Our Hexoskin Smart Clothing, including the Hexoskin ProShirts and the Hexoskin Smart Shirts include 1-lead ECG, 2 channels for Respiratory Inductance Plethysmography, and a 3-axis accelerometer for activity tracking.
All Hexoskin Shirts (ProShirt and Smart Shirts) are equipped with cardiac and respiratory sensors. This wearable garment serves as an analog data collector. Hexoskin smart garments are connected to a small device (the Hexoskin recording device) that records 42,000 raw data points per minute and can store 600 hours of continuous raw data. The unique set of sensors integrated into the Hexoskin smart garment (ECG monitor, RIP sensors, and accelerometer) combined with the annotations and relevant information entered into the Hexoskin platform are reported in both raw data and processed data formats.
The Hexoskin platform provides the following physiological measurements (raw signals, data channels and analysis reports):
Three lead ECG 256 Hz, 1bits - Resolution LSB: 0.0064 mV
- Heart rate, QRS detection, RR intervals
- HRV Statistics and ratios
Dual-channel respiratory inductance plethysmography (RIP) 128 Hz, 16 bits
- Breathing rate, Expiration/Inspiration
- Tidal volume, Minute ventilation
3-axis Accelerometer 64 Hz, 13 bits
- Activity, Steps, Cadence
- Device position
Cardiac Sensors
Hexoskin Shirts are equipped with 3 cardiac sensors: 2 at the chest level and 1 near the right hip. These sensors are arranged in a CC5 lead configuration, which provides a 1-lead ECG.
Hexoskin collects data from a 1-lead ECG at a sampling rate of 256 Hz. The ECG is measured and recorded by 3 cardiac sensors made of 3 nylon silver-plated textile electrodes, embedded in the Hexoskin biometric garment. For clarity, the 1-lead ECG recorded by Hexoskin is specifically a Lead I ECG, offering insights into the electrical activity of the heart similar to the clinical Lead I configuration.
From this signal, the Hexoskin performs QRS detection and measures RR intervals between each QRS.The resulting RR intervals are then used to perform heart rate variability (HRV) analysis and are also used for sleep assessments. To supply the body with the appropriate amount of nutrients and energy, the heart changes its rhythm and power to increase the volume of blood that circulates in the body. Heart rate varies from beat to beat to respond to external or internal stimuli such as emotions, heat and physical exertion, respiration, circadian rhythm, and sleep.
A high HRV means that the heart rate changes rapidly to adapt to any situation. A low HRV means that the heart rate changes slowly and can be associated with stress and health issues. Age, fitness condition, diseases, medication, sleep, and movement are some of the factors that affect HRV. Many HRV values can be used as physiological markers (Kristal-Boneh et al., 1995). The Hexoskin technology computes the HRV index as described in the HRV guideline (Task Force of the European Society of Cardiology the North American Society of Pacing Electrophysiology, 1996) and returns the following values: SDNN, SDANN, RMSSD, LF normalized, HF normalized, LF power, HF power, total power and HRV triangular index.
Respiratory Sensors
The breathing sensors, made of wire lined into the fabric, are based on inductive plethysmography (RIP) technology. The respiration loops are located at the thorax and waist level.
As validated and demonstrated by several research teams, Hexoskin can accurately and reliably measure numerous lung function parameters, such as respiratory rate, minute ventilation, tidal volume as well as VO2 max (Marjanovic et al., 2017; Mouzoune et al., 2017; Villar et al., 2015).
The RIP sensors detect rib cage expansion and compression during respiratory cycles. The embedded loops are located at the thoracic and navel levels and allow for the monitoring of thoracic and abdominal breathing independently.
The Hexoskin generates a low current-low-voltage signal and transmits it to the RIP bands in the shirt. Based on the RIP band lengths, the signal oscillates at different frequencies. We monitor these changes in frequency and translate them to respiration values 128 times per second.
The RIP (Respiratory Inductance Plethysmography) bands have a resolution of 8 mL and there is a latency of 8 ms for inspiration/expiration event detection; the Breathing Rate and Minute Ventilation are calculated using the last 7 respiratory cycles. If you wish to see more details on the datatypes or data channels we collect, take a look at our API documentation page for some in-depth information.
Activity Sensors
Activity is monitored via a 3-axis accelerometer included in the recording device, and the device is placed in a convenient pocket on the right side of the waist. The activity represents the vectorial sum of the 3 signals derived from the accelerometer. It is a measure of changes of direction of the device and, incidentally, change of direction of the hip of the user.
The movement sensor also measures acceleration, cadence, step count, as well as energy expenditure. The acceleration of the device is in three-dimensional space. It also registers gravity, giving it a constant vectorial offset towards the center of the earth. The unit of acceleration is g, i.e., 9.8 m/s2. An acceleration of 1 g represents exactly the downwards acceleration that you would experience if you were jumping from a plane. The cadence represents the number of steps performed in a minute during a walk or a run; it is therefore reported in steps per minute. From the cadence, certain activities are automatically calculated. If the cadence is between 40 and 140 steps per minute, the user is most likely walking. If the cadence is between 140 and 240, the user is most likely running. The step count metric gives the total number of steps for any given activity. The number of steps is calculated for both feet (so the sequence left-right-left gives three steps). Finally, the energy expenditure takes into consideration the heart rate, gender, and age of the individual.
Sleep
Our team has also developed and validated decision tree algorithms for sleep state classification based on all physiological data collected by the Hexoskin sensors. The Hexoskin Smart Garment is comfortable and easy to set up and use, and patients can sleep in their natural environment. Also, Hexoskin allows for the recording of multiple nights’ sleep, and monitors movement, cardiac and respiratory function simultaneously. The Hexoskin sleep algorithm calculates various sleep metrics, such as total sleep time, sleep efficiency, sleep latency, sleep percent, as well as HRV. Hexoskin has been used in a number of sleep monitoring studies and can eventually be used as a screening test for sleep disorders (Gutta et al., 2015; Harrison et al., 2015; Pion-Massicotte, 2014; Rahman et al., 2015).