Airtraq(®) versus Macintosh laryngoscope: A comparative study in tracheal intubation.

BACKGROUND: The curved laryngoscope blade described by Macintosh in 1943 remains the most widely used device to facilitate tracheal intubation. The Airtraq(®) (Prodol Meditec S.A, Vizcaya, Spain) is a new, single use, indirect laryngoscope introduced into clinical practice in 2005. It has wan exaggerated blade curvature with internal arrangement of optical lenses and a mechanism to prevent fogging of the distal lens. A high quality view of the glottis is provided without the need to align the oral, pharyngeal and tracheal axis. We evaluated Airtraq and Macintosh laryngoscopes for success rate of tracheal intubation, overall duration of successful intubation, optimization maneuvers, POGO (percentage of glottic opening) score, and ease of intubation.
MATERIALS AND METHODS: Patients were randomly allocated by computer-generated random table to one of the two groups, comprising 40 patients each, group I (Airtraq) and group II (Macintosh). After induction of general anesthesia, tracheal intubation was attempted with the Airtraq or the Macintosh laryngoscope as per group. Primary end points were overall success rate of tracheal intubation, overall duration of successful tracheal intubation, optimization maneuvers, POGO score and ease of intubation between the two groups.
RESULTS: We observed that Airtraq was better than the Macintosh laryngoscope as duration of successful intubation was shorter in Airtraq 18.15 seconds (±2.74) and in the Macintosh laryngoscope it was 32.72 seconds (±8.31) P < 0.001. POGO was also better in the Airtraq group 100% grade 1 versus 67.5% in the Macintosh group, P < 0.001. Ease of intubation was also better in the Airtraq group. It was easy in 97.5% versus 42.5% in the Macintosh group, P < 0.001.
CONCLUSION: Both Airtraq and Macintosh laryngoscopes are equally effective in tracheal intubation in normal airways. Duration of successful tracheal intubation was shorter in the Airtraq group which was statistically significant.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Intubating trachea and securing the airway remains a challenge although it is a routine practice for the anesthesiologist. Failure to successfully intubate the trachea remains a leading cause of morbidity and mortality in anesthetic and emergency setting.[12345] Despite various innovations and numerous developments in the airway devices, the Macintosh laryngoscope (1943) remains the most frequently used device for orotracheal intubation since 1943. It is considered to be the “gold standard” for endotracheal intubation and it is against this device that the various airway devices are evaluated.[6] Difficult airway is not recognized until the induction of anesthesia as there is no single factor to predict the existence of a difficult airway.[7] The Airtraq® laryngoscope (Prodol Meditec SA, Vizcaya, Spain) is a recently developed video laryngoscope for use in patients with normal or difficult airways. The curvature of the Airtraq blade and the special internal arrangement of the optical components allow visualization of the glottic plane without alignment of the oral, pharyngeal, and tracheal axis. The resultant indirect laryngeal exposure may require less movement of the cervical spine as compared to conventional Macintosh laryngoscopes. The blade of the Airtraq consists of two side channels, one for the insertion of the endotracheal tube (ETT) and the other containing a series of lenses, prisms, and mirrors that transfer the image from the illuminated tip to a proximal viewfinder, giving a high-quality wide-angle view of the glottis and surrounding structures, and the tip of the tracheal tube. The Airtraq is anatomically shaped and can be used with standard ETTs. The blade of the Airtraq laryngoscope must be inserted in the center of the mouth along the longitudinal axis of the tongue, with the tip positioned in the left vallecula. If necessary, the epiglottis can be lifted by elevating the blade into the vallecula. The ETT does not obstruct the endoscopic view of the vocal cords during tracheal intubation. This study was conducted to compare the conventional (Macintosh) laryngoscope with newer Airtraq® laryngoscope for duration of successful tracheal intubation and optimization maneuvers needed.

MATERIALS AND METHODS

This study was conducted on 80 patients undergoing elective surgery under general anesthesia. After approval of Institutional ethical committee, written informed consent was obtained from all patients. Inclusion criteria were ASA physical status I and II, age group 16-65 years of either sex, patients with head injury, psychiatric disorder, respiratory tract (oropharynx, larynx) pathology, endocrine disorder, predicted difficult airway (such as mouth opening <2 cm, modified MPS class 3 and 4, BMI > 35 kg/m2). Patient having gastroesophageal reflux disease, hiatus hernia, and pregnancy were excluded. Patients were randomly allocated by computer-generated random tables to one of two groups comprising 40 patients in each: group I (Airtraq) and group II (Macintosh).

