The interaction effect of COVID-19 infection and hypoxia at high altitudes on the physiological functions of multiple systems- A cross-sectional study based on people at high altitudes

Abstract Backgroud: Both the low-oxygen environment at high altitudes and COVID-19 infection can independently cause cardiopulmonary dysfunction. There are multiple intersections at the pathophysiological level between the two, but their synergistic effects and long-term impacts remain unclear. Methods This study adopted a cross-sectional design and included 290 Han residents from Lhasa City, who were divided into a COVID-19 recovery group (COVID-19) and an uninfected control group(N-COVID).Demographic characteristics and psychological behavior data were collected through standardized questionnaires. CPET, muscle strength and balance tests were used to assess cardiopulmonary and muscle neuropsychological functions between the two groups. The aim was to reveal the functional recovery characteristics and potential mechanisms of COVID-19 recovered patients in high-altitude hypoxic environments. Result VO 2 peak/kg,VE/VCO 2 ,VE/VCO 2 slope and RER in COVID-19 were significantly increased ( P < 0.05); The grip strength, balance ability, SDS, SAS and FACIT-F fatigue scores of the subjects with N-COVID were significantly higher than those with COVID-19 ( P < 0.05). Regression analysis after adjusting for confounding factors showed that: COVID-19 infection and VO 2 peak/kg [B(95%CI): 1.796 (0.292–3.301)], VE/VCO 2 slope[B(95%CI): 1.886(0.207–3.565)], RER[B (95%CI): 0.035 (0.017–0.052)], balance left/right [B(95%CI):14.869(19.807–9.932)/14.959(9-10.149-19.76)] have an independent correlation effect ( P < 0.05), The cumulative length of residence on the plateau (every 10 years) has an impact on VD/VT[B(95%CI): 0.006 (0.002–0.01)], SAS [B (95%CI) : 1.827 (0.949–2.705)], SDS[B (95%CI):1.353 (0.457–2.249)] and FACIT-F [B (95%CI):0.935(0.046–1.824)] had an independent correlation effect ( P < 0.05). Both COVID-19 infection and the cumulative length of residence at high altitudes (per 10 years) were negatively correlated with grip strength ( P < 0.05), and the effect size of COVID-19 infection was approximately 2.46 times that of the cumulative length of residence at high altitudes (per 10 years). There was no interaction effect between the cumulative length of residence in the plateau (every 10 years) and COVID-19 ( P > 0.05). Conclusions During the long-term recovery from COVID-19 at high altitude, the reduction of VE/VCO 2 slope persists, and its sensitivity to recognizing cardiopulmonary dysfunction is superior to that of VO 2 peak. Meanwhile, the hypoxic environment at high altitude has a significant independent impact on VD/VT. The resulting pattern of functional dimension separation constitutes the specific pathophysiological phenotype of recovered COVID-19 patients at high altitude. Trial registration: All subjects signed the informed consent form at the time of inclusion. This study was approved by the Medical Ethics Committee, with the approval number 2021(53).