The Bonfils rigid fibrescope (Karl Storz GmbH, Tuttlingen, Germany) is an instrument used to perform tracheal intubation. Although proven to be effective both in patients with normal airways and in those with difficult airways [1–6], relatively few papers about the Bonfils fibrescope are currently available in the literature.
The Bonfils fibrescope is a rigid 40 cm long endoscope with a 40° curved tip, on which a tracheal tube with an internal diameter of at least 5.5 mm can be loaded, and a 15 mm tracheal tube adapter that allows the position of the distal end of the tube to be adjusted a few millimetres beyond the tip of the fibrescope. The instrument view through the end of the tracheal tube and its shape make it easier to locate the laryngeal inlet in patients with difficult airways [1,6].
Generally, about 20  elective intubations are considered to provide sufficient experience for its standard clinical use, whereas, for difficult airways, experience of at least 50 cases has been suggested . However, these recommendations are not so well documented, as series of intubations of a single anaesthesiologist are seldom reported [1,2].
The aim of this study is two-fold: assessing the effectiveness of the Bonfils fibrescope in a consecutive series of 100 intubations of a single anaesthesiologist and analysing the learning process of the technique. The study was approved by the Institutional Ethical Committee. Informed consent was obtained from all patients. Patients without criteria for difficult intubation  were eligible unless emergency surgery was needed.
The Bonfils fibrescope was connected to a video monitor system. In order to prevent fogging, an O2 flow was administered via the connector fitting onto the tracheal tube adapter.
Patients were placed in the sniffing position and monitored with ECG, SpO2, capnography, and noninvasive blood pressure. Atropine (0.005–0.01 mg kg−1) and fentanyl (1–1.5 μg kg−1) were administered intravenously a few minutes before the procedure.
After preoxygenation, anaesthesia was induced with thiopental (3–5 mg kg−1) or propofol (2–2.5 mg kg−1), and, if ventilation with a face mask was successful, patients were paralysed. The instrument was introduced by the dominant hand into the oral cavity using a midline approach, whereas the nondominant hand lifted the mandible to open the oropharynx . Once the tip of the tube was adjacent to the vocal cords, the mandible traction was released and the tube was passed down into the trachea. Intubation attempts were interrupted whenever SpO2 showed O2 desaturation or if any further attempt was considered dangerous or futile.
If the chin-lift manoeuvre proved to be inadequate, the Macintosh laryngoscope could be used along with the Bonfils fibrescope. Total intubation times were the sum of each intubation attempt, starting from the moment the Bonfils fibrescope was first touched until an appropriate capnograph trace appeared (or attempts were discontinued) in seconds (s).
The study was subdivided into two phases: the learning phase up to the 50th intubation and the standard phase afterwards . Each phase was further subdivided in five groups of 10 intubations each to evaluate the progress of learning. Comparisons were made using the chi-squared test, Student's t-test, Mann–Whitney U test, and Kruskal–Wallis test with post-hoc Bonferroni correction of P, as appropriate.
One hundred consecutive patients were included. Mean ± SD age was 60.3 ± 17.0 years, 59% were women, median Mallampati class was 1 [interquartile range (IQR), 1–2], and mean thyromental and interincisor distances were 7.6 ± 1.1 and 4.3 ± 0.6 cm, respectively.
Intubation was successful in 98 patients [98%; 95% confidence interval (CI), 93.5–99.6], with a median intubation time of 30 s (IQR, 25–40 s). Intubation was successful at the first attempt in 89 patients (90.8%; 95% CI, 83.8–95.4), whereas two and three attempts were needed in six (6.1%; 95% CI, 2.5–12.2) and three patients (3.1%; 95% CI, 0.7–8.1), respectively. Failed intubations, all without the aid of a laryngoscope, occurred in the first and third patient. Both patients were subsequently intubated without difficulty using a Macintosh laryngoscope. In two patients, Bonfils fibrescope intubations succeeded only with the aid of a Macintosh laryngoscope.
There was no evidence of airway trauma (0%; 95% CI, 0.0–2.9). The most frequent problems encountered were fogging (12%; 95% CI, 6.6–19.5), difficulties in getting the Bonfils fibrescope tip under the epiglottis (7%; 95% CI, 3.1–13.3), difficult advancement of the tube due to inadequate lubrication (6%; 95% CI, 2.4–12.0), and gross mucous secretions obscuring laryngeal anatomy (5%; 95% CI, 1.8–10.7).
The learning and standard phases differed only in terms of median intubation time (P = 0.011) and number of attempts (P = 0.022). Regarding these aspects, there was larger data dispersion during the learning phase, as demonstrated by the coefficients of variation and the trend of interquartile ranges (Table 1). Moreover, the Kruskal–Wallis test detected significant differences between the first group (A) and groups B, C, and E for intubation times and groups C and E for the number of attempts. There were no statistically significant differences among the groups of the standard phase.
The literature reports five series (n = 235) of intubations performed with the Bonfils fibrescope on patients with normal airways. The success rates ranged from 86.1 to 100%, with median intubation times ranging from 25 to 80 s [1–5]. Our data compare well with these reports, although the operator's experience varies among different studies. The two failures in our study were actually due to inexperience, as both patients were successfully intubated without difficulty with a Macintosh laryngoscope.
Minor difficulties were similar to those encountered by other authors [1,2], fogging being the most frequent. Only an O2 flow of at least 8 l min−1 eliminated the problem, but antifogging agents are probably more efficient [1,2]. The incidence of gross secretion reducing the view was significantly lower among our patients (5 vs. 30% ): an antisialogogue premedication should always be considered, particularly in patients with a difficult airway.
Once the manoeuvres to open the oropharynx, by lifting the mandible, are learned, the aid of a Macintosh laryngoscope is rarely necessary. Although we did not detect any evidence of traumatic injury, our data allow only the inference of a maximum rate of dental or airway trauma of 2.9% (with a confidence interval of 95%).
Our results support the theory that about 20 intubations provide sufficient experience for clinical use in patients with normal airways , as intubation times and number of attempts significantly decreased after the 10th. No significant differences were detected among the groups from B to E, nor among the groups of the standard phase (Table 1), whereas coefficients of variation and IQR were larger for groups of the learning phase. These data suggest that no further learning occurred after the 50th intubation, indirectly supporting the definition of ‘experienced user’ suggested by Bein et al..
This study has several limitations, the most important being its observational and uncontrolled design and the fact that it reports the experience of a single operator. However, our study corroborates the good results reported in the literature with the Bonfils fibrescope, and it confirms the steep learning curve of this technique.
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