Teaching guided fibreoptic nasotracheal intubation

An anaesthetic technique suitable for training in fibreoptic intubation is described. It uses a capped oropharyngeal airway which leaves the nose free for fibreoptic intubation and allows the airway to be maintained and ventilation to be controlled if necessary. An assessment is made of the technique after 50 fibreoptic intubations with the Olympus LF-1 fibrescope. There were no failed intubations and no serious complications.     

Cardiovascular effects of fibrescope-guided nasotracheal intubation

The cardiovascular effects of fibrescope-guided nasotracheal intubation were compared to those of a control group of patients who were intubated using the Macintosh laryngoscope. The 60 patients studied received a standard anaesthetic technique which included a muscle relaxant and were allocated randomly to one of two groups immediately before tracheal intubation. Systolic and diastolic arterial pressures in the fibreoptic group were significantly lower than in the control group during the first minute after intubation. The maximum increase in diastolic pressure was significantly lower in the fibreoptic group. The heart rate in the fibreoptic group was significantly higher than in the control group during all five minutes after intubation. The maximum increase in heart rate was significantly higher in the fibreoptic group. The cardiovascular responses to fibreoptic nasotracheal intubation under general anaesthesia should not cause undue concern in fit patients, but appropriate measures should be taken to prevent excessive tachycardia in compromised patients.     

Simulated difficult intubation

A randomised study was carried out to compare the efficacy of the gum elastic bougie and the stylet in a simulated difficult intubation. A laryngoscopy assessment, as described by Cormack and Lehane, was made in 100 patients. A Grade 3 view was then simulated. In the Bougie First Group (50 patients) two attempts were made to pass a gum elastic bougie and a tracheal tube into the trachea. If these first two attempts were not successful, two further attempts at intubation were allowed with a stylet placed in the tracheal tube. In the Stylet First Group (50 patients) the order was reversed. After two attempts the tube was correctly placed in the trachea in 96% of cases in the Bougie First Group compared to only 66% of cases in the Stylet First Group (p < 0.001). We recommend that a gum elastic bougie should be readily available and that anaesthetists should use it in preference to a stylet whenever a good view of the glottis is not immediately available.     

A laryngoscope adaptor for difficult intubation

Tracheal intubation may be hindered by difficulty in insertion of the laryngoscope blade into the patient's mouth because the handle impinges on the patient's chest or on the hand of an assistant applying cricoid pressure. An adaptor is described which modifies the standard Penlon laryngoscope to enable lateral swivelling of the handle, thus avoiding the obstruction.     

Successful difficult intubation

The reliability of two signs of tracheal placement of a gum elastic bougie was studied. These signs were clicks (produced as the tip of the bougie runs over the tracheal cartilages) and hold up of the bougie as it is advanced (when the tip reaches the small bronchi). Ninety-eight simulated and two genuine Grade 3 difficult intubations were attempted with the aid of a gum elastic bougie. Seventy-eight tracheal and 22 oesophageal placements of the bougie resulted. No clicks or hold up occurred with the bougie in the oesophagus. Clicks were recorded in 89.7% of tracheal placements of the bougie. Hold up at between 24-40 cm occurred in all tracheal placements. We conclude that these signs are reliable and that they should be taught as part of any difficult intubation drill in which the gum elastic bougie is used.     

Tissue expander causing iatrogenic difficult intubation

Difficulty during tracheal intubation may occur due to a number of anatomical factors and pathological conditions. These factors may be influenced by earlier surgical manoeuvres, so that dificulty may occasionally be encountered at subsequent operation. One such case of'iatrogenic'dificulty, where a tissue expander beneath the anterolateral skin of the neck caused transient intubation problems, is reported.     

To shape or not to shape...simulated bougie-assisted difficult intubation in a manikin

Thirty anaesthetists attempted to place a derived 'optimal' curve bougie or a straight bougie in the trachea of a manikin, in a randomised cross-over study. A Grade 3 Cormack and Lehane laryngoscopic view was simulated. The anaesthetists were blinded to success (tracheal placement) or failure (oesophageal placement). The success rates with the curved and straight bougies were 83 and 7%, respectively, giving a difference (95% confidence interval) of 77% (54-87%) between the two bougies (p < 0.0001). On a separate occasion, under identical laboratory conditions, 30 anaesthetists attempted to place a straight coudé (angled)-tipped bougie or a straight straight-tipped bougie in the trachea of a manikin. The success rates with the coudé- and straight-tipped bougies were 43 and 0%, respectively, giving a difference (95% confidence interval) of 43% (21-61%) between the two bougies (p < 0.001). These results suggest that bougies used to facilitate difficult intubation should be curved and have a coudé tip.     

