A region of the lung that had low oxygen and conversely high CO2 would be suggestive that that part of the lung is poorly ventilated. So there's something going wrong with bringing enough blood, good air in and out of that area. And then finally, the skeletal muscle, which we alluded to earlier, sympathetic nervous system can dilate here,. unlike most other areas of the vasculature of the tissues. The metabolites are really big control mechanisms for blood flow as well; increase of denizine, potassium, hydrogen ions.