Saturday, March 31, 2007

Putting The Parts Together

I have gotten many of the parts I need to build a prototype for the Pandemic Ventilator. I have two 120V Asco ½” solenoid valves for the inhalation and exhalation valves, and a 120V Burkert ¼” solenoid valve for the bellows fill valve. These valves must be direct acting and not the pilot operated type. They are rated for air as well as water. I got all the pipe fittings needed to connect the valves and other equipment. The magnetic switches are the type usually used for security systems. The PLC unit is a Direct Logic 06 DO-06DR from Automation Direct. I recycled an old control box from another project and I can rewire the switches and lights and buzzer to fit this project.

I tested the bellows unit I made last week to see how long the bag would last. In order to accelerate failure so as to find the weak points I cycled it manually under much higher pressure than it would normally be subjected to. It seems the weak areas are around the tube that is taped in, the taped end, and the edges that rub on the side of the bellows unit. I made some improvements in a second unit by clamping the taped end, allowing more space around the tube for flexing, and removing the sides and end of the bellows unit. It does not need the sides or end to contain the bag once the taped end is clamped into place. The clamp provides physical support to the taped end. I can use the bellows I made before as a lung simulator when I test the control system of the unit.

The plumbing work is done. It just needs the electrical connections made. I hope to be able to test the software for the control unit soon.

2 comments:

David Curran said...

This is a great idea. A similar thing was described at http://www.hackaday.com/2007/05/25/diy-powered-respirator/
He uses a power fan rather then a respirator. I wonder what the trade off is?

Dreamer said...

I checked out the hackaday site. The respirator described there is really for use when working in dusty environments. When someone works with a regular respirator, it can be a lot of work to pull the air in through the filter, and the fan will make it more comfortable. A similar system is used for medical applications however. It is called a CPAP unit for Continuous Positive Airway Pressure. These units can provide some assistance to someone who has difficulty breathing, but the patient must still be able to control their own breathing, and have the strength to exhale against the positive pressure. The system I am working on has a control system that will replace the breathing function entirely for a person whose lungs and breathing muscles are so compromised that they can not breath on their own.

Thanks for that file you sent me on the home made iron lung machine. That would actually do the job for a pandemic flu victim, however it is a large unit and most ICU staff are not experienced working with negative pressure ventilating equipment such as that. Still, it would work.