COMPARISON OF VIDEO LARYNGOSCOPY AND DIRECT LARYNGOSCOPY IN A CRITICAL CARE TRANSPORT SERVICE Francis X. Guyette, MD, MPH, Kathryn Farrell, MD, Jestin N. Carlson, MD, MS, Clifton W. Callaway, MD, PhD, Paul Phrampus, MD
INTRODUCTION
Prehosp Emerg Care Downloaded from informahealthcare.com by St Francis Hospital & Med Center on 12/17/12 For personal use only.
ABSTRACT
Prehospital endotracheal intubation (ETI)1 has highly variable (45–85%) success rates, requires comprehensive initial training, and requires continued practice to maintain procedural competency.2,3 Many devices are available to assist providers with ETI, including video laryngoscopy (VL). Video laryngoscopy improves ETI success in the operating room and emergency department.3–5 One VL device, the GlideScope (Verathon Medical, Bothell, WA), has been shown to improve ETI success among ground paramedics.4–7
Objective. We evaluated video laryngoscopy (VL) (C-MAC, Karl Storz, Tuttlingen, Germany) for use in a critical care transport system. We hypothesized that the total number of airway attempts would decrease when using a video laryngoscope versus use of direct laryngoscopy (DL). Methods. We performed a nonrandomized group-controlled trial where six aircraft were outfitted with VL and the remainder utilized DL responding to a mix of scene runs and interfacility transports. Our primary outcome measure was the number of intubation attempts. We also compared the first-pass success (FPS) rates, laryngoscopic grades, and frequencies of rescue device use (including utilization of surgical airways) between VL and DL. Results. Crews intubated 348 patients with VL and 510 with DL. Successful endotracheal intubation within three attempts occurred 97.6% (confidence interval [CI] 96.5–98.6) of the time. The FPS rate was 85.8% (CI 83.4–88.1). In this cohort of patients, VL did not differ from DL with respect to total number of airway attempts (1.17 [CI 1.11–1.22] vs. 1.16 [CI 1.12–1.20]), FPS rate (85.6% [CI 82–89%] vs. 86.1% [CI 83-89]), or use of rescue airways (2.6% vs. 2.2%). The laryngoscopic view was superior in the VL group relative to the DL group (median Cormack-Lehane grade 1 [interquartile range (IQR) 1, 2] vs. 2 [IQR 1, 2]). Conclusion. VL using the C-MAC video laryngoscope did not reduce the total number of airway attempts or improve intubation compared with DL in a system of highly trained providers. Key words: prehospital; intubation; video laryngocopy; HEMS
Video laryngoscopy improves intubation performance by novice prehospital providers in training scenarios.8,9 Video laryngoscopy has been evaluated in simulations of difficult prehospital intubation, including patient immobilization, entrapment, and air medical evaluation.10–12 Use of VL improves laryngoscopic view and success rates in simulators among paramedic students and untrained providers.13,14 Use of video abstracted from VL is useful for the evaluation and retraining of prehospital providers.15 However, there are few data about the effects of VL on procedural success during actual patient encounters. In one study, the use of one variety of video laryngoscope (GlideScope) by a group of experienced paramedics reduced the number of attempts and time required for airway management.5 If confirmed, VL may be an important addition to prehospital care. We evaluated the use of a different version of video laryngoscope (C-MAC, Karl Storz, Tuttlingen, Germany) in a critical care transport system that performs a mix of scene runs and interfacility transports. We describe the total number of attempts at intubation per patient associated with DL and VL. We hypothesized that the total number of airway attempts would decrease when using VL. Our secondary outcomes were first-pass success (FPS) and laryngoscopic view.
PREHOSPITAL EMERGENCY CARE 2013;Early Online:1–6
Received June 21, 2012, from the Department of Emergency Medicine (FXG, KF, JNC, CWC), University of Pittsburgh, Pittsburgh, Pennsylvania; the Medical Department (FXG), STAT MedEvac, West Mifflin, Pennsylvania; and the WISER Center (PP), University of Pittsburgh, Pittsburgh, Pennsylvania. Revision received July 13, 2012; accepted for publication July 26, 2012.
METHODS
The authors report no conflicts of interest. The devices were provided by the Karl Storz corporation at a reduced cost. The corporation had no input into the content of the manuscript.
