Repeated Remote Ischaemic Preconditioning Can Prevent Acute Mountain Sickness after Rapid Ascent to a High Altitude: Repeated RIPC can prevent AMS

BACKGROUND Acute Mountain Sickness (AMS) is a syndrome with nonspecific neurological symptoms that can occur in unacclimatized persons after Rapid Ascent to a High Altitude. Since Repeated Remote Ischaemic Preconditioning (RIPC) can protect remote organs from subsequent hypoxic or ischaemic damage, the aim of the present study was to assess the effectiveness of 4 different RIPC protocols varying in duration and frequency for preventing AMS after Rapid Ascent to a High Altitude. METHODS We designed a prospective but not blinded study in which we randomly divided participants into five groups. The participants in the four RIPC groups received different RIPC treatments in the arms at a low altitude (Group A, once daily for 1 week; Group B, twice daily for 1 week; Group C, once daily for 4 weeks; and Group D, twice daily for 4 weeks); the control group did not receive a specific sham treatment. The participants were then flown to a high altitude (3650 m). The primary outcome was the incidence and severity of AMS evaluated by the Lake Louise score (LLS) after arrival; vital signs were collected simultaneously. We performed an intention-to-treat analysis. RESULTS A total of 250 participants, aged 38.56 ± 0.76 years, were included, and 50 participants were allocated to each group. The total AMS incidence in all participants was 26.4%. A total of 20 AMS cases (40%) occurred in the control group after arrival at high altitude, whereas 15 AMS cases (30%) occurred both in the RIPC A and RIPC B groups (relative risk 1.3; 95% confidence interval 0.8 - 2.3; χ2 = 1.099; p = 0.29), and 8 AMS cases (16%) occurred both in the RIPC C and D groups (RR 2.5; 95% CI 1.2 - 5.2; χ2 = 7.143, p   0.05) were lower in the RIPC groups than in the control group. The blood oxygen saturation level (SpO2) decreased less in the RIPC B, C and D groups than in the control after arrival at a high altitude (F = 11.42, p < 0.001). The number of RIPC treatments each participant received was moderately correlated with SpO2 (R = 0.38, p < 0.001), and SpO2 was moderately inversely correlated with the LLS (R = -0.48, p < 0.001). CONCLUSION This study demonstrated that a four-week RIPC intervention but not a one-week regimen reduced AMS incidence and severity; however, a placebo effect might have contributed to the results of this study.