Breathless medical crisis simulated by parabolic experimenters

Paris, 25 Jun 2004

The inability to breathe is one of the most serious medical situations there is: emergency workers receive extensive training in methods of airway ventilation. So how well would these same techniques work on a stricken astronaut in zero-gravity?

That was the question a group of European students and young professionals interested in space asked themselves, and to answer it they put together an experiment accepted to fly during ESA's latest parabolic flight campaign at the start of June. With the flights now successfully completed, they hope to have their results ready by next month.

In the run-up to the campaign they received medical training in airway ventilation, participated in surgical operations and even practiced their procedures underwater.

"Several of us had met while participating at last year's International Space University master program at Strasbourg and we were enthusiastic about coming up with a useful subject for a zero-gravity experiment," explains Alexander Soucek, currently a Young Graduate Trainee at ESA's European Space Research Institute (ESRIN) in Frascati, Italy.

"The final suggestion came from a friend at Innsbruck called Gernot Grömer, who I have worked with on many space outreach activities. He is studying astrophysics but has also been an emergency paramedic for the last 12 years, and emergency medicine is an area of increasing relevance to human spaceflight.

"As more people enter space on more expanded missions, the chance of a medical emergency increases. In low-Earth orbit a crew can evacuate home in a few hours, but if you are in orbit around Mars that will not be an option. The key concept is autonomy – crews are going to have to rely on themselves to deal with all kinds of medical emergencies."

Also taking part with Austrians Soucek and Grömer were Cristina de Negueruela from Spain and Michael Thomsen from Denmark. The diverse backgrounds of this four-person team reflected the likely make-up of a spacecraft crew: one experienced paramedic with three non-medics – two with technical, one with non-technical backgrounds - relying solely on the pre-flight training they received.

Drs Christian Keller and Thomas Hass of the University Hospital for Anaesthesiology and General Medicine of Innsbruck provided the scientific backbone of the experiment, christened Advanced Airway Management or ADAMA.

The team decided to assess two different means of inserting an airway down a patient's throat, known respectively as endotracheal and larynx mask intubations. Such intubations are required when a patient is under general anaesthetic or otherwise unconscious, but also when their breathing is obstructed or a heart attack or other serious ailment leaves them unable to breathe unsupported.

"An endotracheal intubation involves inserting a tube all the way down to the trachea, or windpipe, that connects the nose and mouth to the lungs," says Thomsen. "As we found out during practice it can be a difficult procedure – you have to pass the tube between the vocal cords to make it to the trachea. Go too far and you the tube may go to one side and ventilate only one lung. Miss the trachea and enter the oesophagus and you'll inflate the patient's stomach instead of his lungs!"

Larynx mask intubation is a newer less-invasive method in which the tube does not require insertion down to the trachea but rests on inflatable cuffs above the vocal cords, or larynx. The experiment would evaluate the relative effectiveness of both methods in weightless conditions. They were taught intubation during a training session at Innsbruck University Hospital, each team member practicing around 50 intubations on a computerised medical mannequin containing a realistic mouth, throat and lungs. This same mannequin would eventually accompany them during the parabolic flight campaign.

"The mannequin even has a tongue and teeth – hit a tooth too hard and it clicks, which tells you that in real life you would have knocked it out," de Negueruela explains. "If you successfully ventilate the mannequin's lungs his chest rises and falls, and using a stethoscope you can hear him 'breathing'."

Following two practice sessions the team were permitted to spend a day at the University Hospital observing and assisting anaesthesiologists performing intubations during surgical operations: "This was quite an experience for us, watching operations on actual human patients from start to finish. We treated the mannequin a lot more gently after that!"

To prepare for the experience of weightlessness the team also carried out intubations in conditions of so-called 'neutral buoyancy' – diving underwater at the University swimming pool.

"That is often described as the closer match to weightlessness, although we found it is a long way from capturing it," Grömer says. "When you are moving underwater it all happens slowly, but in weightlessness things can move very quickly indeed."

Enter the 'Zero-G' Airbus A300 through the red boxes and move around using your mouse to see what it is like in zero-g

Ready for flight

You can experience zero-gravity without going into space. ESA provides access to weightlessness for European scientists - and also students - with a specially adapted Airbus A300, operated by French company Novespace out of Bordeaux-Mérignac Airport.

The aircraft is flown in such a way that it commences a parabolic arc through the sky, and as its engines are throttled back almost to zero it enters a state of free-fall. For 20 seconds at a time the aircraft's occupants become weightless, until its arc is completed and the engines start up again to level it out. The Airbus typically carries out 30 parabolas per flight, providing a precious total of 10 minutes of microgravity per day.

ESA offers two parabolic flight campaigns a year for scientists, and one campaign dedicated to students. After having developed the experiment in autumn 2003, and applied to ESA in January 2004, the team were extremely pleased when they were told a slot was available on the June scientific campaign.

They planned their activities so that one intubation would be performed per parabola, with an intubator and assistant performing the procedure while a controller assessed the results and a camera man recorded everything. The intubation sequence was randomised so the intubator was told which method would be used only seconds before entering the microgravity phase.

"This, along with the fact that the intubation had to be completed within the 20 seconds of microgravity, helped simulate the stress that astronauts would feel in a genuine incident, with a friend lying injured and maybe dying," Grömer explains. "In normal conditions on the ground, you can take a little longer to perform it, but faster is better. At the end of the procedure the intubator would look away because they were not to know whether they were successful or not – we did not want a learning curve."

For half the 90 parabolas during the three campaign days the mannequin had been securely strapped down. The other 45 parabolas were more challenging because the intubations were carried out while the 'patient' was free-floating.

"That was the real challenge because the mannequin has to be held in a fixed position for the procedure," Soucek says. "But even exerting the force needed to push the mannequin's tongue out of the way is enough to set you moving in the opposite direction.

"We tried out different working positions as we went, like resting on the mannequin's chest, holding his head between our knees, or cradling his head in one arm while working with the other arm – this last was probably the most effective, because it gave the point of view needed well down into the throat. All the time we are doing this we are also trying to get used to microgravity, which is quite an overwhelming sensation."

Following the results release in July, the team will be setting up an outreach exhibition based on their work: "The idea is to inform the general public what sort of activity can be carried out in space, and also during parabolic flights.

"Some people might think that experiments in 20-seconds of microgravity are not much use, when you have the International Space Station, but carrying out what research we can on Earth frees up more time for the extraordinary useful and valuable zero-gravity work being done on the Station."

The team hope they might be able to add to their research data during a future flight campaign: "A higher number than 90 parabolas would be scientifically useful. First time around we were learning right up to the last moment!"

European Space Agency
http:///www.esa.int/export/esaCP/index.html
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