Objective:To provide basis for preventing flight safety accidents caused by hypoxia by exploring the subjective and objective performance of pilots in hypobaric hypoxia environment.Methods:The relevant data of pilots′ high altitude physiological training were retrospectively analyzed and a symptom questionnaire upon the training were summarized. The pilots were divided into excellent group (time of useful consciousness >6 min), good group (3 min ≤time of useful consciousness <6 min) and qualified group (2 min ≤time of useful consciousness <3 min) according to the time of useful consciousness. The hypoxia symptoms and physiological parameters of pilots in each group were statistically analyzed.Results:A total of 919 pilots were included, in which 416 were in excellent group, 490 were in good group and 13 were in qualified group. Among the 25 hypoxia symptoms, there were significant differences in the components of numbness and difficulty in calculation among 3 groups ( χ2=6.04, 7.79, P=0.049, 0.020), but there were no significant differences in the components of the other 23 hypoxia symptoms (all P>0.05). The changes of blood oxygen saturation were significant in group main effect, time main effect and their interaction ( F=25.65, 1 039.77, 25.22, all P<0.001). The change of heart rate was statistically significant in the main effect of time ( F=66.41, P<0.001) but in time main effect and their interaction (both P>0.05). There was no significant difference in respiratory rate among group main effect, time main effect and their interaction (all P>0.05). The distribution and variation of blood oxygen saturation were statistically significant differences among the 3 groups in the ranges of 81%-90%, 71%-80% and 65%-70% ( H=125.93, 372.83, 13.10, all P≤0.001) unlike the range of 91%-100% ( H=2.48, P=0.289). Conclusions:The excellent group showed better blood oxygen saturation maintaining and useful consciousness time enduring capabilities, and those imply them in better performance and consciousness that enable the operation in hypoxic environment with more ease.

Objective:To provide scientific basis for pilots′ hypoxia training by comparing and analyzing the effects of hypoxia training under normobaric and hypobaric environments.Methods:Forty-two healthy subjects were selected. The pilot reduced oxygen breathing device and hypobaric chamber were used to simulate 7 500 m hypoxia training, and blood oxygen saturation, heart rate, respiratory rate and hypoxia endurance time were monitored and recorded. The hypoxia symptom questionnaire was filled out by the subjects after 2 training sessions. The hypoxia endurance time and hypoxia tolerance grade of normobaric and hypobaric hypoxia training were analyzed, and the differences of blood oxygen saturation and hypoxia symptoms were compared between 2 hypoxia trainings.Results:Forty-two subjects completed the normobaric and hypobaric hypoxia trainings. The survival curve analysis of hypoxia endurance time showed that the median hypoxia endurance time of normobaric and hypobaric hypoxia training was [3.17(2.70, 3.64)] min and [3.67(3.46, 3.88)] min respectively, with no significant difference ( P>0.05). There was no significant difference in the grade distribution of hypoxia tolerance between 2 hypoxia trainings ( P>0.05). The blood oxygen saturation curves of 2 hypoxia trainings were basically consistent. There was no significant difference between 2 hypoxia trainings on blood oxygen saturation, heart rate and respiratory rate (all P>0.05). There were significant differences in difficulty in calculation, difficulty in concentration and with palpitation ( χ2=4.81, 3.97, 3.98, P=0.028, 0.046, 0.046). Conclusions:The analysis showed that most physiological responses and subjective symptoms of pilots are quite similar in the normobaric and hypobaric hypoxia training at simulated 7 500 m. Both normobaric and hypobaric exposures show the similar hypoxia training effect.

