Emergency. 2018; 6 (1): e58 OR I G I N A L RE S E A RC H Evaluation of Airway Management Proficiency in Pre- Hospital Emergency Setting; a Simulation Study Shahrzad Ghiyasvandian1, Afshin Khazaei2∗, Masoumeh Zakerimoghadam3, Rasoul Salimi4, Ali Afshari5, Abbas Mogimbeigi6 1. Department of Medical Surgical Nursing, School of Nursing and Midwifery, Tehran University of Medical Sciences, Tehran, Iran. 2. Intensive Care and Management Nursing Department, School of Nursing and Midwifery, Tehran University of Medical Sciences, Tehran, Iran. 3. Intensive Care and Management Nursing Department, School of Nursing and Midwifery, Tehran University of Medical Sciences, Tehran, Iran. 4. Emergency Department, Besat Hospital, Hamadan University of Medical Sciences, Hamadan, Iran. 5. Intensive Care and Management Nursing Department. School of Nursing and Midwifery, Hamadan University of Medical Sciences, Hamadan, Iran. 6. Department of Biostatistics and Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran. Received: July 2018; Accepted: September 2018; Published online: 2 October 2018 Abstract: Introduction: Infrequency and low exposure to critically ill patients requiring airway management will lead to reduction in the skills and performance of the Emergency Medical Technicians (EMTs) over time. The present study was conducted primarily aiming to evaluate airway management in stationary ambulance simulations and identify the factors affecting Endotracheal Intubation (ETI) success rate. Methods: This is a simulation study. The study population comprised of active EMTs in prehospital emergency bases in Hamadan province. The participants were placed at the back of an ambulance to perform the airway management scenario, which had already been prepared. To investigate the factors affecting the success (≤3 attempts) or failure rate of in- tubation, both unadjusted and adjusted odds ratios (95% confidence intervals) for univariate and multivariate regressions were reported. Results: 184 subjects with the mean age of 33.91+6.25 years and the median work experience of 8 years were studied (54.3% with a history of training in the past year). The median number of previous intubations performed by technicians in the last year was 7 times (IQR 4-9). The total success rate at ventilation, intubation and back-up airway were 50.67%, 53.29%, and 50.0%, respectively. Out of the total 552 attempts for ETI placement, 58.2% of the technicians were able to perform ETI within 3 attempts. Univari- ate analysis showed that age (OR=1.06, P=0.022), previous number of ETIs (OR=2.49, P<0.001), work experience (OR=1.13, P<0.001), and previous ETI training (OR=1.85, P=0.041) were significantly associated with ETI success rate. After adjustment, previous number of ETIs (OR=2.66, P<0.001) was the most effective factor on ETI success rate. Conclusion: Success rate in airway management, especially ETI, is low. Therefore, improvement in modi- fiable factors such as increasing the number of ETIs performed and gaining experience in the same conditions as pre-hospital emergency is necessary. Keywords: Airway Management; Endotracheal Intubation; Emergency Medicine Technicians © Copyright (2018) Shahid Beheshti University of Medical Sciences Cite this article as: Ghiyasvandian Sh, Khazaei A, Zakerimoghadam M, Salimi R, Afshari A, Mogimbeigi A. Evaluation of Airway Management Proficiency in Pre-Hospital Emergency Setting; a Simulation Study. Emergency. 2018; 6(1): e58. ∗Corresponding Author: Khazaei Afshin; Intensive Care and Management Nursing Department, School of Nursing and Midwifery, Nosrat St, Tehran, Iran. Email: khazaei-a@razi.tums.ac.ir, Tel: 00989183143075 1. Introduction Airway management in the out of hospital setting is asso- ciated with major challenges [1]. Conditions such as lim- ited access to advanced airway equipment, immobilized pa- tients, confined spaces with dim light, shortage of person- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com Sh. Ghiyasvandian et al. 2 nel, lack of back-up force and limited choice of alternative methods are substantial challenges of airway management in pre-hospital emergencies [2]. In the pre-hospital con- ditions, airway management involves a series of sequential steps and action to ensure airway openness to provide ven- tilation in the patient’s lungs [3]. Inadequate performance at any step during airway management leads to irrepara- ble injuries and complications in the patient [4, 5]. The most important stages of airway management include