Effectiveness of prehospital Magill forceps use for out-of-hospital cardiac arrest due to foreign body airway obstruction in Osaka City

The target area for this study was Osaka City in Japan, which has an urban area of 221 km² and had a residential population of 2,598,774 as of 2000 (population density; approximately 11,700 persons/km²) [6]. Males make up 49.0% of the population, 17.1% of whom are 65 years old or older.

We retrospectively reviewed ambulance records of all patients who had FBAO in airways, including oral cavity, pharynx, larynx, trachea and bronchus, who were treated by EMS and then transported to medical institutions in Osaka City from January 1, 2000 through December 31, 2007. Diagnoses from the ambulance records were clinically determined by a physician in charge, working in collaboration with the EMS personnel. Approval for the study was obtained from the Ethics Committee of Kyoto University Graduate School of Medicine.

The 119 emergency telephone number is accessible anywhere in Japan, including Osaka City. Upon receiving a 119 call, an emergency dispatch center sends the nearest available ambulance to the site. In the year 2000, the Osaka Municipal Fire Department had a total of 50 EMS teams, one dispatch center, 25 fire stations, and 22 branches of fire stations [7]. Each ambulance consists of a 3-person unit providing life support 24 hours a day. To relieve FBAO, the trained EMS personnel are allowed to use Magill forceps in addition to finger sweep, back blows or slaps, abdominal thrusts, and chest thrusts. The size of Magill forceps used by EMS personnel in this study area was the same irrespective of patient age. Most highly-trained EMS personnel are called Emergency Life-Saving Technicians (ELSTs), the majority of whom are only allowed to insert an intravenous line and an adjunct airway, and to use a semi-automated external defibrillator for OHCA patients. Specially-trained ELSTs has been allowed to perform tracheal intubation since July 2004, and to administer epinephrine to only OHCA patients since April 2006 [8].

In order for EMS personnel in Japan to use Magill forceps in prehospital settings, fire department personnel must be an Emergency Medical Technician (EMT) or an ELST. To become an EMT, they are required to have received fundamental medical education in emergency care for 250 hours through a training academy. There are two options to becoming certified as an ELST in Japan [9]. The first is through the educational system within the fire department itself. After being actively engaged in pre-hospital setting as an EMT for more than 5 years or 2,000 hours, EMTs must pass the national examination of ELST after having basically received at least one additional year of medical education and training at the fire academy. The second way is through the education system in an accredited EMT school or college. To become an ELST, candidates must pass the national examination of ELST after receiving medical education and training in emergency care at the certified EMT school or college for at least two years.

The EMS ambulance record included patients’ age, gender, location of accident, region of foreign body, patients’ condition at time of EMS arrival, Magill forceps use, epinephrine, intubation, and ambulance time courses. If the patient had cardiopulmonary arrests when EMS arrived at the scene or during EMS treatments, data on the resuscitation course were collected using a data form according to the Utstein-style reporting guidelines [10],[11]. Information on the type of bystander resuscitation attempts and activities of daily living (ADL) before arrest was obtained from bystanders by an EMS interview before leaving the scene. In this study, ADL before arrest was divided in the following categories; good (defined as having ability to perform common life without assistance by other persons), disability (other than good), and unclassified. EMS times of calls received, time of vehicle arrival at the scene, contact with patients, initiation of cardiopulmonary resuscitation (CPR), defibrillation by EMS, and hospital arrival time were recorded with a clock used by each EMS system. All survivors who suffered from OHCA were followed up for up to one month after the event by EMS personnel in charge. One month neurological outcomes were determined by the physician in charge, using the cerebral performance category (CPC) scale: category 1, good cerebral performance; category 2, moderate cerebral disability; category 3, severe cerebral disability; category 4, coma or vegetative state; and category 5, death [10],[11]. Neurologically favorable survival was defined as a CPC category 1 or 2, no change from baseline CPC [10],[11].

The annual incidence per 100,000 inhabitants was calculated based on the population in the year 2000. The age-adjusted annual incidence of OHCAs per 100,000 inhabitants was calculated by direct methods using year 2000 census data and the Japanese model population of 1985 [2]. Patient characteristics were evaluated with t-test for numerical variables and a chi-square test for categorical variables. Trend tests for continuous variables were performed with the Spearman rank statistic method. To investigate between Magill forceps use and neurological outcomes after OHCA, we focused on bystander-witnessed OHCA patients with FBAO in larynx and pharynx, because it was possible to remove intraoral foreign bodies with finger sweep, but it would be inappropriate to remove trachea and bronchus foreign bodies with Magill forceps. Multivariable analysis was used to assess the contribution of Magill forceps use to neurologically favorable survival; odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated. Potential confounding factors included gender, age, location of accident, ADL before arrest, bystander-initiated CPR, time interval from collapse to call and time interval from call to arrival at the hospital. All the tests were 2-tailed, and p values of <0.05 were considered statistically significant. All statistical analyses were performed using the SPSS statistical package version 16.0 J (IBM Corp. Armonk, NY).

This manuscript was written based on the STROBE statement to assess the reporting of cohort and cross sectional studies [12].

This study has some inherent limitations. First, data are lacking regarding what type of foreign bodies caused of airway obstruction, and whether they were removed or not in the prehospital settings. Second, this study enrolled only emergency patients transported by EMS and did not obtain information on those who went to the hospital directly by themselves. Another limitation was that this study was a retrospective observational study, and an association between prehospital Magill forceps and the outcomes after OHCA due to FBAO should, therefore, be confirmed by other cohorts or randomized controlled trials. Finally, there might be unmeasured confounding factors influencing the association between prehospital Magill forceps use and outcomes after OHCA due to FBAO.