Comparison of the ease of tracheal intubation by postgraduate residents of anesthesiology using Airtraq™ and Macintosh laryngoscopes: An observational study

Abstract

Context:

Airtraq™ (Prodol Meditec, Vizcaya, Spain) is a recently developed laryngoscope, which facilitates easy visualization of glottis through a matrix of sequentially arranged lenses and mirrors. In this observatory study, we sought to compare the ease of tracheal intubation with Airtraq™ and Macintosh laryngoscope when performed by 2^nd year postgraduate residents of Anesthesiology in NRI Medical College, Mangalagiri.

Aims:

To compare the ease of tracheal intubation by Airtraq™ laryngoscope with that by Macintosh laryngoscope among the 2^nd year postgraduate residents of anesthesiology in terms of time taken for intubation and the rise of rate-pressure product (RPP) with intubation.

Settings and Design:

Prospective randomized observational study.

Subjects and Methods:

Eighty adult and healthy patients with an easy airway, scheduled for general anesthesia were allocated into two groups A, and M. Patients in Group A were intubated with Airtraq™ laryngoscope and those in Group M were intubated with Macintosh laryngoscope by the 2^nd year postgraduate residents of anesthesiology. The time taken for intubation, the RPPs at baseline, after induction of general anesthesia, postintubation, at 3 and 5 min after intubation, the rise of RPP to intubation and the occurrence of a sore throat were compared between the two groups.

Statistical Analysis Used:

Descriptive and inferential statistical methods were used to analyze the data.

Results:

The mean time for intubation in Macintosh group was 28.18 s and was 40.98 s in Airtraq group. The mean rise of RPP to intubation was 4644.83 in Airtraq group and 2829.27 in Macintosh group. The incidence of a sore throat was equal in both the groups.

Conclusions:

The time for intubation and the sympathetic response to airway instrumentation were more with Airtraq™ laryngoscope than with Macintosh laryngoscope.

INTRODUCTION

Airway management has been the domain of dominance for anesthesiologists over ages. Laryngoscopy and tracheal intubation are the fundamental skills that every clinician aspires to learn, practice, and excel once he/she enters the fraternity of anesthesia. There has been an untiring research in search of ideas dedicated to the development of most effective equipment as well as a technique for securing airways. Ever since the branch of anesthesiology established its identity in the divine tree of medicine, countless clinical trials were carried out evaluating the merits and demerits of various devices and techniques meant for tracheal intubation. The most frequent end point for almost all the studies was the ease of intubation, which was measured in terms of time taken for intubation along with the ability to minimize the sympathetic response to tracheal instrumentation. Airtraq™ is a recently developed laryngoscope, which facilitates easy visualization of glottis through a matrix of sequentially arranged lenses and mirrors. In this observatory study, we sought to compare the ease of tracheal intubation with Airtraq™ and Macintosh laryngoscope when performed by 2^nd year postgraduate residents of Anesthesiology in NRI Medical College, Mangalagiri.

SUBJECTS AND METHODS

Objective of the study

To compare the ease of tracheal intubation by Airtraq™ laryngoscope with that by Macintosh laryngoscope among the 2^nd year postgraduate residents of anesthesiology in terms of time taken for intubation and the rise of rate-pressure product (RPP) with intubation.

