Objective To study the changes in physiological indicators of the human body in hypoxic environments and explore the physiological indicators that can be quantified to assess the degree of hypoxia. Methods In October 2023, 16 male staff members from the Air Force Medical Center were selected as the subjects and were randomly divided into a sedentary group and a mental workload group. Hypoxia tests were conducted at simulated altitudes of 1 500, 2 500, 3 000, 4 000, 5 000, 6 000, 7 000, and 7 500 m in the hypobaric chamber. Results The results of multiple linear regression analysis showed that levels of blood oxygen saturation impacted the duration of hypoxia（B=3.283, 95%CI: 1.896－4.670）. The curves for changes in levels of blood oxygen saturation with the duration of hypoxia at different altitudes were fitted, and the duration of hypoxia at which levels of blood oxygen saturation decreased to the target critical value at each altitude was determined. Conclusion During acute high-altitude hypoxia, the levels of blood oxygen saturation can make a difference in the duration of hypoxia. This study is expected to contribute to related identification, early warning and interventions.

Objective To analyze the body composition of military aviators. Methods A total of 184 aviators who visited the Aircrew Department of the Air Force Hospital of the Eastern Theater Command between June and December 2024 were enrolled and divided into a fighter pilot group（n=85）and a bomber/transport/helicopter（B/T/H）aircrew group（n=99）. Basic information was collected, and body composition was measured using bioelectrical impedance analysis. Multiple linear regression was employed to analyze the body composition of military aviators. Results Statistically significant differences were observed between the two groups in age and hours of flight（Z=－7.813, －7.185, both P<0.001）. Significant differences were also found in body mass index, InBody scores, body fat percentage, muscle percentage of right and left lower limbs, visceral fat areas, trunk fat percentage, fat percentage of right and left upper limbs, fat percentage of right and left lower limbs, the waist-to hip ratio and the extracellular water ratio（t=2.990－6.667, all P<0.05）. However, no significant differences were observed in smoking status, skeletal muscle mass, skeletal muscle mass indexes, basal metabolic rates, or muscle percentages of the upper limbs and trunk（χ²/t=0.808－1.723, all P>0.05）. Multiple linear regression analysis indicated that the types of aircraft impacted all dependent variables except the muscle percentage of right and left lower limbs（B=－2.977－29.140, all P<0.05）. Age made a huge difference in all dependent variables except for the fat percentage of left lower limbs（B=－0.384－1.923, all P<0.05）. BMI had significant effects on all dependent variables except the extracellular water ratio and muscle percentage of right and left lower limbs（B=0.005－21.720, all P<0.05）. Hours of flight showed no significant association with any of the dependent variables（all P>0.05）. Conclusion Age is a big contributor to muscle loss in aviators. Fighter pilots generally have healthier body composition profiles than B/T/H aircrews. It is recommended that fighter pilots enhance core muscle resistance training, and that B/T/H aircrews focus on visceral fat reduction and dietary modifications.

Objective To study the differences in brain functions between pilots of different aircraft types when performing selective tasks, and to analyze the correlations between related indicators and cardiopulmonary exercise testing so as to provide data for daily training and selection of pilots. Methods Fourteen pilots（8 fighter pilots and 6 transport pilots）and 9 healthy subjects underwent functional magnetic resonance imaging（fMRI）scan and cardiopulmonary exercise testing（CPET）during selective tasks. The activated brain regions were located, while the relationships between the degree of activation of brain regions and the cardiopulmonary exercise testing were analyzed. Results The response of the left middle frontal gyrus, anaerobic threshold, relative anaerobic threshold and maximum oxygen pulse level of cardiopulmonary function of the pilot group were higher than those of healthy controls（t=4.215, 3.898, 4.231, 2.386, all P<0.05）. There was no difference in the extent to which the left middle frontal gyrus was activated between pilots of different aircraft（P>0.05）, and the anaerobic threshold of the transport pilots was higher than that of fighter pilots（t=－2.611, P=0.023）. The response of the left middle frontal gyrus was negatively correlated with the anaerobic threshold（r=－0.242, P=0.043）. Conclusion The left middle frontal gyrus may be a key brain area for selective attention among pilots, and anti-load training may help fighter pilots keep the left middle frontal gyrus highly activated.

