Cooke William H, Lurie Keith G, Rohrer Mary Jo, Convertino Victor A
Department of Health and Kinesiology, University of Texas at San Antonio (W.H.C.), San Antonio, Texas, and Department of Emergency Medicine, Minneapolis Medical Research Foundation and Hennepin County Medical Center, Minneapolis, Minnesota, USA.
J Trauma. 2006 Jun;60(6):1275-83. doi: 10.1097/01.ta.0000221348.82115.a2.
We evaluated the influence of breathing through an inspiratory Impedance Threshold Device (ITD) on autonomic neural and cerebrovascular function.
Eight subjects breathed through a sham ITD (0 cmH2O) and an active ITD (-7 cmH2O) in the supine position. We recorded the ECG, finger photoplethysmographic arterial pressure, cerebral blood flow velocity, and muscle sympathetic nerve activity (MSNA). In a randomized, counterbalanced design, subjects breathed spontaneously and also breathed at a set cadence of 15 breaths/min (0.25 Hz) for 3 minutes each. Data were analyzed in both time and frequency domains.
Breathing through the active ITD increased mean arterial pressure by approximately 5 mm Hg, heart rate by 2 bpm, and mean cerebral blood flow velocity by 10% (p<0.05) with no effect on MSNA or estimates of vagal-cardiac control (p>0.05). The active ITD did not affect oscillations of interbeat R-R intervals, arterial pressures, or cerebral flow velocities within the low frequency (LF) domain of the power spectrum (p>0.05). Cross spectral analysis revealed no effect of the active ITD on transfer function magnitudes among arterial pressures and R-R intervals, or between arterial pressures and cerebral blood flow velocities at the LF (p>0.05).
Our results demonstrate that the ITD increases arterial pressure, heart rate, and cerebral blood flow velocity independent of changes in autonomic cardiovascular control or dynamic cerebral autoregulation. Use of an active ITD in situations of acute central hypovolemia, such as during hemorrhage, may slow the progression to hemodynamic instability in bleeding patients who retain the ability to ventilate spontaneously and robustly.
我们评估了通过吸气阻抗阈值装置（ITD）呼吸对自主神经和脑血管功能的影响。
八名受试者在仰卧位通过假ITD（0 cmH₂O）和活性ITD（-7 cmH₂O）进行呼吸。我们记录了心电图、手指光电容积描记动脉压、脑血流速度和肌肉交感神经活动（MSNA）。采用随机、平衡设计，受试者自主呼吸，并以15次/分钟（0.25 Hz）的设定节奏呼吸，每次3分钟。对数据进行时域和频域分析。
通过活性ITD呼吸使平均动脉压升高约5 mmHg，心率升高2次/分钟，平均脑血流速度升高10%（p<0.05），对MSNA或迷走神经心脏控制估计值无影响（p>0.05）。活性ITD不影响功率谱低频（LF）域内心搏间期R-R间期、动脉压或脑血流速度的振荡（p>0.05）。交叉谱分析显示，活性ITD对LF时动脉压与R-R间期之间或动脉压与脑血流速度之间的传递函数幅值无影响（p>0.05）。
我们的结果表明，ITD可增加动脉压、心率和脑血流速度，而与自主心血管控制或动态脑自动调节的变化无关。在急性中枢性低血容量情况下，如出血期间，使用活性ITD可能会减缓有自主且有力通气能力的出血患者血流动力学不稳定的进展。
