Journal of clinical monitoring and computing
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J Clin Monit Comput · Oct 2016
The use of heart rate variability measures as indicators of autonomic nervous modulation must be careful in patients after orthotopic heart transplantation.
The precise relation between heart rate variability (HRV) and autonomic re-innervation has not been established explicitly in patients after orthotopic heart transplantation (OHT), but can be inferred from the fact that the HRV is reduced immediately after OHT and may increase gradually with time. The aim of this study was to investigate the residual HRV in patients about 1-2 years after OHT, as compared with patients after coronary artery bypass graft (CABG) surgery. Thirteen patients who had received OHT and 14 patients who had received CABG surgery were recruited. ⋯ The slope of the power law relation of HRV became positive in OHT patients, instead of negative in CABG patients. We conclude that patients after OHT have residual HRV which were characterized by severely depressed time and frequency domain HRV, increased HR and nHFP, decreased nVLFP, and positive slope of the power-law relation of HRV. The use of nHFP as the indicator of vagal modulation and the use of nVLFP as the indicator of renin-angiotensin modulation, thermoregulation and vagal withdrawal must be careful in the OHT patients.
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Resonance in pressure monitoring catheters is a well-known problem which was studied several years ago. Current piezoelectric devices have mechanical properties providing a resonance frequency and damping factor that theoretically assure resonance-free data. However, in particular cases, the coupling between the device, the catheter, and the vascular compliance of the patient could introduce artefacts in clinical settings leading to wrong pressure waveforms and values displayed in the monitor. ⋯ Results indicate that the presence of different catheters may alter significantly the acquired signal, up to an unacceptable level. Particular care should be used in the selection of the appropriate catheter. In particular, smaller diameters introduce higher damping coefficient that could help in avoiding undesired oscillations.
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J Clin Monit Comput · Oct 2016
Data clustering methods for the determination of cerebral autoregulation functionality.
Cerebral blood flow is regulated over a range of systemic blood pressures through the cerebral autoregulation (CA) control mechanism. The COx measure based on near infrared spectroscopy (NIRS) has been proposed as a suitable technique for the analysis of CA as it is non-invasive and provides a simpler acquisition methodology than other methods. The COx method relies on data binning and thresholding to determine the change between intact and impaired autoregulation zones. ⋯ The determination of the lower limit of autoregulation (LLA) was compared to a traditional binned data approach. Good agreement was found between the methods. The work highlights the potential application of using data clustering tools in the monitoring of CA function.