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Dive Medicine: Carbon Monoxide Poisoning
CPT Jeffrey Morgan, MC, USAIntroduction: Carbon monoxide is a colorless, odorless and tasteless gas that binds very strongly to
hemoglobin. It is typically produced by incomplete combustion of fuels. When filling SCUBA tanks, there is a
risk that the air intake of the compressor is located near a source of carbon monoxide (exhaust pipe of engine,
etc.). Carbon monoxide (CO) has 210-250 times the affinity for hemoglobin that oxygen does. If hemoglobin
is bound to CO it cannot bind to and transport oxygen to tissues. The severity of symptoms is not directly
correlated to the percent of hemoglobin bound to carbon monoxide. Carbon monoxide poisoning causes
hypoxia and other intra-cellular problems stemming from the production of free radicals. Factors that affect
carbon monoxide absorption are concentration of inhaled CO, duration of CO exposure, and respiratory rate.
Symptoms usually begin while ascending from a dive (due to dropping partial pressure of oxygen). Significant
exposure may cause the symptoms to begin anytime during the dive. Hyperbaric oxygen therapy reduces the
half-life of carbon monoxide saturation considerably.
Subjective: Symptoms
Headache, nausea, vomiting, dizziness, dyspnea, tinnitus, weakness, irritability, memory loss, confusion, col-
lapse, stupor, unconsciousness, coma and death. Unconsciousness can occur with very few prior symptoms
or warning signs.
NOTE: Delayed CO symptoms can occur up to 21 days after exposure. Up to 23% of patients who have mild
initial symptoms and are only treated with 100% oxygen will have delayed symptoms.
NOTE: Pregnant women who have been exposed to CO and have no symptoms may have a fetus in
distress. The fetus must be evaluated also. Fetal hemoglobin binds with CO at approximately 15 times
that of the mother.
Objective: Signs
Using Basic Tools: Abnormal mini-mental status exam; weakness; vomiting; increased respiratory rate but
lungs clear to auscultation; bright, cherry-red lips are a rare and late sign of CO poisoning.
Using Advanced Tools: Depressed S-T segments or arrhythmias on EKG. Cannot assess hypoxia with
pulse oximeter.
Assessment:
Differential Diagnosis - cyanide poisoning, hypoxia (both can be treated with HBO also)
Plan:
Treatment: Treat a diver with suspicious clinical symptoms, including any CNS symptoms beyond a mild
headache.
Primary: Remove diver from source of carbon monoxide. Administer 100% oxygen as soon as possible
pending hyperbaric oxygen (HBO) therapy. Maintain hydration to ensure urine output remains at least 30 cc
per hour (urinating every 2-3 hours). Perform pregnancy test for all women of childbearing age. If patient
is pregnant, benefit of recompression treatment needs to outweigh risk to unborn child (possible: retrolental
fibroplasias, in utero death, birth defects).
Alternative: if HBO chamber is not available, treat with 100% oxygen until symptoms have resolved.
Patient Education
General: High pressures of oxygen are needed to offset the CO. If mild symptoms are treated only with
100% oxygen, monitor the patient for about 24 hours. Return daily for follow-up for three days. CO poisoning
symptoms may begin over the next 21 days. If symptoms occur, patient needs to return for HBO treatment.
Diet: Keep patient hydrated.