气管内脉搏氧饱和度监测的信号来源及其影响因素

目的 探索气管内脉搏氧饱和度监测的信号来源,并观察影响信号质量的相关因素.方法 将杂种犬麻醉后经口腔插入前端贴附一次性儿童氧饱和度探头的气管导管.开胸直视下,让气管内氧饱和度探头发射的红光对准单侧气管旁大动脉,暂时阻断气管旁大动脉,观察阻断前后经气管脉搏血氧饱和度(SptO_2)的脉搏光容积描记(PPG)波形和读数变化.用照片采集SptO_2的最佳信号,调节气管导管套囊内压力,观察不同套囊压力下机械通气与否对信号波形和读数的影响,并与来自犬尾的脉搏氧饱和度(SpO_2)做比较.结果 当气管内氧饱和度探头所对准的气管旁大动脉被阻断时,SptO_2的信号消失.机械通气和套囊压力均可使SptO_2信号产生变化(P<0.001).套囊压力为0、10 cm H_2O时SptO_2信号与套囊压力为20～60 cm H_2O时相比差异有统计学意义(P<0.001),机械通气下的SptO_2波形与无机械通气时不同(P<0.01),且与SpO_2的差异有统计学意义(P<0.01).结论 SptO_2的信号主要来自于气管周围的大动脉而非气管壁本身,气管套囊压力与机械通气对SptO_2信号的读数均有影响,套囊压力在20～60 cm H_2O时比10 cm H_2O的SptO_2信号更好,机械通气主要影响信号的波形.

The Source and Factors that Influence Tracheal Pulse Oximetry Signal

Objective To investigate the source and factors that influence tracheal pulse oximetry signal. Methods The adult mongrel dog was intubated after anesthesia. The tracheal tube was modified by attaching a disposable pediatric pulse oximeter to the cuff. The chest of the dog was cut open and a red light from the tracheal oximeter was aligned with the deeper artery. The changes in tracheal pulse oxygen saturation (SptO_2) signal were observed after the deeper artery was blocked temporarily. The photoplethysmography (PPG) and readings were recorded at different intracuff pressures. The influence of mechanical ventilation on the signal was also tested and compared with pulse oxygen saturation (SpO_2). Results The SptO_2 signal disappeared after deeper artery was blocked. The SptO_2 signal changed with different intracuff pressures(P<0.001). Stronger SptO_2 signal appeared under 20-60 cm H_2O of intracuff pressure than under 0-10 cm H_2O of intracuff pressure(P<0.001). The PPG of SptO_2 signal under a condition with mechanical ventilation differed from that without mechanical ventilation (P<0.01), which, was also different from SpO_2(P<0.01). Conclusion SptO_2 signal is primarily derived from deeper arteries around the trachea, not from the tracheal wall. Both intracuff pressures and mechanical ventilation can influence SptO_2 signal. The SptO_2 signal under 20-60 cm H_2O of intracuff pressure is stronger than that under 0-10 cm H_2O of intracuff pressure. Mechanical ventilation mainly changes PPG.