Objective To investigate the minimum detectable angular deviation between the longitudinal axis of the human body and the G-load direction under different G-load conditions, known as the angle perception threshold（APT）. Methods In March-June 2024, 18 male volunteers were recruited. Using a subjective visual vertical testing device（eye mask）, their APT values were measured for both clockwise and counterclockwise roll tasks under 1.4 G_z and 3.0 G_z load conditions. The mean values were calculated. Results During clockwise rotation, the APT under the 3.0 G_z condition was significantly smaller than that under the 1.4 G_z condition（t=3.567, P=0.002）. The case was the same with counterclockwise rotation（t=3.241, P=0.005）. Overall, the mean APT under the 3.0 G_z condition was significantly smaller than under the 1.4 G_z condition（t=3.685, P=0.002）. Conclusion During roll motion in a human centrifuge cabin, there exists a range of angles that can't be perceived by humans. Within this range, individuals are unable to detect the directional difference between their body's longitudinal axis and the G-load vector. Furthermore, the angle perception threshold slightly decreases as the G-load increases. Under G-loads ranging from 1.4 G_z to 3.0 G_z, the human angle perception threshold is greater than 5 degrees.

Objective To investigate the impact of simulated ejection on blood pressure and heart rate of fighter pilots of different age groups in order to provide data for flight training and formulation of ejection protection measures. Methods Fighter pilots were divided into groups ages 20-24, 25-29, 30-34, and >34 years. Ejection experiments were conducted using an ejection seat simulator, and blood pressure and heart rate were recorded before and after ejection. The blood pressure, heart rate, and their changes（ΔSBP, ΔDBP, ΔHR）before and after ejection were compared across age groups. Results The systolic blood pressure（SBP）of pilots in groups ages 20-24, 25-29, and 30-34 increased after simulated ejection training（t=2.418, 2.278, 2.270, P=0.020, 0.025, 0.028）, but decreased in the group above 34（t=2.195, P=0.042）. The diastolic blood pressure（DBP）of pilots in the group ages 30 to 34 was higher after training（t=2.078, P=0.043）, so was the heart rate（HR）of pilots in the group ages 25-29（t=2.099, P=0.038）. Pearson correlation analysis showed a negative correlation between age and ΔSBP（r=－0.172, P=0.011）. Significant differences in ΔSBP and ΔDBP were observed between the four groups（F=4.132, 3.689, P=0.007, 0.013）. The ΔSBP and ΔDBP of pilots in the first three age groups were higher than in the >34 age group（all P<0.05）. Conclusion Age-related physiological changes affect the cardiovascular adaptation mechanisms of pilots during ejection. Before high-stress training such as simulated ejection, the age and physical condition of pilots should be taken into consideration to adjust the levels of difficulty and risk of training so as to ensure that their physiological and psychological states meet the requirements of training.

Objective To investigate the distribution of serum Helicobacter pylori IgG antibodies and its impact on PGⅠ, PGⅡand PGR level in aircrew. Methods A total of 325 military aircrew who underwent health examinations at the Lintong Rehabilitation and Convalescent Center from April 2017 to August 2017 were enrolled in the study. Based on Helicobacter pylori antibody test results, they were divided into the positive group（107 cases）and the negative group（218 cases）. Additionally, 92 ground crews who underwent health examinations from December 2016 to December 2017 were selected as the control group. Differences in Helicobacter pylori antibody positivity rates among aircrew members of varying ages and aircraft types were analyzed. Furthermore, serum pepsinogen levels were compared across different Helicobacter pylori antibody positivity statuses. Results Positive results Helicobacter pylori IgG antibodies test in aircrew accounts for 32.92%, with the statistically significant difference among all groups（χ²=11.957, P=0.008）. Infection rate in the age 41~50 group were significantly higher than the group of age less than 30（P<0.05）. Positive results of Helicobacter pylori IgG antibodies test in ground crews accounts for 29.35% with no statistically significant difference among all groups. There was no significant difference between different aircrafts（P>0.05）. Additionally, positive Helicobacter pylori IgG antibodies group showed significantly higher level of PGⅡ and lower PGR values（Z=3.072, 3.224, P=0.002, 0.001）. Conclusion Infection with Helicobacter pylori might have an influence on the level of serum pepsinogen. The analysis of serum Helicobacter pylori IgG antibodies and pepsinogen may give us the guidance in evaluating the gastric mucosal status.

