Use of the bougie in simulated difficult intubation. 2. Comparison of single-use bougie with multiple-use bougie*
Presented in part at the Difficult Airway Society Meeting, London, 21–22 November 2002.
Summary We studied the success rates for tracheal intubation in 32 healthy, anaesthetised patients during simulated grade IIIa laryngoscopy, randomised to either the multiple-use or the single-use bougie. Success rates (primary end-point) and times taken (secondary end-point) to achieve tracheal intubation were recorded. The multiple-use bougie was more successful than the single-use one (15/16 successful intubations vs. 9/16; p = 0.03). With either device, median [range] total tracheal intubation times for successful attempts were < 54 [24–84] s and there were no clinically important differences between these times. We conclude that the multiple-use bougie is a more reliable aid to tracheal intubation than the single-use introducer in grade IIIa laryngoscopy.
The tracheal tube introducer or ‘bougie’ is the most commonly used aid in the UK to facilitate intubation during difficult grade III laryngoscopy [1–4]. Traditionally, the multiple-use (gum elastic) bougie has been used. According to the manufacturer, this can be used up to five times when the recommended disinfectant solutions are employed .
However, there is increasing concern about the risk of cross-infection with multiple-use devices [6–11], and a new, single-use polyurethane introducer has been introduced. Anecdotally, it appears that this bougie, which lacks flexibility and curvature, is more difficult to use [12, 13]. Annamaneni et al.  reported that the single-use introducer compares poorly with the multiple-use device, when tested objectively in simulated grade III intubation in manikins.
We previously compared success rates for tracheal intubation between the single-use bougie and intubating fibrescope in two simulated grade III laryngeal views in patients . We were surprised at the very low rates of success of the single-use bougie. We considered the possibility that one reason for this poor performance was that the single-use bougie is intrinsically difficult to use. The purpose of this study was to assess if this was the case, and to compare, in patients, the success rates of the single-use and multiple-use bougies for tracheal intubation in simulated grade IIIa laryngoscopy.
The study was approved by the Central Oxford Research Ethics Committee. Participants provided written, informed consent. We studied 32 ASA I or II patients, aged 18–70 years, scheduled for day-case dental surgery who fulfilled the same criteria as in our previous study . They were randomly assigned (after airway assessment, consent and recruitment, but before induction of anaesthesia) to undergo orotracheal intubation with the aid of either multiple-use or single-use bougies.
Anaesthesia was induced and maintained as described previously . After induction, either a size 3 or 4 Macintosh laryngoscope blade was used to confirm that the laryngoscopic grade was I or II as we had planned not to study patients with grade III or IV views. Simulation of grade IIIa laryngeal view was achieved as described previously [4, 15–17]. One operator maintained the Macintosh laryngoscope in position while an investigator confirmed the simulated grade and commenced intubation. The trachea was intubated with the aid of either a multiple-use (Reusable Tracheal Tube Introducer, Coudé Tip, 15Ch, length 600 mm, angle 40°, 25 mm from tip; Portex, Hythe, UK) or single-use (Portex Single-Use Tracheal Tube Introducer, Coudé Tip, 15Ch, 600 mm, angle 40°, 25 mm from tip; Portex) device. Investigators could preshape the bougie as desired before its introduction into the patient's mouth. A reinforced tracheal tube (8 mm i.d. in males, 7 mm i.d. in females) was railroaded over the bougie after its insertion into the trachea. The operator holding the Macintosh laryngoscope looked away to remain blinded to the performance of the investigator, so that no adjustment of the Macintosh laryngoscope could be made to aid or hinder the investigator. However, neither operator nor investigator were blinded to the study device.
Times were recorded from the moment the investigator picked up the introducer to the moment the introducer was thought to have entered the trachea (the ‘insertion time’); and finally to the moment that carbon dioxide appeared on the capnograph after intubation (the ‘total time’). The difference between the total time and the insertion time was the ‘intubation time’.
Only one continuous attempt at insertion and intubation was allowed. No movements of the laryngoscope, patient's head or external laryngeal pressure were allowed. Insertion of either introducer was abandoned if the Spo2 dropped below 95%.
