The topic is not new to us. I am unable to open the link to the publisher therefore unable to determine if there is open access. http://www.ncbi.nlm.nih.gov/pubmed/25817901 Arterial flow waveforms, vascular tone, and chronic fatigue: A case report. Zundel MT1, Pattyn M2, Chelimsky TC3, Riess ML4. Author information Abstract We present the case of a patient with chronic fatigue secondary to Postural Orthostatic Tachycardia Syndrome (POTS) who had distinctive abnormalities in his arterial waveform morphology as assessed by pulse oximetry. Moreover, the patient's arterial waveform changed markedly from being supine to upright, suggesting that arterial flow patterns may be abnormal in our patient. Analysis of the waveform suggested a positional hypovolemia as the cause of his orthostatic intolerance. We review general aspects of arterial flow waveform analysis pertinent to health care providers and discuss the pathophysiology of POTS.