induction sequence or in patients with limited cardio-respiratory function. If not used for intubation, the VOIS at least may help to confirm tracheal tube position before it is removed from the ETT. Possibly, the technique may be also useful for patients in whom head-neck extension and cardiovascular response to forced laryngoscopy should be avoided.
The VOIS presented does not contain a port for suctioning or administering oxygen during tracheal intubation. This increases the susceptibility to problems inherent to fibre-optic scopes in general, such as fogging of the lens or interference with secretions and blood. A further limitation is the reduced manoeuvrability of the ETT tip due to the limited oro-pharyngeal space. This problem can be, partially, overcome by insertion and steering of the ETT from the angle of the mouth. Second, ETT insertion through the cords was affected by the narrow airway of children. This implies that a protruding stylet would be helpful to enter the glottis first, with subsequent passage of the ETT over the stylet. However, this requires a less traumatic and more flexible stylet to avoid airway trauma.
Recently, different fibre-optic stylets with viewfinders were developed to give a view from the tip of the ETT to a proximal viewfinder to facilitate difficult tracheal intubation.17,18 These can be used without external light sources and video-camera systems, and therefore are considered to be superior to video-optical equipped devices.18 However, in our opinion, video-transmission of the endoscopic view facilitates the endoscopic procedure, improves manual dexterity and allows nearly simultaneous observation of the video-display, patient and monitors in a comfortable and efficient position for intubation. The use of a miniature screen video system, as recently presented by Popat, considerably improves feasibility.19 Gravenstein et al. reported on a similar video-enhanced optical intubation stylet, but preferred to avoid direct laryngoscopy and to grasp the mandible and elevate the jaw and tongue during tracheal intubation.20
To use optical stylets alone without the use of a laryngoscope may reduce the potential hemodynamic changes and the morbidity associated with direct laryngoscopy.21,22 However, the presented video-intuboscopic intubation technique is not a primary endoscopic intubation technique but an option to aid conventional tracheal intubation when unexpected difficulties with direct laryngoscopy arise. In addition, the use of the VOIS with conventional laryngoscopy remains a familiar procedure, maintains the airway open, and reduces the risk of contamination of the distal lens by blood or secretions.20,23
Some caveats with regard to this study must be considered. We evaluated the technique in a simulated difficult intubation setting. Although it is an accepted model for testing, comparing and teaching intubation techniques, further experience with genuine grade 3 and 4 laryngoscopic view is required to confirm our preliminary results. Second, the study was performed in children, rarely presenting intubation difficulties in experienced hands. On the other hand, the limited manoeuvrability of the stylet and the smaller airways in children may increase the validity of the simulation model tested. Further studies would benefit from evaluating the presented technique in regard to complications such as trauma, bleeding or sore throat, particularly in comparison with other techniques such as tracheal intubation with the lighted stylet or tracheal intubation through the intubating laryngeal mask.
In conclusion, our preliminary clinical experience in children suggests that video-intuboscopic assisted tracheal intubation is a valuable and simple aid for intubation in the presence of unpredicted difficult laryngoscopy. Little training, even for anesthesiologists without experience in endoscopic intubation techniques, is required.
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Footnotes |
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Revision received April 4, 2001. Accepted for publication March 13, 2001.
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References |
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