I. P. Latto

Difficult Airway Society guidelines for management of the unanticipated difficult intubation

Problems with tracheal intubation are infrequent but are the most common cause of anaesthetic death or brain damage. The clinical situation is not always managed well. The Difficult Airway Society (DAS) has developed guidelines for management of the unanticipated difficult tracheal intubation in the non‐obstetric adult patient without upper airway obstruction. These guidelines have been developed by consensus and are based on evidence and experience. We have produced flow‐charts for three scenarios: routine induction; rapid sequence induction; and failed intubation, increasing hypoxaemia and difficult ventilation in the paralysed, anaesthetised patient. The flow‐charts are simple, clear and definitive. They can be fully implemented only when the necessary equipment and training are available. The guidelines received overwhelming support from the membership of the DAS.

Simulated difficult intubation.: Comparison of the gum elastic bougie and the stylet

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.

Successful difficult intubation Tracheal tube placement over a gum‐elastic bougie

A randomised study was carried out to assess the effect of tracheal tube rotation on the passage of a tube over a gum‐elastic bougie into the trachea in 100 patients. The effect of the presence or absence of a laryngoscope on successful tube placement was also assessed. A grade 3 difficult intubation was simulated in patients with a laryngoscope. There was a significant difference in the rates for successful first‐time intubation in those patients with tube orientation of ‐90° (with the bevel facing posteriorly) as compared with a tube orientation of 0° (the normal orientation with the bevel facing left). The unsuccessful first‐time intubations with a 0° orientation were frequently converted to successful intubations with the ‐90° position at a second attempt. The presence of a laryngoscope in the mouth while rail‐roading a tube over the bougie also made a significant difference to the rate of successful first‐time intubations. The most successful method was to leave the laryngoscope in the mouth and rotate the tube to ‐90°.

Respiratory complications associated with tracheal extubation. Timing of tracheal extubation and use of the laryngeal mask during emergence from anaesthesia.

Sixty patients were randomly allocated to one of three groups and the incidences of respiratory complications which occurred during emergence from anaesthesia were compared under the following three circumstances: tracheal extubation after the patient had regained consciousness (awake group); tracheal extubation while the patient was still anaesthetised (anaesthetised group); and the use of the laryngeal mask during emergence from anaesthesia (mask group). In the mask group, the laryngeal mask was inserted under deep anaesthesia before tracheal extubation and the lungs were ventilated through the laryngeal mask after tracheal extubation. In the awake group, straining (bucking) occurred in 18 patients and desaturation (arterial oxygen haemoglobin saturation < 95%) in two patients. In the anaesthetised group, airway obstruction occurred in 17 patients and desaturation in one of these patients. In the mask group, ventilation through the laryngeal mask was temporarily difficult immediately after tracheal extubation in one patient and coughing occurred before removal of the mask in three patients. No respiratory complications occurred in two patients in the awake group, three patients in the anaesthetised group and 16 patients in the mask group. The incidence of respiratory complications during recovery from anaesthesia was significantly lower in the mask group than in the other two groups (pooled) (p << 0.001). Therefore, the use of the laryngeal mask after tracheal extubation decreases the incidence of respiratory complications during recovery from anaesthesia.

The distance between the grille of the laryngeal mask airway and the vocal cords Is conventional intubation through the laryngeal mask safe

The distance between the grille of the laryngeal mask airway and the vocal cords was measured with afibreoptic bronchoscope in 30 male and 30 female patients. The mean distance was 3.6 cm (SD 0.5 cm; range 2.5–4.7 cm) in males and 3.1 cm (SD 0.5 cm; range 2.0–4.2 cm) in females. These results suggest that the cuff of an uncut 6.0 mm tracheal tube would often lie between the vocal cords when the tube is fully inserted through a laryngeal mask airway. To avoid this complication, the tracheal tube must protrude more than 9.5 cm beyond the grille of the laryngeal mask airway. When either neck extension or flexion is required, the laryngeal mask airway should be removed as the margin of safety is small.

