It’s Man and Manikin; a letter.
It’s Man and Manikin; a letter.
In response to Ward and Irwin’s editorial , we would like to describe two randomised, controlled, cross-over trials (RCT’s) using Basic Life Support (BLS) airway providers, defined as inexperienced users (IU’s) with annually trained Guedel/Facemask skills who compared ventilation using either the Tulip GT® (TGT®) or a Guedel/Facemask (G/F) in 60 subjects, first in manikins  and then in humans  using identical protocols but within the limitations of estimation of end tidal CO2 (etCO2) in manikins.
The manikin study showed that the TGT® increased ventilation by 9.1% (p < 0.0423) in the manikin study but by 76.6% (p < 0.0002) in the human study. This was the biggest difference between the man and manikin study, with the remainder of the results being remarkably similar. The studies suggested manikins, if anything, are harder to ventilate than humans, which raises the bar for training through added difficulty.
The average Tv’s generated was significantly greater with TGT® (397ml) compared with the G/F (364ml, p = 0.0423) in manikins, whilst in humans the TGT® generated 77% bigger Tv’s, 101% higher etCO2 readings, 36% higher PIP’s and no failures (p<0.0001). In both man and manikin 100% of IU’s were able to ventilate with a TGT® on their first ever encounter with the device, with 0% requiring assistance in either man or manikin. 20% of IU’s using a G/F required assistance in the manikin (p<0.0003) and 25% in the human study. Interestingly, whilst 25% (15/60) of IU’s requested assistance in the human study, an additional 16.7% (10/60) of G/F users failed to ventilate at all but did not ask for assistance, showing high combined failure rates of 41.7% (25/60) in BLS G/F airway management by IU’s in real patients. 5% (3/60) of TGT® users failed to achieve the required ventilation parameters in humans with 41.7% (25/60) of G/F users failing to achieve adequate ventilation parameters in the same study.
There were no significant differences in the number of attempts made to insert each airway device in either trial, with manikin results revealing 98.3% (59/60) IU’s introducing the Guedel first time and 93.3% (56/60) introducing the TGT® first time, whilst the human study showed 78.3% (47/60) for the Guedel and 96.7% (59/60) for the TGT®, which was considered easier to use in both studies (man p < 0.005, manikin p < 0.05). With the manikin study 76.7% (46/60) of IU’s preferred the TGT® with a near identical 78.3% (47/60) of IU’s preferred the TGT® in the human study.
It should be noted that a significant number of IU’s failed to ventilate at all in humans (16.7%) with a G/F but still did not ask for assistance. It is well documented that IU’s have difficulty with the G/F combination  so our studies were conducted to investigate whether the TGT® should replace the 83 year old Guedel airway. Our studies suggest that this should be considered as the TGT® is the only second generation oropharyngeal airway alternative to a Guedel available and offers significant results versus G/F, despite the inexperienced users being annually trained with a G/F combination and these studies being the first contact the IU’s had with the TGT® airway. Many airway interventions are required in semi-conscious patients who may tolerate an oropharyngeal Guedel airway but are simply too awake to tolerate a iGEL/LMA-type supraglottic airway but until recently no other oropharyngeal alternative has been available.
In humans the etCO2, Tv and peak inspiratory pressures (PIP) were significantly better (p < 0.0001) for all parameters with the TGT®, which was found to be easier to insert and demonstrated a steep learning curve for the BLS trained IU’s. These results are similar to the manikin study and this suggests a close correlation between human and manikin studies for this device. No other studies comparing an identical protocol in both manikins and humans could be found on searches. The Tulip GT® is the first airway device to be introduced using this method of testing and study.
These studies raise the question as to why BLS airway management using the Guedel/Facemask is still performed when failure rates are as high as 41.7% despite annual BLS training and out of hospital cardiac arrest survival without neurological deficit being approximately 1.25-2.5% .
Dr. Amer Shaikh is the inventor of the Tulip® airway and was not involved in the conduct of the clinical study but was involved in its writing, planning and design. The airways used in the study were purchased by the Trust from Age of Aquarius™, UK, of which Dr. Shaikh is the owner and director. No other competing interests declared.
1. Ward PA, Irwin MG. Man vs. manikin revisited – the ethical boundaries of simulating difficult airways in patients. Anaesthesia 2016; 71: 1399-1403
2. Kynoch M, Saini R, Robinson PN, Shaikh A, Hasan M, Vaughan D. Randomised crossover comparison of the Tulip airway compared with the Guedel airway for inexperienced users in a manikin. Anaesthesia 2013; 68: 317.
3. Shaikh A, Robinson NP, Hasan M. The Tulip GT® airway versus the Guedel airway and facemask: a randomised, controlled, cross-over clinical study comparing airway ventilation with Basic Life Support (BLS) trained airway providers in anaesthetised patients. Anaesthesia 2016; 71: 315-9.
4. Alexander R, Hodgson P, Lomax D, Bullen C. A comparison of the laryngeal mask airway and Guedel airway, bag and facemask for manual ventilation following formal training. Anaesthesia 1993; 48: 231-4.
5. Hasegawa K, Hiraide A, Chang Y, Brown DFM. Association of pre-hospital advanced airway management with neurologic outcome and survival in patients with out of hospital cardiac arrest. Journal of the American Medical Association 2013; 309: 257-266.
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