EquivitalTM Technical
How the Equivital System works : System Overview
Fig 1. Sensor Application Diagram
system is the Sensor Electronics Module (SEM) which attaches to the chest via a strap arrangement (prolonged use) or self-adhesive pads (short term use by paramedics or first responders). The SEM collects data concerning a wearer's cardio-respiratory status, activity status, thermal status and neurological status.
The sensor transmits this data on a wireless "personal area network" (PAN) to a receiving device. (A PAN is a short range (a few meters) wireless link which allows data to be sent between two or more devices on or near a person)
The choice of receiving device used is selectable at the point of order and currently the following personal area network options can be supplied:
- Type 0 PAN interface - A low power packet radio interface designed for use in applications within the United States Military.
- Type 1 PAN interface - Bluetooth Transceiver supporting the Bluetooth defined Serial Port Profile (SPP).
The sensor communicates with the wireless receiving device which may either record and display the data locally (e.g. on a PC which contains an integral Bluetooth transceiver) or relay the data over further wide area communications networks before it is displayed on a remote monitoring station.
The wireless receiving device used is dependent on the type of PAN interface ordered.
For the Type 0 PAN interface, the sensor is designed to use a protocol suitable to send data to a US Department of Defense developed receiver/data logger.
The Type 1 PAN interface is designed to allow a system operator more flexibility in choice of receiving device and hence uses the communications standard Bluetooth to provide the wireless data transfer. This allows the device to be used with any receiving unit which has a Bluetooth compliant radio embedded in it providing it supports the Bluetooth defined Serial Port Profile. In the simplest case, this can be a personal computer running a viewing application which allows a health care professional to monitor the data output from the sensor. However, it is also possible that the sensor may be integrated in a larger scale monitoring system and data network (e.g. including location and mapping functions), in which case the system operator will provide overall information on how to operate the sensor within the environment.
The system is provided with a Windows based viewing application "Equivital Viewer" which enables the following data from a sensor to be displayed and recorded.
- Heart Rate
- Heart Rate Indications
- Respiration Effort Rate
- Skin Temperature
- Body Position
- Motion
- Sensor information and diagnostics
It also allows the health care professional to set thresholds and limits specific to the monitoring task being undertaken and also to store data for future analysis.
Disclosure Control
The sensor sends data in two forms:
1. Partial disclosure, where the SEM processes the data to form a "Physiological Welfare Index". This algorithm gives the following classifications (other application-specific ones are available):
o RED — high risk/unsustainable physiology
o YELLOW — physiology level requiring more detailed analysis
o GREEN — low risk/normal physiology
2. Full disclosure, where all life signs are transmitted back to a remote centre or local device for analysis. This allows de tailed monitoring during medical evacuations and remote triage before the patient arrives at hospital.
| Heart rate |  | The QRS detection algorithm used offers performance benefit over a simple R wave detector, which has known vulnerabilities. The SEM conforms to ANSI/AMIEE standard EC13 for Cardiac Monitors and uses a novel two lead ECG measurement to provide high quality Cardiac data. |
| Resp rate |  | Respiration rate or effort is primarily obtained from the expansion of a belt around the wearer's chest. Future versions of the SEM will also derive respiration rate from ECG measurements and from thoracic impedance measurements. |
| Motion / Position |  | An indication of the wearer's motion is obtained from a motion sensor built into the SEM and is classified into three levels of activity: 'Stationary', 'Low' or 'High' activity. The sensor is also used to detect the wearer's orientation, classified as: 'Upright', 'Prone', 'Supine', 'Inverted' or 'Side'. |
