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EMS House of DeFrance http://www.emshouse.com Studies Trials Abstracts Courtesy the EMS House of DeFrance http://www.defrance.org Feasibility of Laryngeal Mask Airway Use By Prehospital Personnel in Simulated Pediatric Respiratory Arrest ABSTRACT
Introduction. Pediatric respiratory arrest is a technically challenging scenario infrequently faced by prehospital providers. Prehospital endotracheal intubation (ETI) is a complex procedure, and one study showed that it may result in worse neurological outcome in these patients. Alternatives to ETI include bag-valve- mask (BVM) ventilation and the laryngeal mask airway (LMA). Although the LMA has been used successfully for pediatric resuscitation in the hospital setting, there is no data describing its use in the prehospital setting. Hypothesis. Prehospital providers can successfully place and ventilate the pediatric LMA in a simulated pediatric respiratory arrest. Methods. Paramedic students received a 1-hour training session covering the use of the pediatric LMA. Subjects performed airway management of a simulator manikin using both the LMA and the BVM. Rate of successful LMA placement, time to first ventilation, tidal volume by weight, and ventilations per minute were recorded. A generalized estimating equation analysis was completed to determine the effects of time and ventilation technique. Results. All 13 subjects (100%) successfully ventilated the mannequin with both techniques. The median number of attempts required to successfully place the LMA was one. Median time from the start of the scenario to BVM ventilation was 4 seconds (IQR 3, 5), and the median for LMA ventilation was 30 seconds (IQR 25, 52). Tidal volumes were significantly greater with BVM ventilation (5.07 mL/kg [IQR 4.47, 5.43]) than with LMA ventilation (2.88 mL/kg [IQR 2.17, 4.04]). An obvious air leak was present in all LMA cases, potentially resulting in reduced tidal volume delivery. Excessive ventilatory rates were noted in both BVM (42 ventilations per minute [IQR 33, 46]) and LMA (37 ventilations per minute [IQR 31, 39]) groups. Conclusions. Prehospital providers were able to place and ventilate a simulated pediatric respiratory arrest patient using the LMA after a brief educational intervention. Obvious air leakage was noted when ventilating with the LMA and likely represents one technical limitation of using a simulator. Key words: emergency medical services (EMS); simulation; respiratory arrest; airway management; laryngeal mask airway.
PREHOSPITAL EMERGENCY CARE 2007;11:245-249
INTRODUCTION
Pediatrie prehospital airway management is a critical intervention in pediatrie cardiopulmonary arrest and trauma care, yet it remains a difficult and contentious skill. Endotracheal intubation (ETI) by paramedics, the standard of care for decades, has been called into question.1 In the prehospital environment, ETI has been performed inconsistently in the pediatrie population with success rates varying from 50% to 88%.2-4 Previous studies have identified ETI as a weakness of prehospital pediatrie care and questioned its utility and safety.5-7 Specifically, ETI has been associated with poor outcomes in trauma and arrest populations.8,9 Gausche et al. noted that patients suffering respiratory arrest and receiving ETI were significantly more likely to have a poor neurological outcome than those receiving bag-valve-mask (BVM) ventilation.8 Moreover, the relative infrequency of pediatrie ETI makes it a difficult skill for prehospital providers to maintain.10
Potential alternatives to pediatrie ETI include both BVM and the laryngeal mask airway (LMA). BVM ventilation is effective; however, it is a complex psychomotor skill that requires frequent reassessment of mask placement and two rescuers for optimal performance.11,12 The two-rescuer method is not always feasible in the prehospital setting because there may be only one rescuer in the back of the ambulance during patient transport.
The LMA is a supraglottic airway management device inserted without laryngoscopy and has been used as an alternative to ETI in both the operating room and the emergency department.13-18 It has been shown to be effective in the hospital setting for both neonatal and pediatrie resuscitation.19,20 However, no data exist for the pediatrie LMA as a prehospital device for airway management and resuscitation.21,22
New methods should be investigated without compromising patient safety. Simulators have been used to permit similar low-frequency, high-consequence events to be executed in a controlled environment without compromising patient safety.23,24
The objective of our study is to describe the use of an LMA by prehospital providers during a simulated pediatrie respiratory arrest. We hypothesize that prehospital providers can use a LMA reliably in this simulated scenario after a focused training session.
METHODS
Subjects consisted of a convenience sample of volunteer paramedic students at the Center for Emergency Medicine of Western Pennsylvania (Pittsburgh, PA). These individuals had previously completed traditional Basic Life Support training with Emergency Medical Technician-Basic (EMT-B) certification but had not yet completed paramedic training. The subjects had been trained on the 2000 American Heart Association CPR guidelines but did not have invasive airway experience prior to completing this study. The University of Pittsburgh Institutional Review Board approved this study as exempt from informed consent.
