Hermida R C, Ayala D E, Mojón A, Fernández J R
Bioengineering and Chronobiology Laboratories, University of Vigo, Campus Universitario, Vigo, Spain.
Hypertension. 2001 Sep;38(3 Pt 2):746-52. doi: 10.1161/01.hyp.38.3.746.
To recognize the highly statistically significant circadian variability of blood pressure in pregnancy is to admit that the diagnosis of gestational hypertension or preeclampsia should be based not just on whether a casual blood pressure value is too high or too low, but rather on more pertinent questions: How long is blood pressure elevated above a given time-varying threshold? What is the excess blood pressure? When does most of the excess occur? Answers to these questions may be obtained by establishing (1) an adequate reference threshold for blood pressure and (2) a proper measurement of blood pressure elevation. Accordingly, we derived time-specified reference standards for blood pressure as a function of gestational age. We analyzed 1408 blood pressure series systematically sampled by ambulatory monitoring for 48 consecutive hours every 4 weeks from the first obstetric visit (usually within the first trimester of pregnancy) until delivery in 235 women with uncomplicated pregnancies. Data from each blood pressure series were synchronized according to the rest-activity cycle of each individual to avoid differences among women in actual times of daily activity. Data were then used to compute 90% circadian tolerance intervals for each trimester of pregnancy, in keeping with the trends in blood pressure along gestation previously documented. The method, derived on the basis of bootstrap techniques, does not need to assume normality or symmetry in the data, and therefore, it is highly appropriate to describe the circadian pattern of blood pressure variability. Results not only reflect expected changes in the tolerance limits as a function of gestational age, but also upper limits markedly below the thresholds currently used for diagnosing hypertension in pregnancy. The use of these time-qualified tolerance limits for the computation of a hyperbaric index as a measure of BP excess has already been show to provide high sensitivity and specificity in the early identification of gestational hypertension and preeclampsia.
认识到孕期血压具有高度统计学意义的昼夜变化，就意味着要承认，妊娠期高血压或先兆子痫的诊断不应仅仅基于偶然测得的血压值过高或过低，而应基于更相关的问题：血压高于特定随时间变化的阈值的时长是多久？血压超出值是多少？大部分超出值出现在何时？通过确立（1）适当的血压参考阈值和（2）对血压升高进行恰当测量，或许可以找到这些问题的答案。因此，我们得出了随胎龄变化的特定时间的血压参考标准。我们分析了235例无并发症妊娠女性从首次产科就诊（通常在妊娠早期）直至分娩期间，每4周通过动态监测连续48小时系统采样的1408个血压序列。每个血压序列的数据根据每个个体的休息 - 活动周期进行同步，以避免不同女性日常活动实际时间的差异。然后根据先前记录的孕期血压变化趋势，利用这些数据计算出妊娠各期的90%昼夜耐受区间。该方法基于自助法技术得出，无需假设数据呈正态分布或对称分布，因此非常适合描述血压变异性的昼夜模式。结果不仅反映了耐受限度随胎龄变化的预期变化，而且上限明显低于目前用于诊断妊娠高血压的阈值。将这些具有时间限定的耐受限度用于计算作为血压超出量度的高压指数，已被证明在早期识别妊娠期高血压和先兆子痫方面具有高灵敏度和特异性。
