The Nonlinear Index SD1 Predicts Diastolic Blood Pressure and HRV Time and Frequency Domain Measurements in Healthy Undergraduates

• Published in: Applied psychophysiology and biofeedback Vol. 40; no. 2; p. 134
• Main Authors: Zerr, Christopher, Kane, Alexander, Vodopest, Teresa, Allen, Jabari, Hannan, Joe, Cangelosi, Alec, Owen, Dan, Fabbri, Marissa, Williams, Chris, Cary, Brian, Crawford, Amanda, West, Alex, Shrestha, Reejan, Palcheff, Joe, Barylski, Tommy
• Format: Journal Article
• Language: English
• Published: Springer 01.06.2015
• Subjects: Analysis; Blood pressure; College students; Electrocardiogram; Electrocardiography; Heart beat; Measurement
• ISSN: 1090-0586

The present study explored the predictive relationship between the nonlinear index SD1, diastolic and systolic blood pressure, four heart rate variability (HRV) time domain, and three frequency domain measurements in healthy undergraduates. SD1 is the standard deviation of the distance of each point from the y = x axis of a Poincare plot. SD1 measures short-term HRV in milliseconds, which makes it appropriate for brief measurement periods, and correlates with baroreceptor reflex sensitivity. Twenty-nine undergraduates (15 male and 14 female), 19-24 years of age, participated in this study. A Thought Technology Pro-CompT Infiniti system monitored ECG and respiration. Active ECG electrodes were placed about 2 inches above the navel and 4 inches to the left and right of the midline and the reference electrode was centered over the angle of the sternum. A respirometer was positioned over the navel to measure abdominal excursion and respiration rate. Subjects were stabilized for 5 min and then monitored for 5 min sitting upright, with eyes open, no feedback, and instructions to breathe normally. Data were artifacted within CardioPro and then detrended in Kubios 2.1 using a smoothness priors procedure. Frequency domain analysis utilized a Fast Fourier Transformation (FFT)-based Welch's periodogram procedure. While SD1 was unrelated to systolic blood pressure, it predicted diastolic blood pressure, F(1, 27) = 6.77, p = 0.015, eta-squared = 0.20. SD1 predicted four HRV time domain measures: HR MaxHR Min, F(1, 27) = 57.79, p = 0.001, eta-squared = 0.68 RMSSD, F(1, 27) = 3309.98, p = 0.001, eta squared = 0.99, pNN50, F(1, 27) = 25.94, p = 0.001, eta-squared = 0.76, and SDNN, F(1, 27) = 174.51, p = 0.001, eta-squared = 0.87. SD1 also predicted three HRV frequency domain measures: low-frequency power, F(1, 27) = 85.08, p = 0.001, eta-squared = 0.76, high-frequency power, F(1, 27) = 237.60, p = 0.001, eta-squared = 0.90, and total power, F(1, 27) = 173.90, p = 0.001, n2 = 0.87. Based on these findings, clinicians should consider utilizing SD1 to assess clients who resemble our healthy undergraduates. Future researchers should replicate these findings with a clinical population. Keywords * Heart rate variability * Blood pressure * College students * SD1