The LMA device used for this study was a size 11/2 pediatrie Laryngeal Mask Airway Classic (LMA North America, San Diego, CA). The BVM device used for this study was a 500-mL Ambu SPUR Pediatric Disposable Resuscitator (Ambu Inc., Glen Burnie, MD), which is a self-inflating resuscitation bag with a #2 infant face mask. Tidal volume was measured by a Bird Partner Volume Monitor Model #15060 flow meter (Viasys, Conshohocken, PA). The mannequin used for the simulated respiratory arrest was a fullsize infant (simulated weight of 7 kg) Laerdal Sim Baby (Laerdal Medical Corporation, Wappingers Falls, NY).
Subjects received 1 hour of didactic training by the investigators on the indications, contraindications, and use of the pediatric LMA. The following week, they participated in a brief hands-on session during which they practiced placement of and ventilating with the LMA. Two weeks later, each subject was evaluated by performing a simulated pediatric respiratory arrest using a SimBaby infant simulator. Subjects were instructed to manage the simulator as they would a real-life patient found in respiratory arrest. First, subjects were instructed to use the BVM and ventilate for a period of 1 minute from the time of the initial delivered breath. Next, subjects were instructed to place the LMA and ventilate the simulator with the LMA for 1 additional minute. Subjects were blinded to the outcome measures being evaluated.
The following data were recorded during the simulation: 1) time (in seconds) subject required to prepare BVM and begin successful ventilations, 2) number of breaths delivered in 1 minute with the BVM, 3) time (in seconds) subject required to prepare the LMA and begin successful ventilations, 4) number of attempts at LMA placement until subject successfully ventilated the mannequin, and 5) number of breaths delivered in 1 minute with the LMA. A successful insertion of the LMA was defined as correct supraglottic positioning of the device, proper inflation of the cuff, and successful ventilation. Successful ventilation was defined as the presence of chest rise during positive pressure ventilation with a bag valve attached either to a mask or the LMA and was visually verified by two researchers (FXG, JCR).
During the 1-minute ventilation periods, tidal volume of the delivered breaths was recorded. Tidal volume was extrapolated from flow through the BVM and LMA using the Bird Partner Volume Monitor. One evaluator (KR) recorded the flow data in 10-second intervals for the entire 1-minute ventilation period. Subjects were blinded to the tidal volume data. Tidal volumes were adjusted for the simulated weight of the infant mannequin and are presented as milliliters per kilogram of simulated weight.
Data were entered into a personal computer and analyzed with descriptive statistics (means, medians, confidence intervals, and interquartile ranges). Because the tidal volume measurements are made over time, we required a statistical test that allows us to evaluate the following 1) the effect between the BVM and LMA groups and 2) the effect of time on tidal volume. Therefore, a generalized estimating equation (GEE) analysis was completed. Data were analyzed with Stata 9.0 (Stata, Inc., College Station, TX).
RESULTS
Thirteen subjects completed the study. All had completed EMT-B training and 69% were male. Ages ranged from 18 to 27 with a mean of 22 years. The subjects had an average of 3 years of prehospital experience (range 2.1, 4.2). Each subject successfully placed the LMA (100%). Ventilation data are presented in Table 1. Median times from the start of the scenario to BVM ventilation and LMA ventilation were 4 (IQR 3, 5) and 30 seconds (IQR 25,52) respectively.
Ventilation rates are summarized in Table 2. Rates varied widely among the group with a median of 42 per minute (IQR 33, 46) with the BVM and 37 (IQR 31,39) with the LMA. Tidal volumes were significantly greater with BVM ventilation (5.07 mL/kg [IQR 4.47, 5.43]) than with LMA ventilation (2.88 mL/kg [IQR 2.17, 4.04]). The GEE analysis also note\d lower tidal volumes in the LMA group than in the BVM group (â = -12.73; 95% CI -17.17, -8.40; r^sup 2^ value 0.39). This difference was not affected over time (Figure 1).
DISCUSSION
Pediatric airway management in the prehospital setting is a high- consequence, low-frequency event that is imperative to the treatment of prehospital trauma and cardiopulmonary arrest victims. ETI, once considered the standard of care, has been called into question because studies have shown varying success rates in the prehospital setting. The LMA, which can be inserted blindly without direct laryngoscopy, may be a feasible alternative.
In this study, a brief 1-hour training session enabled inexperienced subjects to successfully place an LMA in a simulated pediatric respiratory arrest in 100% of the cases. The majority of subjects were able to successfully place the LMA in one attempt. One subject, however, did require four attempts to place the LMA. It should be noted that during his third attempt, the LMA was judged to be successfully placed by both evaluators. The subject felt the placement was not correct and replaced it a fourth time. This placement was also correct and the subject successfully ventilated the mannequin thereafter.