as- sessment, positioning, cleaning up the upper airway, adjunct oral airway insertion, supplemental oxygen administration, Bag-valve Mask Ventilation (BMV ), placement of an Endo- tracheal Tube (ETT), ETT placement verification, stabilizing ETT and applying alternative methods after unsuccessful En- dotracheal Intubation (ETI) [3]. The current training of EMTs is not enough to improve the patient’s airway management outcome [6]. Furthermore, infrequency and low exposure to critically ill patients requiring airway management (espe- cially ETI) has added to the complexity of the situation and leads to poor skills and performance of the personnel over time [7]. The gold standard for advanced airway manage- ment is ETI [8]. Studies assessing ETI success rate in an am- bulance or a simulator are scarce. With the current overall out of hospital ETI success rates ranging from 77 to 85% [9, 10] and a complication rate of 48 per 1000 intubations [10], the need to assure high levels of skill for performance and maintenance in a simulated environment is felt [10, 11]. Con- sequently, accurate and continuous assessment and evalua- tion procedures for retention of airway management perfor- mance are critical to the improvement of patient outcomes [10, 11]. Therefore, the primary objective of this study was evaluation of airway management in a simulated environ- ment and the secondary purpose was identifying the factors affecting the success rate of ETI in the EMTs. 2. Methods 2.1. Study design and setting This is a simulation study. The study was conducted in 115 Emergency medical services in Hamadan province, with 20 urban bases, 30 roadside bases and an air base (12). The present study was conducted from March 2018 to May 2018. EMTs participated in the study voluntarily and indi- vidual performance results were not reported to EMS au- thorities. EMTs willing to participate in the study were re- quested to complete a brief demographic questionnaire and consent to video recording of their performance on the sim- ulation practice. This study was approved by the Ethics Com- mittee of Hamadan University of Medical Sciences as re- search project No. 9611247613 and with the unique ID No. IR.UMSHA.REC.1396.808. 2.2. Participants The population of this study comprised EMTs in 115 emer- gency bases in Hamadan province, which were recruited. In a study carried out by Wang HE et al. ETI success rates were reported as 0.77% [9]. Using this data and taking into account the relative error of 5% and 95% confidence interval, as well as applying the coefficient of the limited population (a total of 307 active EMTs, by formula ); we calculated that a sam- ple size of 184 is required. The active EMTs who were present on a full-time basis in urban, road-side and air emergency and announced their oral and written consent were included in the study. Non-active EMS personnel were excluded from the study. The participants were placed in the back of an am- bulance to perform the airway management scenario, which has already been prepared by experts. All stages of airway management by the EMTs were performed on a mannequin located in an ambulance resembling the pre-hospital emer- gency situation. 2.3. Scenario 1 You have departed, along with your colleague, to a mission where a client’s consciousness is declined in a car accident. While examining, you notice that there is an incomprehensi- ble voice in him. With painful stimuli, he opens his eyes and withdraws. On the left side of the temple, there is boggy con- tusion. It will take at least 20 minutes from the place of acci- dent to the hospital. Perform the required ventilation proce- dures based on the airway management protocol in the pre- hospital emergency in order a) through bag-valve mask, and b) then ETI for the patient. 2.4. Scenario 2 During the course, you notice that the patient’s ET Tube has been accidentally dislodged. You have attempted to intubate this patient twice since your first successful ETI. You have noted that the airway was significantly edematous, full of se- cretions and you were unable to visualize the ET tube pass through the vocal cords. Pulse oximetry is also 80%. Take the necessary measures in accordance with the Airway Manage- ment Standard in the pre-hospital emergency. 