Except for neonates and specific malformations in children, management of the paediatric airway is not a major problem for the anaesthetist. Failure to successfully intubate the trachea and secure the airway remains a leading cause of morbidity and mortality in operative settings.1
The airway in small children is very different from that in infants and older children. Differences include a large head that tends to flex the short neck and obstruct the airway, and a disproportionately large tongue, short jaw, long palate, long epiglottis, more cephalad-located larynx and soft airway that may cause airway obstruction and more difficult laryngoscopy.2
Many different designs of laryngoscopes have been developed in an effort to reduce the incidence of this problem.3,4
The Truphatek TruView EVO2 system (Truphatek International Ltd, Netanya, Israel) is a new laryngoscope blade system with an optical assembly that illuminates the larynx. Therefore, a potentially better view of the larynx may be obtained in patients who present a poor view with the traditional laryngoscope. The blade of the laryngoscope is a modified blade incorporating a magnified optic side port that provides a wide and magnified laryngeal view at a 46° anterior refracted angle. The blade has an integrated oxygen jet cleaning system to prevent moisturing and provide oxygen insufflation.4
The aim of the study was to compare the effectiveness of the TruView EVO2 laryngoscope with the Miller laryngoscope in paediatric patients.
Participants and methods
Ethical approval for this study (Ethical Committee N° TUTFEK 2009/141) was provided by the Ethical Committee of Trakya University Hospital, Edirne, Turkey (President Professor D. Dokmeci) on 11 June 2009. Written informed consent was obtained from the parents of each participating child. Patients of 2–8 years of age undergoing surgery for which tracheal intubation was necessary were enrolled into the study.
Exclusion criteria included the presence of raised intracranial pressure, high risk for pulmonary aspiration such as gastric outlet obstruction, bowel stasis, and hiatus hernia, coagulopathy, and presence of any disorder of the head and neck.
Preoperatively, patient demographics and Mallampati scores5,6 were all recorded. Preoperative airway evaluation was performed by anaesthetists who were unaware of the patients' group allocation.
In the operating room, all patients were monitored using electrocardiogram, non-invasive blood pressure, capnometer and pulse oximeter. After preoxygenation, anaesthesia was induced by facemask with sevoflurane and 60% nitrous oxide in oxygen. After placement of an intravenous cannula, the trachea was intubated with rocuronium bromide in a dose of 0.8 mg kg−1 and mechanically ventilated. Anaesthesia was maintained by sevoflurane (2.0–2.5%), and fentanyl 1–2 μg kg−1 was given for analgesia. Two anaesthetists (M.T.I. and M.K.), each with at least 4 years of experience, performed the intubations. Each anaesthetist had performed at least 20 preliminary intubations using the TruView laryngoscope prior to the start of the study.
Randomisation to intubation with the TruView EVO2 or Miller laryngoscope was performed using sealed envelopes opened by the anaesthesiologist in the operating room. The patients were randomly divided into two groups: endotracheal intubation using a Miller blade (Group M, n = 25) or a TruView EVO2 blade (Group T, n = 25). Only the oral route for intubation was chosen in all patients. Several measures were used to reduce fogging of the distal lens of the TruView EVO2, including insufflation of oxygen from the side port, warming of the blade with hot water and use of chemical defogging agents.
The primary endpoint was the Intubation Difficulty Scale (IDS) score, and the secondary endpoints were the duration of the tracheal intubation procedure and the rate of successful placement of the endotracheal tube in the trachea. The IDS score, developed by Adnet et al.,7 is a quantitative scale including multiple indices of intubation difficulty such as the number of intubation attempts, the number of operators, the number of alternative intubation techniques used, glottic exposure, lifting force required during laryngoscopy, necessity for external laryngeal pressure and position of the vocal cords at intubation.8
The time to intubation was measured from the time the instrument entered the patient's mouth until the time it was taken out after the placement of an endotracheal tube in the trachea. A failed intubation attempt was defined as an attempt in which the trachea was not intubated, or which required more than 60 s to perform. A maximum of three intubation attempts were permitted. If more than one attempt was required, the patient received mask ventilation between attempts. In the event that tracheal intubation was unsuccessful with the device tested, desaturation (peripheral oxygen saturation <90%) and bradycardia [heart rate (HR) < 100], tracheal intubation was performed with another laryngoscope, and atropine was used (0.01–0.02 mg kg−1). Additional endpoints included the view of the glottis at laryngoscopy according to the Cormack and Lehane grading criteria,9 mean arterial pressure (MAP) and HR before and after intubation, lowest peripheric oxygen saturation during intubation attempts and all complications (minor laceration, dental or other airway trauma).
