不同吸气末停顿及吸呼比对胸科手术单肺通气患者呼吸功能的影响

目的探讨需单肺通气(OLV)的胸科手术中不同吸气末停顿(EIP)及吸呼比对患者呼吸功能的影响。方法选择该院择期行胸科手术OLV患者60例,根据随机数字表法将其分为OLV吸呼比1∶2组(A组)和OLV吸呼比1∶1组(B组),每组30例。将两组根据吸气末停顿设置的不同分别随机分为2个亚组,即OLV后吸呼比1∶2,吸气末停顿0%、10%、20%先后通气30 min组(A_1组);吸气末停顿0%、20%、10%先后通气30 min组(A_2组);OLV后吸呼比1∶1,吸气末停顿0%、10%、20%先后通气30 min组(B_1组);吸气末停顿0%、20%、10%先后通气30 min组(B_2组)。每组15例。分别于OLV前(T_1)、OLV后30 min(T_2)、60 min(T_3)、90 min(T_4)记录患者血流动力学指标、呼吸力学指标并采集动脉及中心静脉血进行血气分析。结果在A组与B组中,吸气末停顿20%与吸气末停顿0%、10%比较,患者动脉血二氧化碳分压(Pa CO_2)、死腔率降低(P<0.05)。B组在联合吸气末停顿0%、10%、20%时与A组比较,患者气道压峰值、平台压降低,肺顺应性提高(P<0.05)。结论对胸科手术OLV患者,吸气末停顿20%有利于二氧化碳交换,减少死腔率;吸呼比1∶1可降低气道压,提高肺动态顺应性。两者对患者血流动力学指标无影响。

Distribution,characteristics and influencing factors of fresh groundwater resources in the Loess Plateau,China

The fresh groundwater in the Loess Plateau serves as a major source of water required for the production and livelihood of local residents and is greatly significant for regional economic and social development and ecological protection.This paper analyzes the hydrogeological conditions and groundwater characteristics in the Loess Plateau,expatiates on the types and distribution characteristics of the fresh groundwater in the plateau,and analyzes the influencing factors and mechanisms in the formation of the fresh groundwater in the plateau as a priority.Based on this,it summarizes the impacts of human activities and climatic change on the regional fresh groundwater.The groundwater in Loess Plateau features uneven temporal-spatial distribution,with the distribution space of the fresh groundwater closely relating to precipitation.The groundwater shows a distinct zoning pattern of hydrochemical types.It is fresh water in shallow parts and is salt water in deep parts overall,while the fresh water of exploration value is distributed only in a small range.The storage space and migration pathways of fresh groundwater in the loess area feature dual voids,vertical multilayers,variable structure,poor renewability,complex recharge processes,and distinct spatial differences.In general,the total dissolved solids(TDS)of the same type of groundwater tends to gradually increase from recharge areas to discharge areas.Conditions favorable for the formation of fresh groundwater in loess tablelands include the low content of soluble salts in strata,weak evaporation,and special hydrodynamic conditions.Owing to climate change and human activities,the resource quantity of regional fresh water tends to decrease overall,and the groundwater dynamic field and the recharge-discharge relationships between groundwater and surface water have changed in local areas.Human activities have a small impact on the water quality but slightly affect the water quantity of the groundwater in loess.