Laryngeal tube use in out-of-hospital cardiac arrest by paramedics in Norway

The study was designed as a dual-centre, retrospective evaluation of a single new airway device: the laryngeal tube. The recruited centers comprise two of the national health trust regions, the Haukeland University Hospital region and the Innlandet Hospital region, covering a population of around 900 000 people and 70,000 km2 (roughly half the size of England) with approximately 75 ground ambulance units. Being a retrospective study, we did not have a formal written protocol establishing the sequence of actions using the LT in OHCA. However, both participating ambulance services have similar standard operating procedures (SOP) for OHCA, stating the sequence of actions to be taken in these situations. The actual LT procedure with emphasis on minimising hands-off time during CPR, the LT was inserted directly without previous BMV, during on-going chest compressions. Successful attempt is defined as completed insertion of the LT combined with adequate ventilation of the patient assessed by inflation of the lungs, or visible chest movement, and confirmed by auscultation or capnography. If the attempt is not successful within 30 seconds, the patient has to be ventilated/oxygenated with BMV or pocket mask before a new attempt can be made. After a maximum of three LT attempts the method is abandoned, returning to BMV or pocket mask.

The Norwegian EMS is organised in an uniform way where the emergency medical communication centres (EMCC) are accessed by a national three digit number (113), from which the nearest ambulance and/or primary care doctors on-call are alarmed. The EMCC use the Norwegian Index of Medical Emergencies as a decision tool for level of emergency, and dispatch health resources accordingly [32, 33]. In pre-hospital cardiac arrests, the EMCC provides telephone guided CPR to lay people if the patient is unconscious with abnormal breathing. Simultaneously, the nearest ambulance/primary care doctor on-call and first-responder with automated external defibrillator (AED) are dispatched to ensure advanced life support (ALS). If available, the nearest helicopter emergency medical service (HEMS) staffed by anesthesiologist may also be dispatched.

The ambulance system is part of the hospital organization, and all personnel are employed by the health trusts. The educational background can vary, from basic EMTs (emergency medical technicians), via paramedics to nurse anaesthetists working in the capacity of ambulance personnel in EMS, and also anesthesiologist if the air ambulance service is responding to the actual OHCA. The term”anesthesia-trained providers” refers to nurse anaesthetists and anesthesiologists.

During basic training they are introduced to the LT during their airway management module, in addition to bag-mask-ventilation. All ambulance personnel received an initial 3 hour lesson on airway management followed by supervised training on manikins with the LT. The training session was followed by a written and practical test in a manikin assessed by supervisors. The EMS personnel also had to take part in an annual formal retest, where LT use was tested in simulated cardiac arrest scenarios.

The LT is a SGA and comes in single lumen (LT + LT-D) or dual lumen versions (LTS II + LTS-D with suction/drain tube), both available in reusable or disposable forms (VBM Medizintechnik GmbH, Germany). The LT has 2 cuffs inflated by one syringe, sealing both the oesophagus and the oropharynx, and with ventilation holes over the laryngeal inlet. Our ambulance services have used various laryngeal tube models (LT/LTSII/LTS-D) in accordance with their enhancements, as their primary device for airway management in OHCA patients since 2002 (Haukeland) and 2005 (Innlandet). Suitable LT size was in each case chosen based on estimated patient height and according to product guidelines. LT size 3, 4 and 5 are used in adults.

Post-resuscitation forms and data on airway management in OHCA patients were assessed with regard to LT insertion success rates, insertion time, insertion-related problems, and the ease of insertion. 347 adult non-traumatic out-of-hospital cardiac arrest patients in our 2 regions between 2002-2010, where LT was used as airway method, were included in this study. All cardiac arrest ambulance personnel were instructed to document the related airway data variables every time of involvement. Data variables included the choice of primary airway method (mouth-mask-ventilation (MMV), bag-mask-ventilation (BMV), or laryngeal tube (LT)) and verification of correct placement (auscultation and end-tidal carbon dioxide measurement). In addition all insertion-related problems like air leakage, problematic initial tube positioning, tube dislocation, absence of respiratory sounds on auscultation, insertion time exceeding 30 seconds, and provider-rated ease of insertion (“Easy”, “Intermediate” or “Difficult”) were recorded. A provider self-reporting method was used and in our study this covered his/hers perception of the procedure difficulty as a whole, from insertion attempt to confirmation of ventilation. End tidal carbon dioxide (ETCO2) measurements were performed using the Easy Cap II CO2 Detector® (Covidien, USA) or were available on the Lifepak® 12 Defibrillator (Physio-Control Inc., USA).

Microsoft Excel 2011 for Mac Version 14.0® (Microsoft Corporation, USA) and SPSS version 19.0® (IBM SPSS Inc., USA) were used for data analysis and presentation.

The Regional Committee for Medical Research Ethics (REK-Vest) exempted the study from ethical approval, regarding it as a quality improvement study. The ethics committee declared no objections toward the study or the publication of the results. The Data Protection Official for Research (Helse Bergen) approved the study. Permission was only given for anonymous data review, and the post-resuscitation forms and data from airway management were anonymous to personal data. As such, outcome data and demographics from EMS or in-hospital patient medical records could not be obtained.

A total of 402 insertions were performed in 347 OHCA patients. Overall, LT insertion was successful in 85.3% of patients, with a 74.4% first-attempt success rate. Insertion success is shown in Figure 1. In the 89 patients (25.6%) where primary insertion attempt failed, the reattempt airway device used was either the LT (42.7%), ETI (20.2%), BMV (6.7%), or a combination of the three (6.7%). Data reporting rescue airway technique in 21 of the primary failed insertions was missing. In 2.4% of the successful insertions, the LT was converted to ETI by anesthesia-trained providers during the resuscitation.

In a minority of patients (n = 46, 13.3%), the LT insertion time exceeded 30 seconds. The mean number of insertion attempts was 1.16 (range 1-4). Insertion time exceeding 30 seconds was a result of difficult single insertions (n = 15) or multiple insertion attempts (n = 31).

Insertion-related problems were recorded in 52.7% of patients, as shown in Table 1.

The following LT sizes were used in our patient population: LT size 4 (n = 208 patients), size 5 (n = 141 patients), and size 3 (n = 11 patients). The primary methods used to verify correct placement were auscultation (n = 252, 72.6%) and ETCO2 confirmation (n = 213, 61.4%). The mean age of patients was 66.8 years (SD ± 16.4 years).

The difficulty of insertion was scored for 95.4% of the patients, with the majority of insertions being assessed as “Easy” (62.5%) or “Intermediate” (24.8%) by the airway providers. Only 8.1% of the insertions were regarded as “Difficult”.