Thanks for your comment. I have 2 Pulmonologists, one for cancer the other for interstitial lung disease. I do regular pulmonary function tests which are moderate to severe loss and indicate I have pulmonary fibrosis (not COPD - restrictive vs. obstructive lung disease). I have multifocal lung cancer so there is always a nodule to watch. The drop in MCHC occurred after SBRT treatment on two nodules which caused a flareup in my pulmonary fibrosis and I am now on permanent O2 for exertion/sleep. So I am alert to any other cause impacting my breathing. I also am disturbed that Primary Care doctors tell patients that their blood work is normal when the reports indicate something is abnormal.