A comparative evaluation of two decompression procedures for technical diving using inflammatory responses: compartmental versus ratio deco

Abstract

Introduction: The aim of this study was to compare two decompression procedures commonly adopted by technical divers: the ZH-L16 algorithm modified by 30/85 gradient factors (compartmental decompression model, CDM) versus the 'ratio decompression strategy' (RDS). The comparison was based on an analysis of changes in diver circulating inflammatory profiles caused by decompression from a single dive.

Methods: Fifty-one technical divers performed a single trimix dive to 50 metres' sea water (msw) for 25 minutes followed by enriched air (EAN50) and oxygen decompression. Twenty-three divers decompressed according to a CDM schedule and 28 divers decompressed according to a RDS schedule. Peripheral blood for detection of inflammatory markers was collected before and 90 min after diving. Venous gas emboli were measured 30 min after diving using 2D echocardiography. Matched groups of 23 recreational divers (dive to 30 msw; 25 min) and 25 swimmers were also enrolled as control groups to assess the effects of decompression from a standard air dive or of exercise alone on the inflammatory profile.

Results: Echocardiography at the single 30 min observation post dive showed no significant differences between the two decompression procedures. Divers adopting the RDS showed a worsening of post-dive inflammatory profile compared to the CDM group, with significant increases in circulating chemokines CCL2 (P = 0.001) and CCL5 (P = 0.006) levels. There was no increase in chemokines following the CDM decompression. The air scuba group also showed a statistically significant increase in CCL2 (P < 0.001) and CCL5 (P = 0.003) levels post dive. No cases of decompression sickness occurred.

Conclusion: The ratio deco strategy did not confer any benefit in terms of bubbles but showed the disadvantage of increased decompression-associated secretion of inflammatory chemokines involved in the development of vascular damage.

Keywords: Bubbles; Chemokines; Decompression tables; Echocardiography; Inflammation; Scuba diving.

Figure 1

Two technical diving decompression profiles − ratio decompression strategy (RDS, light grey) and compartmental decompression (CDM, dark grey); the descent and bottom-time profile (0–25 min, not shown) was identical for both RDS and CDM dives

Figure 2

Bubble grades 30 min after surfacing using two different decompression schedules − ratio decompression strategy (RDS) and compartmental decompression model (CDM) for a 50 msw, 25 min bottom time technical dive; no grade 5 bubbling was detected

Figure 3

Circulating cytokines and chemokines detected in swimmers before and 90 min after surface swimming, and in three groups of divers (mean +/- SD shown) before and 90 min after surfacing from their different dives: the concentrations of interleukin 6 (IL-6); interleukin 8 (IL-8); C-X-C motif chemokine 10 (CXCL10); C-C motif chemokine ligand 2 (CCL2), macrophage inflammatory protein-1 beta (MIP-1β) and C-C motif chemokine ligand 5 (CCL5) were simultaneously measured in the plasma of swimmers and divers by multiplexed Luminex®-based immunoassay; ∗ indicates statistically significant differences (see text for details)

Figure 4

Urinary 8-hydroxy-2'-deoxyguanosine (8-OH-dG) taken 90 min after surface swimming and in three groups of divers before and 90 min after surfacing from their different dives (mean +/- SD)