2.5. Data gathering The research instrument included a) demographic question- naire of EMT (including age, work experience, degree, em- ployment status, intubation experience, previous training in airway management field); and b) Airway Management Pro- ficiency Checklist (AMPC) designed by David P. Way et al. in 2017 [12]. This checklist consists of 3 standard perfor- mance scales for airway management, including ventilation, intubation and back-up airway, and a total of 37 psychomo- tor skills (8 skills for the ventilation scale, 17 skills for the This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com 3 Emergency. 2018; 6 (1): e58 Flowchart 1: Course of the airway management proficiency and the success rate of technicians in each of the stages of ventilation, intubation and back-up airway as well as outcome. BVM: Bag Vale Mask. ETI scale and 12 skills for the back-up airway scale) required for a comprehensive airway management. All 37 items were considered easily observable and rated by a qualified evalu- ator, and it’s had internal consistency in the three stages of ventilation (KR-20=0.95), intubation (KR-20=0.88) and back- up airway (KR-20=0.82) (13). This checklist was filled out through direct observation made by two pre-hospital emer- gency training experts and under the supervision of an emer- gency medicine specialist. During the performance assess- ment, a trained supervisor read a standardized orientation (Included an overview of the scenario, the available equip- ment, and a reminder to follow standard EMS protocols for airway management) to the EMTs. All EMTs (184 cases) were evaluated individually with the two scenarios. Also, all tech- nicians, both those who were successful and those who failed in the first scenario were allowed to continue to the second scenario. Based on the Standard Airway Management Guide- lines [3], the maximum attempts (successful intubation) for ETI was determined 3 times. If the technicians failed to per- form ETI in three attempts the result was recorded as failed intubation. Also, if the technician had successful intubation during three attempts, it was recorded as successful intuba- tion. The evaluators watched the recording and scored their performance using the 37 item checklist. The 37 items on the checklist were scored dichotomously either a “1” repre- senting successful execution of the task, or a “0” represent- ing a failed attempt or no attempt at all. After data collection, the status of technicians’ proficiency was determined at each stage of ventilation, intubation, back-up airway and sectors related to such stages. The evaluators used Karl Storz 8403ZXK C-MAC Video Laryn- goscope, which allows observation and video recording of ET tube placement, but EMTs were not shown the screen views during the simulation. The forward-only translation tech- nique was used due to the lack of a Persian version of the tool [13]. Thus, after obtaining permission from the devel- oper, the English version of the instrument was first trans- lated individually into Persian by two emergency medicine specialists. Then the points of difference were investigated at a meeting with the presence of experts and pre-hospital emergency experts and specialists. Finally, a single Persian version of instrument was provided. For content and face va- lidity, the checklist was given to 10 faculty members, emer- gency medicine specialist and emergency technicians, and their comments and suggestions were taken into considera- tion. Tool reliability (in the mentioned three steps) was also confirmed via completion of 15 checklists by two emergency experts and determining the intra-rater reliability and calcu- lating Kappa coefficient (0.84%, 0.79%, and 0.91%). 2.6. Statistical Analysis Continuous variables that were normally distributed were expressed as mean ± standard deviation (SD) while non- normally distributed variables were expressed as median This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com Sh. Ghiyasvandian et al. 4 (IQR). We dichotomized ETI intervention into ≤3 attempts (successful) and >3 attempts (failure). ETT correct position- ing was determined by the placement of the tube within the trachea approximately 2-3 cm above the carina [17]. Univari- ate logistic regression (Unadjusted) was used to identify fac- tors (Continuous variables such as age, work experience, and previous number of ETIs and categorical variables such as previous training history [yes-no], degree [emergency med- ical technicians, nurse, operation room technician, anes- thetist technician], and employment status [formal and in- formal]) associated with success or failure rate of ETI. Also, we used a multivariate logistic regression model for adjust- ing ORs of continuous and categorical variables with ETI suc- cess rate. To select covariates for the adjusted models used, the forward selection (wald) method was applied. ORs and 95% CIs were calculated. The selection of variables for the model was done according to factors known from the litera- ture, which had previously assessed ETI success rate [14-16]. All statistical analyses were performed using IBM SPSS Statis- tics (V.17). P<0.05 was considered significant (two-tailed). 