In a pre-recording phase, PPG wave amplitudes are normalized, allowing a real-time evaluation of the test as it proceeds. The operator is guided through an automated exam procedure, with continuous recording of pulse volume changes derived from the PPG sensor signals. An inflatable cuff is attached to the upper or forearm on the side where the hyperemic reaction will be tested. Reusable photo pulse plethysmograph or PPG sensors are clipped to the two index fingers of the test subject. While FSM evaluates the hyperemic response of brachial artery Pulse Wave Velocity, PAR records arterial pulse volume changes in the microvasculature of the fingertip. EndoCheck PAR profits from many years of experience in FMS testing in the same device. Over the last years, the automated and operator-independent EndoCheck PAR test procedure was developed, now available in the Vicorder® instrument, a proven device in clinical and research applications. The reusable PPG sensor is easily and comfortably clipped to a fingertip, similar to a pulse oximeter. Among other features the optical PPG signal is able to provide detection of blood volume changes in microvascular beds. for operator independent determination of Ankle Brachial Index (ABI). For more than 30 years in clinical and diagnostic use, mainly in internal medicine and angiology, photo plethysmographs, also photo pulse plethysmographs, or PPGs constitute an established technique in evaluating digital perfusion, e.g. In recent years, novel modalities were developed and introduced applying photo plethysmography in recording of arterial pulse amplitudes. This established technique is based on fingertip tonometry with the necessity of rather expensive disposable digital cuffs. Previous studies mainly applied fingertip peripheral arterial tonometry (PAT) to derive pulse volume amplitude changes after reactive hyperemia. Several testing variants are available in assessing vasomotor function by evaluating perfusion of the digital arteries. A deficiency of NO, strongly related to endothelial dysfunction, is a hallmark of cardiovascular diseases, predictive of poor clinical outcomes and of other complications. During brachial artery occlusion peripheral resistance is substantially reduced leading to a pronounced post-occlusive hyperemia in distal arterial segments, depending on bioavailability of nitric oxide due to shear stress.
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