Approval from the Institutional Ethics Committee and written informed consent from the patients were obtained. The patients belonging to American Society of Anesthesiologists (ASA) physical status 1 and 2, with an expected easy airway, scheduled for general anesthesia between January 2015 and June 2015 were included in the study. The patients with a difficult airway, coronary artery disease, beta blocker medication, and patients who required rapid sequence intubation were excluded from the study. The patients were allocated into two groups “A” and “M” using a computer-generated randomization program. After being wheeled into the operating room, intravenous (IV) access was secured, standard monitors were connected and the baseline readings of heart rate (HR), oxygen saturation, systolic, diastolic, and mean arterial pressures were recorded. All the patients were preoxygenated with 100% oxygen for 3 min and received glycopyrrolate 5 μg/kg. Anesthesia was induced with midazolam 0.02 mg/kg, fentanyl 1 μg/kg, and titrated doses of propofol until the loss of verbal contact. Vecuronium bromide in a dose of 0.1 mg/kg was administered to facilitate tracheal intubation and anesthetic depth was maintained with mask ventilation using 1% sevoflurane in oxygen until tracheal intubation. Laryngoscopy and tracheal intubation were performed after 5 min by 2^nd year postgraduate anesthesiology residents using Airtraq™ (Prodol Meditec, Vizcaya, Spain) in Group A patients and Macintosh laryngoscope in Group M patients. All the residents who participated in the study had an experience of doing at least 20 intubations using Airtraq. The time from introduction of the laryngoscope blade into the mouth to the visual appearance of capnography trace on the monitor following intubation was considered as the intubation time. Rate-pressure product (RPP) was calculated by multiplying systolic blood pressure with HR. RPP was recorded at baseline, postinduction, immediately after intubation, at 3 and 5 min after intubation along with the intubation time. Incidence of sore throat after extubation was also recorded. Intubation was stopped and bag and mask ventilation commenced, if the oxygen saturation dropped to below 90% or if the handle of the laryngoscope was removed out of the mouth to facilitate proper insertion and the patient was excluded from the study.

Statistical analysis

Descriptive and inferential statistical methods were used to analyze the data. In descriptive statistics, calculation of means, and standard deviation were done using Microsoft Excel. In inferential statistics, Z-test of difference between two means was used to test the difference in the quantitative parameters viz., age, weight, intubation time, RPP at various time points, and the rise of RPP to intubation. Power of the study was calculated using online power calculator for two independent sample study.

RESULTS

A total of 93 patients were enrolled in the study in the stipulated period of 6 months with 44 in Macintosh group and 49 in Airtraq group. Four patients in Group M required gum elastic bougie for intubation and were excluded. In Group A, light failed in one case and the secretions obliterated the vision through the lens in eight patients, excluding nine patients from the study. Thus, 80 patients were analyzed with 40 in each group. The power of the study calculated based on the difference in the mean time for intubation among the two groups is 100%. Thus, the sample size was adequate for the study. The demographic profile was comparable between the groups. A highly significant difference was observed in the intubation time between the two groups. The mean time for intubation in Macintosh group was 28.18 s, which was far <40.98 s in Airtraq group. The mean rise of RPP to intubation was observed to be more in Airtraq group (4644.83) than in Macintosh group (3286.28) [Table 1]. The incidence of sore throat observed in the postoperative period was 10 out of 40 in both the groups.

Table 1.