Identifying the more patent nostril before nasotracheal intubation

We have studied the reliability of two simple pre-induction tests used to select the more patent nostril for nasotracheal intubation by comparing their results with those obtained from fibreoptic examination of the nostrils, in 75 maxillo-facial patients requiring nasotracheal intubation under general anaesthesia, who had no history of nasal obstruction. The tests comprised (1) estimation of the rate of airflow through each nostril during expiration by palpating the passage of air when the contralateral nostril was occluded, and (2) asking for the patient's assessment of airflow through the nostrils, following the administration of a vasoconstrictor. After each test, noses were classified as left or right nostril clearer or nostrils equally clear. After the induction of general anaesthesia, bilateral nasendoscopies were performed and videotape recordings of these were later analysed by an otolaryngologist who had no knowledge of the test results. Intranasal abnormalities were identified and noses were again classified as left or right nostril clearer or nostrils equally clear. There was no significant difference between the overall diagnostic success rates of the two tests (44% and 47%, respectively). In patients with intranasal abnormalities, the numbers of correct diagnoses made by the two tests were not significantly different and were also not significantly different from the number of correct selections made if only the right nostril or only the left nostril had been used for the intubation. In view of the relatively high diagnostic failure rates, anaesthetists should not rely on the two tests investigated when selecting the best nostril for nasotracheal intubation.     

A comparison of simulated difficult intubation with multiple-use and single-use bougies in a manikin

In a randomised cross-over study, 20 anaesthetists attempted to place a multiple- or single-use bougie in the trachea of a manikin, in which a grade 3 Cormack and Lehane laryngoscopic view was simulated. The anaesthetists made two attempts at placement with each bougie and were blinded to success (tracheal placement) or failure (oesophageal placement). The success rates for the first attempts with the multiple- and single-use bougies were 85 and 15%, respectively [mean (95% CI) difference between the two bougies 70% (40-84%); p < 0.001]. The success rates for the second attempts were similar to those for the first attempts with both bougies. There is an increased risk of failure to intubate the trachea when using a single-use bougie, and this must be weighed against the unquantified risk of cross-infection from prions when using a multiple-use bougie.     

Predicting difficult intubation

Two pre-operative tests for the prediction of difficult intubation are assessed. A modified Mallampati test and a measurement of thyromental distance were performed at the pre-operative visit of 244 patients whose tracheas were subsequently intubated under general anaesthesia. Patients in whom the posterior pharyngeal wall could not be visualised below the soft palate, who also had a distance of less than 7 cm between the prominence of the thyroid cartilage and the bony point of the chin proved significantly more likely to present difficulty with intubation. The performance of these two simple tests on all patients before operation should allow the majority of cases of difficult intubation to be anticipated.     

Nasotracheal intubation for head and neck surgery

Nasotracheal intubation offers the head and neck surgeon more scope for surgical manoeuvre in operations of the mouth, pharynx, larynx and also the neck. Concern over the complications of using this route of intubation and lack of training may be limiting its use. A thorough knowledge of the anatomy, benefits of using nasal vasoconstrictors and attention to technique are prerequisites to maintaining the skill. This article reviews each of these topics and aims to encourage the appropriate use of nasotracheal intubation in current practice.     

