Heart rate variability and subsequent psychological distress among family members of intensive care unit patients

Objective To determine whether heart rate variability (HRV; a physiological measure of acute stress) is associated with persistent psychological distress among family members of adult intensive care unit (ICU) patients. Methods This prospective study investigated family members of patients admitted to a study ICU. Participants' variability in heart rate tracings were measured by low frequency (LF)/high frequency (HF) ratio and detrended fluctuation analysis (DFA). Questionnaires were completed 3 months after enrollment to ascertain outcome rates of anxiety, depression, and post-traumatic stress disorder (PTSD). Results Ninety-nine participants were enrolled (median LF/HF ratio, 0.92 [interquartile range, 0.64-1.38]). Of 92 participants who completed the 3-month follow-up, 29 (32%) had persistent anxiety. Logistic regression showed that LF/HF ratio (odds ratio [OR] 0.85, 95% confidence interval [CI] 0.43, 1.53) was not associated with 3-month outcomes. In an exploratory analysis, DFA alpha (OR 0.93, 95% CI 0.87, 0.99), alpha(1) (OR 0.97, 95% CI 0.94, 0.99), and alpha(2) (OR 0.94, 95% CI 0.88, 0.99) scaling components were associated with PTSD development. Conclusion Almost one-third of family members experienced anxiety at three months after enrollment. HRV, measured by LF/HF ratio, was not a predictor of psychologic distress, however, exploratory analyses indicated that DFA may be associated with PTSD outcomes.