Prediction of a Low Success Rate of Astronauts in Space in Performing Endotracheal Intubation

Abstract

We certainly concur with Rabitsch et al. 1that tracheal intubation using direct laryngoscopy by astronauts in space is likely to have a high failure rate. Roan first presented this concept and the use of the Laryngeal Mask Airway ™ (LMA ™; LMA North America, Inc., San Diego, CA) as a backup emergency airway device to the National Aeronautics and Space Administration in October 1999*and later at the Aerospace Medical Association Conference in 2001.†In fact, since 2003, the LMA-Fastrach ™ has been used on the space shuttle as a backup airway device.Several reasons exist that predict a low success rate of astronauts in space in performing tracheal intubation. Although some crew medical officers (CMOs) are physicians, often the CMO may have no medical background. The training CMOs receive on the proper use of the bag valve mask resuscitator, oral airway, tracheal intubation, and surgical cricothyroidotomy is limited, and even physician CMOs are likely to have had several years pass since the last clinical exposure to this scenario. Studies have found that experienced emergency medical technicians (basic), with two to three times the amount of training provided to CMOs, have only approximately a 50% success rate of tracheal intubation in human subjects.2,3A compounding factor further increasing the likelihood of failed intubation is the condition of microgravity while in orbit.The ideal airway for astronaut CMOs would possess a very short learning curve as well as require little experience to master and maintain proficiency. Rabitsch et al. 1chose the Esophageal Tracheal Combitube® (Kendall Sheridan Healthcare Products Company, Argyle, NY) as a backup airway device for failed tracheal intubation. Although requiring less training and skill than direct laryngoscopy, the use of the Combitube® as a rescue airway for failed intubation has shown an overall complication rate of up to 40%, including failure to place, aspiration, pneumothorax, esophageal perforation and laceration, among others.4,5Also, the presence of two lumens may prove confusing to the relative novice under the many stressors of an emergency; clearly, the wrong lumen choice would have disastrous consequences.Although an oral airway and manual resuscitator with facemask is another option, it is well known that ventilation with this device can be challenging for even the most highly trained personnel. On the other hand, 100% of 32 nurses without previous experience in the use of the LMA ™ were able to successfully ventilate live patients 3 months after manikin-only training.6The complication rate of the LMA ™ is quite low, and when used as a primary airway rescue device for failed intubation, it has provided rescue ventilation without complication in 94% of failed intubation cases.7Although the standard LMA ™ has a high success rate as a conduit for tracheal intubation, the LMA-Fastrach ™ is specifically designed to facilitate this. Therefore, it was chosen for the shuttle orbiters and the International Space Station because it most closely meets the criteria delineated above of a short learning curve with a high success rate and easily maintained insertion proficiency.‡University of Alabama at Birmingham, Birmingham, Alabama. gboyd@uab.edu