The numeric results were expressed as mean ± SD, and categorical results were expressed as a number. Normality distribution of the variables was tested using one-sample Kolmogorov–Smirnov test. Differences between groups were assessed using the unpaired Student's t-test for normal. The χ2 test was used to compare the differences of categorical variables between the groups. The HR and MAP changes (difference before and after) between groups were compared by analysis of covariance (ANCOVA) test. Statistica 7.0 (StatSoft Inc., Tulsa, Oklahoma, USA) statistical software was used for statistical analysis. A P value less than 0.05 was considered statistically significant.
Post-hoc power analysis was done at the end of study taking the IDS score and time as the main outcomes. The power of this study was 62% for IDS score and 89% for time with α equal to 0.05, n1 equal to 25 and n2 equal to 25.
Twenty-five patients were enrolled in each group (Fig. 1). The mean age in group M was 4.72 ± 1.5 years and in group T was 4.68 ± 1.7 years. The mean weight in group M was 16.88 ± 4.25 kg and in group T was 16.84 ± 4.52 kg. Demographic data are shown in Table 1. The patients in both the groups were similar for sex, age and weight.
Mallampati scores were similar between groups and are shown in Table 2.
The IDS scores were not significantly different between groups. The IDS score distributions with each laryngoscope are shown in Table 3.
The time for laryngoscopy was different between the two groups: 6.36 ± 0.99 s in group M and 13.8 ± 7.99 s in group T. Cormack and Lehane grade views are shown in Table 4. There was a significant difference in Cormack and Lehane grade views between the two groups (P = 0.034). The intubation success rate was 100% in group M and in group T.
The HR change (difference before and after) in group M was significantly lower than the HR change in group T (P < 0.001). However, the MAP change was similar between groups (Table 4). The lowest peripheric oxygen saturation during intubation attempts was 99.4 ± 0.57% in group M and 97.6 ± 2.41% in group T. There was a significant difference between groups (P < 0.001). No desaturation (peripheric oxygen saturation <90%) or bradycardia was detected during the study.
No dental or more severe airway laceration was detected with any laryngoscope. There were no between-group differences in the incidence of complications.
We aimed to compare the effectiveness of the TruView EVO2 laryngoscope with that of the Miller laryngoscope in paediatric patients. The results suggest that the IDS scores of the two laryngoscopes were similar. However, the time taken for tracheal intubation using the TruView EVO2 laryngoscope was longer than that for the Miller laryngoscope, but the TruView EVO2 laryngoscope provided an improved laryngoscopic view as compared to the Miller laryngoscope.
The IDS developed by Adnet et al.7 is a quantitative scale incorporating multiple indices of intubation difficulty that more objectively quantify the complexity of tracheal intubations. The IDS score was recently used in children and adults to assess intubation difficulty.8,10 In a study by Malik et al.,10 the authors compare different laryngoscopes, including the Macintosh and TruView EVO2 laryngoscope, in patients with cervical spine immobilisation. In that study, the authors found that the TruView EVO2 did reduce the IDS, and the IDS was significantly higher in the Macintosh compared with all other laryngoscopes. In our study, we found no difference between the IDS scores of the two laryngoscopes.
Malik et al.10 found that the duration of tracheal intubation with the TruView EVO2 blade was longer than that with other laryngoscopes. The authors concluded that using the TruView EVO2 with its camera attachment on the top of the blade and fogging on the distal lens were the primary reasons for the increased duration of tracheal intubation. Singh et al.11 compared the effectiveness of the TruView EVO2 and the Miller blade in neonates and infants and found the time for laryngoscopy was 18 s for the TruView EVO2 laryngoscope and 16 s for the Miller laryngoscope. They found that the average time for tracheal intubation using the TruView EVO2 laryngoscope was 1.88 s longer than that using the Miller blade, which was not clinically significant. The authors concluded that this situation may have been due to the greater experience of the anaesthesiologist with the Miller blade and the fact that the TruView EVO2 requires the user to perform intubation in an indirect manner, seeing the tube through the lens. Barak et al.12 did a study to compare the effectiveness of the TruView EVO2 and the Macintosh blade in adult patients. They concluded that the duration of intubation was 62 s for the TruView EVO2 system and 51 s for the Macintosh blade. They found no statistical difference and drew the same conclusions as the study by Singh for the reason of increased duration of tracheal intubation. In our study, we found the time for laryngoscopy was 6.36 s using the Miller laryngoscope and 13.8 s for the TruView EVO2 laryngoscope, which was statistically significant. In our opinion, the principal reasons for the increased duration of tracheal intubation, first, may have been the greater experience of anaesthesiologists with the Miller laryngoscope, although the anaesthesiologists who participated in this study had practised with the TruView blade several times prior to starting the study. Second, the use of the TruView blade requires good eye-hand coordination and practice. At first, as the anaesthesiologists are looking through the TruView lens, they focus on the vocal cords and do not see the tube at all. The tube needs to be advanced blindly until its tip enters the TruView's visual field. Then, the tube should be introduced through the vocal cords while looking through the lens. Performing this manoeuvre requires good eye-hand coordination and practice. In addition, there were also problems with fogging on the distal lens, which reduced image quality and increased the intubation duration. Similar to other studies, several methods were used in our study to reduce lens fogging, including insufflation of oxygen from the side port, warming of the blade with hot water and use of chemical defogging agents.
