The regional pulmonary vascular activity and flow distribution during hypoxia.
碩士 === 國防醫學院 === 海底醫學研究所 === 95 === Humans encounter hypoxia thoughout their lives. The vasoconstriction of the hypoxia area in the lung plays an important role in shunting away the blood flow and in maintaining a matched ventilation/perfusion. This redistribution of pulmonary blood flow improves a...
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| Other Authors: | |
| Format: | Others |
| Language: | zh-TW |
| Published: |
2007
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| Online Access: | http://ndltd.ncl.edu.tw/handle/05512709859452547393 |
| Summary: | 碩士 === 國防醫學院 === 海底醫學研究所 === 95 === Humans encounter hypoxia thoughout their lives. The vasoconstriction of the hypoxia area in the lung plays an important role in shunting away the blood flow and in maintaining a matched ventilation/perfusion. This redistribution of pulmonary blood flow improves arterial oxygenation. Hypoxic hypoxia is the most frequently to see in many types of hypoxia. The purpose of this study are the regional pulmonary vascular activity and the role of nitric oxide in pulmonary blood flow distribution during hypoxia. There are 6 to 8 of New Zealand rabbits in each group were selected to observe the hemodynamics and lung perfusion distribution changing, under the low FiO2 inspiration or low FiO2 inspiration moreover restrain nitric oxide by administration of L-NAME. We use multiple inner gas elimination technique (MIGET) to evaluate ventilation / perfusion and fluorescents microsphere technique to evaluate pulmonary perfusion. Our study result in physical parameters: exposure to 12%O2 reduce the mean arterial pressure from 91±6 to 71±4 mmHg and systemic vascular resistance from 180±20 to 166±18 mmHg/l/min in hypoxia 30 mins（n=8）. In hypoxia group acute hypoxia did not elevate mean pulmonary arterial pressure. L-NAME pretreatment significantly enhanced the increase in pulmonary vascular resistance during acute hypoxia and attenuated the decrease in systemic vascular resistance. MIGET parameters: There is no significant changing in pulmonary shunting, the ratio of dead space and the region of high-low ventilation / perfusion distribution in all segment of lung in control groups and hypoxia group. L-NAME pretreatment increase the ratio of dead space during acute hypoxia. The status of fluorescents microsphere technique: there is no L-NAME pretreatment or not significant difference of total blood flow distribution in dorsal to ventral during acute hypoxia. Height separated from regression line mean raise pulmonary vascular activity in L-NAME+hypoxia group. Relavine of perfusion decrease mean vasoconstriction percentage increase. The vasoconstriction percentage in L-NAME+hypoxia group higher than the other two group. In conclusion, exogenous nitric oxide is an impotant vasodilator in pulmonary circulation. That nitric oxide lead vasodilation to balance hypoxic pulmonary vasoconstriction during hypoxia. But the other unknown vasoconstrictor or vasodilator to mediate pulmonary circulation during hypoxia.
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