Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom. Glenfield Hospital, NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Leicester, United Kingdom.
Physiol Meas. 2020 Apr 17;41(3):035006. doi: 10.1088/1361-6579/ab7ddf.
Transfer function analysis (TFA) of dynamic cerebral autoregulation (dCA) requires smoothing of spectral estimates using segmentation of the data (S). Systematic studies are required to elucidate the potential influence of S on dCA parameters.
Healthy subjects (HS, n = 237) and acute ischaemic stroke patients (AIS, n = 98) were included. Cerebral blood flow velocity (CBFV, transcranial Doppler ultrasound) was recorded supine at rest with continuous arterial blood pressure (BP, Finometer) for a minimum of 5 min. TFA was performed with durations S = 100, 50 or 25 s and 50% superposition to derive estimates of coherence, gain and phase for the BP-CBFV relationship. The autoregulation index (ARI) was estimated from the CBFV step response. Intrasubject reproducibility was expressed by the intraclass correlation coefficient (ICC).
In HS, the ARI, coherence, gain, and phase (low frequency) were influenced by S, but in AIS, phase (very low frequency) and ARI were not affected. ICC was excellent (>0.75) for all parameters, for both HS and AIS. For S = 100 s, ARI was different between HS and AIS (mean ± sdev: 5.70 ± 1.61 vs 5.1 ± 2.0; p < 0.01) and the significance of this difference was maintained for S = 50 s and 25 s. Using S = 100 s as reference, the rate of misclassification, based on a threshold of ARI ⩽ 4, was 6.3% for S = 50 s and 8.1% for S = 25 s in HS, with corresponding values of 11.7% and 8.2% in AIS patients, respectively.
Further studies are warranted with S values lower than the recommended standard of S = 100 s, to explore possibilities of improving the reproducibility, sensitivity and prognostic value of TFA parameters used as metrics of dCA.
动态脑自动调节（dCA）的传递函数分析（TFA）需要通过对数据进行分段（S）来平滑谱估计。需要进行系统研究来阐明 S 对 dCA 参数的潜在影响。
纳入健康受试者（HS，n=237）和急性缺血性脑卒中患者（AIS，n=98）。在仰卧位休息时，使用经颅多普勒超声（TCD）连续记录脑血流速度（CBFV），并使用 Finometer 连续记录动脉血压（BP）至少 5 分钟。TFA 的持续时间分别为 S=100、50 或 25 秒，重叠率为 50%，以得出 BP-CBFV 关系的相干性、增益和相位估计值。通过 CBFV 阶跃响应估计自动调节指数（ARI）。用组内相关系数（ICC）表示受试者内的可重复性。
在 HS 中，ARI、相干性、增益和相位（低频）受 S 的影响，但在 AIS 中，相位（极低频）和 ARI 不受 S 的影响。对于 HS 和 AIS，所有参数的 ICC 均良好（>0.75）。对于 S=100 秒，HS 和 AIS 之间的 ARI 不同（平均值±标准差：5.70±1.61 与 5.1±2.0；p<0.01），当 S=50 秒和 25 秒时，这种差异的显著性仍然存在。以 S=100 秒为参考，基于 ARI ⩽4 的阈值，HS 中 S=50 秒的错误分类率为 6.3%，S=25 秒的错误分类率为 8.1%，而 AIS 患者的相应值分别为 11.7%和 8.2%。
需要进一步研究 S 值低于推荐的 S=100 秒的标准，以探索改善作为 dCA 指标的 TFA 参数的可重复性、敏感性和预后价值的可能性。
