| The high acceleration (>9Gz) and rapid ousel rate of the modern high performance fighter, which exceeds the physiological tolerance of human being, was a main threat to the security of the pilots. Thus, a multi anti-G counter-measure was in a great need. Generally, human centrifuge was used to AGSM training, which helped pilots to master AGSM, experience G-LOC, and so did to promote pilot's +Gz tolerance. But human centrifuge was expensive and complex and cannot be popularized.When the pilot's systolic blood pressure of eye level reached 200mmHg during the ground training, they often didn't do their best to accomplish AGSM for the discomforts of head. This was more dangerous for those trainers of hypertension or cerebral vascular abnormalities. So a simple, efficacious, easily popularized device was in need to be invented as an alternate for the human centrifuge.During spaceflight, there were some adverse changes as cardiovascular deconditioning. muscle and bone a trophy, etc, induced by microgravity. Those adverse changes greatly affected the astronauts' working abilities. So to invent a good device or to find a countermeasure, which could help them to adapt to 1G environments quickly when returning back was still in a great need.Lower body negative pressure (LBNP) was an experiment, which gave the lower bodya negative pressure. It made the blood transferring from upper to the lower body and reserves of blood in the lower body. Thus blood volume and the blood returning back to heart decreased which could reduce the systolic blood pressure of heart level and the blood supply of the brain. As the blood volume and distribution could be controlled artificially. LBNP became and ideal noninvasive way in hemodynamic physiology research and an effective means in simulating gravity-inertia. LBNP researches of these years indicated that the seated LBNP could simulate the effects of +Gz effects on cardiovascular function. So was born the LBNP chamber. LBNP had been applied in the field of aerospace medical evaluation and the training of astronauts against the adverse changes induced by microgravity. But the way, duration, obvious effects of such training was uncertain till now. Besides, LBNP could be an alternate for the human centrifuge in ASGM training. Results showed that LBNP was applicable and useful in these training.This work was mainly to find more supports for LBNP in counteracting microgravity induced adverse changes and the training of anti-G. There were two kinds of LBNP apparatus was used to evacuate the cardiovascular function with different training ways in this work.The main results and findings of this work were as follows:1. Effects of repeated LBNP on LBNP tolerance and cardiac function Changes of LBNP tolerance and the cardiac function were investigated by the comparison of the effects of two different, -50mmHg/8min, -50mmHg/4min, 1 time/day, LBNPs of 8 continuous days. Results showed -50mmHg/8min LBNP greatly promoted the cumulative stimulate index (CSI) and duration of negative pressure (DNP), While repeated -50mmHg/4min LBNP promoted the LVET, SV, CO and CI (P<0.05), besides TPR was decreased significantly (P<0.05). The results indicate -50mmHg/8min may greatly elevate the endurance of LBNP. promote the cardiac function. -50mmHg may be an optimal stimulation for LBNP.2. Development of self-generated lower body negative pressure device The device consists of a flexible hollow cylinder, circled by several circular band steel and sealed by gasproof adhesive plaster. An adjustable valve, a one-way flap valve, shoulder straps and handles are designed on the top of the cylinder. As the user push the legs footward along longitude to expand the cylinder, the air pressure in the cylinder decreases. The negativepressure is -58mmHg, -46mmHg, -38 mmHg and -26 mmHg with the adjustable inlet valve completely closed, one-quarter opened, hajf opened, and fully opened respectively. This self-generated LBNP apparatus can apply to the need of research.3.Changcs of cardiov... |
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