Abstract
Background
The Airtraq® Optical Laryngoscope is a new type of laryngoscope that provides a direct view of the glottis without alignment of the mouth, pharynx and trachea. Data show that it has advantages over the Macintosh laryngoscope.
Objective
The aim of this study was to compare the use of the Airtraq laryngo-scope versus the No. 3 Macintosh blade for routine airway management in terms of intubation time, complications during and after laryngoscopy, and ease of use.
Methods
In this single-center, randomized, clinical trial, 63 patients scheduled for elective operation were randomly allocated to two groups. Thirty-five patients were intubated with the Airtraq laryngoscope and 28 with the traditional Macintosh laryngoscope. All intubations were performed by experienced anesthesiologists who had a similar level of experience with the Airtraq laryngoscope. The time needed for intubation, any assistance required, complications during and after laryngoscopy and intubation, and the number of unsuccessful intubation attempts were documented and compared between the groups.
Results
Intubation with the Macintosh laryngoscope was quicker (mean±standard deviation: 23.7±5.9 seconds) than with the Airtraq laryngoscope (29.6±8.5 seconds). Although the difference (5.9 seconds) was statistically significant (p<0.05), it was not clinically significant. The anesthesiologists who used the Airtraq laryngo-scope less frequently required assistance (p<0.05) to place the endotracheal tube. No differences were found regarding complications during and after laryngoscopy and intubation. There were no differences in any of the outcomes in patients with Mallampati class > 2.
Conclusion
The Airtraq laryngoscope is easier to use but it does not have any significant advantages compared with the Macintosh laryngoscope for routine airway management. More studies are needed to evaluate its use in patients with a difficult airway, and in emergency procedures.
Keywords
laryngoscopes: Airtraq; laryngoscopes: Macintosh;
1. Introduction
Management of a difficult airway is a challenging situation for anesthesiologists. Many different devices have been developed in response to these problems. One of the most recently introduced devices is the Airtraq® Optical Laryngoscope (Prodol Meditec, Vizcaya, Spain).
This device consists of a series of lenses and an exaggerated curvature and provides a direct, illuminated view of the glottis without alignment of the mouth, pharynx and trachea. The device also has a side channel for endotracheal attachment, and is inserted into the trachea for viewing the vocal cords. Intubation can also be done without neck extension. A camera can also be attached to obtain live video for teaching purposes. Recent data indicate that laryngoscopy and intubation seem to be easier for experienced and inexperienced personnel when using the Airtraq laryngoscope than when using the Macintosh laryngoscope. In addition, the incidence of adverse events, such as esophageal intubation, failed intubation and airway injury, appears to be significantly lower.
The aim of this study was to compare the Airtraq laryngoscope (Figure 1) with the No. 3 Macintosh blade (Figure 2) for routine airway management in terms of intubation time, complications during and after laryngoscopy, and ease of use.
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2. Methods
2.1. Patients
After thorough explanation of the study, 63 patients with American Society of Anesthesiologists status I−III agreed to participate in our study and provided written, informed consent. The patients were scheduled to undergo various types of elective surgery between October 22, 2007 and May 23, 2008, at the 424 Military Hospital in Thessaloniki, Greece. The exclusion criteria were: (1) patients requesting regional anesthesia; (2) the need for endotracheal tubes that are armored, cranial-facing or caudal-facing, or the need for a nasotracheal tube, as indicated by the type of surgery; (3) history of an impossible or difficult intubation; and (4) emergency surgery.
2.2. Study design
This was a single-center, randomized, clinical trial. The 63 patients were randomly allocated to two groups using computer software for randomization. The patients in the first group (group A) were intubated with the Airtraq laryngoscope while the patients in the second group (group B) were intubated with the traditional Macintosh laryngoscope. A No. 3 Macintosh blade was used in all patients. Four anesthesiologists were involved in this study. They were all consultants with similar experience and none of them had ever used the Airtraq laryngoscope prior to this study. They each performed 15 intubations with the Airtraq laryngoscope before data collection. The size of the tube was chosen by the anesthesiologist responsible for the surgery. The total time of the intubation procedure and the number and type of any complications were documented, and the two groups were compared for any statistically significant differences.
2.3. Protocol
For each patient, we documented the age, sex, weight, height, body mass index (BMI), Mallampati classification and previous anesthetic history. The Mallampati classification was examined by the anesthesiologist who would perform the intubation in the operating room. The patients were connected with the monitors on arrival at the operating theater.
The monitoring used was at the anesthesiologist’s discretion. All patients were preoxygenated via a face mask with 100% oxygen for 3 minutes. General anesthesia was then induced by 2 μg/kg of fentanyl, 2−3 mg/kg of 1% propofol and 0.2 mg/kg of cisatracurium.
