| Background:Flight work is under the special environment, including atmospheric environment, mechanical environment, temperature and radiation environment, and so on. Due to the particularity of flight, pilots often need to face and overcome all kinds of extreme environment in daily work, such as different heights of oxygen concentration and pressure, acceleration, temperature, among these changes hypoxia is more common. High-altitude hypoxia refers to the low air pressure in high altitude. The effect of high-altitude hypoxia on pilots is mainly manifested in the nervous system, circulation system and respiratory system and so on. In the past, they often used methods such as ergonomics(neuropsychological scale), electroencephalogram(EEG) and brain event related potential(ERP) to study the effect of hypoxia on the brain function of pilots. And they adopt the method of transcranial Doppler ultrasound which focus on one cerebrovascular to studythe effect of hypoxia on the dynamics of the cerebral blood perfusion. Because of the limitations of experimental equipment, these methods couldn’t get the anatomical location and neural network connection. In the current study, we used the resting-state blood oxygen level dependent functional magnetic resonance imaging(BOLD-f MRI) technology and arterial spin-labeling(ASL) technique to investigate the basic brain activity change and cerebral blood perfusion change in a simulated 3000 m high altitude hypoxic exposure conditions. It provided the imaging basis for the brain function identification of pilots under the hypoxic conditions.Objects:1) To explore the feasibility of simulating the 3000 m high altitude hypoxic exposure in the magnetic resonance equipment to observe the change of resting state brain functional magnetic resonance imaging and cerebral blood perfusion. 2) To provide the imaging basis for the brain functional identification of pilots under hypoxic environment by the way of observing the change characteristics of resting state brain function and cerebral blood perfusion of pilots under the simulated hypoxic conditions.Methods:1) 35 healthy male pilots were successively subjected to normal and hypoxic exposure which the oxygen concentration was 14.5%. Both the fractional amplitude of low frequency fluctuation(f ALFF) and regional homogeneity(Re Ho) methods were adopted to analyze the resting-state functional MRI data of 35 cases of healthy male pilots before and after hypoxic exposure, then we observed the brain areas with fractional amplitude of low frequency fluctuation(f ALFF) and regional homogeneity(Re Ho) changes after hypoxic exposure. 2) 35 healthy male pilots were successively subjected to normal and hypoxic exposure which the oxygen concentration was 14.5%.We inspected the cerebral blood perfusion by arterial spin labeling technology and compared the differences between the two state.Results:1) After hypoxic exposure, the pulse of 30 pilots which met with requirement was( 63.97±10.57) beats / min, it was lower than before which was( 71.40±10.85) beats/min( P<0.01), the oxygen saturation was( 92.37±3.85)%, it was also lower than before which was(96.27±1.29)%and P<0.01. Compared with the condition before hypoxic exposure, the fractional amplitude of low frequency fluctuation(f ALFF) showed decrease in the bilateral superior temporal gyrus, the right frontal gyrus, the fractional amplitude of low frequency fluctuation(f ALFF) in left precuneus was increased(P<0.05), while, the value of regional homogeneity(Re Ho) just displayed decrease in the right frontal gyrus(P<0.05). We couldn’t find the brain areas with regional homogeneity(Re Ho) values increase. 2) After hypoxic exposure, the pulse was(63.97±10.43) beats / min, it was lower than before which was(71.46±10.63) beats / min and P<0.01, while the oxygen saturation was(92.46±3.64)%, it was lower than before which was(96.31±1.23)% and P<0.01. ASL in pilots after hypoxic exposure showed lower CBF values prominently in the following regregions: the bilateral superior temporal gyrus, the bilateral middle temporal gyrus, the left inferior temporal gyrus, the right middle occipital gyrus, the right inferior occipital gyrus, the bilateral lingual gyrus, the right fusiform gyrus, the right cuneus and cerebellum(P<0.05).Conclusion:1) It has potential application value to simulate 3000 m high altitude hypoxic exposure in magnetic resonance equipment and observe the changes of resting state brain function and cerebral blood perfusion of pilots by using the technology of resting state blood oxygen level dependent functional magnetic resonance imaging and arterial spin labeling. 2) Hypoxic exposure significantly effected the brain functions of pilots, which may be related to their cognitive ability. 3) The cerebral blood perfusion after hypoxic exposure was decreased mainly in the temporal and occipital lobe.4) The results of both the resting state brain function and the cerebral blood perfusion have the characteristics of partial laterality. |
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