Objective:To provide basis for preventing flight safety accidents caused by hypoxia by exploring the subjective and objective performance of pilots in hypobaric hypoxia environment.Methods:The relevant data of pilots′ high altitude physiological training were retrospectively analyzed and a symptom questionnaire upon the training were summarized. The pilots were divided into excellent group (time of useful consciousness >6 min), good group (3 min ≤time of useful consciousness <6 min) and qualified group (2 min ≤time of useful consciousness <3 min) according to the time of useful consciousness. The hypoxia symptoms and physiological parameters of pilots in each group were statistically analyzed.Results:A total of 919 pilots were included, in which 416 were in excellent group, 490 were in good group and 13 were in qualified group. Among the 25 hypoxia symptoms, there were significant differences in the components of numbness and difficulty in calculation among 3 groups ( χ2=6.04, 7.79, P=0.049, 0.020), but there were no significant differences in the components of the other 23 hypoxia symptoms (all P>0.05). The changes of blood oxygen saturation were significant in group main effect, time main effect and their interaction ( F=25.65, 1 039.77, 25.22, all P<0.001). The change of heart rate was statistically significant in the main effect of time ( F=66.41, P<0.001) but in time main effect and their interaction (both P>0.05). There was no significant difference in respiratory rate among group main effect, time main effect and their interaction (all P>0.05). The distribution and variation of blood oxygen saturation were statistically significant differences among the 3 groups in the ranges of 81%-90%, 71%-80% and 65%-70% ( H=125.93, 372.83, 13.10, all P≤0.001) unlike the range of 91%-100% ( H=2.48, P=0.289). Conclusions:The excellent group showed better blood oxygen saturation maintaining and useful consciousness time enduring capabilities, and those imply them in better performance and consciousness that enable the operation in hypoxic environment with more ease.

Objective:To provide scientific basis for pilots′ hypoxia training by comparing and analyzing the effects of hypoxia training under normobaric and hypobaric environments.Methods:Forty-two healthy subjects were selected. The pilot reduced oxygen breathing device and hypobaric chamber were used to simulate 7 500 m hypoxia training, and blood oxygen saturation, heart rate, respiratory rate and hypoxia endurance time were monitored and recorded. The hypoxia symptom questionnaire was filled out by the subjects after 2 training sessions. The hypoxia endurance time and hypoxia tolerance grade of normobaric and hypobaric hypoxia training were analyzed, and the differences of blood oxygen saturation and hypoxia symptoms were compared between 2 hypoxia trainings.Results:Forty-two subjects completed the normobaric and hypobaric hypoxia trainings. The survival curve analysis of hypoxia endurance time showed that the median hypoxia endurance time of normobaric and hypobaric hypoxia training was [3.17(2.70, 3.64)] min and [3.67(3.46, 3.88)] min respectively, with no significant difference ( P>0.05). There was no significant difference in the grade distribution of hypoxia tolerance between 2 hypoxia trainings ( P>0.05). The blood oxygen saturation curves of 2 hypoxia trainings were basically consistent. There was no significant difference between 2 hypoxia trainings on blood oxygen saturation, heart rate and respiratory rate (all P>0.05). There were significant differences in difficulty in calculation, difficulty in concentration and with palpitation ( χ2=4.81, 3.97, 3.98, P=0.028, 0.046, 0.046). Conclusions:The analysis showed that most physiological responses and subjective symptoms of pilots are quite similar in the normobaric and hypobaric hypoxia training at simulated 7 500 m. Both normobaric and hypobaric exposures show the similar hypoxia training effect.

The 4-hydroxyphenylacetate 3-hydroxylase (4HPA3H), originated from Escherichia coli, converts p-coumaric acid to caffeic acid. In order to improve the efficiency of caffeic acid biosynthesis, we engineered E. coli for overexpression of 4HPA3H. The high-density fermentation of the engineered E. coli was conducted in a 5 L bioreactor. Subsequently, the conditions for whole-cell biocatalysis were optimized. The dry cell weight of the 4HPA3H-expressed strain reached 34.80 g/L. After incubated in the bioreactor for 6 h, 18.74 g/L (0.85 g/(L·OD₆₀₀)) of caffeic acid was obtained, with a conversion rate of 78.81% achieved. To the best of our knowledge, the titer of caffeic acid is the highest reported to date. The high-density fermentation of E. coli for overexpression of 4HPA3H and the efficient biosynthesis of caffeic acid may facilitate future large-scale production of caffeic acid.
Caffeic Acids ; Escherichia coli/metabolism* ; Fermentation ; Metabolic Engineering ; Mixed Function Oxygenases/metabolism* ; Phenylacetates