In both groups, the equipment required for intubation was prepared by the nursing stuff before the induction of general anesthesia. After the cessation of breathing, the patient was manually ventilated with 3% sevoflurane in 100% oxygen until the nerve stimulator showed no response to a double- burst stimulus. The first stimulus was given 3 minutes after the injection of cisatracurium and, if there was a response, the stimulus was repeated every minute until the absence of a response. On finding the absence of a response, the patient’s blood pressure and heart rate were recorded and the breathing mask was removed. The intubation procedure was started at this time and ended on the correct placement of the endotracheal tube. This was confirmed by a capnograph at the anesthesiologist’s instruction. In all cases, the timing was recorded using an operating theater electronic timer by a member of the surgical nursing stuff, who was blinded to the research protocol.
The anesthesiologist was allowed to use assist- ance, such as applying cricoid pressure, use a gum elastic bougie, or change the laryngoscope blade. The use of assistance and the change to the pa- tient’s position and number of attempts to perform intubation were documented. During the laryngos- copy, the anesthesiologist noted whether there was any bleeding in the larynx and checked for any injuries in the oral cavity (tongue, lips and teeth) after intubation. All adverse events were recorded on the patient’s case report file. Heart rate and pulse oximeter oxygen saturation (SpO2) were con- tinuously recorded and blood pressure was measured every 20 seconds. After extubation, the anesthesi- ologist checked for hoarse voice, airway injuries, swelling of the larynx and laryngospasm. All infor- mation was recorded on the case report file. All perianesthetic care was delivered as in standard clinical practice.
2.4. Outcomes
The primary outcome of this study was the total time to perform intubation and verify correct placement of the endotracheal tube. Secondary outcomes included the frequencies of assistance, complications during laryngoscopy and intubation, complications after extubation and unsuccessful intubation attempts. We documented the application of cricoid pressure, the use of gum elastic bougies, changes in the patient’s position, repeated attempts to perform intubation and any changes in laryngoscope blade. Any other forms of assistance were also recorded. Esophageal or endobronchial intubation, hypertension, tachycardia, O2 desaturation, laryngospasm, and injuries of the lip, dentition, tongue or vocal cords were documented as adverse events during laryngoscopy and intubation. Hypertension and tachycardia were defined as an increase in blood pressure and heart rate, respectively, by more than 10% of the baseline value. Oxygen desaturation was defined as SpO2 < 92%. Hoarse voice, injury of the airway, swelling of the larynx and laryngospasm observed after extubation were recorded as postextubation complications.
2.5. Statistical analysis
First, we examined the normality of our primary outcome (total time needed) using the Shapiro-Wilk test. We excluded outliers (Group A, n = 0; Group B, n = 2) and concluded that we should use nonparametric tests. We used the Mann-Whitney test to identify statistically significant differences between the two groups in the total time needed for intubation. The χ2 test was used to determine statistically significant differences between groups for the secondary outcomes. The same tests were also applied for patients with a Mallampati classification > 2 (16 patients) to examine the above parameters in patients with a difficult airway. All tests were done using SPSS version 14.0 software (SPSS Inc., Chicago, IL, USA). A p value of < 0.05 was considered statistically significant.
3. Results
3.1. Patient characteristics
Of the 122 patients originally enrolled in the trial between October 22, 2007 and May 23, 2008, 63 were randomized and their data were recorded and used for statistical analysis (Figure 3). The demographic characteristics of the patients are shown in Table 1. No statistically significant differences were found in any of these characteristics.
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3.2. Outcomes
The primary outcome (total time needed for intubation) and the secondary outcomes are summarized in Table 2. The results for total intubation time were obtained after excluding five outliers (Group A, n = 2; Group B, n = 3) after reviewing the descriptive statistics for this parameter (Figure 4).
Intubation time was significantly shorter with the Macintosh laryngoscope than with the Airtraq laryngoscope (p = 0.012; Figure 4). In terms of the ease of intubation, assistance was needed for significantly fewer patients with the Airtraq laryngoscope than with the Macintosh laryngoscope (p = 0.038). There were no statistically significant differences in the rate of complications during laryngoscopy and intubation, or after extubation, between the two groups, either individually or in total.
Four patients were unsuccessfully intubated with the Airtraq laryngoscope. For two of these patients, the laryngoscope visual field was blurred.