Study Design We performed a nonrandomized group-controlled trial in which six aircraft were outfitted with a video laryngoscope and the remaining 11 utilized standard direct laryngoscopic equipment. The aircraft groups were selected to match VL and DL bases by the frequency of intubation and casemix (scene vs. interfacility, trauma
Address correspondence and reprint requests to: Francis Xavier Guyette, MD, MPH, University of Pittsburgh, Department of Emergency Medicine, 3600 Forbes Avenue, Iroquois Building, Pittsburgh, PA 15261. e-mail:
[email protected] doi: 10.3109/10903127.2012.729128
1
2
PREHOSPITAL EMERGENCY CARE
vs. medical). The Quality Improvement Committee of the University of Pittsburgh and the Medical Advisory Committee of STAT MedEvac approved use of the VL for medical director review of prehospital airway management. Providers were instructed to use the video laryngoscope as their first-line airway management tool when it was available. The University of Pittsburgh Institutional Review Board (IRB) subsequently considered analysis of the data exempt from requirements for obtaining informed consent.
Prehosp Emerg Care Downloaded from informahealthcare.com by St Francis Hospital & Med Center on 12/17/12 For personal use only.
Population and Setting We evaluated the records of all adult patients requiring airway management by our service. Children known to be less than 18 years of age were excluded. Patients who did not receive advanced airway management or had primary placement of a supraglottic airway were excluded.
Experimental Protocol STAT MedEvac is a Commission on Accreditation of Medical Transport Systems (CAMTS)-accredited critical care transport service with more than 10,000 transports per year. Crews consist of two prehospital professionals, typically a paramedic and a nurse, who receive extensive airway training. Each member of the flight crew performs a minimum of 12 ETIs on patients per year, as well as yearly skills review and high-fidelity simulation training. The Storz C-MAC video laryngoscope was chosen for this study because of its ability to record video and its design similarity to a direct laryngoscope. The CMAC uses a standard Macintosh blade combined with VL technology that allows the user to perform either DL or VL without changing equipment. Prior to deployment of the devices, all personnel were trained on the use of the C-MAC using a mixture of didactics and practice of skills on an airway simulation manikin. In addition, manikins were available for practice at the bases for one week, equivalent to two shifts per provider. Competency was assessed at initial training and twice yearly during simulation training and competency testing.
APRIL/JUNE 2013
VOLUME EARLY ONLINE / NUMBER 2
sided alpha-error rate of 0.05, anticipating 124 missed attempts yearly and an 85% FPS, based on historical quality-improvement data (unpublished). Based on these calculations, 304 intubations would be needed for each group. Given an accrual of approximately 20 intubations per month and accounting for some loss (∼5%), we reviewed 18 months of data.
Data Collection and Analysis Crews documented all airway management events using an electronic medical record. Data points included the type of equipment used, the number of airway attempts, the use of any rescue devices, Mallampati scores, and Cormack-Lehane (CL) airway grade. After charting, crew members completed a survey regarding their experience with the C-MAC device. Participants rated their experience with the video laryngoscope on a five-point Likert scale relative to intubation by direct visualization. We also recorded data on intubation indication, which method (direct vs. video) was used, and location of intubation. Data were analyzed using descriptive statistics, including means for parametric data and medians for nonparametric data. Tests of comparison included the t-test or Wilcoxon test for data not normally distributed. We coded number of attempts as a continuous variable and performed linear regression. We characterized FPS as a dichotomous variable. We assessed univariate associations between variable and the outcomes of number of attempts and FPS. We developed a parsimonious multivariate model using univariate associations with p-values greater than 0.1. We included VL as our key independent variable in the multivariate analysis. The model was further refined to assess interaction terms. We described the goodness of fit with the Hosmer-Lemeshow (HL) test for FPS and R2 for the total number of attempts. Given that STAT MedEvac employs over 160 providers and we anticipated the number of intubations per provider captured in this study to be small relative to the total population, we did not account for clustering in our analysis. We used an intention-to-treat analysis. Data were analyzed using STATA version 11 (StataCorp, College Station, TX).
RESULTS Outcome Measures The primary outcome measure for this study was the number of intubation attempts. An intubation attempt is defined as placing a blade past the teeth. In addition, we examined the FPS rate, laryngoscopic grade, frequency of rescue device use, and utilization of surgical airways between VL and DL. Sample size was calculated to detect a 50% reduction in missed airway attempts, among patients requiring more than one attempt, with 90% power and a two-
Crews performed airway management on 875 patients, including 17 in whom a supraglottic airway was placed as the primary airway. Of those undergoing ETI, crews treated 348 with VL and 510 with DL. One hundred sixty-seven providers performed intubations (median 4.5; interquartile range [IQR] 2, 8), with VL being performed by 83 individuals (median 3; IQR 1, 7) during the study period. Successful ETI within three attempts occurred 97.6% (confidence interval [CI] 96.5–98.6) of the time. The FPS rate during this period
Guyette et al.