Objective:To evaluate the protection performance of military transport aircraft oxygen system for aircrew and provide the physiological tests basis for product design finalization.Methods:Four dummies and 4 healthy volunteers who were equipped with individual protection equipment and military transport aircraft oxygen system completed 4 tests in altitude chamber including the oxygen supply performance physical test of oxygen system, the rapid decompression physical test of oxygen system, the physiological tests of oxygen continuously supplying for 6 h and oxygen supply performance test in rapid decompression at 12.0 km. Oxygen concentration, respiratory resistance, safety pressure, peak value, peak duration and steady pressure of mask under rapid decompression were tested. Electrocardiograph and oxygen saturation of volunteers were monitored.Results:The oxygen partial pressure provided by military transport aircraft oxygen system under 12.0 km was ≥19.1 kPa corresponding to the respiration ventilation volume of 20 L/min of dummy. The expiratory resistance was no higher than 441.3 Pa and the inspiration resistance was no higher than 490.3 Pa before the safety pressure connected. The peak pressure value in rapid decompression with 1.0 L lung volume of dummy was no higher than 5.8 kPa. The oxygen partial pressure provided by military transport aircraft oxygen system for volunteers was over 21.9 kPa in the 6 h cruising flight. All 4 volunteers successfully completed the rapid decompression physiological tests at 12.0 km with good subjective and objective responses.Conclusions:The protection performance of military transport aircraft oxygen system for aircrew can provide enough protection against the hypoxia up to 12.0 km

Objective:To study the simplified oxygen supply protection scheme below 15.0 km, and to evaluate its protection performance through tests.Methods:The parameter of YX-5 oxygen system was modified, by reducing its total oxygen supply pressure and closing a large number of oxygen supply mechanisms, and compensatory suit was cancelled. A dummy and 4 volunteers with helmet and oxygen mask using modified YX-5 oxygen system underwent 5 tests in hypobaric chamber, included ① normal oxygen supply performance test at 0-10.0 km; ② pure oxygen supply performance test at 0-10.0 km; ③ positive pressure supplying oxygen performance test at 13.0, 15.0, 16.0 km; ④ impact test of pressured oxygen supply; ⑤ pressured oxygen supplying performance physiological test at 15.0 km.Results:Under the normal oxygen supply, the oxygen pressure of modified YX-5 oxygen system below 12.0 km was >21.0 kPa. When high-altitude pressurized oxygen supply was used, the oxygen pressure was >15.8 kPa at 12.0-15.0 km. Inspiration resistance of modified YX-5 oxygen system was <0.34 kPa when the dummy′s respiration ventilation rate was 20 L/min. The impact pressure of mask was 1.25 kPa when pressured oxygen supply switched on but without compensatory suit connected to modified YX-5 oxygen system. Four volunteers completed the human physiological test up to 15.0 km high-altitude pressurized oxygen supply to verify the protective performance of the scheme, and they had no adverse physiological reactions after the test.Conclusions:The simplified protection scheme can provide protection against hypoxia for pilots at 0-15.0 km altitude.

