# Differential Measurement of Involuntary Breathing Movements

## TL;DR

A low-cost device called bioSense was developed to measure involuntary breathing movements in free divers during breath-holding.

## Contribution

The novel bioSense device uses differential accelerometer measurements to capture breathing movements in a non-intrusive and posture-agnostic way.

## Key findings

- The device successfully captured involuntary breathing movements during static breath holds.
- Data was collected and compared with a force plate measurement system in a pilot study.
- The device's design allows for non-intrusive and posture-agnostic data acquisition.

## Abstract

Free divers are known to experience a physiological response during extreme breath holding, causing involuntary breathing movements (IBMs). To investigate these movements, a low-cost multi-core ESP32-Pico microcontroller prototype was developed to measure IBMs during a static breath hold. This novel device, called the bioSense, uses a differential measurement between two accelerometers placed on the sternum and the xiphoid process to acquire breathing-related movements. Sensor placement allowed for data acquisition that was posture- and body-shape-agnostic. Sensor placement was also designed to be as non-intrusive as possible and precisely capture breathing movements at configurable sampling rates. Measurements from the device were sent over WiFi to be accessed on a password-protected webserver and backed up to a micro-secure digital (microSD) card. This device was used in a pilot study, where it captured the various phases of breathing experienced by recreational free divers alongside a force plate measurement system for comparison.