Developing and testing a Smart Wearable System for Sensing Stress of Veterans with PTSD

Abstract

Post-traumatic stress disorder (PTSD) is a mental disorder that can develop after having experienced a traumatic event and in which a person experiences trauma-related symptoms or impairments in everyday functioning that last for at least a month and sometimes for life (Friedman, F2015). In order to be diagnosed with PTSD, a person must have four typical symptoms: intrusion symptoms, avoidance symptoms, negative alterations in cognition and mood and alterations in arousal and reactivity (Friedman, 2015).

Currently, two therapies show a high effectiveness rate (around 70%) in treating PTSD: Cognitive behavioral therapy (CBT) and Eye Movement Desensitization and Reprocessing (EMDR). But they are restricted to conditions and devices. There are other self-management methods like meditation, breathing exercise and yoga. But those methods focus on regulating symptoms in the short term and the effectiveness is not well supported by studies.

It is envisioned that by integrating biofeedback sensors into a wearable product, verifying symptoms can be unobtrusive and stress can be monitored very often. By looking into the existing products, there are already many wearables which can detect stress by measuring some physiological signals like heart rate, heart rate variability, breathing rate or electrodermal activity. Physiological signals are more accessible to detect and are ideals measures for real-time monitoring. However, their accuracies are not high and easily compromised by the environment. The most sensible bio-signal combination is still not found out yet. And the cognitive or emotional aspects of stress is more difficult to detect. Thus a more intuitive method is decided to combine bio-signal with subjective feeling.

Based on those literature study and preliminary field work, the vision of the project was formulated and the mission was focused on sensing the stress and making the communication between data and users with a later aim of coping with it.

The embodiment of the concept was divided into two design iterations. The first design iteration aimed at selecting the right physiological sensors and validating the sensor quality and a self-reporting tool. The second design iteration focused on improving the product wearability and product style. In the first design iteration, some physiological sensors were chosen regarding different criteria. Four categories of sensors were selected including a heart rate sensor, a GSR sensor, a temperature sensor and an accelerometer. Based on the sensor sensibility on different body positions, the first prototype was decided to be a chest vest.

The first user test was conducted with 11 male students from TU-Delft to identify the technological features of the prototype 1 in recognizing different stress levels and development of the stress experiences. Besides, a self-reporting method was validated in this experiment by providing a self-reporting tool to the participants. The result was that physiological sensors are able to recognize the stress but they are not accurate enough to distinguish the different level of stress. And the self-reporting tool can reflect users’ real-time perception of stress to some extent. Some design insights were collected from the interviews to apply to the next prototype.

In the second design iteration, an interaction vision was generalized based on the updated concept. The product style was formulated after a style study and the wearability was improved by changing some details and making it wireless. The second user test was conducted with on participant from TU-Delft. The final integrated prototype can detect the stress and body movement to some extent. But it is still not accurate enough to differentiate stress levels. More experiments and research should be done to develop this wearable product further.