Abstract

Background: Heart rate variability (HRV) analysis is a relevant indicator of autonomic nervous system function over the cardiovascular system. The usual way to measure this variability is from the electrocardiogram (ECG).

Objective: To assess the validity of HRV measurements obtained from a heart rate monitor (HRM) Polar^® V800 in critically ill adult subjects.

Materials and Methods: A prospective, repeated measures, observational study was conducted in two in the Chilean intensive care units. Twenty-one different HRV variables were simultaneously assessed using a Polar^® V800 HRM and an ECG Mortara^® H3 Holter device. The data was collected from the clinical record and physical examinations. The evaluations were conducted for 10 minutes at a time and simultaneously, during which the subjects had to remain supine and at rest. The sampling frequency was 1000 Hz, providing a temporal resolution of 1 millisecond for each RR period.

Results: Thirty adult subjects were included with an average age of 33.63 ± 8.91 years. When comparing both HRV assessment methods, only 3 variables showed statistically significant differences (p ≤ 0.05). As well, the correlations showed 4 strong and 17 near-perfect associations, which were positive and statistically significant (p ≤ 0.001). In addition, intraclass correlation coefficients (between 0.744 and 1) and bias determined using the Bland-Altman method found both methods to be concordant.

Conclusion: The Polar^® V800 monitor is a valid tool for assessing HRV in critically ill adult subjects.

Keywords: Heart rate variability, electrocardiography, monitoring, autonomic nervous system, critical care, critical illness.