Intubating laryngeal mask airway versus laryngoscopy and endotracheal intubation in the nuclear, biological, and chemical environment

Military Medicine, Nov 2003 by Talbot, Timothy S, Cuenca, Peter J, Wedmore, Ian S

Objective: Intubation is a difficult skill under normal circumstances and more so with a limited visual field such as wearing a protective mask in a chemical or biological incident. This study sought to determine whether successful intubation using the intubating laryngeal mask airway (ILMA) under protective mask conditions was equivalent to standard endotracheal intubation. Methods: A pilot study was conducted using emergency medicine personnel. Participant's attempted intubation of a manikin while wearing a standard U.S. Army M-40 protective mask. Two attempts were performed with each method. Results: One hundred percent of the ILMA placements were successful with only 78% success with endotracheal intubation (p = 0.1). Time to successful intubation and ventilation was significantly less for the ILMA versus endotracheal intubation (p = 0.005). Conclusion: This study suggests that under simulated chemical and biological conditions using an M-40 protective mask, intubation is accomplished faster and with more success with the ILMA.

Introduction

The world medical community's attention has recently been focused on the ability to react to significant hazardous material incidents/accidents. Industrial accidents, such as the Union Carbide incident in Bhopal, India,1 or a terrorist act, such as the 1995 sarin attack in Tokyo, Japan,2 dictate health care providers be trained to react to such events. The majority of these hazardous material incidents significantly impact respiratory function, quickly causing death due to respiratory failure. Reacting to a mass casualty situation caused by a hazardous material incident requires the ability to rapidly and successfully control a patient's airway while operating in a contaminated environment.

Intubation is a difficult skill. Repetitive training and a significant number of attempts with patients are required to acquire and maintain successful skills. Intubation is a visual skill requiring the ability to recognize and adapt rapidly to changing airway conditions. Even in optimum in-hospital conditions, successful intubation rates range from 46% to 95%.3-6 In a chemical and biological-contaminated environment, use of full protective gear will invariably decrease success rates. The physiological and psychological stress associated with the use of the protective equipment reduces working ability by as much as 30%.7 Visual fields are significantly restricted by the use of the M-40 protective mask (Fig. 1) to approximately 90 degrees.8 TurKaspa et al.9 advocate the use of intubating manikins and intubation stations in hazardous material drills to adapt to this restriction in visual field. However, this training rarely takes place secondary to limited availability of equipment. In the majority of facilities, use of protective equipment will most likely occur with the first real-world incident.

Intubation while using a protective ensemble was studied previously by Hendler et al.10 They demonstrated successful intubation with mean times to intubation increasing by 47%. Furthermore, the authors postulated that time to intubation of a manikin does not simulate a real casualty with multiple secretions that would lead to greater difficulty of intubation and time to intubation. Coates11 studied the ability of emergency staff to perform medical tasks in full protective clothing. He found 9 of 10 physicians could intubate within 30 seconds, with one physician able to intubate after several esophageal intubations. Again, this was a manikin study and successful intubation rates would be expected to decrease and intubation times to increase due to complications of airway visualization in actual casualties.

The intubating laryngeal mask airway (ILMA) was recently developed and fielded in the United States. Multiple studies demonstrate successful intubation rates approaching 96% with little or no training with the ILMA.12,13 A recent study by Cuenca et al.14showed that the success rate of intubation in a visually constrained environment using the ILMA was equivalent to direct laryngoscopy and intubation. The ILMA is a blind intubation technique ideal for the visually limited environment of a protective mask. Use of an ILMA while wearing protective equipment has never been studied. Our study is the first to compare intubation using the ILMA versus standard endotracheal intubation (ETI) while wearing a nuclear, biological, and chemical (NBC)-protective mask.

Methods

We designed a prospective observational pilot study to evaluate endotracheal intubation of a manikin using the ILMA versus standard ETI while wearing NBC protective equipment. The Madigan Army Medical Center Institutional Review Board approved this study. Participants consisted of 16 volunteer residents and staff of the Madigan Army Medical Center-University of Washington Emergency Medicine Residency. Direct comparison of ILMA versus ETI was performed. Intubation was performed using Laerdal intubating head manikin, a size 4 intubating laryngeal mask with 7.5-mm cuffed endotracheal tube (Fastrach, LMA North America, San Diego, California), one 30-mL syringe attached to the ILMA cuff, one 10-mL syringe attached to the endotracheal tube, and a standard bag valve mask (Fig. 2). The ILMA was prelubricated with Surgilube water-soluble lubricant. For the CTI portion of the study, participants were provided a size 4 Miller laryngoscope. All participants wore a medium U.S. Army M-40 protective mask while performing ETI and ILMA intubation (Fig. 1).