Objective To investigate the effect of dexmedetomidine combined with etomidate on the incidence of perioperative neurocognitive disorder（PND）and hemodynamics in elderly orthopedic surgery patients. Methods Elderly patients ages 60 to 90 and undergoing elective orthopedic general anesthesia surgery at the Air Force Medical Centre between June 2022 and August 2023 were selected as the subjects, and randomly divided into the propofol group, etomidate group, and the dexmedetomidine combined with etomidate group（the combined group）using the random number table method. Neurocognitive function tests were performed on the 1st preoperative day, the 1st postoperative day and the 3rd postoperative day. The indexes of intraoperative heart rate, mean arterial pressure and depth of anesthesia changes were recorded and compared between these groups. Contributors to PND on postoperative days 1 and 3 were analyzed using univariate analysis and multifactorial logistic regression. Results A total of 208 patients were included in the study, with 69 in the propofol group, 69 in the etomidate group, and 70 in the combined group. There was no statistically significant difference between the three groups of patients in terms of age, body mass index, and gender（all P>0.05）. The results of repeated measures ANOVA show that, the heart rate of the etomidate group was higher than that of the combined group, and the difference was statistically significant（P=0.007）. The incidence rates of PND on the 1st and 3rd postoperative days in the combined group were both lower than those of the propofol group and the etomidate group, and the differences were of statistical significance（all P<0.05）. Multivariate logistic regression analysis indicated that the combination medication was a protective factor against PND on the 1st postoperative day（OR=0.388, 95%CI: 0.173－0.869）. A preoperative history of diabetes（OR=3.765, 95%CI: 1.533－9.245）, a pre-frail status（OR=8.877, 95%CI: 1.082－72.811）, and a semi-sitting surgical position（OR=6.901, 95%CI: 1.035－45.995）were risk factors for PND on the 3rd postoperative day. The combination medication（OR=0.272, 95%CI: 0.090－0.824）and a higher preoperative Mini-Mental State Examination score（OR=0.754, 95%CI: 0.595－0.957）were protective factors against PND on the 3rd postoperative day. Conclusion Intravenous anesthesia with dexmedetomidine combined with etomidate can reduce the incidence of PND and effectively improve the quality of life of elderly patients undergoing orthopedic surgery. Intravenous anesthesia with etomidate can increase heart rate compared with the combination of dexmedetomidine and etomidate, but has less impact on circulation, suggesting that intravenous anesthetic drugs should be selected according to the patient’s circulation and surgical needs.

Objective To investigate the protective effect of intraoperative intravenous infusion of dexmedetomidine（DEX）against endothelial glycocalyx shedding and on liver function in patients undergoing partial hepatectomy. Methods A total of 80 patients scheduled for partial hepatectomy at Tianjin Cancer Hospital Airport Hospital were randomly divided into the DEX group（n=40）and control group（n=40）. Patients in the DEX group received an intravenous infusion of DEX at a loading dose of 1 μg/kg fifteen minutes prior to the induction of anesthesia before intravenous maintenance 1 μg/（kg·h）was continued until the end of the surgery. The control group received an equal volume of normal saline. Peripheral blood was collected from patients before anesthesia（T₁）, at the end of surgery（T₂）, and 24 hours postoperatively（T₃）. ELISA was used to detect serum levels of endothelial injury-related markers-syndecan-1, hyaluronic acid, and heparan sulfate, inflammatory parameters-C-reactive protein（CRP）, TNF-α, and IL-6, and liver injury markers-total bilirubin, ALT, and AST. Pain visual analogue scale scores, the incidence rates of postoperative nausea and vomiting（PONV）, shivering, emergence agitation, and bradycardia were recorded at different time points. Results Compared to T₁, the serum levels of endothelial injury-related markers, inflammatory parameters, and liver injury markers were significantly elevated at T₂ and T₃（all P<0. 001）. At T₂ and T₃, serum levels of syndecan-1, hyaluronic acid, and heparan sulfate were significantly lower in the DEX group than in the control group, so were the levels of CRP, TNF-αand IL-6 in the DEX group（all P<0.05）. Levels of total bilirubin, ALT and AST were lower in the DEX group than in the control group at 24 hours postoperatively（all P<0.05）. Furthermore, the incidence of postoperotive nausea and vomiting in the DEX group was significantly lower than that of the control group（χ²=6.275, P=0.012）. Conclusion Intraoperative infusion of DEX can significantly reduce endothelial glycocalyx shedding caused by surgical trauma, mitigate the inflammatory response and liver ischemia-reperfusion, and reduce the incidence of PONV.

