Fuehrlein Brian, Melker Richard, Ross Edward A
Department of Anesthesiology, University of Florida, Gainesville, FL 32610-0224, USA.
J Clin Monit Comput. 2007 Aug;21(4):211-8. doi: 10.1007/s10877-007-9075-y. Epub 2007 May 25.
Hemodialysis (HD) hemoconcen tration measurements may not predict hypotension, and are confounded by impaired compensatory responses to ultrafiltration (UF). We devised noninvasive photople thysmograph (PPG) technology to monitor carotid blood flow at the nasal alar, quantify cardiac and respiratory components, and study the effect of UF and resistance breathing in HD patients and blood donors.
The PPG was recorded using a novel alar probe in 40 subjects (20 each group), before and after their procedure, with 3 airway resistances. Raw data were separated into a low frequency component (LFC, based on the effect of respiration on thoracic pressure and blood capacitance) and a rapid pulsatile cardiac component (PCC), yielding 3 measures of carotid flow and vascular tone.
The device produced stable signals amenable to automated processing. The LFC (respiration-induced variation in carotid flow) increased with UF (P as low as 0.03, depending on airway resistance), not changing in blood donors. Two PCC variables (measuring blood vessel distention with each heart beat) decreased (P < or = 0.03) with blood donation, but not UF.
This new noninvasive PPG method detects altered respiration-associated carotid circulation during UF. With blood donation there is dampening of pulsatile vessel distention, consistent with increased vascular tone. That compensatory mechanism was impaired in HD patients and helps explain their instability with fluid removal.
血液透析（HD）时的血液浓缩测量可能无法预测低血压，并且会因对超滤（UF）的代偿反应受损而受到干扰。我们设计了一种非侵入性光电容积脉搏波描记法（PPG）技术，用于监测鼻翼处的颈动脉血流，量化心脏和呼吸成分，并研究超滤和阻力呼吸对HD患者及献血者的影响。
使用一种新型鼻翼探头在40名受试者（每组20名）进行操作前后记录PPG，设置3种气道阻力。原始数据被分离为低频成分（LFC，基于呼吸对胸内压和血容量的影响）和快速搏动性心脏成分（PCC），从而得出3种颈动脉血流和血管张力的测量值。
该设备产生了适合自动处理的稳定信号。LFC（呼吸引起的颈动脉血流变化）随超滤增加（P低至0.03，取决于气道阻力），在献血者中未发生变化。两个PCC变量（测量每次心跳时血管扩张情况）在献血时降低（P≤0.03），但在超滤时未降低。
这种新的非侵入性PPG方法可检测超滤过程中与呼吸相关的颈动脉循环变化。献血时搏动性血管扩张减弱，这与血管张力增加一致。HD患者的这种代偿机制受损，这有助于解释他们在液体清除时的不稳定性。