3. Results 3.1. Demographic information 184 EMTs took part in the study after being qualified for the inclusion criteria. The mean age of participants was 33.91+6.25 years and their median work experience was 8 years (IQR 5-13). The median number of intubations per- formed by technicians in the past year was 7 (IQR 7-9) times. 54.3% of the technicians reported a history of airway man- agement training in the past year. 51.1% of the technicians had formal employment and some had academic degrees as emergency medical technicians (36.4%), nurses (27.2%), operation room technicians (20.1%) and anesthesiologists (16.3%). Hosmer-Lemeshow test showed good fit for the model (p = 0.48). 3.2. Ventilation stage At the ventilation stage, the highest (65.2%) and the lowest (31.5%) success rates belonged to choosing correct adjunct airway size and checking pulse using thenar eminence tech- nique, respectively. In the first section, 60.9% participants placed simple adjuncts prior to intubation to facilitate bag valve mask (BVM) performance. Choosing the correct ad- junct airway size was only observed in 60.9% of the techni- cians. 54.3% of the technicians succeeded in inserting ad- junct airway with proper depth. The rate of BVM ventilation was also one of the evaluated sections. Out of all the par- ticipants, less than 50% of the technicians ventilated the pa- tient at the correct rate of 10–12 breaths per minute. In the next section, 42.9% (79 of 198) of the participants were ob- served for BVM technique for 30 seconds. Using thenar em- inence technique (E-C grip), in which downward pressure is applied with the thenar eminences while the four fingers of each hand pull the jaw upwards toward the mask, was only performed by 31.5% of the technicians. Another significant section that was evaluated at the ventilation stage was taking precautions for cervical spine injuries (jaw-thrust maneuver, head-tilt/chin-lift maneuver), which only 48.9% of the tech- nicians focused on this issue in our study while inserting air- way and ventilating the patient with the BVM. Eventually, the main outcome evaluated at this stage was ventilating the pa- tient immediately (w/in 30 sec) with BVM and 53.8% of the technicians were able to do it. Table 1 presents other results of the ventilation stage. 3.3. Enodotercheal Inutubation (ETI) stage The complete item list for this process is listed in table 2. In the ETI stage, the highest (89.7%) and the lowest (20.7%) success rates belonged to grasping laryngoscope with the left hand and checking end-tidal CO2 after ETT placement, respectively. In the first section of this stage, nearly three-quarters (71.2%) of the technician used straight- to-cuff stylette curvature technique. 34.8% of the techni- cians passed ETT through cords with limited or no impinge- ment. Also, 61.4% maintained their view correctly until ETT stopped advancing. less than 50% of the technicians pro- vided the correct position for the patient’s head before in- sertion of the laryngoscope into the mouth. Passing tube through cords (laryngoscope in mouth to tracheal place- ment) in ≥20 seconds was only perfomed by 34.8% of the technicians. Investigation of end-tidal CO2 is another signifi- cant section of this stage which is considered one of the non- invasive methods for determining the correct position of the ETI. Only 20.7% of the EMTs checked end-tidal CO2 after ETT placement. In our study, nearly half of the EMTs (49.2%) suc- ceeded in placing the tube at the appropriate depth in the trachea. Passing the tube through cords (laryngoscope in mouth to tracheal placement) in less than 20 seconds was also another important section of the intubation stage that only 22.8% of the technicians were able to perform this skill. One of the maneuvers that facilitate passing of the tube into the trachea is the use of pressure on the epiglottis to better see the trachea when inserting the tube [18]. In this section, only 39.1% of the technicians requested the assistant to apply pressure on the patient’s epiglottis. Finally, the technicians lacked enough skill to evaluate the main consequence of this stage, which was placement ETI with one attempt, and only 12.5% of the technicians were able to show this skill. Table 2 presents the other parts of the intubation stage. 