The Cormack and Lehane grading system, though originally designed to compare glottic views at direct laryngoscopy,9 provided a useful comparison of the direct and indirect laryngoscopic views achieved in this study. Recent studies demonstrated that the TruView EVO2 laryngoscope provides a better view during laryngoscopy. Malik et al.10 found that the TruView EVO2 laryngoscope had significantly lower Cormack and Lehane scores compared with the Macintosh laryngoscope, but no patients with Mallampati scores more than II were detected in their study. Barak et al.12 found that the Cormack view was significantly better with the TruView EVO2 laryngoscope in a group of patients with a significantly higher oropharyngeal Mallampati view and a higher number of restricted cervical or temporomandibular joint mobility. The authors concluded that the TruView EVO2 was a useful option for tracheal intubation in patients with normal and anticipated difficult airways. Another study13 found that the TruView EVO2 laryngoscope overall provided a better view of the glottis as scored by the same grading system. The authors concluded that, therefore, a potentially better view of the larynx may be obtained with a TruView laryngoscope in patients who would present a grade 3 or 4 laryngoscopic view with a traditional laryngoscope, and demonstrated that the design of the TruView EVO2 was the main reason for this situation, because the TruView EVO2 laryngoscope is designed to offer an optical view ‘around the corner,’ allowing a view of the glottis via the prismatic lens without having to align oral, pharyngeal and tracheal axes. In our study, similar to these results, we found that the TruView EVO2 laryngoscope provided a better view of the glottis as scored by the Cormack and Lehane scores. The design of the TruView EVO2 laryngoscope was the main reason for this situation.
Recent studies found different results for intubation success rates.10–13 Malik et al.10 found an overall success rate of 93.3% for the TruView EVO2 group. Singh et al.,11 Barak et al.12 and Li et al.13 found no cases of failure to intubate. Similar to these studies, we found the same success rate for the TruView blade and the Miller blade at 100%. The success may be related with experienced users of each device.
In the study by Malik et al.,10 the authors found that HR and MAP were increased significantly in all groups, and the effects of laryngoscopy and tracheal intubation on the MAP and HR were relatively modest. The authors concluded that these findings may reflect the fact that these devices provide a view of the glottis without the need to align the oral, pharyngeal, and tracheal axes, thereby reducing the potential for haemodynamic stimulation. In our study, the HR change in group M was significantly lower than that in group T. However, the MAP change was similar between groups. The reason for this was the longer duration of intubation time in the TruView EVO2 group.
Malik and Barak showed no difference between the lowest haemoglobin oxygen saturations in their studies. In our study, we demonstrated statistically different lowest haemoglobin oxygen saturation during intubation attempts. This may have been due to the long duration of intubation time with the TruView EVO2 laryngoscope in paediatric patients. In critically ill children, this may be important.
In our study, similar to other studies,10,11,13 we found no dental or more severe airway laceration. Barak et al.12 concluded that soft tissue damage and bleeding gums/lips were higher detected by using the Macintosh blade. The authors concluded that the TruView blade is designed to enable indirect laryngoscopic view; thus, the anaesthetist applies less force on the anterior larynx, resulting in fewer patients with bleeding and soft tissue damage.
The main limitation of this study was that it was not blinded, due to the unfeasibility of blinding the anaesthetist to the laryngoscope type being used. Second, this study was carried out by experienced users of each device. The results seen may differ in the hands of less experienced users. Another potential limitation of our study was that sample size estimation was not done prior to undertaking the study. However, a post-hoc power analysis was done at the end of study taking the IDS score and time as the main outcomes. The power of this study was 62% for IDS score and 89% for time with α equal to 0.05, n1 equal to 25 and n2 equal to 25.
In conclusion, when compared with the Miller laryngoscope, the TruView EVO2 laryngoscope appears to improve the view of the larynx, but requires a longer time for tracheal intubation. The IDS scores were similar. Thus, the TruView EVO2 laryngoscope can be a good alternative to the traditionally used Miller laryngoscope. The TruView EVO2 is a useful option for tracheal intubation in patients with anticipated difficult airways. Further studies with larger sample size are recommended to compare these tools in patients with anticipated difficult airways.
The authors wish to thank all anaesthesia residents for helpful suggestions. No person involved in this study has any financial relationship with the TruView EVO2 laryngoscope or Truphatek International Ltd. There was no support from a pharmaceutical company or a manufacturer. None of the authors had any conflicts of interest.
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