3
VIDEO LARYNGOSCOPY IN CRITICAL CARE TRANSPORT
TABLE 1. Characteristics of Patients Intubated with Video Laryngoscopy and Direct Laryngoscopy
Prehosp Emerg Care Downloaded from informahealthcare.com by St Francis Hospital & Med Center on 12/17/12 For personal use only.
Age—mean (CI), yr Weight—mean (CI), kg Mallampati score—median (IQR) GCS—median (IQR) Scene transport, % (CI) Cervical immobilization, % (CI) Number of attempts—mean (CI) First-pass success, % (CI) Rescue, % (CI) Laryngoscopic view—median (IQR)
Total Intubations (N = 858)
Direct Laryngoscopy (n = 510)
Video Laryngoscopy (n = 348)
p-Value
48.1 (46.5 to 49.7) 80.5 (78.8 to 82.3) 2 (1, 3) 6 (3, 12) 72 (69 to 75) 52 (49 to 55) 1.16 (1.13 to 1.20) 85.8 (83.4 to 88.1) 2.4 (1.4 to 3.5) 2 (1, 2)
48.5 (46.3 to 50.7) 78.7 (76.2 to 81.2) 2 (1, 3) 6 (3, 12) 67 (63 to 71) 49 (45 to 54) 1.16 (1.12 to 1.20) 86.1 (83 to 89) 2.2 (1 to 3.4) 2 (1, 2)
47.5 (45.1 to 49.9) 83.1 (80.7 to 85.5) 2 (1, 3) 6 (3, 11) 80 (75 to 84) 56 (51 to 61) 1.17 (1.11 to 1.22) 85.6 (82 to 89) 2.6 (1 to 4.3) 1 (1, 2)
0.51 0.06 0.09 0.61 0.001 0.06 0.79 0.86 0.61 0.001
CI = confidence interval; GCS = Glasgow Coma Scale score; IQR = interquartile range.
was 85.8% (CI 83.4–88.1). Patients in whom ETI was unsuccessful had a supraglottic rescue airway placed (20/21) or a surgical airway (1/21) (Fig. 1). The VL and DL patients did not differ with respect to age, weight, initial Glasgow Coma Scale score (GCS), cervical immobilization, or provider-reported Mallampati score (Table 1). Video laryngoscopy was performed more frequently on scene runs than on interfacility transports. In this cohort of patients, VL did not differ from DL with respect to total number of airway attempts, FPS rate, or use of rescue airways. The CL grade of the laryngoscopic view was better with VL (median 1 [IQR 1, 2]) than with DL (median 2 [IQR 1, 2]) (Table 1). Video laryngoscopy resulted in significantly more grade I views than DL and significantly fewer grade II and IV views. There was no difference between the two methods for grade III views (Fig. 2). The total number of airway attempts had univariate associations with laryngoscopic grade, VL, scene
FIGURE 1. Consolidated Standards of Reporting Trials (CONSORT) diagram for the study.
TABLE 2. Multivariate Predictors of Total Attempts Variables
Video laryngoscope Mallampati 2 Mallampati 3 Mallampati 4
Coefficient
95% Confidence Interval
0.04 0.08 0.20 0.44
(–0.03 to 0.11) (–0.01 to 0.16) (0.11 to 0.29) (0.29 to 0.59)
runs, patient weight, and aircraft base. The FPS rate had univariate associations with laryngoscopic grade, VL, Mallampati score, scene runs, and aircraft base. Additionally, comparing the VL intubations in which the providers stated that they used the video laryngoscope screen versus those in which the providers used only DL revealed no difference in the total number of airway attempts (F = 0.715) or FPS rate (odds ratio [OR] 1.11 [CI 0.74–1.67]). In the multivariate models, only a Mallampati grade of 3 or 4 was associated with an increased number of airway attempts (Table 2) or reduced FPS rate (Table 3). The multivariate model for FPS rate has an acceptable goodness of fit based on the HL test probability >0.997. The majority of providers reported that VL was easier (2 on the Likert scale) or much easier (Likert 1) than DL (median 2 [IQR 2, 3]). Only 8% described it as more difficult (Likert 4) or much more difficult (Likert 5).
FIGURE 2. Association of the C-MAC with laryngoscopic view. DL = direct laryngoscopy.
