Complement levels before and after dives with a high risk of DCS.
BACKGROUND
Previously, complement activation has been associated with decompression sickness (DCS). However data, both in humans and in animals, are controversial.


OBJECTIVE
Complement activation and depletion occurs after exposure to the hyperbaric environment and is associated with increasing risk of DCS.


METHODS
We obtained serological samples from 102 dives (120-300 feet of seawater) with a constant partial pressure of O2 set at 1.3 ATA in thirty-five U.S. Navy diver volunteers. Blood was obtained within one hour of diving and within one hour of surfacing. Plasma was extracted and analyzed for complement depletion. The risk of DCS was estimated using a validated model of DCS risk.


RESULTS
Pre-post dive concentrations of C3a were significantly related to estimated risk of DCS (Figure 1), but the variation in predicted DCS explained by C3a was small (correlation co-efficient (r2 = 0.19, p < 0.0001).


CONCLUSIONS
There was a reduction in total Ca3 levels in divers after exposure to dives with a high estimated risk of DCS. This decomplementation appeared to increase as the estimated risk of DCS increased.
Department of Neurology and Anesthesia/Critical Care, Cerebrovascular Division, Johns Hopkins School of Medicine, Rm 125 Phipps, 600 North Wolfe Street, Baltimore, Maryland 21287-6953, USA.
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Nyquist
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Ball
M J
MJ
Sheridan
D003167:Complement Activation / Q000502:physiology*; D015926:Complement C3a / Q000378:metabolism; D015934:Complement C4a / Q000378:metabolism; D015936:Complement C5a / Q000378:metabolism; D003665:Decompression Sickness / Q000097:blood / Q000276:immunology*; D004242:Diving / Q000009:adverse effects* / Q000502:physiology; D006801:Humans; D018570:Risk Assessment
D015926:Complement C3a; D015934:Complement C4a; D015936:Complement C5a