呼出气氧浓度监测评价吸入氧浓度基线水平对急诊患者插管前面罩通气时间的影响

Effect of fraction of inspired oxygen baseline level on the mask ventilation time before intubation in emergency patients by monitoring of expiratory oxygen concentration

目的以呼出气氧浓度(EtO_(2))作为监测指标,探讨急诊患者气管插管前不同吸入氧浓度(FiO_(2))基线水平下进行纯氧面罩通气对EtO_(2)达标时间的影响。方法采用回顾性观察性研究方法,收集2021年1月1日至11月1日在北京协和医院急诊科接受气管插管患者的临床资料。为了避免因操作不规范或漏气等造成通气不充分而干扰最终结果,故选择已行气管插管患者FiO_(2)调至纯氧后持续机械通气的过程来模拟插管前纯氧下面罩通气的过程。结合电子病历和呼吸机记录,分析患者在不同FiO_(2)基线水平下,调整FiO_(2)至纯氧后EtO_(2)达到0.90所需时间(即EtO_(2)达标时间)和达标所需呼吸周期的变化。结果最终收集到42例患者共113次EtO_(2)监测记录;其中,2例患者由于FiO_(2)基线水平即为0.80,故仅有1次EtO_(2)记录,其他患者均有2次及以上不同FiO_(2)基线水平对应的EtO_(2)达标时间和呼吸周期记录。42例患者中,以男性为主(占59.5%),老年人居多〔中位年龄62(40,70)岁〕,大多为呼吸系统疾病(占40.5%);不同患者肺功能差异较大,但以功能正常患者居多〔氧合指数(PaO_(2)/FiO_(2))>300 mmHg(1 mmHg≈0.133 kPa),占38.0%〕;在呼吸机参数设置上,结合患者稍低的动脉血二氧化碳分压〔33(28,37)mmHg〕,考虑普遍存在轻度的过度通气现象。随着FiO_(2)基线水平升高,EtO_(2)达标时间和呼吸周期数均呈逐渐下降趋势。当FiO_(2)基线水平为0.35时,EtO_(2)达标时间最长〔79(52,87)s〕,所需呼吸周期数最多〔22(16,26)个〕;当FiO_(2)基线水平从0.35提升至0.80时,EtO_(2)达标时间可从79(52,87)s缩短至30(21,44)s,呼吸周期数也从22(16,26)个减少到10(8,13)个,差异均有统计学意义(均P<0.05)。结论急诊患者气管插管前面罩通气的FiO_(2)基线水平越高,EtO_(2)达标时间就越短,面罩通气时间也就越短。

Objective To investigate the effect of different fraction of inspired oxygen(FiO_(2))baseline levels before endotracheal intubation on the time of expiratory oxygen concentration(EtO_(2))reaching the standard in emergency patients with the EtO_(2)as the monitoring index.Methods A retrospective observational study was conducted.The clinical data of patients receiving endotracheal intubation in the emergency department of Peking Union Medical College Hospital from January 1 to November 1 in 2021 were enrolled.In order to avoid interference with the final result due to inadequate ventilation caused by non-standard operation or air leakage,the process of the continuous mechanical ventilation after FiO_(2)was adjusted to pure oxygen in patients who had been intubated was selected to simulate the process of mask ventilation under pure oxygen before intubation.Combined with the electronic medical record and the ventilator record,the changes of the time required to reach 0.90 of EtO_(2)(that was,the time required to reach the standard of EtO_(2))and the respiratory cycle required to reach the standard after adjusting FiO_(2)to pure oxygen under different baseline levels of FiO_(2)were analyzed.Results 113 EtO_(2)assay records were collected from 42 patients.Among them,2 patients had only one EtO_(2)record due to the FiO_(2)baseline level of 0.80,while the rest had two or more records of EtO_(2)reaching time and respiratory cycle corresponding to different FiO_(2)baseline level.Among the 42 patients,most of them were male(59.5%),elderly[median age was 62(40,70)years old]patients with respiratory diseases(40.5%).There were significant differences in lung function among different patients,but the majority of patients with normal function[oxygenation index(PaO_(2)/FiO_(2))>300 mmHg(1 mmHg≈0.133 kPa),38.0%].In the setting of ventilator parameters,combined with the slightly lower arterial partial pressure of carbon dioxide of patients[33(28,37)mmHg],mild hyperventilation phenomenon was considered to be widespread.With the increased in FiO_(2)baseline level,the time of EtO_(2)reaching standard and the number of respiratory cycles showed a gradually decreasing trend.When the FiO_(2)baseline level was 0.35,the time of EtO_(2)reaching the standard was the longest[79(52,87)s],and the corresponding median respiratory cycle was 22(16,26)cycles.When the FiO_(2)baseline level was increased from 0.35 to 0.80,the median time of EtO_(2)reaching the standard was shortened from 79(52,78)s to 30(21,44)s,and the median respiratory cycle was also reduced from 22(16,26)cycles to 10(8,13)cycles,with statistically significant differences(both P<0.05).Conclusion The higher the FiO_(2)baseline level of the mask ventilation in front of the endotracheal intubation in emergency patients,the shorter the time for EtO_(2)reaching the standard,and the shorter the mask ventilation time.