Department of Internal Medicine, Albert Einstein College of Medicine, Bronx, New York, NY 10467, USA.
Physiol Meas. 2010 Sep;31(9):1185-201. doi: 10.1088/0967-3334/31/9/009. Epub 2010 Jul 28.
The aim of this study was to determine the minimal sampling rate (SR) required for blood pressure (BP) waveform recordings to accurately determine BP and heart rate (HR) variability indices and baroreceptor reflex sensitivity in rats and mice. We also determined if an 8-bit (versus 12-bit) analog-to-digital converter (ADC) resolution is sufficient to accurately determine these hemodynamic parameters and if spline interpolation to 1000 Hz of BP waveforms sampled at lower SRs can improve accuracy. BP and ECG recordings (1000 Hz SR, 12-bit ADC resolution) from two strains of rats and BP recordings (1000 Hz SR, 12-bit ADC resolution) from two strains of mice were mathematically converted to lower SRs and/or 8-bit ADC resolution. Time-domain HR variability and frequency-domain HR and BP variability indices and baroreflex sensitivity (using the sequence technique) were determined and the results obtained from the original files were compared to the results obtained from the mathematically altered files. Our results demonstrate that an ADC resolution of 8 bit is not sufficient to determine HR and BP variability in rats and mice and baroreceptor reflex sensitivity in mice. Average values for systolic, mean and diastolic BP and HR can be accurately derived from BP waveforms recorded at a minimal SR of 200 Hz in rats and mice. Spline interpolation of BP waveforms to 1000 Hz prior to extracting derived parameters reduces this minimal SR to 50 Hz in rats but still requires 200 Hz in mice. Frequency-domain BP variability (very low and low frequency spectral powers) can be estimated accurately at a minimum SR of 100 Hz in rats and mice and spline interpolation of BP waveforms to 1000 Hz reduces this minimal SR to 50 Hz in rats but does not reduce the minimal SR in mice. Time- and frequency-domain HR variability parameters require at least a SR of 1000 Hz in rats and mice. Spline interpolation of BP waveforms to 1000 Hz reduces this minimal SR to 100 Hz in rats and to 200 Hz in mice. Estimation of baroreflex sensitivity using the sequence technique requires a SR of at least 1000 Hz in rats and mice. Spline interpolation of BP waveforms to 1000 Hz reduces this minimal SR to 100 Hz in rats but does not reduce the minimum SR in mice. Finally, our results indicate that HR time series derived from BP waveforms are not totally consistent with HR time series derived from the ECG in rats. In conclusion, accurate assessment of HR variability and baroreflex sensitivity from BP waveform recordings requires a SR of at least 1000 Hz in rats and mice. If lower SRs are used for BP waveform recordings, a cubic spline interpolation to 1000 Hz (or an even higher SR) prior to extracting derived parameters significantly improves accuracy.
本研究旨在确定血压（BP）波形记录所需的最小采样率（SR），以准确确定血压和心率（HR）变异性指数和压力感受器反射敏感性。我们还确定 8 位（与 12 位）模拟数字转换器（ADC）分辨率是否足以准确确定这些血流动力学参数，以及在较低 SR 下对 BP 波形进行样条插值至 1000 Hz 是否可以提高准确性。我们将两种大鼠和两种小鼠的 BP 和心电图（1000 Hz SR，12 位 ADC 分辨率）记录以及 BP 记录（1000 Hz SR，12 位 ADC 分辨率）进行数学转换至较低的 SR 和/或 8 位 ADC 分辨率。确定时域 HR 变异性、频域 HR 和 BP 变异性指数以及压力感受器反射敏感性（使用序列技术），并将原始文件中获得的结果与数学改变文件中获得的结果进行比较。我们的结果表明，8 位 ADC 分辨率不足以确定大鼠和小鼠中的 HR 和 BP 变异性以及小鼠中的压力感受器反射敏感性。大鼠和小鼠中，BP 波形记录的最小 SR 为 200 Hz 时，可准确得出收缩压、平均压和舒张压和 HR 的平均值。在提取衍生参数之前，将 BP 波形样条插值至 1000 Hz 可将大鼠的最小 SR 降低至 50 Hz，但在小鼠中仍需要 200 Hz。大鼠和小鼠的最小 SR 为 100 Hz 时，可准确估计频域 BP 变异性（极低和低频谱功率）；在大鼠中，将 BP 波形样条插值至 1000 Hz 可将最小 SR 降低至 50 Hz，但在小鼠中不降低最小 SR。大鼠和小鼠的时频域 HR 变异性参数需要至少 1000 Hz 的 SR。在大鼠中，将 BP 波形样条插值至 1000 Hz 可将最小 SR 降低至 100 Hz，在小鼠中降低至 200 Hz。使用序列技术估计压力感受器反射敏感性需要大鼠和小鼠的最小 SR 至少为 1000 Hz。在大鼠中，将 BP 波形样条插值至 1000 Hz 可将最小 SR 降低至 100 Hz，但不降低小鼠中的最小 SR。最后，我们的结果表明，大鼠的 HR 时间序列源自 BP 波形，与源自心电图的 HR 时间序列并不完全一致。总之，准确评估大鼠和小鼠的 HR 变异性和压力感受器反射敏感性需要至少 1000 Hz 的 SR。如果在 BP 波形记录中使用较低的 SR，则在提取衍生参数之前，对 BP 波形进行三次样条插值至 1000 Hz（或更高的 SR）可显著提高准确性。
