Journal of Anesthesia & Clinical Care Category: Clinical Type: Research Article
Learning Curve of the Infant GlideScope® Cobalt Video Laryngoscope in Anesthesiology Residents
- Mazen Faden1, Hossam El-Beheiry2, Carolyne Pehora3, Cengiz Karsli4*
- 1 Department Of Anesthesia And Critical Care, King Abdulaziz University, Jeddah, Saudi Arabia
- 2 Department Of Anesthesia, Trillium Health Centre, Toronto, Canada
- 3 Department Of Anesthesia And Pain Medicine, The Hospital For Sick Children, University Of Toronto, Toronto, Canada
- 4 Department Of Anesthesia And Pain Medicine, The Hospital For Sick Children, University Of Toronto, Toronto M5G 1X8, Canada
*Corresponding Author:Cengiz Karsli
Department Of Anesthesia And Pain Medicine, The Hospital For Sick Children, University Of Toronto, Toronto M5G 1X8, Canada
Received Date: Feb 09, 2015 Accepted Date: Mar 31, 2015 Published Date: Apr 14, 2015
Objective: The purpose of this study was to evaluate the learning curve associated with infant GlideScope® Cobalt Video Laryngoscope intubation by anesthesiology residents compared to direct laryngoscopy.
Methods: Sixteen anesthesiology residents who had no prior experience with infant airway management performed a total of 10 tracheal intubations each (5 GlideScope® and 5 direct laryngoscope, randomized) in infants weighing 10 kg or less. Primary end points included time to optimum view of the vocal cords and time to tracheal intubation. Multivariate ANOVA and pair-wise comparisons were used to analyze the data.
Results: There were no significant differences in time to optimum view of the cords or time to intubate between the 1st and 5th intubations for either device. Intubating conditions were similar for both devices.
Conclusion: The learning curve associated with infant GlideScope® laryngoscopy and intubation by resident’s novice to infant airway management seems to be flat and identical to that with direct laryngoscopy.
The sample size for this study was calculated assuming the expected ‘time to intubate’ using direct laryngoscopy is 20 ± 8 s and the expected mean difference between direct and GlideScope® laryngoscopy is 6 s  Thus the effect size is the mean difference divided by the standard deviation of mean difference, or 1.4. G*Power 3.1.5 software (Department of Psychology, Dusseldorf, Germany) determined the sample size of residents based on one sample two-tailed paired t-test. The calculated sample size was 8 residents . We increased the number of residents from eight to sixteen in order to decrease the chance of a type I error.
|Glidescope Video Laryngoscopy||Direct Laryngoscopy||p-value|
|Age (months)||6.38 ± 3.14||6.20 ± 3.77||0.735|
|Weight (kg)||7.26 ± 1.98||6.61 ± 2.01||0.131|
|Laryngeal view (1/2/3/4)||78/0/0/2||76/4/0/0||0.407|
|Time to visualization (s)||7.08 ± 4.34||11.38 ± 10.28||0.072|
|Time to intubate (s)||21.7 ± 9.61||24.36 ± 11.67||0.229|
Two-way MANOVA was conducted to determine the effect of the successive intubations performed by residents when using the devices (GCV and DL) on the two dependent variables TOV and TTI. Bartlett’s test verified the hypothesis of equality of variances for the TOV and ITT data (p=0.12 and 0.156 respectively). Also, Bartlett’s confirmed the homogeneity of the variances among the time points in each group separately. Dixon’s Q test did not identify any outliers and all the values within every set of data had a Q value less than the limit value for the test at 95% confidence. Significant differences in times to optimum view or intubation were not found among the successive intubations performed by residents when using the GCV and DL devices on TOV and TTI, Wilks’ lambda = 0.88, F(18,178) = 0.67, p = 0.83. Figures 1 and 2, show the mean and standard deviations of the dependent variables for the intubations performed by residents for the two devices (GCV and DL). Additionally, MANOVA did not detect any difference between the mean TOV and TTI among the GCV or DL devices. The interaction between the intubation number (from 1 to 5) and the repeated use of the devices (GCV and DL) was not statistically significant, Wilks’ lambda = 0.95, F (8,178) = 0.57, p = 0.8. Subsequent one-way repeated measures ANOVA and pairwise comparisons did not show statistical significance within the GCV or DL durations, namely the TOV and TTI. There was also no statistically significant difference within the mean TOV and TTI at each intubation number when infants were intubated with the GCV or DL (Table 2).
