吸入不同氧含量气体高原环境下平原犬动脉血与脑脊液血气的变化

Influence of gas inhalation with different oxygen contents on the changes of blood gas in arterial blood and cerebrospinal fluid of dogs in plateau

目的:评价吸入不同氧含量气体对平原犬模拟高原后动脉血及脑脊液的血气变化及酸碱平衡失调的影响。方法:实验于2003-09/2004-07在解放军第三军医大学高原医学系完成。选用20只重庆本地(海拔308m)健康杂种犬,雌雄不拘。经减压舱减压至海拔5000m气压,模拟高原环境保持3d,同步动态抽取动脉血和脑脊液进行血气分析,随后随机分为4组,每组5只。①对照组:于减压舱正常呼吸。②吸O2组:吸入体积分数0.97O2,120min,流量4L/min。③吸CO2组:吸入含体积分数0.03CO2高原气,120min,流量4L/min。④吸混合气组:吸入体积分数0.97O2+体积分数0.03CO2混合气,120min,流量4L/min。每只犬分别于减压前、减压3d及吸气后120min同步动态抽取动脉血与脑脊液,用IL1620型血气分析仪分析。结果:进入结果分析犬20只,每组5只。①经减压仓减压3d后,犬动脉血pH、二氧化碳分压、氧分压、细胞外液碱过剩、总二氧化碳含量、标准碳酸氢根和碳酸氢根离浓度各项均明显下降(P<0.01);脑脊液除pH上升(P<0.01)外,其他各项变化与动脉血一致,且变化辐度均比动脉血要小。②单纯吸体积分数0.97O2与吸入体积分数0.97O2与体积分数0.03CO2混合气均可明显改善动脉血及脑脊液代谢性酸中毒状态,而单纯吸入含体积分数0.03CO2高原气对代谢性酸中毒改善不明显。③?

AIM: To assess the effect of gas inhalation with different oxygen contents on the changes of blood gas in arterial blood and cerebrospinal fluid and acid-base imbalance of plain dogs in mimic plateau. METHODS:The experiment was carried out in the Department of High Altitude Medicine,Third Military Medical University of Chinese PLA from September 2003 to July 2004.Twenty healthy hybrid dogs (male or female) in Chongqing (height above sea level was 308 m) were used in this study. The air pression was decompressed to that at 5000 m with depression chamber for 3 days, arterial blood and cerebrospinal fluid samples were synchronously extracted for blood gas analysis.The samples were randomly divided into 4 groups with 5 dogs in each group:①control group: breathed normally in the depression chamber; ②oxygen inhalation group: inhaled oxygen with the volume fraction of 0.97 for 120 minutes, the flow was 4 L per minute;③carbon dioxide group: inhaled carbon dioxide plateau gas with the volume fraction of 0.03 for 120 minutes, the flow was 4 L per minute;④mixed gas inhalation group: inhaled mixed gas containing oxygen with the volume fraction of 0.97 and carbon dioxide plateau gas with the volume fraction of 0.03 for 120 minutes, the flow was 4 L per minute. The arterial blood and cerebrospinal fluid were synchronously extracted and analyzed with IL1620 blood gas analyzer before depression and 3 days after depression and 120 minutes after gas inhalation respectively. RESULTS:Twenty dogs were involved in the analysis of results, there were 5 dogs in each group. ①Three days after decompression, potential of hydrogen (pH),partial pressure of carbon dioxide, partial pressure of oxygen, bass excess in extracellular fluid, total carbon dioxide content, standard bicarbonate and concentration of bicarbonate ion in arterial blood were all obviously decreased (P< 0.01); In cerebrospinal fluid, except for the increase of pH (P< 0.01), the changes of all the other items were coincident with those in arterial blood, and the ranges of changes is smaller than those in arterial blood.②Inhalation of oxygen with the volume fraction of 0.97 only and inhalation of the mixed gas containing oxygen with the volume fraction of 0.97 and carbon dioxide plateau gas with the volume fraction of 0.03 could obviously ameliorate the metabolic acidosis in arterial blood and cerebrospinal fluid, but the ameliorative effect of inhalation of carbon dioxide with the volume fraction of 0.03 only was not obvious.③The partial pressure of carbon dioxide, bass excess in extracellular fluid, total carbon dioxide content, standard bicarbonate and concentration of bicarbonate ion in the mixed gas inhalation group [(1.093±0.082) kPa, (3.380±0.363), (4.240±0.451), (4.600±0.485), (3.220±0.356), (4.360 ±0.439) mmol/L] were markedly higher than those in the carbon dioxide inhalation group [(0.617±0.050) kPa, (1.820±0.205), (2.300 ±0.274), (2.540±0.297), (2.060±0.152), (2.420±0.277) mmol/L] (P< 0.01). The indexes of blood gas analysis were remarkably higher in the mixed gas inhalation group than in the carbon dioxide inhalation group (P< 0.01).④Compared with carbon dioxide and oxygen inhalation groups, the indexes of blood gas analysis of arterial blood and cerebrospinal fluid in the mixed gas inhalation group were more close to those before depression (P< 0.01). CONCLUSION: After entering plateau,the pH value is obviously lower and partial pressure of carbon dioxide in cerebrospinal fluid than in arterial blood. The decrease of partial pressure of carbon dioxide and acid-base imbalance are the basic changes of blood gas. Inhalation of the mixed gas containing oxygen with the volume fraction of 0.97 and carbon dioxide plateau gas with the volume fraction of 0.03 can obviosly ameliorate the metabolic acidosis and relatively increase the partial pressure of oxygen in arterial blood and cerebrospinal fluid.