Evaluation of airtraq against macintosh laryngoscope

DISCUSSION

“Change” is the doctrine of evolution. A motivated driving of that change for the betterment of mankind is nothing but research. The phenomenal progress that took place in the field of surgery in the last 50 years is undoubtedly because of the enhanced safety in providing anesthesia. Effective airway management plays a pivotal role in the safety of anesthesia. The comfort of advanced techniques of securing and maintaining the airway, which the current generation of anesthesiologists is privileged to practice and teach, did not appear out of blue. The technique of tracheal intubation, which today's residents of anesthesiology are excited to learn, has its roots dated back to latter half of 19^th century when Joseph P. O'Dwyer performed blind tracheal intubations.[1] Later on the technique of laryngoscopy was developed by Kirsetein in Germany in 1895. Various blades were made subsequently, with the most popular being the one developed in 1921 by Dr. Robert R. Macintosh. To visualize the glottis in direct laryngoscopy, the oral, pharyngeal, and the laryngeal axes are needed to be synchronized, which is possible only with an optimal cervical flexion coupled with an effective atlanto-occipital extension. Thus, direct laryngoscopy is jeopardized in conditions of compromised mobility of the cervical spine, inadequate mouth opening, large tongue, and defective dentition. In the last 20 years, there has been a tremendous development in designing the airway equipment suited to overcome the said problems. Numerous articles were published, evaluating the effectiveness of the advanced airway devices such as intubating LMA,[2] C-trach,[3] video laryngoscope,[4] Glidescope,[5] Bullard laryngoscope,[6] fiber-optic bronchoscope,[7] etc. Indirect laryngoscopy offers the advantage of viewing the glottis even without aligning the three axes. In this study, we studied the effectiveness of Airtraq laryngoscope, compared to that of the conventional Macintosh laryngoscope. There were indeed studies done earlier on Airtraq versus direct laryngoscopy. In 2009, Savoldelli et al.[8] conducted a study on nurses and residents of anesthesiology, evaluating the learning curves in the usage of Glidescope, McGrath, and Airtraq laryngoscopes using manikins with a normal airway model. They concluded that Airtraq displayed the most favorable learning curve. Similar studies were performed using manikins with difficult airway model,[9,10,11,12] in which the role of Airtraq was observed to be very promising. However, in the study done by Trimmel et al.,[13] in the real prehospital scenario, exactly opposite results were observed. They concluded that the clinical learning process of the Airtraq laryngoscope was much longer than reported in the anesthesia literature. In 2012, White et al.[14] evaluated the efficacy of Airtraq against conventional laryngoscopy in infants and children. They found out that although the Airtraq laryngoscope provided an improved view of the larynx compared with conventional laryngoscopy, tracheal intubation took longer. Thus, basically all those studies were aimed at evaluating the effectiveness of Airtraq laryngoscope in compromised airway conditions. In contrast, our study is purely an observatory study, basically aimed at comparing the learning dynamics of postgraduate residents of anesthesiology in a real operating room scenario. Thus, in this study, we included only adults of ASA physical status 1 and 2 without any airway difficulty. There was also no scope for multiple attempts at laryngoscopy or intubation. In this study, we observed that visualizing the glottis with Airtraq was relatively easier, but passing the endotracheal tube took more time, as the direction of movement of the tube was fixed by a slot in the device. The observations in our study matched those in earlier studies. To study the sympathetic response to intubation, we used RPP in contrast to the earlier studies where the blood pressure and HR were compared separately. Mean arterial pressure is the best predictor for tissue perfusion. The sympathetic response to laryngoscopy and tracheal intubation is best reflected in the product of HR and systolic blood pressure.[15,16] In our study, we observed that the rise in the RPP following intubation was significantly more with Airtraq, than with the Macintosh laryngoscope [Figure 1]. This could be probably due to the longer duration of laryngoscopy in the Airtraq group as the time for intubation was more in this group than in Macintosh group [Figure 2]. The most significant factor during laryngoscopy influencing cardiovascular responses was found to be the duration of laryngoscopy.[17] The most common difficulty with Airtraq reported by the postgraduate residents was that, though glottis was visualized quickly, the endotracheal tube was hitching either to the epiglottis anteriorly or to the arytenoids posteriorly and maneuvering the tube through the vocal cords was not always smooth as it has to pass through a fixed slot in the device. However, the incidence of sore throat was exactly equal in both the groups in our study, in contrast to what was observed in the earlier studies. From the observations of our study, we opine that there is a lot of scope for further research in this arena. The time for visualization of the glottis, ease of passing the endotracheal tube, attempts at intubation, and the incidence of soft tissue injury can be separately evaluated in the scenario of various degrees of difficulty in the airway.

Figure 1.

Rise of rate pressure product to intubation. RPP = Rate pressure product

Figure 2.

Time taken for intubation

CONCLUSION

In this observatory study, we conclude that the time for intubation and the sympathetic response to airway instrumentation were more with Airtraq laryngoscope than with Macintosh laryngoscope when performed by 2^nd year postgraduate residents of anesthesiology in patients without difficult airway.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest