Medical engineering & physics
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Surgical or critically ill patients often require continuous assessment of cardiac output (CO) for diagnostic purposes or for guiding therapeutic interventions. A new method of non-invasive CO estimation has been recently developed, which is based on pressure wave analysis. However, its validity has been examined only in silico. ⋯ SVB yielded very reproducible CO estimates (ICC=0.84, mean difference 0.27 ± 0.73 L/min, PR = 16.7%). SVB-derived CO was comparable with Doppler measurements, indicating a good agreement and accuracy (ICC = 0.74, mean difference = -0.22 ± 0.364 L/min, PR ≈ 15). The basic mathematical and physical principles of the SVB method provide highly reproducible and accurate estimates of CO compared with echocardiography.
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Pilon fractures are commonly caused by high energy trauma and can result in long-term immobilization of patients. The use of an external fixator i.e. the (1) Delta, (2) Mitkovic or (3) Unilateral frame for treating type III pilon fractures is generally recommended by many experts owing to the stability provided by these constructs. This allows this type of fracture to heal quickly whilst permitting early mobilization. ⋯ The results indicate that the model with the Delta frame produced the lowest relative micromovement (0.03 mm) compared to the Mitkovic (0.05 mm) and Unilateral (0.42 mm) fixators during the stance phase. The highest stress concentrations were found at the pin of the Unilateral external fixator (509.2 MPa) compared to the Mitkovic (286.0 MPa) and the Delta (266.7 MPa) frames. In conclusion, the Delta external fixator was found to be the most stable external fixator for treating type III pilon fractures.
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Reconstruction quality maintenance is of the essence for ECG data compression due to the desire for diagnosis use. Quantization schemes with non-linear distortion characteristics usually result in time-consuming quality control that blocks real-time application. In this paper, a new wavelet coefficient quantization scheme based on an evolution program (EP) is proposed for wavelet-based ECG data compression. ⋯ By using the ECG signals saved in MIT and PTB databases, many experiments were undertaken for the evaluation of compression performance, quality control efficiency, data dependency influence. The experimental results show that the new EP-based quantization scheme can obtain high compression performance and keep linear distortion behavior efficiency. This characteristic guarantees fast quality control even for the prediction model mismatching practical distortion curve.
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Rapid and effective determination of biomechanical properties is important in examining and diagnosing skin thermal injury. Among the methods used, viscoelasticity quantification is one of the most effective methods in determining such properties. This study aims to rapidly determine skin viscoelasticity by optically tracking the local surface wave. ⋯ The viscoelastic coefficients from four healthy samples show a potential viscoelasticity variation of porcine skin. In one sample, the two coefficients were evidently higher than those in a healthy area if the skin was slightly burned. These results indicate that the proposed method is sensitive, effective, and quick in determining skin viscoelasticity.
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Integration of various brain signals can be used to determine cerebral autoregulation in neurocritical care patients to guide clinical management and to predict outcome. In this review, we will discuss current methodology of multimodal brain monitoring focusing on secondary 'reactivity indices' derived from various brain signals which are based on a 'moving correlation coefficient'. ⋯ Of the various primary neuromonitoring sources which can be used to calculate reactivity indices, we will focus in this review on indices based on transcranial Doppler (TCD), intracranial pressure (ICP), brain tissue oxygenation (PbtO2) and near infrared spectroscopy (NIRS). Furthermore, we will demonstrate how reactivity indices can show transient changes of cerebral autoregulation and can be used to optimize management of arterial blood pressure (ABP) and cerebral perfusion pressure (CPP).