Emergency War Surgery NATO Handbook: Part I: Types of Wounds and Injuries: Chapter VI: Chemical Injury
Choking Agents
United States Department of Defense
This group, so called because of the pronounced irritation of the upper as well as the lower respiratory tract, consists of phosgene (CG). diphosgene (DP), and chlorine (CL). Phosgene gas, approximately three times heavier than air, hugs the ground as a white cloud that spills into bunkers and fighting pits.
The choking agents are treacherous in that the onset of fulminating pulmonary edema is delayed several hours following exposure. Thus, a soldier with dyspnea and mild substernal discomfort may have normal auscultatory and radiographic signs and be returned to duty, only to progress to extremis a few hours later.
It is imperative that any casualty with known phosgene exposure, no matter how minor his dyspnea or upper respiratory irritation, be observed for 4-6 hours at the very least, then carefully checked for impending pulmonary edema before being returned to duty (see below).
Diagnosis: Phosgene has the characteristic odor of freshly mown grass. The threshold for detecting phosgene's characteristic odor is so close to the irritant threshold as to be useless as a warning. The individual's sense of dyspnea as the lung stiffens still serves as the best indicator of impending pulmonary edema.
Irritant effects on the eyes and tracheo-bronchial tree - accompanied by tearing, cough, or chest discomfort - and dyspnea or tachypnea are the first effects noted. These symptoms may appear to be rather minor at first, resembling the symptoms of a common cold or anxiety reaction. From one half hour to four or six (rarely twelve) hours following exposure, cough, chest pain, cyanosis, and progressive dyspnea herald impending overt pulmonary edema. Painful cough, frothy sputum, cyanosis, rales, dullness to percussion, and radiographic evidence support the diagnosis.
Uncomplicated cases recover without permanent after effects. However, the possibility of secondary bacterial pulmonary infection is considerable. Circulatory failure or the patient appearing "mouse-grey cyanotic" are ominous signs. The "plum-blue cyanotic" patient, conversely, has a good chance to survive. These gross observations may be helpful in mass casualty triage.
Treatment: Recall the treacherous "silent period" that follows the inhalation of a pulmonary irritant. Observe the symptom-free patient with known exposure to a choking agent for at least 4-6 hours and the casualty with known exposure and minimal symptoms (itching eyes, runny nose, mild cough, vague chest discomfort) for at least 12 hours. In either case, do not release these personnel to duty without a careful re-examination of the chest.
Treatment of non cardiac pulmonary edema in the field is mostly supportive, with enforced rest to minimize exertion. Oxygen with air admixed to 40% is sufficient and will help conserve limited supplies. Intravenous fluids (as in any case of pulmonary edema) should be administered sparingly. The risk of bronchopneumonia is greatest when pulmonary edema begins to subside. The clinician must be alert for changes in sputum color or a sudden rise in body temperature.
According to current thinking, (a) prophylactic antibiotics are of no proven benefit, (b) steroids, whether given intravenously or by inhalation, appear to offer no advantage, (c) early positive end-expiratory pressure (PEEP) breathing may well reduce the severity of the subsequent pulmonary edema, and (d) patients in severe distress will require endotracheal intubation or tracheostomy and positive pressure mechanical ventilation.
Phosphorus pentoxide, the dense white smoke associated with white phosphorus munitions, presents the same clinical picture as phosgene exposure. Experience has shown that the chemical burn of the alveolus produced by phosphorus pentoxide is irreversible and fatal in those who progress to pulmonary edema. It is a sobering and frustrating experience to observe a totally asymptomatic soldier, exposed to phosphorus pentoxide inhalation, progress from the asymptomatic state to intractable pulmonary edema and death over the span of eight hours in spite of every supportive effort.