Cardiovascular engineering
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The purpose of the study was to asses the potential use of pulse wave velocity (PWV) and digital volume pulse (DVP) as estimators of systolic (SBP) and diastolic (DPB) blood pressure. Single and multiple correlation studies were conducted, including biometric parameters and risk factors. Brachial-ankle PWV (baPWV) and DVP signals were obtained from a Pulse Trace PWV and Pulse Trace PCA (pulse contour analysis), respectively. ⋯ The best SBP multiple regression model for SBP achieved r = 0.997 by considering the heart-finger PWV (hfPWV measured between R-wave and index finger), WHR and heart rate. Only WHR was significant in the DBP model. Our findings suggest that the hfPWV photoplethysmography signal could be a reliable estimator of approximate SBP and could be used, for example, to monitor cardiac patients during physical exercise sessions in cardiac rehabilitation.
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Comparative Study
Methods for calculating coronary perfusion pressure during CPR.
Coronary perfusion pressure (CPP) is a major indicator of the effectiveness of cardiopulmonary resuscitation in human and animal research studies, however, methods for calculating CPP differ among research groups. Here we compare the 6 published methods for calculating CPP using the same data set of aortic (Ao) and right atrial (RA) blood pressures. CPP was computed using each of the 6 calculation methods in an anesthetized pig model, instrumented with catheters with Cobe pressure transducers. ⋯ The CPP achieved by standard closed chest CPR is typically reported as 10-20 mmHg. Within a single study the CPP values may be comparable; however, the CPP values for different studies may not be a reliable indicator of the efficacy of a given CPR method. Electronically derived true mean coronary perfusion pressure is arguably the gold standard method for representing coronary perfusion pressure.
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Measuring heart rate variability (HRV) is widely used to assess autonomic nervous system function. It requires accurate measurement of the interval between successive heartbeats. This can be achieved from recording the electrocardiogram (ECG), which is non-invasive and widely available. ⋯ However, we found that the PPG signal is especially vulnerable to motion artifacts when compared to the ECG, preventing any HRV analysis at all in a significant minority of PPG recordings. Our results demonstrate that even though PPG provides accurate interpulse intervals to measure heart rate variability under ideal conditions, it is less reliable due to its vulnerability to motion artifacts. Therefore it is unlikely to prove a practical alternative to the ECG in ambulatory recordings or recordings made during other activities.
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The aim of the present study was to investigate, whether pulse transit time (PTT), a popular index of arterial stiffness at rest, can be also used as such, during steady state exercise. For this purpose, twelve male volunteers exercised on a cycle ergometer for 70 min on three separate occasions whereas, cycling cadence and workload were manipulated in order to produce diverse cardiorespiratory responses. PTT, blood pressure, cardiac output and respiratory frequency were measured during exercise. ⋯ However, forward stepwise multiple regression analysis revealed that 71% (P < 0.001) of PTT changes from rest (DeltaPTT) variability was attributed to changes in cardiac output, SP and SP to cardiac output ratio. In the same model, total peripheral resistance did not exert significant influence on DeltaPTT variability. In conclusion, PTT is a reflection not only of SP but also of cardiac output changes per se and in combination with cardiac output (SP to cardiac output ratio) and should not be used as a pure marker of arterial stiffness under marked exercise cardiovascular and respiratory perturbations.