3.4. Back-up airway stage At the backup airway placement stage, the highest (93.5%) and the lowest (16.8%) success rates belonged to immedi- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com 5 Emergency. 2018; 6 (1): e58 Table 1: Frequency of paramedics who correctly performed tasks related to airway (n = 184) Description Frequency (%) Inserts oropharyngeal (adjunct) airway 112 (60.9) Chooses correct adjunct airway size 112 (65.2) Inserts adjunct airway to proper depth 100 (54.3) Ventilates patient at rate of 10–12/min 87 (47.3) Observes BVM technique for 30 seconds* 79 (42.9) Orients mask correctly 106 (57.6) Uses thenar eminence technique (E-C grip) 58 (31.5) Maintains C-spine precautions during BVM 90 (48.9) Ventilates patient immediately (w/in 30 sec) with BVM 99 (53.8) * Evaluates volumes (visible chest rise); Endotracheal Tube (ETT); C-spine: Cervical spine; BVM: Bage Valve Mask. ately disconnecting syringe after inflating cuff and check- ing end-tidal CO2 after backup airway placement, respec- tively. The need for backup airway in the patients was only recognized by 36.4% of technicians in the designed scenario (scenario 2). However, in this scenario, technicians who did not recognize the need for a back-up airway in the patient were asked to complete the back-up airway process based on the protocol. Identifying an appropriate backup airway de- vice was only done by 58.7% of the technicians. Only 36.4% of the technician confirmed proper placement by auscul- tation bilaterally over each lung-Backup airway. Also, ap- proximately 50% of technicians succeeded in inserting la- ryngeal mask airway in one step as the main outcome of this stage. Table 3 indicates other results in this section. Logistic regression results also showed that implementation of previous intubation in the last 12 months (OR=2.66) and work experience (OR=1.52) in the presence of other variables (such as dgree, previous ETI training, employment status), are the most impactful factors that can increase the chance of successful intubation. In the unadjusted univariate anal- ysis, number of previous ETIs (OR=2.49: CI 95% [1.98-3.59], P<0.001), age (OR=1.06: CI 95% [1.00-1.11], P=0.022), work experience (OR=1.13: CI 95% [1.06-.1.2], P<0.001) and previ- ous ETI training (OR=1.85: CI 95% [1.02-3.36], P=0.041) were significantly associated with ETI success rate. Also, factors such as degree (EMT: OR=0.92 CL 95% [0.38-2.23], P = 0.868, Nurse: OR=0.92 CI 95% [0.36-2.31], P=0.860, Operating room technician: OR=0.87 CI 95% [0.32-2.32], P=0.869), employ- ment status (OR=0.74: CI 95% [0.41-1.33], P=0.319) were not significantly associated with ETI success rate. When adjusted for previous number of ETI, age, degree, and previous ETI training and employment status, only number of previous ETIs (OR=2.70: CI 95% [1.98-1.38], P<0.001) and work experi- ence (OR=1.52: CI 95% [1.15-2.01], P=0.003) correlated with ETI success rate (sensitivity [85.7], specificity [89.7]). Age (OR=0.78: CI 95% [0.62-0.98], P=0.037) was a negative pre- dictive factors with ETI success rate. Hosmer–Lemeshow test also showed goodness of fit for the model (p=0.496). 4. Discussion The total success rate in the three stages of ventilation, intu- bation and airway back-up were 50.67%, 53.29%, and 50.0%, respectively. Out of the total 552 attempts for ETI place- ment, 58.2% of the technicians were able to perform ETI in ≤3 attempts and 43.9% of technicians took more than 3 at- tempts to perform this skill. Also, 12.5% (23 of 184) of the EMTs were successful at ETI in their first attempt, which in- creased to 17.9% and 27.7% in the 2nd and 3rd attempts, re- spectively. These results are quite disappointing compared to other studies performed in this area. In the Panchal study, the first pass ETI success rate was 55.6% [19]. The study by Griesdale et al. also indicated that 94% of the experienced EMTs succeed in ETI within 2 attempts and only 6.6% of in- tubation cases by technicians required three attempts [20]. The poor results of our study at the ETI stage are highlighted by the fact that re-intubation on the real patients will lead to complications, such as hypoxemia, aspiration, bradycar- dia and cardiac arrest [21]. Passing the tube through cords (laryngoscope in mouth to tracheal placement) in less than 20 seconds was also