| Breif Req | Requirement | Justification | Specifcation |
| Attachment | The device must stay attached to the user throughout its use. | The device is to be worn on the legs during its use, so it must stay attached so the device can function as intended. | 1.1 The device must not be displaced 5% of the total lower leg length after use. |
| Size | The device must be able to fit into a confined area. | Places of intended use are typically of small dimensions such as office space, truckers, or passengers on a plane |
2.1 The device attached to patient’s leg must function within a seat pitch (distance from one point on a seat to that same point of the seat behind it) of 28 in. 2.2 The device must allow at least a 120 deg angle of the lower leg to ensure blood flow is not 100% constricted. |
| Fit | The device must be able to fit the average circumference of a male and female human leg or foot when in use. |
VTE effects both males and females equally. Recurrent VTE is higher in males and pregnancy increases risk for females. | 3.1 The device must fit average male and female circumference of the upper calf of 35.9 ± 2.4 cm and 34± 2.5 cm respectively 3.2 The device must fit average male and female circumference of the ankle of 23.4 ± 1.5 cm and 21.9 ± 1.3 cm respectively. |
| Compression | The device must apply intermittent compression to the human lower leg. |
Compression mimics calf muscle contraction in order to increase blood flow to the popliteal vein. Intermittent pneumatic compression devices are currently the best modality of prevention of VTE. |
4.1 The compression must apply between 80 and 120 mmHg of pressure to the lower leg. 4.2 When activated by the sensors the compression device must apply pressure for 50 seconds followed by 50 seconds of deflation. This must continue until the sensors deactivate the compression. |
| Sound | The device must not produce obtrusive sounds and noises. |
Reduce social stigma of wearing the device and ensure that others aren’t bothered by the noise produced. |
5.1 The level of noise that the device produces must not exceed 55 dB. |
| Control System | The device must activate and inactivate due to specific threshold measurements from sensors. |
Individuals are only at risk for VTE if the correlates are detected above a specified threshold. |
6.1 The device must activate the compression system once a 1℃ increase is detected by the temperature sensor. 6.2 The device must activate the compression system once a 100 mL increase in lower leg volume is detected. 6.3 The device must deactivate the compression once the temperature and volume sensors return to their baseline measurements. |
| Battery (Duration of Use) |
The device’s battery must last for the duration of at risk period for VTE. |
Intended use is during long haul flights of 12 hours, an 8 hour work day and periods of sitting +4 hrs. The device must be able to stay powered for monitoring and during periods of activationthroughout the whole sitting. |
7.1 The device’s battery must be able to provide 12 hours of functionality including monitoring and compression. |
| Comfortability | The device must be made out of a comfortable material |
The device will be worn for hours at a time, so the device must be comfortable where the user won’t be irritated when wearing the device. |
8.1 The device must score XXX on a survey. |
| TSA Approved | The device must pass TSA guidelines for flights |
An intended user is those on long haul airplane flights, so the device must be allowed to go on an airplane. |
9.1 The device must pass TSA prescreening. |
| Leakage Current | Leakage current can lead to an electric shock, which is dangerous to the user. |
Device must comply with IEC 60601-1 series standards regarding battery operated medical devices. |
10.1 IEC 60601-1 series. |
| Skin Temperature Measurement | The device must measure local skin temperature in front of the tibia |
According to one study, skin temperature in the front of the tibia increased significantly during a study in which subjects remained sitting for 12 hours. Increases were seen in 4 – 12 hours. |
11.1 Device must be able to measure skin temperature of 32℃ +/- 2 degrees 11.2 Must be able to differentiate within a 1°C increase. |
| Volume Measurement | The device must measure volume in the leg below the knee. |
According to one study, the leg volume in the calf increased significantly during a study in which subjects remained sitting for 12 hours. Increases were seen in 4 – 12 hours. |
12.1 The device must detect volume increases of 4%. 12.2 The device must be able to be calibrated to the user’s normal leg size. |