WOB questions

[Brad_Horn]

I have some questions about WOB chart.
1. Is the X-axis unit Volume (liter)? If yes, what volume it is referring to? Lung? According to the chart, X value is decreasing during inhale, so I guess it's not the volume of lung?

2. I assume Y-axis is not absolute pressure value but difference pressure between 2nd stage and the environment. Is that correct?

3. If it's a P-V diagram, I guess I can say that the color area is the "work" of breathing. But if it's "work", the unit should Joule. How does is transform to Joule/liter?

4. If I google "Work of breathing", I could find some more articles that is discussing P-V diagram and respiratory work. However, the figure they described is more like the picture below. The shape goes diagonal and it passes the origin point. Are they talking the same thing?

The following might be useful for you in stepping you through how the WOB of the OC side of a BOV has been tested http://www.deeplife.co.uk/or_files/DV_DL_ALVBOV_Breathing_Params_A3_100318.pdf