| Temp |  | Skin temperature of the wearer’s chest is measured by a clinical grade thermistor. This temperature is included in a calculation of the wearer’s activity status to derive a measure of predicted thermal strain. |
| Impact Detection |  | The motion sensor in the SEM can detect potentially harmful movements that could have been caused by heavy impacts and falls. |
| Welfare Indication |  | The parameters described above are correlated together in context with each other according to a proprietary algorithm in order to form a Physiological Welfare Indicator, providing a measure of the wearer's primary cardio-respiratory status and supplemental information on the user's thermal, neurological and activity status. |
Technical Specifications - General
| Device Classification | |
| Shock Protection: | Type BF Applied Part , Internally Powered Equipment |
| Environmental Protection: | IP67 (0.4m/30mins) |
| Flammable Gas Protection: | Unprotected |
| Mode of Operation: | Continuous |
| FDA Device Classification: | Class II |
| EU Device Classification: | Class IIb |
| Chest Harness /Belt | ||
| Size (circumference): | Small: | 40mm x 108mm |
| Medium: | 40mm x 116mm | |
| Large: | 40mm x 124mm | |
| Extra Large: | 40mm x 131mm | |
| Weight: | 100g | |
| Duration of Use: | 24 HRs | |
| Operating temperature: | -10°C to +55°C | |
| Operating Humidity: | 10% to 75% RH Non-Condensing | |
| Storage Temperature: | -20°C to +65°C | |
| Storage Humidity: | 5% to 90% RH Non-Condensing | |
| Air Pressure: | 570hPA - 1060hPA | |
Sensor Electronics Module
| General | |
| Size (overall dimensions): | 123mm x 75mm x 14mm |
| Weight: | 75g |
| Power: | 2 x 1.5v AAA LR03 Alkaline cells or |
| 3.7V 740mA Li-Ion rechargeable cell | |
| Li-Ion Recharge Time: | From Flat 2hrs |
| Operating temperature: | -10°C to +55°C |
| Operating Humidity: | 0% to 95% RH Non-Condensing |
| Storage Temperature: | -20°C to +65°C |
| Storage Humidity: | 0% to 95% RH Non-Condensing |
| ECG | |
| No of leads: | 2 |
| Sampling frequency: | 256 Hz |
| Resolution: | 10 bits |
| Voltage range: | +/- 5mV |
| CMRR: | >85 dB |
| Frequency Range: | Diagnostic Setting: 0.3 - 50 Hz (3dB points) |
| Monitor/Ambulation Setting: 7Hz - 50Hz (3dB points) | |
| Heart Rate Range: | 0 - 255 bpm |
| 0 - 300 bpm (Type 1) | |
| Heart Rate Calculation Frequency: | 15 seconds |
| Heart Rate Accuracy: | <+/-5bpm/10% |
| Lead Off Sensing: | 50KHz AC / 2uA |
| Chest Expansion Respiration Effort | |
| Measurement type: | Resistive strain gauge |
| Sampling frequency: | 25.6 Hz |
| Resolution: | 10 bits |
| Frequency Range: | 0.05 - 7 Hz |
| Breathing Rate Range: | 0 - 60bpm |
| Breathing Rate Accuracy: | +/- 2 bpm Static Use |
| +/- 3 bpm Moderate Ambulation Activity (e.g. walking) | |
| +/- 6 bpm High Ambulation Activities (e.g. running/ heavy carrying) | |
| Breathing Rate Reporting Frequency: | 15 seconds |
| Temperature | |
| Sampling frequency: | 0.25Hz |
| Resolution: | 10 bits |
| Range: | 10°C - 45°C |
| Sensor Accuracy: | <35.8C and > 41C +/- 0.3 C |
| 35.8C to 37C +/-0.2C | |
| 37 to 39 C +/- 0.1C | |
| 39C to 41 C +/- 0.2 C | |
| Measurement type: | Thermistor |
| Temperature Reporting Frequency: | 15 seconds |
List of approvals: (note some formal certification is still in progress (environmental)):
- ANSI/AAMI EC13: 2002 – Cardiac Monitors, Heart Rate Monitors and alarms
- ANSI/AAMI ES1 – Safe current limits for electro-medical apparatus 1995
- ASTM E1112-00 Standard Specification for Intermittent Determination of Patient Temperature
- IEC/EN60601-1 Part 1(2001) Medical Electrical Equipment : General Requirements for Safety
- IEC60601-1-2 Part 1 : Collateral Standard : Electromagnetic Compatibility – Requirements and Test
- EN300-019-2-7 : Environmental engineering ; Environmental conditions and environmental tests for telecommunications equipment; Part 2-7: Specification of environmental tests; Portable and Non Stationary Use
- EN300-019-2-1 : Environmental engineering ; Environmental conditions and environmental tests for telecommunications equipment; Part 2-1: Specification of environmental tests; Storage
- IEC60068-2-18 – IP67 0.5m/30min
- FCC CFR47 Pt15