Have you had pulmonary function testing where you blow through a tube???? It is used in diagnosing COPD - an obstructive lung disease and Pulmonary Fibrosis - a restrictive lung disease. There will be a report on it. It should be available online provided by your doctor by law.
Based on your height, weight gender, etc., they predict what your value should be and then compare your actual result, and calculate the percent your results are of the predicted value. Such a test includes:
TLC = Total Lung Capacity and % Predicted
FVC (L) = Forced vital capacity in liters and % Predicted
FEV 1 = Forced expiratory volume in first second and % Predicted
FEV1/FVC = ratio of the two
Tracking these values tells doctor is you are getting worse.
My Inogen has settings 1-6 but they are pulse flow and NOT CONTINUOUS FLOW and the max setting may barely be comparable to 2L continuous flow (for night I have a stable concentrator which provides continuous flow)
My prescription is in continuous flow (2Liters), Unfortunately it is difficult to get measured in pulse flow.