Changes in physiological parameters and thermal comfort when wearing protective clothing in long-range aeromedical evacuation: a prospective, non-blinded, two-stage crossover self-controlled study.

BACKGROUND

The thermos-physiological characteristics of medical personnel wearing protective clothing during prolonged activities under low oxygen pressure (LOP) and normal oxygen pressure (NOP) are crucial.

METHODS

The average age of the 24 participants was 22.13 ± 1.849 years, with an average height of 168.58 ± 6.268 cm, an average weight of 61.62 ± 8.128 kg, and an average BMI of 21.59 ± 1.761 kg/m. Participants were first exposed to an LOP environment. The 6-h experiment involved a three-phase cycle (sitting, walking, and cardiopulmonary resuscitation (CPR)) repeated every hour. After a 2-week washout period, 24 participants were exposed to a NOP environment and repeated the aforementioned experimental procedure. Logistic regression and Cox analysis were used to assess the relationship between different oxygen pressures and human indicators. Restricted cubic spline (RCS) analysis was employed to examine the temporal changes in physiological indicators, and the Kaplan-Meier (K-M) method was used to plot survival curves.

RESULTS

Each observation time point identified 120 min as the optimal protection time, with the greatest intergroup differences observed for both continuous (5/8 variables) and categorical (8/12 variables) parameters at this time point. Stepwise Regression analyses combining logistic and Cox regression identified six significant variables (P < 0.05): temperature, SpO₂, pulse pressure, thermal sensation vote (TSV), sultriness, and rating of perceived exertion (RPE). K-M analysis revealed significantly higher probabilities of adverse outcomes in the LOP group compared to the NOP group: SpO₂ abnormalities (HR = 1.439, 95% CI: 1.026-2.017; log-rank P = 0.022), High TSV scores (HR = 2.463 [1.537-3.946]; P < 0.001), High sultriness scores (HR = 1.603 [1.260-2.040]; P < 0.001). RCS analysis of LOP group data showed significant temporal effects: RPE exhibited a nonlinear upward trend (overall P < 0.001; nonlinear P = 0.002), reaching an inflection point at 200 min. SpO₂ demonstrated linear decline (P = 0.002/0.143; inflection point = 200 min). Pulse pressure showed covariate-dependent effects: nonsignificant before adjustment (P = 0.430) but significant after adjustment (P = 0.008/0.891; inflection point = 200 min).

CONCLUSIONS

Our research shows that 120 ~ 200 min is an optimal working time that does not affect the work efficiency of medical personnel.