Embedded Files
Vacuum System
The internal frame consists of polycarbonate arches that support nylon rods. The nylon rods slide into slots in the polycarbonate arches and support the fabric structure of the LBNP. (Figure A)
Internal Frame
The fabric shell, made of air-tight nylon can be wiped down with alcohol and is thin enough so the patient can interface with the existing hospital mattress. The shell includes a clear vinyl window for patient monitoring and a velcro lined neoprene seal that attaches to the patients waist. On the side wall of the fabric shell, two plastic ports are in place, the first to connect a vacuum and the second has a port to connect a pressure monitor.
Fabric Shell
The Lower Body Negative Pressure (LBNP) chamber's design of a polycarbonate and nylon internal frame, surrounded air tight fabric shell allows for easy assembly and use on an existing hospital bed.
Figure A: CAD of final LBNP on a mattress.
Figure D: Final LBNP design with the fabric shell partially unzipped to show frame.
To monitor the chamber's conditions, an electronic pressure transducer and flow meter can be connected to ports on the LBNP. Both of these sensors connect to a shared readout, powered by an Arduino, that can feed live data about air flow through the chamber, and pressure to both an LCD readout and to a computer through USB. The flow meter works by channeling air flow through a 120mm PC fan with an internal encoder (Figure B), rotations of the fan can be counted and converted to airflow. The pressure transducer is an analog pressure transducer rated for a range of -14 to 14 kPa. The pressure transducer sends a 0 to 5V signal to be interpreted by the Arduino. The path of the air flow through the LBNP, flow meter and vacuum is shown in Figure C.
Flow Rate and Pressure Monitoring
To regulate pressure, there is a ball valve that can be placed in line with the vacuum hose connection to cut off flow, or can be located in parallel with the connection to the LBNP to divert some air flow and pressure away from the LBNP to the atmosphere, this reduces strain on the vacuum.
Figure C: Block diagram showing the air flow path.
Figure B: CAD of flow meter.
Page updated
Report abuse