Pulmonary Chemical-Warfare Agents
There are many types of chemical-warfare agents that affect different parts of the body. Pulmonary agents affect the lungs and airways. They include traditional “choking” agents, such as chlorine, phosgene, diphosgene, and chloropicrin, and some blistering agents, such as sulfur mustard, Lewisite, and phosgene oxime (which also affect the skin), as well as military smokes, products of combustion, and many toxic industrial chemicals. Most of these compounds are gases or highly volatile liquids.
Agents are divided into two types depending on which part of the respiratory tract is largely affected:
Mixed-effect agents can affect large airways, small airways, and the alveoli.
Type 1 agents include ammonia, hydrogen chloride, hydrogen fluoride, riot-control agents, most smokes, sulfur dioxide, and sulfur mustard.
Type 2 agents include chloropicrin, methyl isocyanate, phosgene, and carbon tetrachloride.
Mixed-effect agents act in both large airways and alveoli in low to moderate doses. They include chlorine, HC (hexachloroethane plus zinc oxide) smoke, and Lewisite.
Initial exposure to type 1 agents causes sneezing, coughing, and spasm of the windpipe, which can block the airway. Eye irritation can also occur. People with windpipe spasm are hoarse, have wheezing, and make a gasping sound as they breathe in. This sound is called stridor. However, with high doses of type 1 agents, delayed-onset chest tightness or shortness of breath (type 2 effects) may also occur.
With type 2 agents, victims usually feel well at first except for some initial coughing and irritation, which then resolve. However, several hours later they develop chest tightness or shortness of breath due to fluid buildup in the lungs (pulmonary edema). Shortness of breath that develops within 4 hours of exposure is a sign that the person may have been exposed to a potentially lethal dose.
Doctors and first responders base the diagnosis of exposure to a chemical weapon on the person's symptoms. They listen to the person's breathing. People with an initially noisy chest and prominent symptoms were likely exposed to a type 1 agent. People with a relatively quiet chest and whose shortness of breath is delayed were probably exposed to a type 2 agent.
Chest x-ray may initially appear normal but later on develop characteristic abnormalities. Sometimes doctors insert a flexible tube with a camera into the airways (bronchoscopy) to see the extent of airway damage. Bronchoscopy can confirm damage done by type 1 agents but may miss early damage done by type 2 agents.
Laboratory testing is not helpful to doctors as they make an initial diagnosis, but they usually monitor the oxygen level in the person's blood to help determine whether the person is deteriorating.
Because mixed effects are common, doctors base treatment on the person's symptoms rather than on the specific agent. Decontamination is not usually necessary for people exposed to vapor or gas, and there are no specific antidotes for these agents.
For people whose symptoms mainly involve the large airways (type 1 effects), doctors give warm, humidified 100% oxygen by face mask. They may need to remove debris from the person's large airways using bronchoscopy. Doctors may need to place a breathing tube in the person's windpipe, and they may give the person bronchodilators, a type of inhaled drug that widens the airways (similar drugs are used for asthma). Inhaled corticosteroids may be given to help decrease the inflammation that often accompanies lung damage.
People exposed to a possible type 2 agent are admitted to an ICU and given oxygen. Sometimes oxygen is given under pressure through a special tight face mask or through a breathing tube placed in the windpipe. Doctors give medicine to remove fluid from the lungs and may give oral corticosteroids depending on the type of damage they suspect.
The views expressed in this article are those of the author and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.