渐进性引导呼吸下的脉搏波传导时间变异性分析

Change of Pulse Transit Time During Stepwise Paced Breathing

研究渐进性引导呼吸对脉搏波传导时间(PTT)的影响。对22名健康成年人采集引导呼吸率依次为14.0次/min—12.5次/min—11.0次/min—9.5次/min—8.0次/min—7.0次/min这一过程的同步心电、呼吸以及桡动脉体表脉搏波信号,通过心电R波顶点到桡动脉脉搏波的二阶微分极值点的时间间隔计算PTT,观察每个引导呼吸率下的PTT幅度变异性以及PTT基线变化情况。经验模式分解(EMD)被用于PTT信号处理,以有效提取PTT中与呼吸相关的幅度振荡成分以及与基础血压相关的PTT基线成分。计算结果显示:所有受试者的PTT幅度变异性随呼吸率的逐渐降低均呈现增大的变化趋势;渐进性引导呼吸过程中大部分受试者(14人)表现出PTT基线上升的现象。实验结果表明:在渐进性引导呼吸过程中,呼吸运动对PTT幅度的调制作用逐渐增强;同时渐进性引导呼吸能产生PTT基线上升的累积效果。由于PTT与血压变化呈负相关关系,因此PTT基线上升表征了系统血压的下降。该研究表明渐进性引导呼吸通过心血管反射可以起到降低系统血压的作用。发展能够有效表征引导呼吸有效性的特异性指标并将呼吸调节技术用于原发性高血压患者,是后续工作中亟需开展的研究内容。

To investigate the effect of stepwise paced breathing （PB） on pulse transit time （PTT）, we collected phys- iological signals of electrocardiogram （ECG）, respiration and arterial pulse wave during a procedure of stepwise PB, which consists of 6 different breathing rates changing in a protocol of 14.0-12.5-11.0-9.5-8.0-7.0 breath per minute （BPM）, with each breathing rate lasting 3 minutes. Twenty two healthy adults involved in this experiment and the change of PTT was analyzed during the stepwise PB procedure. In our study, the PTT was measured by calculating the time interval from the R-spike of the ECG to the peaks of the second derivative of the arterial pulse wave. Ensem- ble empirical mode decomposition （EEMD） was applied to PTT to decompose the signal into different intrinsic mode function, and respiratory oscillation and trend component （baseline） in PTT were further extracted. It was found that the respiratory oscillations in the PTT increased with decreasing of the PB rate, and many of the subjects （14 out of 22） showed the phenomena of PTT baseline increasing during the stepwise PB procedure. The results indica- ted that the stepwise PB procedure induced a high level of cardiovascular oscillation and produced an accumulative effect of PTT baseline increase. As PTT is capable of predicting changes in BP over a short period of time, increase of PTT baseline indicates the decrease of blood pressure. The experiments showed that the stepwise PB procedure could reduce blood pressure for most subjects. For future work, it is necessary to develop certain indices differentia- ting the effectiveness of the stepwise PB procedure on the PTT baseline change, and to test the effectiveness of this stepwise PB procedure on blood pressure reduction for patients with essential hypertension.