6-12
Prevention and Hygiene: Use only approved USN air sources for diving.
No Improvement/Deterioration: Return to a medical care provider or emergency room immediately.
Follow-up Action
Return evaluation: Follow up daily for three days after symptoms have resolved to evaluate for recurrence.
Avoid diving for at least four weeks after symptoms resolve, and until cleared by a Diving Medical Officer
(DMO).
Consultation Criteria: DMO consultation as soon as possible.
Evacuation: Avoid altitude over 1000 feet unless in aircraft with pressurized cabin.
Dive Medicine: Carbon Dioxide Poisoning
CPT Jeffrey Morgan, MC, USAIntroduction: Carbon dioxide (CO 2 ), a colorless, odorless, tasteless gas, is a normal component of the
atmosphere that can be toxic in high concentrations. A diver may experience CO 2 poisoning (hypercapnia)
even without a deficiency of oxygen. Hypercapnia often results from improperly venting expired CO 2 in
chamber or hard hat diving operations. Difficulties with rebreather (closed circuit or semi closed circuit) rigs
like the MARK XVI and LAR V (MARK XXV), which use chemicals to remove CO 2 from the breathing supply
can also lead to hypercapnia. Skip breathing (voluntary hypoventilation) while diving also causes CO 2 to build
up in the blood stream. Increased work rates and shivering due to cold water increase CO 2 generation and
the chances of CO 2 poisoning. Patients usually recover within 15 minutes by breathing fresh air, but headache,
nausea, and dizziness may persist after treatment.
Subjective: Symptoms
Headache, dizziness, confusion, euphoria, unconsciousness. Note: a diver may experience no signs or
symptoms other than sudden unconsciousness.
Focused History: Have you been diving with a rebreather? In a chamber/hard hat? (common causes)
Objective: Signs
Using Basic Tools: Increased rate and depth of respirations, shortness of breath, increased pulse rate.
Neurological exam including mini-mental status exam (see Appendices): decreased mental status (usually
obvious during history questions), decreased balance, decreased strength, numbness in the extremities and
unconsciousness; diver may become unconscious underwater and drown.
Assessment:
Differential Diagnosis
Hypoxia - more pronounced fatigue and confusion, more frequent cyanosis, more visual changes.
Oxygen toxicity - convulsions, tunnel vision, twitching of facial muscles
Pulmonary Over Inflation Syndrome (POIS), including Arterial Gas Embolism (AGE) - often specific and/or
catastrophic neurological findings within 10 minutes of surfacing; pneumothorax, subcutaneous emphysema.
See POIS section in this chapter.
Decompression sickness (DCS) - focal or general neurological findings, which typically begin hours after a
dive
Plan:
Treatment
- Treat for AGE or hypoxia if these conditions are suspected or cannot be ruled out. See respective sections
in this chapter. - Otherwise, have patient rest and breathe fresh air with deep inspirations for about 30 minutes. Significant
recovery should quickly occur with the possibility of some residual headache, nausea and dizziness. - If patient has not made significant improvement in 30 minutes, consider immediate evacuation and
reconsider differential diagnoses.