Therapeutic management of severe spinal cord decompression sickness in a hyperbaric center

Abstract

Introduction: Spinal cord decompression sickness (scDCS) unfortunately has a high rate of long-term sequelae. The purpose of this study was to determine the best therapeutic management in a hyperbaric center and, in particular, the influence of hyperbaric treatment performed according to tables at 4 atm (Comex 30) or 2.8 atm abs (USNT5 or T6 equivalent).

Methods: This was a retrospective study that included scDCS with objective sensory or motor deficit affecting the limbs and/or sphincter impairment seen at a single hyperbaric center from 2010 to 2020. Information on dive, time to recompression, and in-hospital management (hyperbaric and medical treatments such as lidocaine) were analyzed as predictor variables, as well as initial clinical severity and clinical deterioration in the first 24 h after initial recompression. The primary endpoint was the presence or absence of sequelae at discharge as assessed by the modified Japanese Orthopaedic Association score.

Results: 102 divers (52 ± 16 years, 20 female) were included. In multivariate analysis, high initial clinical severity, deterioration in the first 24 h, and recompression tables at 4 atm versus 2.8 atm abs for both initial and additional recompression were associated with incomplete neurological recovery. Analysis of covariance comparing the effect of initial tables at 2.8 versus 4 atm abs as a function of initial clinical severity showed a significantly lower level of sequelae with tables at 2.8 atm. In studying correlations between exposure times to maximum or cumulative O2 dose and the degree of sequelae, the optimal initial treatment appears to be a balance between administration of a high partial pressure of O2 (2.8 atm) and a limited exposure duration that does not result in pulmonary oxygen toxicity. Further analysis suggests that additional tables in the first 24-48 h at 2.8 atm abs with a Heliox mixture may be beneficial, while the use of lidocaine does not appear to be relevant.

Conclusion: Our study shows that the risk of sequelae is related not only to initial severity but also to clinical deterioration in the first 24 h, suggesting the activation of biological cascades that can be mitigated by well-adapted initial and complementary hyperbaric treatment.

Keywords: bubbles; decompression sickness; diving; helium; hyperbaric oxygen therapy; lidocaine; neurological sequelae; spinal cord.

Figure 1

Initial recompression tables. When the injured diver had a MEDSUBHYP score of initial severity ≤7, a B18 table was performed, whereas a C18 table or Comex 30 table was used for an initial score > 7.

Figure 2

Additional recompression tables. Heliox tables at 18 m (2.8 atm abs) and 30 m (4 atm abs) or 100% O2 tables were performed in the first 24–48 h after the initial table followed by consolidation sessions with daily 100% O2 tables at 15 m (2.5 atm abs).

Figure 3

Flow chart describing the inclusion of the 102 subjects and the recompression tables performed.

Figure 4

Scatter plot of the 102 DCS divers treated with initial tables at 2.8 atm abs (blue) or 4 atm abs (red) as a function of initial clinical severity (MEDSUBHYP score) and level of sequelae (mJOA score). The mJOA score has been normalized according to the MEDSUBHYP score and according to the two treatments (2.8 and 4 atm). Each point represents one or more divers. The analysis of covariance comparing the regression lines according to the two treatments shows a significant difference between the treatment at 2.8 atm and the treatment at 4 atm abs.

Figure 5

Histograms (mean, standard error and p-value) showing mJOA score comparisons between initial tables at 2.8 atm abs or 4 atm abs for DCS injuries with an initial MEDSUBHYP score > 7. The mean values with standard deviation of the MEDSUBHYP scores are specified, with no statistical difference between the two groups.

Figure 6

Histograms (mean, standard error and p-value) showing mJOA score comparisons between Short and Long initial oxygen tables at 2.8 atm abs for DCS injuries with an initial MEDSUBHYP score > 7 and < 19. The mean values with standard deviation of the MEDSUBHYP scores are specified, with no statistical difference between the two groups.

Figure 7

Subgroup analysis of patients with equivalent clinical severity at the end of the first recompression. Comparison of the number of sequellar patients (mJOAS <16) according to the additional hyperbaric treatment performed in the first 24–48 h, i.e., the O2 100% table at 2.5 atm abs vs. the Heliox 50% table at 2.8 atm abs.

Figure 8

Subgroup analysis of patients with equivalent clinical severity at the end of the first table. Comparison of the number of sequelae patients (mJOAS <16) according to the administration or not of a lidocaine infusion.

Figure 9

Proposed hyperbaric therapeutic management of spinal cord DCS based on results suggested by this study.