Unmasking Procedures following a Chemical Attack: A Critical Review with Recommendations

Military Medicine, Jul 2005 by Rosenberg, David B

U.S. Marine Corp and Army doctrine specifies a process for troops to remove the field protective mask in the aftermath of a chemical weapon attack. At the company/battery level, this procedure culminates in exposure of the respiratory system of selected troops to potential gas vapor. Commanders in the field rely on front-line corpsman and medics to provide lifesaving first aid in the event that toxic exposures take place. After this initial stabilization, casualties would be evacuated to an Echelon I medical facility, typically a Battalion Aid Station. The current tactical unmasking procedure, as specified in doctrine, is critically analyzed from a field medical perspective. Easy to implement recommendations are made, both to prevent lethal exposures and to better treat toxicity should prevention fail.

Introduction

Chemical weapons remain a credible threat to American Forces around the globe. In the years following Operation Desert Storm, U.S. ground troops have seen dramatic improvements in chemical protective equipment. The ability to don and conduct operations in chemical protective masks is well rehearsed by both Marine Corps and Army units during training and was battlefield tested during both wars against Iraq. No documented chemical attacks actually took place, however, and unmasking procedures were not definitively validated in combat. As a result of the common practice of tactical force dispersal on the battlefield, many units likely would conduct unmasking at the company/battery level. The safe transition from a chemically contaminated environment to a clean environment presents a potential vulnerability for our forces, especially at the small unit level (company/battery). U.S. Marine Corp and Army doctrine specifies a process for troops to remove the field protective mask in the aftermath of a chemical weapon attack. At the small unit level, this procedure culminates in exposure of the respiratory system of selected troops to potential gas vapor. Commanders in the field rely on front-line corpsman and medics to provide lifesaving first aid in the event that toxic exposures take place. After this initial stabilization, casualties would be evacuated to an Echelon I medical facility, typically a Battalion Aid Station (BAS) for further care.

Review of Current Procedure

The current U.S. Marine Corps and Army doctrine for unmasking contaminated personnel following a chemical weapon attack is presented in Table I. This process, which was used during Operation Iraqi Freedom, is problematic for several reasons. First, the utility is limited to those chemical agents that have rapid onset of symptoms after respiratory exposures. Such chemicals include the nerve agents, the cyanides ("blood agents"), chlorine, and lewisite. Although the mustards and the other pulmonary toxins (diphosgene, phosgene) can affect the respiratory system, symptoms are typically delayed for hours following even large dose exposures.1 second, from a psychological standpoint, a chemical attack, by itself, stresses welltrained troops, and the unmasking process adds anxiety. In this situation, leaders may find it difficult to give unmasking orders to junior troops, and individuals selected to unmask may have to be forced to do so. Such situations conceivably could lead to mistrust and reduced unit cohesion. Last, and most important, the preventable death of an American service member may result from strict adherence to the current procedure.

Although the sensitivity of selective unmasking to detect certain toxic substances is limited, the fact remains that after a chemical attack someone has to be first to remove his/her field protective mask. Given this reality, there are ways to improve this procedure and minimize battlefield casualties, both chemical and psychological.

Proposed Modifications

The current procedure can be improved by making four major modifications (Table II). First, adequate preparation for defense against a chemical attack must include prepackaging a medical unmasking kit. This kit should contain all supplies necessary for intravenous (IV)/intramuscular (IM) administration of antidotes, as well as all basic equipment needed for ventilatory support in a contaminated environment. Medications at the unmasking site should include IV atropine, IV pralidoxime, IV diazepam, FV sodium nitrite, IV sodium thiosulfate, IM dimercaprol, as well as either subcutaneous terbutaline or epinephrine. An airway kit including both oral and nasopharyngeal airways, a Resuscitation Device Individual Chemical, and a Laryngeal Mask Airway (LMA) is essential to sustain the severely toxic patient. The Resuscitation Device Individual Chemical is a self-inflating bag-valve mask containing the same replaceable filter used in the M40 protective mask. It allows rescuers to ventilate a patient with filtered ambient air or supplemental oxygen. Although not a definitive airway, the LMA has received a IIB recommendation as an advanced airway adjunct by the American Heart Association. Efficacy of the LMA approaches that of tracheal intubation.2 Use of the LMA is especially well suited for a chemical environment because it can be inserted blindly and, compared with trachéal intubation, requires only minimal training to achieve competency. In addition, the large distal ring prevents accidental insertion into the esophagus, reducing the likelihood of fatal errors. This feature is appreciated when one considers a corpsman/medic attempting to verify lung sounds through multiple layers of protective clothing while wearing a gas mask and hood. The contents of this unmasking kit are portable, lightweight, inexpensive, and have field utility beyond the contingencies listed in this article.