Dubin M J, Magram G, Prasad A K
Department of Neurobiology and Anatomy, University of Rochester School of Medicine and Dentistry, NY, USA.
Neurol Res. 1998 Sep;20(6):533-41. doi: 10.1080/01616412.1998.11740560.
We studied transmission of arterial blood pressure to intracranial pressure by observing how the two pressure waveforms varied from baseline conditions to after postural change or jugular compression. Such experiments may lead to pressure waveform-based estimates of intracranial compliance. Using a single database of arterial blood pressure, central venous pressure, and intracranial pressure waveforms collected during baseline, jugular compresison, and head-elevated conditions from six Yucatan minipigs, we computed several numerical indicators of waveform shape to find an estimator of intracranial compliance. Of these indicators, two were based on the Fourier-decomposition of all three waveforms, and one was based on a new method for approximating the systolic slope of the intracranial pressure waveform. We computed amplitude transfer functions for the first six harmonics of the Fourier spectrum, treating intracranial pressure as system output and independently treating arterial blood pressure and central venous pressure as system inputs. Using these same inputs and outputs, we computed a single quotient based on the Fourier coefficients of the first six harmonics of the input and output waveforms. Finally, applying a Gaussian high-pass filter, we computed systolic slope approximations for all intracranial pressure wave cycles contained in a single respiratory cycle. Our third indicator was the mean-normalized variation of the slope approximations over a respiratory cycle. We studied how each composite at baseline varied with baseline mean intracranial pressure and how each composite changed from baseline as a result of a physical manipulation. Our analysis suggests that the composite based on respiratory variation of systolic slope approximations was positively correlated with mean intracranial pressure during baseline. The quotient based on Fourier coefficients with arterial blood pressure input seemed to increase from baseline to jugular compression. Composites that treated central venous pressure as input were both less correlated with mean intracranial pressure during baseline and exhibited less predictable changes from baseline to a physical manipulation than their counterparts that used arterial blood pressure as input. However, none of these apparent trends was statistically significant. The lack of statistically significant results may be due to the nature of the composites and/or the small sample size (n = 6). However, we hope this study stimulates further investigation of both central venous pressure-to-intracranial pressure (in addition to arterial blood pressure-to-intracranial pressure) transfer and automated computation of intracranial pressure waveform systolic slope. Such research may lead to noninvasively determined estimators of intracranial compliance.
我们通过观察从基线状态到体位改变或颈静脉压迫后动脉血压和颅内压这两种压力波形如何变化，来研究动脉血压向颅内压的传递。此类实验可能会得出基于压力波形的颅内顺应性估计值。利用从六只尤卡坦小型猪在基线、颈静脉压迫和头部抬高状态下收集的动脉血压、中心静脉压和颅内压波形的单一数据库，我们计算了波形形状的几个数值指标，以找到颅内顺应性的估计值。在这些指标中，两个基于所有三种波形的傅里叶分解，一个基于一种近似颅内压波形收缩斜率的新方法。我们计算了傅里叶频谱前六个谐波的幅度传递函数，将颅内压视为系统输出，分别将动脉血压和中心静脉压视为系统输入。使用相同的这些输入和输出，我们基于输入和输出波形前六个谐波的傅里叶系数计算了一个单一商数。最后，应用高斯高通滤波器，我们计算了单个呼吸周期内所有颅内压波形周期的收缩斜率近似值。我们的第三个指标是呼吸周期内斜率近似值的平均归一化变化。我们研究了每个基线时的综合指标如何随基线平均颅内压变化，以及每个综合指标因物理操作而相对于基线发生了怎样的变化。我们的分析表明，基于收缩斜率近似值呼吸变化的综合指标在基线时与平均颅内压呈正相关。以动脉血压为输入的基于傅里叶系数的商数似乎从基线到颈静脉压迫时有所增加。将中心静脉压作为输入的综合指标在基线时与平均颅内压的相关性都较低，并且与以动脉血压为输入的对应指标相比，从基线到物理操作时其变化的可预测性更低。然而，这些明显的趋势均无统计学意义。缺乏统计学显著结果可能是由于综合指标的性质和/或样本量较小（n = 6）。不过，我们希望这项研究能激发对中心静脉压到颅内压（除动脉血压到颅内压之外）传递以及颅内压波形收缩斜率自动计算的进一步研究。此类研究可能会得出非侵入性确定的颅内顺应性估计值。