Objective:To evaluate the protection performance of military transport aircraft oxygen system for aircrew and provide the physiological tests basis for product design finalization.Methods:Four dummies and 4 healthy volunteers who were equipped with individual protection equipment and military transport aircraft oxygen system completed 4 tests in altitude chamber including the oxygen supply performance physical test of oxygen system, the rapid decompression physical test of oxygen system, the physiological tests of oxygen continuously supplying for 6 h and oxygen supply performance test in rapid decompression at 12.0 km. Oxygen concentration, respiratory resistance, safety pressure, peak value, peak duration and steady pressure of mask under rapid decompression were tested. Electrocardiograph and oxygen saturation of volunteers were monitored.Results:The oxygen partial pressure provided by military transport aircraft oxygen system under 12.0 km was ≥19.1 kPa corresponding to the respiration ventilation volume of 20 L/min of dummy. The expiratory resistance was no higher than 441.3 Pa and the inspiration resistance was no higher than 490.3 Pa before the safety pressure connected. The peak pressure value in rapid decompression with 1.0 L lung volume of dummy was no higher than 5.8 kPa. The oxygen partial pressure provided by military transport aircraft oxygen system for volunteers was over 21.9 kPa in the 6 h cruising flight. All 4 volunteers successfully completed the rapid decompression physiological tests at 12.0 km with good subjective and objective responses.Conclusions:The protection performance of military transport aircraft oxygen system for aircrew can provide enough protection against the hypoxia up to 12.0 km

Objective:To study the simplified oxygen supply protection scheme below 15.0 km, and to evaluate its protection performance through tests.Methods:The parameter of YX-5 oxygen system was modified, by reducing its total oxygen supply pressure and closing a large number of oxygen supply mechanisms, and compensatory suit was cancelled. A dummy and 4 volunteers with helmet and oxygen mask using modified YX-5 oxygen system underwent 5 tests in hypobaric chamber, included ① normal oxygen supply performance test at 0-10.0 km; ② pure oxygen supply performance test at 0-10.0 km; ③ positive pressure supplying oxygen performance test at 13.0, 15.0, 16.0 km; ④ impact test of pressured oxygen supply; ⑤ pressured oxygen supplying performance physiological test at 15.0 km.Results:Under the normal oxygen supply, the oxygen pressure of modified YX-5 oxygen system below 12.0 km was >21.0 kPa. When high-altitude pressurized oxygen supply was used, the oxygen pressure was >15.8 kPa at 12.0-15.0 km. Inspiration resistance of modified YX-5 oxygen system was <0.34 kPa when the dummy′s respiration ventilation rate was 20 L/min. The impact pressure of mask was 1.25 kPa when pressured oxygen supply switched on but without compensatory suit connected to modified YX-5 oxygen system. Four volunteers completed the human physiological test up to 15.0 km high-altitude pressurized oxygen supply to verify the protective performance of the scheme, and they had no adverse physiological reactions after the test.Conclusions:The simplified protection scheme can provide protection against hypoxia for pilots at 0-15.0 km altitude.

Traumatic rib fractures are the most common injury in thoracic trauma. Previously，the patients with traumatic rib fractures were mostly treated non-surgically，of which 50%，especially those combined with flail chest presented chronic pain or chest wall deformities and over 30% had long-term disabilities，being unable to retain a full-time job. In the past two decades，thanks to the development of internal fixation material technology，the surgical treatment of rib fractures has achieved good outcomes. However，there are still some problems in clinical treatment，including inconsistency in surgical treatment and quality control in medical services. The current consensuses on the management of regional traumatic rib fractures published at home and abroad mainly focus on the guidance of the overall treatment decisions and plans，and relevant clinical guidelines abroad lacks progress in surgical treatment of rib fractures in recent years. Therefore，the Chinese Society of Traumatology affiliated to Chinese Medical Association and Chinese College of Trauma Surgeons affiliated to Chinese Medical Doctor Association，in conjunction with national multidisciplinary experts，formulate the Chinese Consensus for Surgical Treatment of Traumatic Rib Fractures（2021）following the principle of evidence-based medicine，scientific nature and practicality. This expert consensus puts forward some clear，applicable，and graded recommendations from aspects of preoperative imaging evaluation，surgical indications，timing of surgery，surgical methods，rib fracture sites for surgical fixation，internal fixation methods and material selections，treatment of combined injuries in rib fractures，in order to provide references for surgical treatment of traumatic rib fractures.