Airtraq versus standard laryngoscopy by experienced pre-hospital laryngoscopists in a model of difficult intubation: a randomised cross-over trial M Woollard,* † D Lighton,* W Mannion, † I Johns, † P O’Meara,* C Cotton,** M Smyth †† *School of Biomedical Sciences, Charles Sturt University, Bathurst, Australia * † Pre-hospital, Emergency, & Cardiovascular Care Applied Research Group, Coventry University (UK) † ACAP New South Wales Branch **ACAP South Australia Branch †† West Midlands Ambulance Service NHS Trust, Birmingham, UK

Conflict of interest  The authors confirm that the manufacturers of the Airtraq had no involvement in the conceptualisation, design, conduct, analysis, or write-up of this trial  However, samples of the Airtraq were donated by the manufacturers at no cost in support of the trial  Funding was provided by Charles Sturt University and the Australian College of Ambulance Paramedics

Research question  When used by [experienced pre-hospital laryngoscopists managing a model of a difficult airway] does [the Airtraq] [improve intubation success rates] compared with [standard laryngoscopy]?

Airtraq

Airtraq

Glottis Anatomy Epiglottis Vocal cords Arytenoids Oesophagus

Airway Classification Cormack – Lehane Grade

Justification  Some reports of high ETT success rates (98.4%, n= 2,700) (Bulger et al, 2002)  However, paramedic intubation skills are criticised –prospective, multi-centre study reported overall ETI success rate of 91.8% (95% CI=90.2% to 93.3%, n = 1,272)  success rates progressed from 69.9% to 84.9% to 89.9% for the first, second and third attempts respectively (Wang et al, 2006) –prospective observational study (n= 208) misplaced ETT unrecognized in 5.8% of patients (95% CI = 2.6% to 8.9%) (Jones et al, 2004)

Justification  Prospective in-hospital observational study n= 52 –Cumulative success rate of 71.5% after 2 attempts –Success rate by Cormack and Lehane (1984) view  Grade I = 87.5%  Grade II = 56%  Grade III = 0%  Grade IV = 0% –Recommended ETT should be withdrawn as a paramedic skill (Deakin et al, 2005)

Methods  Ethics approval from Charles Sturt University  Convenience sample of pre-hospital practitioners attending the Australian College of Ambulance Professionals conference in Adelaide, Nov 2006 –Previously intubation trained –Authorised to practice intubation  Written informed consent obtained

Methods  Study-related training –Hand-out with text and diagrams –Maximum of five minutes training with Airtraq  Explanation by researcher  Demonstration by researcher  One practice attempt by subject

Methods  Model of difficult intubation: –Manikin immobilised with collar + spine board  Subjects not permitted to loosen / remove collar or straps –Tongue inflated –Cormack & Lehane grade III (epiglottis +/- arytenoids visible) or grade IV (tip of epiglottis / no airway structures visible) view  Depends on operator skill

Manikin model of a grade III/IV view

Methods  Prospective randomisation of sequence in which students attempted intubation with an 8.0mm cuffed tube using either –Airtraq or –Macintosh laryngoscope with size 4 blade and malleable stylet  One intubation attempt undertaken with each device –Attempt limited to 30 seconds –Researcher confirmed ETT placement  ‘Difficulty of use’ scored by subjects for each device using a 100mm visual analogue scale

Results For Macintosh and Airtraq respectively: –Success rates 14/56 (25%) vs. 47/56 (84%) (59% difference, 95% CI 42 to 72%, P<0.0001); –Oesophageal intubation rates 9/56 (16%) vs. 0/56 (0%) (-16% difference, 95% CI -9 to -28%, P=0.0014); –Subject-rated difficulty of use scores 86 (IQ range 71 to 93, range 12 to 100) vs 20 (IQ range 5 to 28, range 1 to 75), p<0.001

Other observations  Significant dental damage inflicted during all Macintosh intubation attempts / successes!  Subjects always reported an excellent (grade I) view when using the Airtraq, regardless of whether intubation successful

Limitations  Recruiting volunteers at a clinically-focused conference risks reducing the generalisability of findings (selection bias): –Population is likely to consist of practitioners with a greater commitment to their on-going education –May, therefore, be more skilled in tracheal intubation than non-attendees  Trials involving models cannot be used as a basis for quantitatively predicting benefit in patients

Conclusions  In experienced pre-hospital laryngoscopists managing a manikin model of a grade III / IV airway view, with minimal additional training, the Airtraq significantly: –Increases first-time intubation success rates –Reduces the number of oesophageal intubations –Reduces the difficulty of intubation attempts  It also has the potential to: –Consistently provide grade I views –Reduce oral / dental trauma during intubation attempts

Contact details: Prof. Malcolm Woollard, Coventry University, Room 304 Richard Crossman Building, Priory Street, Coventry, CV1 5FB, UK Tel:

References  Bulger EM, Copass MK, Maier RV, Larsen J, Knowles J, Jurkovich GJ. An analysis of advanced prehospital airway management. J Emerg Med 2002;23(2):183-9  Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia, 1984;39:  Deakin CD, Peters R, Tomlinson P, Cassidy M. Securing the prehospital airway: a comparison of laryngeal mask insertion and endotracheal intubation by UK paramedics. Emerg Med J 2005;22(1):64-7  Jones JH, Murphy MP, Dickson RL, Somerville GG, Brizendine EJ. Emergency physician-verified out-of-hospital intubation: miss rates by paramedics. Acad Emerg Med, 2004;11(6):  Wang HE, Yealy DM. How many attempts are required to accomplish out-of-hospital endotracheal intubation? Acad Emerge Med, 2006;13(4):372-7.