"Subsalve" Helmet Non-Invasive Ventilation Set-up with safety features
The Respironics piece is a spring-loaded, one-way directional valve. When the flow fails, it leaves three ports on the side open (~2cmH2O).
This still needs to be tested to determine how much fresh gas can be drawn through that port. This setup can be an effective and easy way for any helmet to allow the hood to open instead of close in case of an emergency.
Pressure relief setup: To reduce COVID19 virus aerosolization, you must use viral filters with the helmet. Unfortunately, filters can clog easily with condensate. This following setup will provide a pressure relief feature and prevent the filter from clogging.
First, the standard respiratory limp should point up; this will keep fluids from running down into the filter. You still have your PEEP valve to control pressure; you will need to add a second PEEP valve and point it down low. Set the second PEEP valve on higher pressure than the primary PEEP. If the filter connected to the primary PEEP valve gets clogged, then the secondary PEEP valve will kick in and act as an overpressure valve. As an example: The primary PEEP is set at 10 centimeters and the secondary PEEP is set at 12 or 15 centimeters. The secondary PEEP acts as the overpressure valve while also reducing any significant pressure increase.
Thanks to multiple teams, including Subsalve, helmet developers are continuing work to fight the pandemic, including delivering kits to underdeveloped countries. Countries like Nigeria, the Philippines, and a few places in Central America have approved helmet-based ventilation and will use it for patients in respiratory distress.
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