RespiraWorks / Ventilator

Fully-featured ICU ventilator design, optimized for manufacture using commonly available components and free to license. Repository tracks all mechanical, electrical and systems design, software, requirements and regulatory documentation.

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Controller must not assume a fixed air density value #415

Open jkff opened 4 years ago

jkff commented 4 years ago

Per system requirements in Valispace (RW-SYS-063 "The device shall be have the ability to integrate a hot water humidifier...", RW-SYS-137 "Ventilator shall operate at altitudes below 10k ft"), the device has to operate under a variety of air conditions that affect its density.

What is wrong Currently we assume a fixed air density

Air density varies significantly by altitude and by humidity.

We should have some extra signals to compute the correct air density.

jkff commented 4 years ago

CC @asmodai27

jkff commented 4 years ago

Note: the current equation is not technically correct even at fixed altitude/humidity, because the pressure inside the ventilator is not atmospheric. It differs from atmospheric pressure only by a couple tens of cmH2O, which is a couple kPa which is a relative difference of a couple% in density.

martukas commented 4 years ago

814 and associated software would solve the air density part of this problem

inceptionev commented 4 years ago

On the humidity side:

Inhale side: doesn't matter, because humidifier is between the ventilator and patient.
Exhale side: determine if humidity makes enough of a difference to violate requirements bounds, and implement fix if determined to be an issue.