|Cobalt GlideScope®||Direct Laryngoscope||Difference between means||CI 95% of difference (s)*||P value**|
|Time to visualization (s)|
|1st Intubation||6.30||16.70||-10.40||-28.43 to 7.63||0.338|
|2nd Intubation||6.00||10.90||-4.90||-11.78 to 1.98||0.297|
|3rd Intubation||7.80||10.40||-2.60||-8.00 to 2.80||0.378|
|4th Intubation||8.90||11.50||-2.60||-6.64 to 1.44||0.316|
|5th Intubation||8.10||9.10||-1.00||-7.08 to 5.08||0.585|
|Time to intubate (s)|
|1st Intubation||25.30||31.00||-5.70||-24.76 to 13.36||0.484|
|2nd Intubation||23.80||25.20||-1.40||-11.85 to 9.05||0.610|
|3rd Intubation||25.3||26.2||-0.90||-8.94 to 7.14||0.629|
|4th Intubation||26.00||28.40||-2.40||-13.54 to 8.74||0.544|
|5th Intubation||22.00||25.40||-3.40||-10.01 to 3.21||0.363|
(M1 – M2) ± tCL × SEM1 – M2; where M1 – M2 is the difference between sample means, tCL is the t value for the desired level of confidence, i.e., 1-α=1-0.05=0.95 and the desired degrees of freedom (df), i.e., df = n – 1 for equal sample sizes for the paired t-test, and SEM1-M2 is the estimated standard error of the difference between sample means.
**P value <0.05 is considered statistically significant.
The main findings in this study include the following; 1) There is no significant difference in the time taken by residents with each intubation when using the GCV versus direct laryngoscopy. There was no difference between the learning curves for either device. 2) There was no significant difference in the times to optimum view or intubation over the 5 intubations for each of the devices separately. The learning curves for both devices are ‘flat’. 3) Using the Cobalt GlideScope® does not affect the time taken by residents to achieve visualization or intubation with the direct laryngoscope, and vice versa. The learning curve for one device does not affect the learning curve for the other device. These findings support the notion of teaching the use of the infant GCV to junior anesthesiology residents.
Previous studies have reported either prolonged or similar intubation times with video laryngoscopes when compared with direct laryngoscopy [9-11].
There are several limitations to this study. Residents involved in the current study had no previous experience intubating infants’ tracheas; however all had considerable experience with both direct laryngoscopy and GCV in adults. This may account for the apparent flat learning curves seen in the current study. It may be argued the learning curves came about earlier on in the residents’ training, and the skills and techniques learned in adult practice may have translated to early successful direct and GlideScope® laryngoscopy in small infants. In other words, perhaps the flat learning curves seen in the current study are due to the fact residents had “mastered” the use of this equipment in larger patients. A previous pediatric study suggested that the GlideScope® may provide an equal or better laryngoscopic view compared to direct laryngoscopy, however it required a longer time for intubation . This study involved older children and evaluated the older generation of GlideScope®.
The majority of patients in the current study had an Adnet intubation difficulty score of zero (i.e., easy intubation). Interpretation of any differences in the Adnet scores between DL and GCV intubations using the Adnet Intubation Difficulty Scale is problematic. A recent analysis has found that when the scale is used with indirect laryngoscopes, it may not be indicative of true intubation difficulty . Indeed, compared to direct laryngoscopy, GlideScope® video-laryngoscopy may be associated with improved glottic visualization .
The manufacturer’s guidelines for GCV blade sizing should be adhered to whenever possible, or until there is sufficient evidence to alter the current guidelines. Three sizes of single use blades are available for the infant GCV; the size 0 blade is for infants < 1.5 kg, size 1 is for infants weighing 1.5 - 3.6 kg and size 2 is for patients 1.8 - 10 kg. It is for this reason infants weighing 10 kg or less were enrolled, in order to adhere to manufacturer’s guidelines for use of the infant-sized blades. Based on similar learning curve studies for novel intubation devices, five laryngoscopies per device were deemed sufficient to identify or characterize any learning curve [13,14].
In conclusion, this study suggests that the use of the GlideScope® Cobalt Video laryngoscope in infants by anesthesiology residents is associated with a success rate and with times to optimum view of the vocal cords and tracheal intubation comparable to those with direct laryngoscopy. In the author’s opinion the infant GlideScope® Cobalt Video laryngoscope may be a useful teaching tool and intubation aide.
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Citation:Faden M, El-Beheiry H, Pehora, Karsli C (2015) Learning Curve of the Infant GlideScope® Cobalt Video Laryngoscope in Anesthesiology Residents. J Anesth Clin Care 1: 006.
Copyright: © 2015 Mazen Faden, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.