An additional benefit to the LMA is that it can be placed rapidly. In our study, the median time to set up the device and place it was 30 seconds (IQR 25, 52). Pediatric ETI has been reported to require between 23 seconds and 2 minutes.8,25 One limitation of the LMA is that it may not provide adequate protection against aspiration. Two studies have noted that LMA use did not have clinically significant aspiration. However, these studies were conducted in the operating room and are not readily generalizable to the prehospital arena.26,27 The incidence of aspiration for emergent ETI ranges between 1% and 13%.28,29 Repeated attempts increase the risk of aspiration, and rapid successful placement of an LMA may decrease this risk. However, to date we are unaware of any study that has compared the incidence of aspiration between the LMA and conventional ETI.
Although one may argue that the BVM is more rapid to initiate and equally successful, the LMA still may afford significant advantages over the BVM. Although LMA placement requires a significant initial time investment, the device can be secured in place and does not have to be resealed after every breath as the BVM does. Once secured, the LMA can be ventilated by one rescuer, whereas the BVM may require two rescuers to maintain optimal seal and ventilation.
The brevity of the training session because important as prehospital airway management is an infrequent task for paramedics and the skill would be infrequently reinforced though real-world practice. Although training in live patients in the operating room (OR) has been shown to be beneficial for ETI, it has become impractical and is not available to most prehospital providers.30 Frequent, brief training using a human simulator may compensate for infrequent practical experience. A brief training intervention, such as the one used in this study, could prove to be a useful supplement to OR time and the occasional field experience.
We note that the tidal volumes generated by the LMA were less than those generated by BVM ventilation but were adequate for successful ventilation (defined as the presence of chest rise in this study). Prior work by our group with this simulator demonstrated similar tidal volumes of 5.9 mL/kg in single-rescuer BVM ventilation.12 In both studies, these tidal volumes are less than the recommended volume of 10 mL/kg. We also noted a similar limitation in our prior work using an LMA in an adult simulator.31 We do note that the rubber hypopharynx of the mannequin does not have the same compliance found in the clinical setting. Limitations such as this may prevent accurate measurement of tidal volume with the LMA. Therefore, it is possible that the tidal volume actually delivered by the subjects met or exceeded the recommended volume.
Finally, subjects significantly hyperventilated the mannequin with both the LMA and BVM. The recommended ventilation rate for a 7- kg infant would be 20 breaths per minute. Subjects ventilated at a median of 42 breaths per minute (IQR 33,46) using the BVM and 37 breaths per minute (IQR 31, 39) using the LMA. These results are similar to the findings of Aufderheide et al. in adult cardiac arrest patients.32 These results suggest that prehospital providers require continued education and awareness regarding optimal ventilation rates.
LIMITATIONS
This is a small study designed to show the feasibility of an educational intervention providing new skills to prehospital personnel. Thus, we did not evaluate skill atrophy over time or translation of these skills to the clinical setting. These are important areas for future study. second, the study was limited by the equipment used. We used only one size simulator and one size pediatrie LMA Classic device. Therefore, our observations may not be applicable to all devices or children. Furthermore, the simulator cannot replicate the anatomic variability of the human airway or address real-life situations that contribute to difficult airways, such as blood or regurgitation.
CONCLUSION
Prehospital providers were able to ventilate a simulated pediatrie respiratory arrest patient using the pediatrie LMA after a brief educational intervention. The LMA may be an alternative to the BVM and ETI for prehospital airway management. Future studies should evaluate prehospital providers using the pediatrie LMA in a controlled environment prior to clinical translation.
The Peter M. Winter Institute for Simulation, Education and Research (WISER) provided simulators for the study. Dr. Guyette is supported by the Society for Academic Emergency Medicine EMS Fellowship grant. Dr. Rittenberger is supported by the Clinical Skills Training Core of the Resuscitation Outcomes Consortium through the National Heart, Lung and Blood Institute 5UOl HL077871- 02.
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Francis X. Guyette, MD, MS, Kimberly R. Roth, MD, MPH, David C. LaCovey, BS, EMTP, Jon C. Rittenberger, MD
Received June 16,2006, from the University of Pittsburgh Department of Emergency Medicine, Pittsburgh, PA (FXG, JCR); The Children's Hospital of Pittsburgh, Division of Pediatrie Emergency Medicine, Pittsburgh, PA (KRR); and The Children's Hospital of Pittsburgh, Prehospital and Emergency Care Services, Pittsburgh, PA (DCL). Revision received September 7, 2006; accepted for publication October 1, 2006.
Address correspondence and reprint requests to: Jon C. Rittenberger, University of Pittsburgh, 230 McKee Place, Suite 400, Pittsburgh, PA 15213. e-mail: doi: 10.1080/10903120701205273
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