The Care After Life-threatening Medical Events Study (CALME)

The Care After Life-threatening Medical Events (CALME) Pilot Study: An Investigation of Heart Rate Variability Biofeedback Training

This study tests the feasibility of a home-based heart rate variability biofeedback (HRVB) intervention in survivors of cardiac arrest (CA). Specifically, the primary purpose of this pilot study is to assess feasibility, acceptability, appropriateness, usability, and compliance for an at-home, 3-week HRVB intervention in 10 participants. The study also tests whether cardiac-related interoceptive fear, trait anxiety, and negative affect decrease among CA survivors completing the HRVB intervention.

HRV biofeedback is a technique that combines slow paced breathing with the use of accurate, moment-to-moment physiological monitoring. The goal is to make internal cardiac information available to people in order to help them learn how to increase the beat-to-beat variability in their heart's activity and thereby increase parasympathetic activity of the autonomic nervous system. Apart from active interventions such as exercise training that reliably increase HRV but that may be inappropriate for many cardiac patients, HRV biofeedback is an easy-to-implement technique which allows people to monitor and then ultimately alter their parasympathetic activity. Research is needed to determine whether HRV biofeedback training has beneficial consequences for mental and cardiovascular health in patients who have experienced serious, life-threatening cardiac events. The investigator believes that cardiac arrest survivors, in particular, may stand to benefit from such an intervention because many of them experience clinically significant psychological distress after their medical event. Distressed cardiac patients may be especially motivated to learn to influence their own heart activity in order to improve their own HRV, reduce their cardiovascular risk, and lessen their symptoms of psychological distress. Therefore, it may be wise to harness this motivation in the service of helping these patients deliberately learn to alter their own autonomic activity rather than simply breathing at a rate that automatically improves HRV without any learning process. By providing patients with an external (e.g., visual) form of feedback about their otherwise largely inaccessible autonomic physiology (i.e., vagus nerve activity), the investigator will conduct a feasibility study of HRV biofeedback training with the goal of increasing HRV and reducing anxiety symptoms. The purpose of this pilot study is to examine the feasibility of enrolling 10 participants and assessing the feasibility, acceptability, appropriateness, and usability of the at-home, multi-week HRV biofeedback training as well as participants' compliance with the intervention. Additionally, the purpose of the study is to assess whether participants generally show a decrease in cardiac-related interoceptive fear, a decrease in trait anxiety, a decrease in negative affect, and an increase in HRV during the course of the study. The data collected from participants as part of this feasibility pilot will influence the decision to continue with a larger randomized clinical trial using the methods in this pilot together with a control group. Progress will be monitored with Polar H10 heart rate monitor - a supremely precise heart rate sensor that comes with the Polar Pro chest strap. It will be used with a smartphone app Elite HRV - which is non-experimental.

The intervention involves heart rate variability biofeedback (HRVB) administered via a smartphone app (Elite HRV) that receives real-time cardiac information from a chest-worn heart rate monitor (Polar H10).

Participants in this intervention group complete at-home heart rate variability biofeedback (HRVB) training using a chest-worn heart rate monitor and a smartphone app. They complete at least 10 minutes per day of HRVB training on at least 5 days per week for 3 weeks.

First, participants are taught how to do relaxed, abdominal breathing. Second, they are taught how to breathe at a slow rate of 0.1 Hz (i.e., one completed breath cycle every 10 seconds). Third, they are taught how to monitor their heart rate variability (HRV) in real time using the smartphone app, which receives data wirelessly via Bluetooth from the heart rate monitor. Participants are instructed that their goal is to increase their HRV during the three weeks of at-home practice.

Percentage of Eligible Cardiac Arrest (CA) Survivors Whom we Approach Who Ultimately Agree to Participate in the Pilot Study

This is to assess the feasibility of enrollment in the trial. The denominator for this metric is the number of potential participants who were approached and contacted by the study team who were determined to be eligible for the study. The numerator is the number of participants who enrolled in the study (i.e., 10 participants).

As a measure of intervention compliance, this is to assess the percentage of participants who complete a majority (>= 8 of 15) of the at-home HRVB sessions.

This is to assess the intervention's feasibility. The percentage of participants who report scores >= 4 for the feasibility total score reflects the percentage of participants who indicated that the intervention is adequately feasible.

This is to assess the intervention's acceptability. The percentage of participants who report scores >= 4 for the acceptability total score reflects the percentage of participants who indicated that the intervention is adequately acceptable.

This is to assess the intervention's appropriateness for reducing anxiety, the proportion of participants who report scores >= 4 would be adequate. This is to assess the intervention's appropriateness for reducing anxiety. The percentage of participants who report scores >= 4 for the appropriateness-for-reducing-anxiety total score reflects the percentage of participants who indicated that the intervention is adequately appropriate for reducing anxiety.

We will assess the percentage of participants who report total scores >= 68 for their rating of the intervention's usability using the System Usability Scale.

This is to assess the Visit-2-to-3 change in cardiac-related interoceptive fear measured as the within-person difference in the sum of the four cardiac-related items from the physical subscale of the Anxiety Sensitivity Index. The total score ranges from a minimum of 0 units on a scale to a maximum of 16 units on a scale. Lower scores indicate lower anxiety.

This is to assess the Visit-2-to-3 change in trait anxiety measured as the within-person difference in the total score of the trait version of the State-Trait Anxiety Inventory. The total score ranges from a minimum of 20 units on a scale to a maximum of 80 units on a scale. Higher scores indicate higher anxiety.

This is to assess the Visit-2-to-3 change in trait negative affect measured as the within-person difference in the total score of the negative subscale of the Positive and Negative Affect Schedule. The total score ranges from a minimum of 10 units on a scale to a maximum of 50 units on a scale. Lower scores represent lower levels of Negative Affect.

This is to assess HRV using participants' exported and deidentified data from the Elite HRV smartphone app. Specifically, HRV is operationalized as the natural log of the root mean square of the successive difference (lnRMSSD), a standard measure of beat-to-beat HRV. This HRV measure is recorded for each at-home training session completed by participants using the app and the heart rate monitor.

Inclusion Criteria: Age 18 years or older Fluent in English A diagnosis of cardiac arrest (CA) Time elapsed since their CA is less than 72 months Elevated post-traumatic stress disorder (PTSD) symptom total scores on the 17-item Post-Traumatic Stress Disorder Checklist (PCL) of 30 or higher (i.e., greater than the median in a prior sample of cardiac arrest survivors) or elevated PCL-5 scores of 30 or higher or Acute Stress Disorder Scale (ASDS) scores of 34 or higher Owns either an iPhone or Android smartphone in order to run the app involved in the intervention Exclusion Criteria: Breathing difficulty that does not allow participant to complete the intervention Inability to comply with the protocol (either self-selected or indicated during screening that s/he could not complete all requested tasks). This includes, but is not limited to, patients with a level of cognitive impairment indicative of dementia and patients with current alcohol or substance abuse, and patients with severe mental illness (e.g., schizophrenia).