Does anyone have a reference on how COPD affects the venous waveforms? I'm doing dialysis AVF's and a few of my patients have pretty severe COPD. I'm getting outflow waveforms that are not really pulsitile and "flattened/forward flow only" in the subclavian/innominate with no visual stenosis. Hope that makes sense. Dialysis AVF/AVG's are a whole 'nother animal. I've gotten very good at these studies and wanting to add to my knowledge base.