Whole-Body Cryotherapy as an Innovative Treatment for COVID 19-Induced Anosmia-Hyposmia: A Feasibility Study

Objective: This study assessed the impact of two different doses of whole-body cryotherapy (WBC) on smelling capacities of COVID-19 recovered French patients with persistent anosmia or hyposmia. Methods: A pilot randomized controlled trial was conducted by using a convenience sample of 45 hyposmic/anosmic patients (32 female, 13 male, mean age [standard deviation]: 39.5 [14.7] years). The severity of olfactory deficits was examined by using a visual analogue scale (VAS) at baseline, post-intervention, and followup (1 week). Patients were randomly allocated to either control (no intervention, n= 15) or one of the two treatment groups (low-dose WBC, 2 days, n=15; high-dose WBC, 5 days, n= 15) via block randomization by using baseline anosmia as strata. A mixed-design analysis of variance with group (control, low-dose WBC, high-dose WBC) as between-subject variable and time points (baseline, post-intervention, follow-up) as within-subject variable was conducted, followed by post hoc analysis for significant or interaction effects. Results: The WBC appeared to be safe, and no adverse effects were observed. A significant group by time interaction effect was observed. Although no differences between groups were found at pre- and post-intervention, significant differences were found at follow-up in favor of the high-dose group only. The magnitude of difference in the VAS anosmia score was found to be of large size compared with patients in the control and low-dose groups (Hedges' corrected effect size of 0.96 and 1.04 respectively). Within-group comparisons revealed significant improvements in smelling capacities from pre- to post-intervention, and then again from post-intervention to follow-up in both WBC groups. However, the magnitude of change was less pronounced in patients who received the low-dose WBC intervention. Conclusion: The WBC might be beneficial and safe for patients with severe acute respiratory syndrome coronavirus-2-induced olfactive dysfunction; however, further research is necessary to confirm the findings of this pilot study, and to investigate the mode of action.

Automated summary

This study assessed the impact of whole-body cryotherapy (WBC) on smelling capacities of COVID-19 recovered patients. Results showed significant improvements in the high-dose WBC group at follow-up, with a large effect size. However, the low-dose WBC group had smaller improvements. This suggests that WBC may be beneficial for recovering patients' olfactory function.