经双腔鼻导管吸氧时实际吸入氧浓度的影响因素

Effect of influence factors on the inspired oxygen concentration during oxygen therapy via nasal cannulas

目的研究实际吸入氧浓度(inspired oxygen concentration,FiO_2)的变异大小及各种影响因素对其的影响程度。方法选择健康对照者及中.重度慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)急性加重期稳定后患者各8例,经双腔鼻导管吸氧,均按单纯常规吸氧与连接流量计测量呼吸参数两种情况下进行,随机调节给氧流量为1,2,3,4,5 L/min,气体平衡后随机模拟加快吸气速度、减慢吸气速度及平静呼吸等3种呼吸模式,采用旁流顺磁法测量氧浓度。结果单纯常规吸氧时,健康对照组的FiO_2影响因素影响程度大小的岭回归分析结果为给氧流量、吸气时间与呼吸周期时间比值(inspiratory time/respiratory cycle time,Ti/Ttot)及呼吸频率(respiratory frequency,RR)对FiO_2的影响程度较大。在COPD组,给氧流量及RR的影响程度较大。连接流量计测量呼吸参数后,在健康对照组,给氧流量、潮气量(tidal volume,V_T)、RR、吸气峰流速(peak inspirator flow,PIF)及平均吸气流速(mean inspiratory flow,MIF)对FiO_2的影响程度较大。COPD组的给氧流量、V_T、Ti/Ttot及PIF的影响程度较大。结论实际FiO_2受多种因素影响,其影响程度大小的分析结果显示,强影响因素:给氧流量;较强影响因素:V_T;中影响因素;RR、PIF及Ti/Ttot;弱影响因素:MIF、吸气时间(inspiratory time,Ti)及吸呼比(inspiratory time/expiratory time,I:E)。

Objective To evaluate the variation of the inspired oxygen concentration （FiO2） and its influence factors. Method Eight normal persons and 8 patients with moderate to severe chronic obstructive pulmonary disease （COPD） during convalescent stage were enrolled. All subjects were received oxygen therapy via nasal carmulas simply, and then wore a mini-nasal-mask and pneumotachograp.h to measure the respiratory variables in real time. The oxygen flow rate of 1, 2, 3, 4 or 5 L/rain was given randomly, The subjects were asked to mimic slow inspiration, fast inspiration and quiet inspiration. Oxygen concentration was measured by a sidestream analyzer incorporated with paramagnefic device. Results The ridge regression analysis during normal oxygen breathing showed： in normal subjects group, FiO2 was highly influenced by oxygen flow rate, inspiratory time/respiratory cycle time （Ti/Ttot） and respiratory frequency （RR）, in COPD patients, FiO2 was highly influenced by oxygen flow rate and RR. When pneumotachograph was used for measurement, FiO2 was highly influenced by oxygen flow rate, tidal volume （VT）, RR peak inspiratory flow （PIF） and mean inspiratory flow （MIF） in hormal subjects, while in COPD patients, it was greatly influenced by oxygen flow rate, Vt, Ti/Ttot and PIE. Conclusions The deviation of FiO2 is affected by many factors. The analysis results show that the most powerful influence factor is oxygen flow rate; relatively less powerful influence factor is VT; moderate inluence factors are RR, PIF and Ti/Ttot; and weak influence factors are MIF; inspiratory time （Ti） and inspiratory time/ expiratory time （I ： E）.