Methodological Considerations for Assessing Measures of Spontaneous Cardiac Baroreflex Sensitivity in Humans

Abstract

The arterial baroreflex is a negative feedback control system that plays an important role in short‐term maintenance of arterial blood pressure (BP). Analyses assessing spontaneous beat‐to‐beat fluctuations in BP and heart rate (HR) are increasingly being used to estimate cardiac baroreflex sensitivity. Published results have commonly used 10 min recording durations for these analyses; however, some research protocols require shorter recording durations. Since the validity of using shorter compared to longer recording durations has not been established, we tested the hypothesis that reduced baseline durations diminish the reliability of spontaneous cardiac baroreflex sensitivity measures. Beat‐to‐beat HR and BP were measured continuously during supine rest in 10 healthy individuals for 10 min, and spontaneous cardiac baroreflex sensitivity was estimated using the sequence technique and low frequency transfer function analysis (0.04–0.15 Hz). The 10 min baseline for each subject was divided into two 5‐min segments and two 3‐min segments, and each analysis was repeated. Statistical analysis revealed similar spontaneous baroreflex sensitivity among the various baseline durations for both analyses (P>0.05). For example, spontaneous cardiac baroreflex sensitivity for the sequence technique was 18±3 ms/mmHg for 10 min, 18±2 ms/mmHg for 5 min and 18±3 ms/mmHg for 3 min durations (P>0.05). However, the reliability over the various recording durations as assessed by intra‐class correlation was acceptable only for the sequence technique. These preliminary findings suggest that shorter baseline durations appear adequate to assess spontaneous cardiac baroreflex sensitivity when using the sequence technique.