Anesthetic technique

In the operation theatre after establishing an intravenous route, a ringer lactate solution was started. All patients received intravenous glycopyrolate 0.2 mg, ondensetron 0.1 mg/kg, tramadol 2 mg/kg, and midazolam 0.03 mg/kg 10 minutes before induction of anesthesia. Standard monitors were attached. All the patients were preoxygenated with 100% oxygen for 3 minutes. Induction was done with propofol 2-2.5 mg/kg and muscle relaxation was facilitated with vecuronium 0.1 mg/kg and bag mask ventilation was provided with mixture of oxygen, nitrous oxide, and halothane for 3 minutes. Then tracheal intubation was performed by the Airtraq or Macintosh laryngoscope according to the randomization sequence. Duration of intubation attempt was defined as the time elapsed from insertion of the blade between the dental arches until the ETT was placed through the vocal cords and confirmed by chest rise, auscultation, and square wave capnography. Failed intubation was defined as an attempt in which user could not intubate the trachea even with optimization maneuvers at all or which required >120 seconds to perform the procedure. In the case of failed intubation, intubation with other laryngoscope was allowed.

Optimization maneuvers required to perform tracheal intubation were assessed on a score of 0 to 2:

No maneuvers required.

External laryngeal pressure.

Use of stylet.

During laryngoscopy, POGO (percentage of glottic opening) was assessed on a score of 1-4.

75-100%

50-75%

25-50%

0-25%

Ease of intubation was assessed on a score of 1 to 3:

Easy – tracheal intubation without maneuver.

Satisfactory – tracheal intubation with maneuvers.

Difficult – tracheal intubation not even with maneuvers.

In postoperative period, an investigator who was blinded to the study asked patients about signs of sore throat (throat pain) and for hoarseness of voice.

Throat pain was assessed on a score of 0 to 3: 0. No pain

Mild pain/discomfort only

Moderate pain

Severe pain

Statistical analysis

All data were analyzed using IBM SPSS Statistics 20.0 software. The qualitative data between two groups were compared using the Chi-square test and for comparison of the continuous variable independent t-test was used. P < 0.05 was considered statistically significant.

RESULTS

A total of 80 patients were randomly allocated to one of the two groups for intubation with the Airtraq (group 1) or the Macintosh laryngoscope (group 2). Demographic data were similar in both the groups [Table 1]. Duration of successful tracheal intubation was shorter in the Airtraq group. It was 18.15 (±2.74) seconds in the Airtraq group versus 29.23 (±5.04) second in the Macintosh group (P < 0.001) [Table 2]. Overall successful tracheal intubation rate was 100% (40 patients) with Airtraq and 95% (38 patients) in the Macintosh group. The two patients who were not intubated with the Macintosh laryngoscope were intubated with Airtraq [Table 2]. No optimization maneuvers were required to improve the glottic exposure in 97.5% (39 patients) in the Airtraq group versus 35% of patients (14 patients) in the Macintosh group P < 0.001 [Table 2]. POGO score was also better in the Airtraq group. It was of grade I in 100% (all 40 patients) with the Airtraq group versus 67.5% (27 patients) in the Macintosh group < 0.001 [Table 2]. Ease of intubation was also better in the Airtraq group. It was easy in 97.5% (39 patients) versus 42.5% of patients (17 patients) in the Macintosh group, P < 0.001 [Table 2]. The postoperative complications were comparable in both the groups [Table 3]. The incidence of sore throat was less in the Airtraq group than in the Macintosh group. Laryngospasm and hoarseness were not observed in any patient in both the groups. There was no incidence of lip trauma, dental trauma, and blood tinged secretions over the laryngoscope blade and ETT in any case in both the groups.

