Asphyxia leads to cardiac arrest more often in infants and children than in adults, therefore airway management, including adequate ventilation, is very important during paediatric resuscitation. The 2010 Cardiopulmonary Resuscitation Guidelines state that tracheal intubation is the most secure and effective way to manage the airway in infants and children, but special training and experience are required [1–3]. Therefore, following paediatric asphyxial arrests, successful tracheal intubation and adequate ventilation during cardiopulmonary resuscitation are critical to outcome. Recently, many different types of laryngoscope have been marketed for the purposes of aiding tracheal intubation [4, 5]. Both the Pentax Airway ScopeTM (AWS; HOYA, Tokyo, Japan) and the AirtraqTM (Prodol Meditec SA, Vizcaya, Spain) are anatomically shaped indirect laryngoscopes that provide a view of the glottis without the need to obtain a line of sight between the operator’s eye and the glottis. Both laryngoscopes have a tube channel that holds a tracheal tube and guides it toward the glottis without the need for an intubating stylet . Some studies have reported that these are effective intubation devices compared with other devices including the conventional Macintosh laryngoscope blade [7–11]. The AWS and Airtraq devices have been used in various clinical settings, including difficult airway management scenarios and in emergency situations [12–14]. However, until recently only adult-sized blades were available for use with the AWS and experience with this device has been limited. The Airtraq has been available in several different sizes, including one for infants, for some time now and its effectiveness has already been demonstrated . In 2011, an AWS blade designed for infants became commercially available and we have compared this with the equivalent sized Airtraq in an infant manikin both at rest and during a simulated resuscitation scenario involving external chest compressions.
We compared the Pentax Airway ScopeTM with the AirtraqTM optical laryngoscope in an infant manikin. Twenty-three anaesthetists randomly performed tracheal intubation: at rest, (a) with the Airway Scope and (b) with the Airtraq; and during chest compressions, (c) with the Airway Scope and (d) with the Airtraq. The success rate, modified Cormack and Lehane classification for glottic view, time taken to view the glottis, and time to place the tracheal tube were recorded. There was no difference in intubation success rate or quality of glottic view between the two devices. The median (IQR [range]) time taken to obtain a view of the glottis was 4.5 (3.7–6.4 [1.8–14.0]) s using the Airway Scope compared with 7.1 (5.5–9.6 [3.3–12.0]) s using the Airtraq (p = 0.001), and to successful placement of the tracheal tube was 8.3 (6.8–9.4 [3.7–20.7]) s using the Airway Scope compared with 11.2 (10.4–13.8 [4.9–23.7]) s using the Airtraq (p = 0.001). During chest compressions, the median (IQR [range]) time taken to view the glottis was 5.1 (4.0–7.2 [2.0–12.4]) s using the Airway Scope compared with 7.5 (5.0–13.2 [4.2–26.4]) s using the Airtraq (p = 0.006), and to successful placement of the tracheal tube was 9.5 (6.6–13.7 [4.5–16.2]) s using the Airway Scope compared with 11.7 (9.1–18.1 [6.2–37.4]) s using the Airtraq (p = 0.022). We conclude that both devices provided good quality views of the glottis and successful tracheal intubation in an infant manikin both at rest and during external chest compressions. Use of the Airway Scope resulted in a shorter time to view the glottis and perform successful tracheal intubation compared with the Airtraq.
Following local research ethics committee approval and written informed consent, 23 anaesthetists in our departments participated in this study. Each anaesthetist was given a standardised demonstration of the AWS and Airtraq devices. They were then allowed 5 min to practise the intubation technique on a Laerdal ALS Baby Trainer (Laerdal Medical AS, Stavanger, Norway), a 3-month-old infant trainer for practising advanced resuscitation skills including tracheal intubation and external chest compressions. For tracheal intubation, the AWS with a neonatal blade and the Airtraq-infant (size 0) were used and all intubations were performed using a 3.5-mm internal diameter and a 4.8-mm outer diameter uncuffed tracheal tube (Portex; Smiths Medical, St. Paul, MN, USA). Chest compressions were performed with the encircling hands technique by advanced life support providers at a rate of 100 times per minute and at a depth of one third of the thickness of the manikin’s chest, according to the advanced life support guidelines. If any interruption to chest compressions was required during tracheal intubation, the pause time was measured. Each participant performed in the following settings: (a) intubation with the AWS; (b) intubation with the Airtraq; (c) intubation with the AWS during external chest compressions; and (d) intubation with the Airtraq during external chest compressions. The order in which the intubations were performed was determined randomly using a sealed envelope. The success rate of tracheal intubation, the modified Cormack and Lehane classification of laryngeal view , the time taken to see the vocal cords (defined as the time taken from insertion of the device into the oral cavity until obtaining a view of the vocal cords), and the time taken to place the tracheal tube (defined as the time taken from insertion of the device into the oral cavity until the tracheal tube was successfully placed into the trachea) were recorded.