In addition to the times, the presence or absence of any ‘clicks’ and any complications or difficulties were noted.
If placement of the tracheal tube in the trachea was unsuccessful, it was removed and the patient's lungs ventilated with 100% oxygen and 2% isoflurane via a facemask. After 3 min of re-oxygenation the alternative study device was used in the same manner as described above. If this also resulted in failure, the patient's lungs were further ventilated with oxygen and isoflurane and tracheal intubation performed without simulation of the difficult laryngoscopy.
Preliminary trials suggest that standard deviation of intubating times is ≈ 20 s. If we suppose that the minimum clinically important difference between intubating times is ≈ 20 s, then for a two-sided significance level of 5% and a power of 80%, the number of subjects required in each group would be 16 (unpaired) . The median differences in the insertion and total times were compared using the Mann–Whitney U-test. Comparison of the success rates using two methods was made using a Chi-squared test with Yates' correction. A p-value of < 0.05 was taken to be statistically significant.
There were 18 males and 14 females. Their median [range] age and weight were 31 [18–56] years and 74 [47–104] kg, respectively. All were ASA I or II. No patients were excluded on the basis of previous airway problems. Following induction of anaesthesia, 26 (81%) were assessed to have a Cormack and Lehane laryngoscopic grade of I and 6 (19%) were grade II.
Table 1 shows the median times and success rates for both bougies. The multiple-use bougie performed better than the single-use bougie in terms of success rates, with the associated times being similar.
Table 1. Times for insertion, tracheal intubation, total time and success rates for the initial technique. Values are median (range), or number (proportion; %). Times are reported only for successful attempts.
|Insertion time; s||18 (4–42)||11 (4–38)||NS|
|Intubation time; s||22 (16–36)||26 (21–48)||NS|
|Total time; s||54 (25–64)||42 (30–84)||NS|
|No. of successful intubations; %||9 of 16 (56%)||15 of 16 (94%)||p = 0.03|
Table 2 shows the results of cases in which the first, randomised intubation aid failed.
Table 2. Times for insertion, tracheal intubation, total time and success rates for the alternative technique, after the initial technique had failed. Values are median (range), or number (%). Times are reported only for successful attempts. No statistical comparisons were made.
|Insertion time; s||15||9 (5–22)||–|
|Intubation time; s||24||23 (7–33)||–|
|Total time; s||39||29 (24–42)||–|
|No. of successful intubations; %|| 1 of 1 (100%)||5 of 7 (71%)||–|
The presence of clicks was noted in 19 of 30 (63%) successful bougie insertions, 14 of 20 with the multiple-use bougie and 5 of 10 with the single-use bougie. In three cases (all of them with the single-use bougie), clicks were reported but intubation was oesophageal.
There were no complications with either device and Spo2 remained > 95% in all cases.
This study shows a striking difference between multiple-use and single-use bougies in success rates for tracheal placement.
In this study we simulated only a grade IIIa laryngoscopy view. This was based on the result of our previous study . We found that the likelihood of success using either a bougie or fibrescope in a grade IIIb view (where the epiglottis is in contact with the posterior pharyngeal wall) was so low that we did not feel it productive to attempt to compare the two bougies with grade IIIb laryngoscopy.
We have previously conceded that our method of one operator holding the Macintosh laryngoscope while another performs the intubation does not resemble normal clinical practice, and may therefore introduce some bias . However, in this study we used this method for both groups, so any adverse influences should have been equally distributed. In the absence of an alternative method of simulating grade III laryngoscopy in actual patients, it seems reasonable to use this technique.
Although the operator holding the Macintosh laryngoscope was ‘blinded’, neither the operator nor the investigator performing the intubation were blinded to the study device. It is difficult to overcome this problem. However, the success rates using the single-use bougie in this study (9 of 16) are extremely close to the rates in our previous report with the same device (8 of 16) , which suggests a high degree of repeatability of results.