Table 1

Demographic characteristics in Group I and Group II

Table 2

Times and success rates for tracheal intubation and POGO score, maneuver score and ease of intubation score

Table 3

Postoperative complications

DISCUSSION

The Macintosh laryngoscope with its curved blade is the most commonly used device for orotracheal intubation despite numerous innovations in airway devices. Airtraq a newer intubation device was compared with the Macintosh laryngoscope and its utility was assessed in this study. We observed that the overall duration of successful tracheal intubation was shorter in the Airtraq group 18.15 (±2.74) seconds versus 29.23 (±5.04) seconds in the Macintosh group, similar results were reported by Pierangelo Di Marco et al.[8] Various studies have shown that Airtraq reduces intubation time for experienced as well as novice intubators.[91011] Another study showed that the Airtraq significantly improved intubation time in difficult airways.[910] Overall successful tracheal intubation was 100% (40 patients) in the Airtraq group and 95% (38 patients) in the Macintosh group. No optimization maneuvers were required to improve the glottic exposure in 97.5% (39 patients) in the Airtraq group versus 35% of patients (14 patients) in the Macintosh group P < 0.001. Only in 2.5% (1 patient), one optimization maneuver was required in the Airtraq group while in 55% patients (22 patients) one maneuver and in 10% (4 patients) two optimization maneuvers were required in the Macintosh group. McElwain et al. had a similar experience.[12] POGO score was also better in the Airtraq group. It was of grade I in 100% of patients (all 40 patients) in the Airtraq group versus 67.5% (27 patients) in the Macintosh group, P < 0.001. In the Macintosh group, the POGO score was 2 in 27% (11 patients) and grade 3 in 5% (2 patient). In our study, the two patients, who were not intubated with the Macintosh laryngoscope, were intubated successfully with Airtraq. The POGO score was also improved in these patients from 3 to 1, it was similar to the observations of Koh et al.[13] Dhonneur et al. demonstrated that Airtraq provides superior intubating conditions.[9] Ease of intubation score was also better in the Airtraq group. It was easy in 97.5% (39 patients) versus 42.5% (17 patients) in the Macintosh group, P < 0.001. It was satisfactory in 2.5% (1 patient) in the Airtraq group versus 52.5% (21 patients) in the Macintosh group. In the Macintosh group, it was found difficult in 5% (2 patients). Several studies demonstrated that the Airtraq laryngoscope also reduces tracheal intubation difficulty score in patients with cervical spine immobilization and difficult airways, compared with the Macintosh laryngoscope.[9141516] McElwain et al. observed that Airtraq reduced the intubation difficulty score, enhanced the Cormack and Lehane glottic view, and reduced number of optimization maneuvers compared with the Macintosh laryngoscope, similar to our study.[12] Airtraq was the rescue device for the two failed intubations in the Macintosh group and was successful in each case, improving the Cormack And Lehane grade from 3 to 1 and POGO scores from 0 to (80 and 100) as has been reported by Maharaj et al.[15] The recently reported finding that the Airtraq produces 66% less movement of the cervical spine when compared with the Macintosh, further underlines the utility of this device in these patients.[16] We do not observe any major hemodynamic changes as far as blood pressure, heart rate, and ECG are concerned in both the groups. There appears to be less potential for trauma to the teeth and upper airway with the Airtraq. Dental trauma scores as measured by the number of dental clicks and/or the severity of dental compression were lower with the Airtraq laryngoscope, particularly in the difficult airway scenarios. This is due to the fact that the Airtraq provides a high quality view of the glottis without a need to align the oral, pharyngea, l and tracheal axis, therefore less force has to be applied during laryngoscopy.Results of previous studies both on manikins and in the clinical setting have shown that the Airtraq is easier to use and teach.[17181920] These studies highlight that although classically airtarq has been used in difficult airway scenarios it can be used effectively as a routine device for tracheal intubation. An important potential advantage of the Airtraq is that it is a single-use device, reducing the chance of prion transfer.[2122] These concerns arise from the difficulties in ensuring that all proteinaceous material has been removed from reusable laryngoscope blades during cleaning and sterilization.[2324] In recognition of these concerns, the guidelines of the Association of Anesthetists of Great Britain and Ireland state that ‘single use intubation aids’ should be used whenever possible.[25] However, studies have reported that certain single use laryngoscope blade provide inferior intubating conditions compared to reusable blades such as the Macintosh.[2627] These findings raise concern regarding the safety of single use conventional laryngoscope blades. Airtraq is at least as effective as the reusable Macintosh laryngoscope, attesting to its safety in this regard.

CONCLUSION

Both Airtraq and Macintosh laryngoscopes are equally effective in tracheal intubation in normal airways. We found that there was a significant difference in ease of intubation and glottic view with use of both the devices. Airtraq required a shorter duration for successful tracheal intubation with significantly lesser optimization maneuvers.