Sampling of cardiovascular data; how often and how much?

Abstract

Long-term measurement of cardiovascular variables by telemetry in laboratory animals has become indispensable in recent years. However, limited battery life and management of large volumes of recorded data are major drawbacks. These limitations can often be overcome by intermittent sampling of data. The question is, how much data does one need to collect to accurately reflect the underlying average value? To investigate this, 24-h continuous recordings of rabbit heart rate, arterial pressure, and integrated renal sympathetic nerve activity (RSNA) were resampled using a variety of protocols that differed with respect to the number of individual sampling periods used and the total amount of time that was sampled. The absolute percentage errors of estimates of the daily mean, standard deviation, and interquartile range were calculated for each sampling protocol. A similar analysis was repeated using arterial pressure data from rats. The results show that the number of sampling periods spread throughout the day had more effect than the total amount of data recorded. For example, just 2 h of total sampling time spread over 12 evenly spaced 10-min periods gave estimates of the daily mean of blood pressure and heart rate with <1% error and RSNA with <3% error. We show that accurate estimates of the daily mean of arterial pressure, heart rate, and RSNA can all be made using scheduled recording, and we recommend recording a minimum of 2 h/day spread over a number of periods throughout the day.

A high-salt diet does not influence renal sympathetic nerve activity: a direct telemetric investigation

“…RSNA recording was scheduled for 15 min every 2 h, a protocol that has been shown to accurately represent the underlying average (27). The averaged data presented for all variables were taken only from those periods when RSNA was actively being recorded.…”

New Approaches to Quantifying Sympathetic Nerve Activity

“…This problem can be overcome by intermittent sampling of data, and computer systems can be programmed to switch on the battery at predetermined times. Guild and colleagues [62] showed that a total of 2 h of frequent sampling over 24 h (for example, 10 min every 2 h) gave a good representation of ongoing renal SNA, with less than 3% error. These advances in technology and the ability to sample intermittently make possible the study of SNA and the circadian variation of cardiovascular indices over several weeksand possibly indefinitely-in the same animal [50,59].…”

Comparison of blood pressure and sympathetic activity of rabbits in their home cage and the laboratory environment

“…The signal was filtered between 50 and 5000 Hz, rectified and integrated using a low‐pass filter with a 20 ms time constant. Mean arterial pressure (MAP) and heart rate (HR) data were collected continuously over each 24 h period, and RSNA data was collected for 15 min every 2 h, a regimen which gives a close representation of the underlying average (Guild et al 2008; Fig. 1).…”