Our primary endpoint was to evaluate whether the AWS provided superior intubation profiles compared with the Airtraq. The secondary endpoint was to evaluate whether the AWS reduced the time to successful tracheal intubation compared with the Airtraq. A power analysis was performed using G*Power 3, a free analysis program designed by Faul et al. (Department of Psychology, Christian-Albrechts-University, Germany) . According to our preliminary data, the mean (SD) intubation time using the Airtraq without chest compressions was 12.3 (4.1) s. Considering an α error of 0.05 and a β error of 0.2, we estimated that 18 participants would be required to demonstrate a 33% reduction in intubation time. The preliminary mean (SD) intubation time with the Airtraq during chest compressions was 14.0 (5.1) s. With the same α and β error settings, 22 participants would be required to show a 33% decrease in intubation time during chest compressions. We therefore enrolled 23 anaesthetists in this study. Mann–Whitney tests were used to analyse the data between the devices. Statistical analysis were performed using Prism 5 software (GraphPad Software, Inc., La Jolla, CA, USA), and p values less than 0.05 were considered statistically significant.
A grade-1 view of the glottis was obtained in all cases and all tracheal intubations with both the AWS and the Airtraq were successful, both at rest and during external chest compressions. No pauses were required during chest compressions at the time of tracheal intubation with either device. The times taken to view the vocal cords and perform tracheal intubation were significantly shorter using the AWS compared with the Airtraq both at rest and during external chest compressions (Table 1). The time taken from obtaining a view of the glottis until placement of the tracheal tube was not significantly different between the AWS and the Airtraq, both at rest (median (IQR [range]) 3.4 (2.3–4.4 [1.6–7.7]) s vs 3.8 (3.2–6.5 [1.7–13.0]) s, p = 0.11) and during chest compressions (3.8 (2.6–5.1 [1.8–11.2]) s vs 4.2 (3.6–5.0 [1.4–11.1]) s, p = 0.26).
|AWS (n = 23)||Airtraq (n = 23)||p value|
|Time to view the glottis; s|
|Without compressions||4.5 (3.7–6.4 [1.8–14.0])||7.1 (5.5–9.6 [3.3–12.0])||0.001|
|With chest compressions||5.1 (4.0–7.2 [2.0–12.4])||7.5 (5.0–13.2 [4.2–26.4])||0.006|
|Time for successful tracheal intubation; s|
|Without compressions||8.3 (6.8–9.4 [3.7–20.7])||11.2 (10.4–13.8 [4.9–23.7])||0.001|
|With chest compressions||9.5 (6.6–13.7 [4.5–16.2])||11.7 (9.1–18.1 [6.2–37.4])||0.022|
Both the AWS and Airtraq indirect laryngoscopes are now available in infant sizes which facilitate tracheal intubation using tracheal tubes with internal diameters of between 2.5 and 3.5 mm. In terms of the quality of glottic view obtained and success rate of tracheal intubation, both devices were similar and clinically acceptable. However, use of the AWS resulted in a significantly shorter time to view the glottis and perform tracheal intubation compared with the Airtraq, both at rest and during external chest compressions. Both devices have been demonstrated to be effective in the management of both routine and difficult airways [5, 7, 12] and successful use of the Airtraq in children has been reported previously [17, 18], including by Shimada et al., who performed successful tracheal intubation in all 100 paediatric patients, including three difficult airway cases . Whilst the AWS has been shown to be superior to the Airtraq in adults [20, 21], this is the first time that it has been shown to be superior to the Airtraq in an infant manikin study. A faster view of the glottis was the reason for the shorter tracheal intubation times using the AWS because it provides continuous observation of the laryngeal structures from the moment the device is inserted into the mouth, whereas the Airtraq requires a practitioner to look into the eyepiece for a glottic view, and this is only possible at the middle, to late, phase of insertion. In addition, the infant blade of the AWS is thinner and narrower (9.0 mm thick, 15.5 mm wide) when compared with the Airtraq (12.5 mm thick, 21.0 mm wide) and this may allow easier and faster access to the larynx when using the AWS.
Asphyxia is the most common mechanism for cardiac arrest in infants and children, so successful airway management, including adequate ventilation of the lungs, is of paramount importance during resuscitation. Current resuscitation guidelines recommend securing the airway with minimal interruption to external chest compressions and both the AWS and Airtraq devices have been reported to be useful intubation devices in adults [13, 22, 23]. Koyama et al. reported that the AWS was superior to the Airtraq for tracheal intubation during external chest compressions because the Airtraq device required an operator to look into the eyepiece and movement from external chest compression impaired the view of the glottis . However, in an infant study, the Airtraq was reported as effective in allowing tracheal intubation during external chest compressions compared with the Miller blade . Although our results confirmed a high tracheal intubation success rate and excellent glottic views with both devices, even during external chest compressions, tracheal intubation when using the AWS was significantly faster than when using the Airtraq. Although a 2-s difference in the time for successful tracheal intubation may not seem critical, during resuscitation attempts the faster the airway is secured the better, especially in infants, who have high metabolic rates and increased oxygen demands.
There are some limitations to this study. Firstly, it was a manikin study and there was no blood, vomit or secretions that may have impaired the view of the glottis. Secondly, the devices were not evaluated in difficult infant airways and the results cannot be extrapolated to other patient groups.
In conclusion, although both devices provided excellent views of the glottis during tracheal intubation in infant manikins, both at rest and during external chest compressions, use of the AWS resulted in faster tracheal intubation compared with the Airtraq.
The authors thank S. Tampo (TESOL/TEFL instructor, Hokusei Gakuen University High School, Sapporo, Japan) for grammatical advice.
No external funding and no competing interests declared.