Prehosp Emerg Care Downloaded from informahealthcare.com by St Francis Hospital & Med Center on 12/17/12 For personal use only.
4
PREHOSPITAL EMERGENCY CARE
APRIL/JUNE 2013
VOLUME EARLY ONLINE / NUMBER 2
FIGURE 3. Histogram representing perceived ease of use of the video laryngoscope as compared with direct laryngoscopy (% of responses).
TABLE 3. Multivariate Predictors of First Pass Success Variables
Video laryngoscope Mallampati 3 Mallampati 4
Odds Ratio
95% Confidence Interval
0.87 0.21 0.08
(0.54 to 1.41) (0.11 to 0.42) (0.03 to 0.18)
Crews using the VL reported that they relied entirely (64%) or mostly (14%) on the video screen to guide intubations (Figs. 3 and 4).
DISCUSSION Prehospital ETI is a high-consequence procedure and there exists equipoise regarding its benefit to
patients.16–19 The role of VL in prehospital intubation is undefined, but has been suggested to improve intubation success among novice providers and decrease number of attempts and time to definitive airway in other providers.5,13 A recent meta-analysis has confirmed the benefit of VL in novice providers, but failed to demonstrate a difference with respect to time to intubation and FPS.20 We compared VL and DL in an air medical system with a historical success rate in excess of 95% within three attempts and FPS greater than 85%. In this setting, no difference was observed with respect to total number of airway attempts, FPS rate, or use of rescue airways. Time to definitive airway could not be accurately measured in the DL cohort, preventing any comparison of this parameter between VL and DL in this study.
FIGURE 4. Method of intubation using the video laryngoscope (% of responses).
Prehosp Emerg Care Downloaded from informahealthcare.com by St Francis Hospital & Med Center on 12/17/12 For personal use only.
Guyette et al.
5
VIDEO LARYNGOSCOPY IN CRITICAL CARE TRANSPORT
The use of VL did improve CL airway grade, consistent with a previous study.4 Analysis of CL grade between DL and VL would indicate that VL results in a greater frequency of CL grade I airway views as compared with CL grade II airway views in the DL cohort. It is not clear whether changing the CL grade from II to I is clinically important. Most providers would be able to intubate a patient with a CL grade II, perhaps explaining the absence of effect on FPS rate or number of total attempts with VL use. Higher CL grades are rarely encountered, and the role of VL for those cases could not be adequately tested in this study. Video laryngoscopy may provide other benefits for prehospital providers besides improving success rates. For example, VL reduces the time required for airway management, and VL may provide more accurate metrics to describe intubation.15 On scene, VL allows for a real-time visualization of the airway by other providers. In the event of failure by the initial operator, knowledge of the anatomy may allow the second operator to plan modifications to the conditions of the intubation. Via communications technology, online medical directors might be able to coach prehospital providers during airway management. Finally, recording of the laryngoscopic attempts allows for individual assessment and quality-improvement reviews that are of direct benefit to operators. These videos also offer a breadth of airway scenarios and images for teaching that most prehospital providers may rarely encounter. Future studies using VL may improve systemwide intubation success through improved programs of education and total quality management.
LIMITATIONS This study was conducted in a single agency of skilled providers with a high overall success rate. This may have resulted in a ceiling effect, limiting the ability to show a clinically or statistically significant difference in the primary outcomes. Although time to intubation can be abstracted from the VL cohort, we are unable to accurately record time in the DL cohort. Previous studies have used an observer with a stopwatch, which would be impractical in the helicopter emergency medical services environment. Intubation success is also a function of the skill of the individual provider, which may have led to clustering if only a few providers were performing the majority of the procedures. We do not believe this to be the case, as all 167 providers performed intubations during the study period, with 83 individuals performing VL. Data on airway grades, complications, patient assessment, and the intubation procedure were recorded after completion of the mission at the time the chart was generated. This may have resulted in a recall bias with respect to the details of the mission or a reporting bias in the number of airway attempts. We believe this
to be unlikely, as both crew members have to sign and attest to the chart. A review of a subset (30%) of the VL cohort was consistent with the values reported in the medical record. In addition, the C-MAC video laryngoscope can be used to perform DL, which may have reduced the exposure of the VL cohort. Our providers reported using the screen the majority of the time.
CONCLUSION Video laryngoscopy using the C-MAC video laryngoscope does not reduce the total number of airway attempts or improve the FPS rate in this system of highly trained providers. Video laryngoscopy improves laryngoscopic view as compared with DL.