Objective To investigate the causal relationships between Helicobacter pylori infection and periodontitis via Mendelian randomization analysis. Methods Data on Helicobacter pylori infection was obtained from the European genome-wide association study database, involving 4 683 patient samples, while data on periodontitis single nucleotide polymorphism（SNP）was retrieved from the Finnish database, involving 367 samples. Two-sample bidirectional Mendelian randomization（MR）was used for analysis. The inverse variance weighting（IVW）method, MR-Egger regression method, weighted median method and weighted model method were used for two-sample Mendelian randomized analysis to determine the causal association between Helicobacter pylori infection and periodontitis. Cochran's Q-test method, horizontal pleiotropy and residual one method were adopted to evaluate the robustness of the results. Results By taking Helicobacter pylori infection and periodontitis as exposures, twelve SNPs and nine SNPs were extracted as instrumental variables, and the results of MR analysis and reverse MR analysis showed that there was no causal relationship between periodontitis and Helicobacter pylori infection（IVW OR=1.052, 1.020, P=0.807, 0.170）. Heterogeneity analysis（P=0.247, 0.753）and horizontal pleiotropy analysis（P=0.761, 0.093）confirmed that the results were reliable, and there was no horizontal pleiotropy. The leave-one-out method suggested that the research results were robust. Conclusion MR studies in European populations do not support a causal relationship between periodontitis and Helicobacter pylori infection.

Objective To evaluate the long-term impact of Omicron variant infection on lung function of college students. Methods A prospective observational study was conducted, with 2-year longitudinal follow-up of 71 college students with mild Omicron variant infection. Pulmonary function indicators were dynamically monitored, including inspiratory capacity（IC）, small airway function parameters, and ventilatory function indicators. The changes along with time were analyzed. Results During the follow-up period, the abnormal rate of IC decreased from 59.15%（42/71）at 3 months to 32.39%（23/71）at 24 months. Among the indicators of small airway function, the abnormal rate of maximal mid-expiratory flow（MMEF）ranged from 12.68% to 32.39%, compared with 8.45% to 30.99% for maximal expiratory flow at 25% of forced vital capacity（MEF25）, and 4.23% and 12.68% for maximal expiratory flow at 50% of forced vital capacity（MEF50）. The measured IC value at 3 months was lower than that at 6, 12, and 24 months, while the value at 24 months was higher than that at 6 and 12 months, with statistically significant differences（all P<0.05）. The MMEF value at 24 months was higher than that at 3, 6, and 12 months, and there were statistically significant differences（all P<0.05）. Similarly, the MEF50 value at 24 months was higher than that at 3, 6, and 12 months, with statistically significant differences（all P<0.05）. Conclusion Omicron variant infection can cause subclinical abnormalities in pulmonary function of college students that persist up to 2 years post diagnosis, suggesting that mild infection may induce small airway dysfunction. IC, MMEF, and MEF50 can be included in the long-term respiratory health monitoring system for college students with mild infection to optimize management strategies.

Objective To explore the clinical and imaging features of gastric-type endocervical adenocarcinomas（G-EAC）in order to improve the level of early diagnosis. Methods The clinical and imaging data of 16 patients with pathologically confirmed G-EAC who were admitted to the Air Force Medical Center between January 2021 and February 2025 was retrospectively analyzed. Results Among the 16 patients, 7 had no abnormal gynecological symptoms while 9 had vaginal discharge and/or vaginal bleeding. HPV test was positive in 3 cases and 10 cases had abnormal tumor markers. The tumors were located in the upper half of the cervix in 5 cases，involved the entire cervix in 8 cases, and extended beyond the cervix in 3 cases. Four cases showed barrel-shaped growth and 11 cases were infiltrative, while 1 case presented as exophytic mass. All the 16 cases were accompanied by cysts, including 5 cases with large cysts, 9 cases with small cysts and large ones, and 2 cases with small cysts. Four cases were complicated with a small amount of uterine cavity effusion. When the cystic component was predominant, multiple rounded lesions of varying sizes with long T1 and long T2 signals were observed. There was no or slight restriction in diffusion on DWI sequence, and slightly high signals in ADC image. When the solid component was predominant, slightly long T2 signal soft tissue shadows were seen, with restricted diffusion and low signals on the ADC map. CT images presented with enlarged cervixes, with mixed-density cystic and solid nodules or masses, and some lesions showed "honeycomb-like" changes. Enhanced scanning showed no obvious enhancement in cystic areas or uneven enhancement in solid areas. The preoperative accuracy rate of CT/ MRI diagnosis of malignant lesions was 68.7%. Conclusion Most patients have elevated tumor markers, and some have vaginal discharge/bleeding. Imaging features such as tumor prevalence in the whole cervix（including the upper part）, complications with cyst-like changes, and infiltrative growth can facilitate the early diagnosis of gastric-type adenocarcinomas of the cervix.