Manipulating recorded human breathing for reproduction

When recording human breathing for accurate simulation requires consideration of gaseous exchange. The strict volumes of inspiration and expiration may not match. This is a problem for any breathing machine that tries to accurately replicate human breathing. With no way to create this small imbalance between inhalation and exhalation, the piston extremes of reciprocation gradually move along the cylinder until and end wall is reached and the movement is restricted.

To solve this issue with the Digital Breathing machine, a software solution is applied to the recorded waveform trace. This calculates the start and end points of the trace and allows it to be tilted to ensure the piston does not ‘creep’ to beyond the limits of the piston stroke. This applies a very small correction to each data point. The overall effect is to make the trace fully reproduceable while minimising the error by spreading it incrementally across the recording.

An image of the correction can be seen below:

Conversion of human breathing traces

The top graph shows a sample human breathing recording. The graph below shows the movement required from the piston to reproduce that flow pattern. In blue is the trace required to reproduce it exactly. As can be seen this will gradually move to outside the operable limits of the cylinder. The yellow trace is the manipulated output, allowing the full reproduction of the waveform trace.

Back to part 1.

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