Effect of the size of a tracheal tube and the efficacy of the use of the laryngeal mask for fibrescope-aided tracheal intubation

We randomly allocated 60 patients with normal airways into three groups to compare the ease of fibrescope‐aided tracheal intubation using 8.0‐mm internal diameter (group F8) and 6.0‐mm (group F6) reinforced tracheal tubes and to evaluate the efficacy of the laryngeal mask as an aid for fibreoptic tracheal intubation (group L). In group F8 tracheal intubation was optimal in 2 of 20 patients and in two patients in whom intubation over the fibrescope was difficult the attempts resulted in inadvertent oesophageal intubation. In group F6 intubation was always successful and significantly easier than in group F8 (p < 0.005; 95% confidence interval for the difference in the proportion of the optimal intubation grade: 20–70%). In group L tracheal intubation was optimal in 18 of 20 patients and easier than in group F6 (p = 0.014; 95% confidence interval for difference: 10–60%). In both groups F6 and L tracheal intubation was completed within less than about 1 min. We conclude that conventional fibrescope‐aided tracheal intubation with a 6.0‐mm tracheal tube is easier than with an 8.0‐mm tube and that the laryngeal mask facilitates fibrescope‐aided tracheal intubation.

Evaluation of Frova, single‐use intubation introducer, in a manikin. Comparison with Eschmann multiple‐use introducer and Portex single‐use introducer*

In a randomised cross‐over study, 48 anaesthetists attempted to place a Frova single‐use introducer, an Eschmann multiple‐use introducer and a Portex single‐use introducer in the trachea of a manikin set up to simulate a grade 3 laryngoscopic view. The anaesthetists were blinded to success (tracheal placement) or failure (oesophageal placement). Successful placement (proportion, 95% confidence interval) of either the Frova introducer (65%, 50–77%) or the Eschmann introducer (60%, 46–73%) was significantly more likely than with the Portex introducer (8%, 3–20%). There were no significant differences between the success rates for the Frova and the Eschmann introducers. A separate experiment revealed that the peak force exerted by the Frova and Portex introducers was two to three times greater than that which could be exerted by the Eschmann introducer, p < 0.0001, indicating that the single‐use introducers are more likely to cause tissue trauma during placement.

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

Summary 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.

Evaluation of clinical effectiveness of the Frova single-use tracheal tube introducer.

A prospective observational study design was used to evaluate the clinical effectiveness of the Frova single‐use tracheal tube introducer. Data were collected from 203 patients. Consultants and trainee anaesthetists completed 61 (30%) and 142 (70%) forms respectively, when the Frova introducer was used. It was successfully placed in the trachea in 194/203 (96%) of patients with two attempts at placement by the first clinician. The first clinician failed to either pass the Frova introducer or railroad the tube in six (3%) and 10 (5%) of the 203 patients respectively. The success rate by the first clinician was significantly influenced by the laryngeal view obtained (p < 0.0001). There was only one failure to place the Frova introducer in the trachea by either the first or second clinician. Airway trauma was detected in 11/203 (5%) patients. In six of these 11 patients blood was detected on tracheal suction; ‘distal hold up’ was elicited in five of these six. The Frova introducer has a high success rate for tracheal placement but has noteworthy potential to produce airway trauma.

Prehospital airway management in Ambulance Services in the United Kingdom

A postal survey of the 38 Ambulance Services in the United Kingdom was undertaken to find out what equipment is provided for paramedic crews to aid tracheal intubation and to confirm tracheal placement. The response rate to our survey was 100%. Fourteen (37%) ambulance services provided neither stylet nor bougie to facilitate difficult intubation. The laryngeal mask airway was available to 15 (40%) ambulance services. Seventeen (45%) ambulance services had use of a needle cricothyroidotomy set. Twenty‐nine (76%) ambulance services had no type of device other than a stethoscope to confirm tracheal tube placement. This survey showed wide variations in the equipment for airway management available to paramedic crews in the United Kingdom. We recommend provision of a standard set of airway management equipment to all paramedic crews in the United Kingdom together with introduction of appropriate training programmes.