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.
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Blast-related traumatic brain injury is the most prevalent injury for combat personnel seen in the current conflicts in Iraq and Afghanistan, yet as a research community,we still do not fully understand the detailed etiology and pathology of this injury. Finite element (FE) modeling is well suited for studying the mechanical response of the head and brain to blast loading. This paper details the development of a FE head and brain model for blast simulation by examining both the dilatational and deviatoric response of the brain as potential injury mechanisms. ⋯ The largest predicted strains were generally less than 10%,and occurred after the shock wave passed through the head. For blasts with high impulses, CSF cavitation had a large role in increasing strain levels in the cerebral cortex and periventricular tissues by decoupling the brain from the skull. Relating the results of this study with recent experimental blast testing suggest that a rate-dependent strain-based tissue injury mechanism is the source primary blast TBI.
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Tricuspid regurgitation (TR) is present in trace amounts or more in 82-86% of the population and is greater than mild in 14% of the population. In severe cases, it can contribute to right heart failure and adversely affect mitral valve repair durability. One major cause of TR is the dilation of the tricuspid annulus, which alters the geometry of the annulus from a saddle-shape to a more planar profile. ⋯ In addition displacement of the PMs resulted in a significant (p ≤ 0.01) reduction in TR, although the actual volume reduced was minimal (1.2 mL). Stretch values were measured for the anterior and posterior leaflet under both physiologic and pathologic conditions for the first time. Further, these results provide an understanding of the effects of geometric parameters on valve mechanics and function, which may lead to improved TV repairs.
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Concussions sustained during college and professional football careers have been associated with both acute and chronic neurologic impairment. The contribution of subconcussive impacts to this impairment has not been adequately studied. Therefore, we investigated the relationship between subconcussive impacts and concussion history on clinical measures of neurologic function. ⋯ College football players sustain approximately 1,000 subconcussive impacts to the head over the course of a season, but for the most part, do not demonstrate any clinically meaningful changes from preseason to postseason on measures of neurologic function. Changes in performance were mostly independent of prior concussion history, and the total number, magnitude and location of sustained impacts over one season as observed R(2) values ranged between 0.30 and 0.35. Repetitive subconcussive head impacts over a single season do not appear to result in short-term neurologic impairment, but these relationships should be further investigated for a potential dose-response over a player's career.