A prospective single-blind randomised clinical trial comparing two treatment tables for the initial management of mild decompression sickness

Abstract

Introduction: Limited evidence suggests that shorter recompression schedules may be as efficacious as the US Navy Treatment Table 6 (USN TT6) for treatment of milder presentations of decompression sickness (DCS). This study aimed to determine if divers with mild DCS could be effectively treated with a shorter chamber treatment table.

Methods: All patients presenting to the Fremantle Hospital Hyperbaric Medicine Unit with suspected DCS were assessed for inclusion. Participants with mild DCS were randomly allocated to receive recompression in a monoplace chamber via either a modified USN TT6 (TT6m) or a shorter, custom treatment table (FH01). The primary outcome was the number of treatments required until resolution or no further improvement (plateau).

Results: Forty-one DCS cases were included, 21 TT6m and 20 FH01. Two patients allocated to FH01 were moved to TT6m mid-treatment due to failure to significantly improve (as per protocol), and two TT6m required extensions. The median total number of treatments till symptom resolution was 1 (IQR 1-1) for FH01 and 2 (IQR 1-2) for TT6m (P = 0.01). More patients in the FH01 arm (17/20, 85%) showed complete symptom resolution after the initial treatment, versus 8/21 (38%) for TT6m (P = 0.003). Both FH01 and TT6m had similar overall outcomes, with 19/20 and 20/21 respectively asymptomatic at the completion of their final treatment (P = 0.97). In all cases where two-week follow-up contact was made, (n = 14 FH01 and n = 12 TT6m), patients reported maintaining full symptom resolution.

Conclusions: The median total number of treatments till symptom resolution was meaningfully fewer with FH01 and the shorter treatment more frequently resulted in complete symptom resolution after the initial treatment. There were similar patient outcomes at treatment completion, and at follow-up. We conclude that FH01 appears superior to TT6m for the treatment of mild decompression sickness.

Keywords: Decompression illness; Diving research; Hyperbaric oxygen treatment; Recompression; Recreational diving; Scuba diving; Treatment sequelae.

Figure 1

Fremantle Hospital Hyperbaric Medicine Unit USN TT6 (modified) for monoplace chamber application; pressures are absolute pressures. The total time is 4 hours 35 minutes (275 minutes); compression rate 18 kPa·min^-1, decompression rate 9 kPa·min^-1; BIBS − built in breathing system; kPa – kilopascals; msw − metres of seawater; O₂ − oxygen; Pt − patient

Figure 2

Fremantle Hospital Hyperbaric Medicine Unit USN TT5 (modified) for monoplace chamber application; pressures are absolute pressures. The total time is 2 hours 30 minutes (150 minutes); compression rate 18 kPa·min^-1, decompression rate 9 kPa·min^-1; BIBS − built in breathing system; kPa – kilopascals; msw − metres of seawater; O₂ − oxygen

Figure 3

Fremantle Hospital Hyperbaric Medicine Unit FH01 for monoplace chamber application; pressures are absolute pressures. The total time is 2 hours 40 minutes (160 minutes); compression rate 18 kPa·min^-1; decompression rate 8.4 kPa·min^-1 from 284 to 200 kPa and 10 kPa·min-1 from 200 kPa to ‘surface pressure’. BIBS − built in breathing system; kPa – kilopascals; min – minutes; msw − metres of seawater; O₂ − oxygen; Pt − patient

Figure 4

Fremantle Hospital Hyperbaric Medicine Unit Table 10:120:06 for monoplace chamber application; pressures are absolute pressures. The total timmin^-1min-1; kPa – kilopascals; msw – metres of seawater

Figure 5

Modified CONSORT flow diagram; FH01 − Fremantle Hospital Treatment Table 01; TT6m − United States Navy Treatment Table 6 (modified)