another important section of the intuba- tion stage, in which only 22.8% of the technicians succeeded. There is no doubt regarding the significance of the men- tioned step (rapid intubation) because based on the results of previous studies, rapid intubation in cardiopulmonary re- suscitation can lead to favorable outcomes, including im- proved neurological status and increased survival of patients [22, 23]. Also, inserting the tube with the appropriate depth is another important skill for ETI, which is crucial because ignoring this issue leads to serious complications that may even lead to death in some cases [24, 25]. Unfortunately, 42.9% of the EMTs paid attention to this issue. The initial approach to airway management in the pre-hospital emer- gency is Bag-valve Mask Ventilation (BMV ) [26, 27], which is more vital than intubation procedures in some special cir- cumstances (e.g. severe airway trauma, lack of experience in personnel, children, etc.) [28, 29]. Hansen et al. also in- dicated in their study that for airway management in chil- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com Sh. Ghiyasvandian et al. 6 Table 2: Frequency of paramedics who correctly performed tasks related to endotracheal intubation (n = 184) Description Frequency (%) Uses straight-to-cuff stylette curvature technique 131 (71.2) Checks equipment for cuff leaks 55 (29.9) Positions head properly 85 (46.2) Grasps laryngoscope with left hand 165 (89.7) Elevates mandible from 45–90 degrees w/laryngoscope 122 (66.3) Flips up epiglottis to expose larynx 72 (39.1) Inserts laryngoscope to appropriate depth 79 (42.9) Moves blade tip smoothly without shaking or jerking 83 (45.1) Maintains view until ETT has stopped advancing 113 (61.4) Passes ETT through cords with limited or no impingement 64 (34.8) Passes tube through cords in ≥ 20 seconds * 42 (22.8) Disconnects syringe immediately after inflating cuff of ETT 149 (81.0) Listens over each lung 124 (67.4) Checks end-tidal CO2- After ETT placement 38 (20.7) Checks pulse oximeter-After ETT placement 63 (34.2) Maintains control over ETT placement 124 (67.4) Secures ET tube (with device) 158 (85.9) Successfully intubates within 1 attempt 21 (12.5) ∗ laryngoscope in mouth to tracheal placement; ET: Endotracheal; ETT: Endotracheal Tube. Table 3: Frequency of paramedics who correctly performed tasks related to backup airway (n = 184) Description Frequency (%) Recognizes need for backup airway 67 (36.4) Identifies an appropriate backup airway device 108 (58.7) Checks equipment for cuff leaks 78 (42.4) Immediately inflates cuff, prior to ventilation 163 (88.6) Immediately disconnects syringe after inflating cuff 172 (93.5) Confirms proper placement by auscultation* 67 (36.4) Checks end-tidal CO2 -after Backup airway placement 31 (16.8) Checks Pulse Oximeter-after Backup airway placement 82 (44.6) Appropriately positions equipment needed for backup airway 53 (28.8) Maintains control over backup airway after placement 68 (37.0) Secures backup airway device 118 (64.1) Introduces backup airway and advances to proper depth 97 (52.7) Successfully places backup airway within 1 attempt 90 (48.9) * bilaterally over each lung-backup airway. dren, BVM would lead to a higher survival rate for the pa- tient in hospital compared to ETI [30]. Ventilation with BVM seems a simple technique, though its proper implementa- tion is difficult in practice, especially when the technicians lack enough experience in this area. In our study, the suc- cess rate of ventilating the patient with the rate of 10–12/min was low and this problem is more pronounced when know- ing the increase (hyperventilate) or reduction (hypoventila- tion) in ventilation is determining the patient’s final condi- tion [31]. Unfortunately, in the backup airway stage also only 36.4% of the technicians recognized need for backup airway. When EMTs confronted with failed ETI, using an alternative airway such as combitube and laryngeal mask airway (LMA) would be an effective and efficient way to keep the airway open and ventilate [32]. In the backup airway (16.8%) and intubation stage (20.7%), the lowest success rate belonged to checking end-tidal CO2 after backup airway placement. This method along with auscultation of bilateral breath sounds is the gold standard for determining the correct position of the ET tube in the pre-hospital setting [33], which has 100% sen- sitivity and specificity in pre-hospital conditions [34]. There- fore, the American Heart Association (AHA) recommends it for all intubations [35]. Also, in the present study, the success rate of backup-airway insertion in difficult conditions (sce- nario 2) was higher than the ETI (48.6% VS 18.6%). This result confirms the ease of using laryngeal mask airway compared to ETI, which is consistent with the results of other studies in this area [36, 37]. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: www.jemerg.com 7 Emergency. 2018; 6 (1): e58 Regression test also showed that one of the factors that can affect the success rate of airway management is to perform this skill in situations similar to the pre-hospital environ- ment. After adjustment for confounding variables, gaining experience through implementation of intubation was found to be effective in enhancing the skills of ETI, so that with performing one previous intubation, success rate increased by 2.66%. This result is confirmed by other studies, because achieving a 90% success rate in ETI requires a history of per- forming 50–150 intervention [38, 39]. Also, unadjusted re- gression shows that previous training in intubation was also significantly associated with ETI success rate but when it’s adjusted for other factors such as previous number of intu- bations, this relationship was no longer significant. These results confirm that training methods such as theory-based teaching, lecture-based teaching as well as writing exam, cannot guarantee the success of technicians in managing practical skills. Finally, the results of this study should be cautiously interpreted in the field. A major limitation of this study was the possibility of selection bias because techni- cians who have improved airway management proficiency may have been included in the study. Also, since this study was conducted at a stationary ambulance and did not have the limitations of conducting airway management in a mov- ing ambulance, its results may not reflect the current perfor- mance of the technicians in this study. In addition, the use of simulation in addition to the bias created by the ambulance personnel’s awareness result in the personnel not having en- vironmental stresses such as encountering the scene of an accident, the risk of a patient’s life, the pressure of person- nel to control and stabilize the patient’s condition and the existence of complications such as secretion, hemorrhage, vomiting in airway interventions and these factors may lead to false results of ETI. In conclusion, the results of this study may be different from real situations. 5. Limitation This type of study is not possible in the field due to acuity of illness, inability to accurately observe the details, and in- frequency of airway management. The obtained results in this study should be carefully interpreted and used due to the lack of devices for determining the proper placement of ETI such as end-tidal CO2 detection device, as well as alter- native back-up airway equipment such as combitube and la- ryngeal mask airway in the pre-hospital emergency service of Hamadan province. 6. Conclusion Success rate in airway management, especially ETI, is low. Therefore, improvement in modifiable factors such as in- creasing the number of ETIs performed and gaining expe- rience in the same conditions as pre-hospital emergency is necessary. 7. Appendix 7.1. Acknowledgements The authors are grateful to Vice-Chancellor of Research and Technology in Hamadan University of Medical Sciences for supporting this study with a grant under the project number 9611247613. 7.2. Author contribution Khazaei Afshin, Ghiyasvandian Sharzad and Zakeri- moghadam designed the simulation study. Khazaei Afshin, Salimi Rasoul and Afshari Ali carried out the implementation and supervised the work. Mogimbeigi Abbas analyzed the data and aided in interpreting the results. Finally, Khazaei Afshin and Ghiyasvandian Sharzad discussed the results and contributed to the final manuscript. Authors’ ORCIDs Ghiyasvandian Shahrzad: 0000-0003-0137-5499 Khazaei Afshin: 0000-0002-8063-3419 Zakerimoghadam Masoumeh: 0000-0002-9762-1887 Salimi Rasoul: 0000-0002-6463-6046 Afshari Ali: 0000-0002-4579-5869 Mogimbeigi Abbas: 0000-0002-3803-3663 7.3. Funding/Support This work was supported by the Vice-chancellor of Research and Technology, Hamadan University of Medical Sciences under Grant number 9611247613. 7.4. Conflict of interest The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper. References 1. Prekker, M.E., H. Kwok, J. Shin, D. Carlbom, A. Grabin- sky, and T.D. 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