One patient was initially successfully intubated but was accidentally extubated during the withdrawal of the Airtraq from the mouth. In the fourth case, the laryngoscope could not be inserted into the oral cavity because the mouth opening was too small. Three of these patients were successfully intubated with the Macintosh laryngoscope, and the fourth patient was intubated with an intubating laryngeal mask. In Group B, only one patient was unsuccessfully intubated, and the endotracheal tube was finally placed using a McCoy laryngoscope. In two cases (both in Group B), the total intubation time was very long (4 minutes 26 seconds and 1 minute 20 seconds) compared with the average time.
We repeated the statistical analysis in patients with Mallampati class 3 or 4 (Group A, n = 10; Group B, n = 6). However, there were no statistically significant differences between the two groups in terms of the primary (Figure 5) and secondary outcomes.
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4. Discussion
The results of our study show that intubation by experienced anesthesiologists is performed more quickly with the traditional Macintosh laryngoscope than with the Airtraq laryngoscope. However, although the difference between the two groups (5.9 seconds) is statistically significant, it cannot be considered to be clinically significant. Therefore, we believe that neither laryngoscope has a clinically relevant advantage in terms of the time needed for intubation. In terms of the ease of intubation and the incidence of complications during and after laryngoscopy and intubation, we found that the Airtraq laryngoscope less frequently required assistance than the Macintosh laryngoscope.
To date, only one clinical trial has evaluated routine airway management with the Airtraq laryngoscope, and agrees with the present results. Maharaj et al concluded that the Airtraq laryngoscope may be slightly easier to use, but there was no difference between the Airtraq and the Macintosh laryngoscope in terms of the time needed for intubation.1 Some studies in manikins have shown that the Airtraq laryngoscope seemed to be much quicker and easier to use than the Macintosh laryngoscope, 2−6 even for inexperienced users,3,7 and that intubation with the Airtraq laryngoscope would cause fewer traumatic complications than with the Macintosh laryngoscope.3−5 In these studies, the laryngoscope users were inexperienced medical students. In contrast, all intubations were performed by experienced anesthesiologists in our study and we found no important differences, which could verify that the everyday use of the Airtraq laryngoscope for routine airway management has no advantages over the traditional Macintosh laryngoscope.
In terms of patients with a difficult airway (i.e. Mallampati class 3 or 4), we found no differences between the two laryngoscopes. In contrast, other studies have reported that intubation with the Airtraq laryngoscope requires less cervical mobility8 and is faster and safer to use for patients with cervical spine immobilization compared with the Macintosh laryngoscope.9 Furthermore, the Airtraq laryngoscope was reported to be superior to the Macintosh laryngoscope in the airway management of morbidly obese patients10 and in patients with an anticipated difficult airway.11 However, the number of patients in our study with an anticipated difficult airway was small (Group A, n = 10; Group B, n = 6), which might explain the absence of any differences between the two groups.
Two cases from our study need to be discussed. The first case, a 66-year-old male with Mallampati class 3, BMI 28 kg/m2 was successfully intubated with the Airtraq laryngoscope. However, before starting the operation, he was accidentally extubated. Laryngoscopy was then attempted using a Macintosh blade, but the intubation effort was unsuccessful and the anesthesiologist stated that the airway was of grade 3 severity according to the Cormack and Lehane classification. The Airtraq laryngoscope was used again and intubation was performed successfully within 15 seconds. The second patient, a 46-year-old male with Mallampati class 1, BMI 24.15 kg/m2, was scheduled for laparoscopic cholecystectomy. He had an immobile cervical spine due to ankylosing spondylitis and his head was extremely flexed towards his chest. A No. 3 Macintosh blade was initially used, but the epiglottis and vocal cords could not be visualized (Cormack and Lehane grade 4). The patient was
ventilated manually with a face mask. After checking the patient’s position, a second attempt was made using a McCoy blade. Again, the epiglottis and vocal cords could not be visualized. On the third intubation attempt, the Airtraq laryngoscope was used and the visualization of the vocal cords was excellent. A size 9.0 Portex tracheal tube was easily inserted using the Airtraq laryngoscope. This patient was excluded from the study.
These were the only two cases in which both types of laryngoscope were used in the same patient with a difficult airway by the same anesthesiologist. In both cases, the Airtraq laryngoscope was a rescue device because the intubations were very easy and fast with this device, whereas intubation with the Macintosh laryngoscope was not possible. More studies are needed in patients with a potentially difficult airway to confirm the use of Airtraq in these patients.
5. Conclusion
Although the Airtraq is marginally quicker to use than the Macintosh laryngoscope, there are no advantages for either laryngoscope when used in everyday routine airway management. More studies are needed to verify the potential advantages of the Airtraq laryngoscope for difficult and emergency airway management.