After 6 years of developing symptoms, my wife has recently been diagnosed with Primary lateral sclerosis (for her purposes, much like ALS). Breathing has become a major problem. Pulmonary function test showed marginally okay results (PCO2 of 44, PO2 of 81). Pulse oxygen is usually 94- 96%, but over-night pulse-ox test showed low O2 about 15% of the time. Pulmonologist, who does not have ALS/PLS patients but talked with ALS clinic, ordered O2 supplementation. O2 supplementation has not helped much. She still has trouble breathing, and is always fatigued. Doctor says she is not close to needing NIPPV because O2 is okay. I am concerned that she may still retain too much CO2 (her expiratory volume was 86% and residual volume far above predicted). We are considering buying a home pulse-ox to help gauge her condition, and whether we need to take corrective action. We have read about CO2 problems with PLS/ALS, but I couldn