There are three conventional signs of successful tracheal placement of the bougie: (i) the sensation of clicks as the bougie passes along the tracheal rings; (ii) rotation of the bougie as it enters a main bronchus; (iii) a distal ‘hold-up sign’ as the bougie reaches the small bronchi [19–23]. It has been suggested that, if clicks are present, the clinician should proceed with intubation: if they are not, then the bougie should be advanced to a maximum distance of ≈ 45 cm. If distal hold-up occurs, the clinician should proceed with intubation: if it does not, then the bougie should be removed and a second attempt commenced . Although we noted the presence or absence of clicks as part of this study, we did not rely on this sign absolutely as a certain marker of successful bougie insertion. The reason for this was that our protocol limited us to one attempt at insertion. Our results do not, however, support the notion that clicks are a certain sign of successful tracheal placement.
Our results in patients are in agreement with the report by Annamaneni et al. , who found the single-use bougie to perform poorly in manikins. Their success rates for the first attempt with the multiple-use and single-use bougies were 85 and 15%, respectively. Theirs is a slightly higher success rate with the multiple-use bougie and a lower success rate with single-use bougie than we obtained (Table 1), but our overall conclusion is the same. The small differences might relate to inherent differences between real patients and the manikin.
Our results for the multiple-use bougie are in agreement with previous reports in patients. The success rate for the multiple-use device as the first choice technique in our study was 94%. Previous studies using simulated difficult intubation reported similar success rate figures of 96% and 100%.
It is possible that the differences in success rates between the two bougies reported here are due simply to a ‘learning curve’: anaesthetists are not yet familiar with the new single-use bougie but, with time, success rates will be similar. However, there is no indication (either from the manufacturers or from research) that the single-use bougie requires a different technique for successful placement. It is reasonable to expect that any airway device designed for use with potentially difficult airways should be demonstrably successful from its introduction. Our results do not suggest that the single-use bougie is very successful. The precise reasons why the single-use bougie performs so poorly are unclear. The length, size and angle of the tips of single- and multiple-use bougies are the same . Annamaneni et al. found that the single-use bougie retains its curve less well when shaped optimally, and argued that this was due to the material from which it was made . We did not study this, but subjective experience would lead us to agree with their conclusion.
In a previous study , we compared success rates using a fibrescope with the single-use bougie. For grade IIIa laryngoscopy, the fibreoptic technique was successful in 100% cases (16 of 16) . If we compare the success rate of the multiple-use bougie in this study (98%; 15 of 16) with the fibrescope, we find no statistically significant difference (Chi-squared test). Thus, we conclude that the multiple-use bougie performs as well as the fibreoptic scope in grade IIIa laryngoscopy. We can make no comment about the performance of the multiple-use bougie in grade IIIb laryngoscopy.
Our results add to growing concern regarding the efficacy of the single-use bougie in difficult intubation . Although it is difficult to quantify the risk of cross-infection with a multiple-use device and to balance this against the risk of failed intubation with the single-use one, it is reasonable to conclude that the latter device is a poorer intubation aid. A similar debate has occurred with respect to the disposable surgical equipment for tonsillectomy [24–26].
A reasonable approach, which minimises costs but maximises choice, would be to suggest that both single-use and multiple-use bougies are available on an anaesthetic trolley. Where a bougie is to be used routinely (e.g. simply as a stylet or introducer to facilitate easy tracheal intubation in patient with crowned teeth), the single-use device may be used. However, if a bougie is needed urgently for an unexpected difficult tracheal intubation, the multiple-use device should be available. Hospitals will need to decide, on the basis of cost and risk, whether the multiple-use bougie should, in fact, thereafter be cleaned and reused, or be disposed of.
Finally, our results here lead us to modify slightly one of the conclusions suggested by our earlier study . On the basis that the single-use bougie performed poorly in grade IIIa laryngoscopy as compared with the fibrescope, one might advocate early consideration of the fibrescope if an unexpected grade IIIa laryngoscopy was encountered. We still feel that this conclusion still holds for the single-use device. However, the results of this study would lead us to conclude that, if a multiple-use bougie is available, it is likely to be as successful as fibreoptically assisted intubation in unexpected grade IIIa laryngoscopy and therefore, it is reasonable to make more than one attempt at tracheal intubation with the multiple-use device. However, we did not compare the multiple-use bougie with the fibrescope, and our data do not indicate how many attempts should be made before other methods are used.