How do you simulate a blood filled airway for training?
Emergency airway training is challenging at the best of times. Whilst simulation based training using high fidelity mannikins has greatly enhanced our ability to practice difficult airway scenarios in a safe and controlled manner , a few situations still elude us. Current top line medical simulators in the order of thousands of dollars cost are yet to be able to reliably reproduce the following difficult airway challenges :
- The bloody airway, either actively bleeding from trauma or regurgitated blood from the oesophagus
- The vomitus filled airway
- The obstetric airway
- The bariatric airway
- The neck trauma airway with subcutaneous emphysema or expanding haematoma
Learning how to manage these high risk airway scenarios is extremely difficult as being able to practice under supervision in a controlled hospital setting is so rare an opportunity with any of these cases. The fact that none of the commonly available product lines of medical simulators or skill trainers caters for these difficult airway situations makes the issue even more problematic.
In my search over the years to find better training resources and equipment to learn how to manage the bloody airway, the only useful item I could find was an article written by Dr Scott Weingart of the EmCrit blogsite, on an assembled large bore suction apparatus using a meconium aspirator, endotracheal tube and swivel connector. He was the first person I had come across who had some useful advice on how to prepare to deal with this airway problem.
Bloody airway issues
The bleeding airway or the obtunded patient regurgitating blood into their airway poses several unique challenges. Basic airway techniques may quickly fail, airway suction can be easily overwhelmed, direct laryngoscopy is often difficult due to obscured laryngeal views, aspiration of blood increases risks of critical hypoxia and hypovoloemic shock is a real risk if the bleeding is active and uncontrollable. Even the great hope of many emergency providers nowadays, video larygnoscopy can be defeated by a small amount of blood in the right place.
A novel simulated bloody airway training model
The astute reader will realise that in simulation training , the idea of simply filling a training mannikin’s oral cavity full of fake blood and practising intubation is fanciful and unrealistic. Almost all intubation training manikins have an oesophageal outlet and channel, to simulate gastric insufflation of an oesophageal intubation or poor bag/face mask ventilation. Any attempts to fill the oral cavity with fake blood will fail as it will drain out via the oesophageal outlet. One can try to plug the oesophageal outlet using silicon putty or a roll of gauze. This will allow the oral cavity to be filled with fake blood up to a point. When the blood level reaches the laryngeal inlet ( in the supine positioned mannikin), it will quite realistically spill over into the trachea and the blood level will never rise above that of the posterior wall. One cannot simulate using this method ,of blood obscuring the laryngeal inlet, even intermittently. The difficulty then of a bloody airway is almost impossible to realistically simulate, until now!
The attached video recording is of an airway testing session performed by myself and a colleague, Dr Adam Pritchard. We tested a newly purchased mannikin made by Simulaids, called the Critical Airway management trainer. This mannikin had been purchased for use in a future prehospital airway course run by the RFDS STAR program. It was specifically chosen as it was advertised to have an internal bleeding simulation capability. We were testing this during the session. The testing involved following the manufacturer’s instruction manual to prepare the fake blood that comes with the mannikin. Officially there are three bleeding points on the mannikin. Two on the face and one on the left lateral wall of the posterior pharynx. These are made to bleed by injecting the fake blood with a syringe into three separate ports attached to the external right neck. On our testing of the internal bleeding port, it was immediately apparent this was unrealistic and provided no impediment to normal direct laryngoscopy at all. Essentially the blood would shoot out directly from the left lateral pharyngeal wall in a narrow stream and then flow down into the oesophageal outlet , in the supine placed mannikin.
Adam then had the brilliant idea of removing the plastic stomach and filling the oesophageal tubing with blood. After about 150 mls of fake blood into this tubing it was clear that the posterior pharynx was filling up and the blood level had reached the posterior larynx. I then had the idea to try holding a manual bag resuscitator over the stomach opening and insufflating air into the distal tubing. The attached video shows the results of this technique and we were impressed with the fact it seemed to realistically simulate a patient with active regurgitation of blood from the oesophagus into the airway.
Testing with King Vision and AirTraq devices using the simulated bloody airway model
The video recording is of the view from a King Vision video laryngoscope. It was by far and away the best view using the bloody airway simulation. Testing with the Airtraq optical laryngoscope, quickly revealed that any splash of blood onto the distal viewing aperture completely obscured the view and prevented any attempts at optically guided intubation. The King Vision VL results are shown as recorded and seem to demonstrate an adequate view despite two vigourous splashes of fake blood onto the distal CMOS camera.
Issues to consider in training for the bloody airway
One thing we learnt was that cleaning up the mannikin and equipment takes longer than we had planned. It took me a good hour to clean everything as it involves dismantling the whole mannikin and irrigating and drying the tracheal and oesophageal tubes. The supplied fake blood when prepared as per instructions is sticky and gets on everything. Its best to conduct this type of training on a large disposable plastic sheet. It also stains clothes and skin. My advice is to wear gloves and normal PPE as you would if having to deal with a patient who is vomiting blood! Its reasonable to practice with direct suctioning and we had a Laerdal manual suction unit available for testing. This would be an ideal model to test Dr Weingart’s published technique of an assembled large bore suction setup using a tracheal tube and meconium aspirator! One can try to overwhelm suctioning by pouring more blood into the oesophageal tubing and manually insufflating air more aggressively into the tubing. The utility of this simple technique was interesting. One could fill the tubing with blood and hold the distal end at a level where no blood was apparent in the pharynx. Then as the provider attempted direct or video laryngoscopy, using a combination of tube elevation and manual air insufflations, a sudden welling up of blood from the oesophagus could be realistically simulated. It is likely that this technique could be applicable to other standard airway training manikins by accessing the oesophageal tubing as we have described. Clearly manufacturer’s instructions should be considered as such novel use of a mannikin may void factory warranties. However with the Simulaids critical airway trainer, it is specifically designed to simulate the bloody airway using the supplied fake blood so this is covered by the warranty.
I have provided a brief description of a novel simulated bloody airway model for the purposes of improved training to manage this difficult airway scenario. In addition I have reported on a brief comparison of the King Vision and Airtraq laryngoscopes performance in testing this novel airway model.
Financial disclosures/conflicts of interest declared: Critical Assist Australia provides sponsorship of the RFDS STAR program Prehospital Anaesthesia and Airway courses in 2012 and is the Australian distributor of the King Systems King Vision video laryngoscope. The unit pictured in the testing is a privately purchased device. Simulaids has not provided any sponsorship or financial incentive at all to myself or the RFDS Queensland section, my employer. APL Health care, the distributors of Simulaids simulation products and the mannikin pictured provided no incentive in the production of this article, testing session or video recording.