Local anaesthesia for awake fibreoptic nasotracheal intubation

BACKGROUND: Awake fibreoptic nasotracheal intubation (FNI) is performed in potentially difficult airways under local anaesthesia. This observer-blinded study was designed to evaluate the efficacy of upper airway anaesthesia produced by nebulized lignocaine against combined regional block (CRB) for awake FNI. METHODS: Forty-eight ASA 1 adults were randomly allocated to receive 4 ml of 4%-nebulized lignocaine (nebulization group) or translaryngeal block, bilateral superior laryngeal nerve block and three 4% lignocaine-soaked cotton swabs in the nose (CRB group). Facial grimace and patient comfort were assessed by grimace and airway reactivity scores. Patients reported their discomfort on a 4-point score. RESULTS: All patients underwent successful FNI without significant discomfort; 79% in the nebulization group and 83% of the patients in the CRB group reported the procedure to be comfortable. A higher grimace score was recorded on insertion of the endotracheal tube (ETT) through the nostril in the nebulization group when compared to the CRB group, P<0.005. Similarly, patients in the CRB group were more comfortable during passage of the ETT into the glottis, as compared to the nebulization group. A progressive increase in heart rate was observed in all patients from the beginning of the procedure, but the rise in the nebulization group was greater, (P<0.05) and also lasted longer than in the CRB group (P<0.05). Mean arterial pressure was higher in the nebulization group when compared to the CRB group (P<0.05), with patients belonging to the CRB group demonstrating considerable haemodynamic stability. CONCLUSIONS: Both nebulization and CRB produced satisfactory anaesthesia of the upper airway, but CRB provided better patient comfort and haemodynamic stability.     

Comparison of a new video-optical intubation stylet versus the conventional malleable stylet in simulated difficult tracheal intubation

Handling and efficacy of a new video-optical intubation stylet were assessed in a simulated difficult tracheal intubation setting and compared with a conventional malleable stylet. Forty-five anaesthetists performed 10 tracheal intubations using both techniques. Laryngoscopy was performed by the observer, who created a grade 3 view according the classification by Cormack and Lehane. The time taken to place the tracheal tube and the final tracheal tube positions were documented. Mean (SD) intubation time for the video-optical stylet was 20.4 (7.7) s and for the malleable stylet 10.2 (3.3) s (p<0.01). With the video-optical stylet the trachea was correctly intubated in all 225 attempts; with the malleable stylet 44 (19.6%) oesophageal and 44 (19.6%) endobronchial intubations occurred (p<0.01). The video-optical intubation stylet enabled us to recognise inappropriate tracheal tube positions and to correct them immediately. This equipment can be considered a reliable and effective tool for management of the difficult airway.     

Learning curves for fibreoptic nasotracheal intubation when using the endoscopic video camera

We have followed the progress of 12 anaesthetic trainees as they learnt how to perform fibreoptic nasotracheal intubation with the aid of an endoscopic video camera system. Each trainee had a structured teaching session on a bronchial tree model, viewed an instructional videotape and then performed 20 nasotracheal intubations on anaesthetised oral surgery patients. Trainees were required to perform the endoscopies under full visual control and to demonstrate airway anatomy as they advanced the fibrescope. They were allowed up to two 2½ min periods to complete nasotracheal endoscopy. All 240 endoscopies were completed within the time limit: 228 were completed within 2½ min and 12 (5%) were completed during the second 2½ min period. We constructed a group learning curve from the pooled data. The half-life of the curve was nine endoscopies. The best fit value for the first endoscopy time was 132 s, and after the 18th (two half-lives) it was 49 s. We analysed the theoretical basis for deriving a learning curve from raw data. This information could form a rational basis for the design of fibreoptic training programmes using video imaging systems.     

The rigid nasendoscope as a tool for difficult tracheal intubation: a manikin study

We examined the use of the 30 degrees rigid nasendoscope in aiding difficult tracheal intubations. A Cormack and Lehane grade 4 difficult intubation (no view of glottis or epiglottis) was set up on a manikin. After 10 s of tuition, 40 anaesthetists attempted to pass a standard gum elastic bougie between the cords, with and without the nasendoscope, in randomised order. A bougie curved to an 'optimal curve' was also tested. Using the standard bougie 13/40 (33%) passed the bougie between the cords without the nasendoscope, compared with 31/40 (78%) when using the nasendoscope (p < 0.001). The 'optimal curve' bougie resulted in 29/40 (73%) and 39/40 (98%) success rates without and with the nasendoscope, respectively (p = 0.004). The nasendoscope is a simple and easy to use tool in grade 4 intubation, and results are improved further by the use of an 'optimal curve' bougie.     

Accidental bronchial intubation with RAE tubes

Performed tracheal tubes are used frequently in paediatric anaesthesia. A feature which contributes to their popularity is the belief that they can be positioned more reliably than conventional tracheal tubes because of their design. We studied a group of 40 patients in whom the incidence of bronchial intubation was 20%. The tube was too long in 32% of patients, although the tube size was appropriate for the child's age in all patients. The consequences and outcome of this complication are discussed.