References 1. Wang HE, Yealy DM. Out-of-hospital endotracheal intubation: where are we? Ann Emerg Med. 2006;47:532–41. 2. Wang HE, Seitz SR, Hostler DP, Yealy DM. Defining the learning curve for paramedic student endotracheal intubation. Prehosp Emerg Care. 2005;9:156–62. 3. Wang HE, Yealy DM. How many attempts are required to accomplish out-of-hospital endotracheal intubation? Acad Emerg Med. 2006;13:372–7. 4. Tremblay MH, Williams S, Robitaille A, Drolet P. Poor visualization during direct laryngoscopy and high upper lip bite test score are predictors of difficult intubation with the GlideScope videolaryngoscope. Anesth Analg. 2008;106:1495–500, table of contents. 5. Wayne MA, McDonnell M. Comparison of traditional versus video laryngoscopy in out-of-hospital tracheal intubation. Prehosp Emerg Care. 2010;14:278–82. 6. Cooper RM, Pacey JA, Bishop MJ, McClusky SA. Early clinical experience with a new videolaryngoscope (GlideScope) in 728 patients. Can J Anaesth. 2005;52:191–8. 7. Su YC, Chen CC, Lee YK, Lee JY, Lin KJ. Comparison of video laryngoscopes with direct laryngoscopy for tracheal intubation: a meta-analysis of randomised trials. Eur J Anaesthesiol. 2011;28:788–95. 8. Low D, Healy D, Rasburn N. The use of the BERCI DCI Video Laryngoscope for teaching novices direct laryngoscopy and tracheal intubation. Anaesthesia. 2008;63:195–201. 9. Kim YM, Kang HG, Kim JH, Chung HS, Yim HW, Jeong SH. Direct versus video laryngoscopic intubation by novice prehospital intubators with and without chest compressions: a pilot manikin study. Prehosp Emerg Care. 2011;15:98–103. 10. Cavus E, Callies A, Doerges V, et al. The C-MAC videolaryngoscope for prehospital emergency intubation: a prospective, multicentre, observational study. Emerg Med J. 2011;28:650–3. 11. Nakstad AR, Sandberg M. The GlideScope Ranger video laryngoscope can be useful in airway management of entrapped patients. Acta Anaesthesiol Scand. 2009;53:1257–61. 12. Berg BW, Vincent DS, Murray B, Boedecker BH. Videolaryngoscopy for intubation skills training of novice military airway managers. Stud Health Technol Inform. 2009;142:34–6. 13. Nouruzi-Sedeh P, Schumann M, Groeben H. Laryngoscopy via Macintosh blade versus GlideScope: success rate and time for endotracheal intubation in untrained medical personnel. Anesthesiology. 2009;110:32–7. 14. Aziz MF, Dillman D, Fu R, Brambrink AM. Comparative effectiveness of the C-MAC video laryngoscope versus direct
6
PREHOSPITAL EMERGENCY CARE
Prehosp Emerg Care Downloaded from informahealthcare.com by St Francis Hospital & Med Center on 12/17/12 For personal use only.
laryngoscopy in the setting of the predicted difficult airway. Anesthesiology, 2012;116:629–36. 15. Carlson JN, Quintero J, Guyette FX, Callaway CW, Menegazzi JJ. Variables associated with successful intubation attempts using video laryngoscopy: a preliminary report in a helicopter emergency medical service. Prehosp Emerg Care. 2012;16: 293–8. 16. Davis DP, Peay J, Sise MJ, et al. The impact of prehospital endotracheal intubation on outcome in moderate to severe traumatic brain injury. J Trauma. 2005;58:933–9. 17. Davis DP, Fisher R, Buono C, et al. Predictors of intubation success and therapeutic value of paramedic airway management
APRIL/JUNE 2013
VOLUME EARLY ONLINE / NUMBER 2
in a large, urban EMS system. Prehosp Emerg Care. 2006;10: 356–62. 18. Wang HE, Peitzman AB, Cassidy LD, Adelson PD, Yealy DM. Out-of-hospital endotracheal intubation and outcome after traumatic brain injury. Ann Emerg Med. 2004;44:439–50. 19. Wang HE, Simeone SJ, Weaver MD, Callaway CW. Interruptions in cardiopulmonary resuscitation from paramedic endotracheal intubation. Ann Emerg Med. 2009;54:645–52. 20. Griesdale DEG, Liu D, McKinney J, Choi PT. GlideScope videolaryngoscopy versus direct laryngoscopy for endotracheal intubation: a systematic review and meta-analysis. Can J Anesth. 2012;59:41–52.
