Annals of biomedical engineering
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Multicenter Study Clinical Trial
Heart rate variability dynamics during low-dose propofol and dexmedetomidine anesthesia.
Heart rate variability (HRV) has been observed to decrease during anesthesia, but changes in HRV during loss and recovery of consciousness have not been studied in detail. In this study, HRV dynamics during low-dose propofol (N = 10) and dexmedetomidine (N = 9) anesthesia were estimated by using time-varying methods. Standard time-domain and frequency-domain measures of HRV were included in the analysis. ⋯ Prior to loss of consciousness, an increase in HF component power indicating increase in vagal control of heart rate (HR) was observed for both anesthetics. The relative increase of vagal control over sympathetic control of HR was overall larger for dexmedetomidine which is in line with the known sympatholytic effect of this anesthetic. Even though the inter-individual variability in the HRV parameters was substantial, the results suggest the usefulness of HRV analysis in monitoring dexmedetomidine anesthesia.
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Comparative Study Clinical Trial
Non-invasive estimation of cardiac output in mechanically ventilated patients: a prolonged expiration method.
A non-invasive method for the estimation of cardiac output in mechanically ventilated patients is described. The method is based on prolonged expiration, and relies on measurement of gas concentrations and flow rate. A pneumatic system, with an ad hoc designed orifice resistance, has been made and experimentally characterized to adapt the breathing circuit to this application. ⋯ Difference standard deviations between paired measurements is 0.72 L min(-1) for the first algorithm and 1.07 L min(-1) for the second one. Standard deviation obtained by the application of the first algorithm is slightly lower than those relative to other minimally invasive techniques. Through prolonged expiration, and standardization and automation of the procedure on mechanically ventilated patients, the proposed system allows to obtain a non-invasive estimation of cardiac output.