Real-time effects of lateral positioning on regional ventilation and perfusion in an experimental model of acute respiratory distress syndrome

Low-volume lung injury encompasses local concentration of stresses in the vicinity of collapsed regions in heterogeneously ventilated lungs. We aimed to study the effects on ventilation and perfusion distributions of a sequential lateral positioning (30°) strategy using electrical impedance tomography imaging in a porcine experimental model of early acute respiratory distress syndrome (ARDS). We hypothesized that such strategy, including a real-time individualization of positive end-expiratory pressure (PEEP) whenever in lateral positioning, would provide attenuation of collapse in the dependent lung regions. A two-hit injury acute respiratory distress syndrome experimental model was established by lung lavages followed by injurious mechanical ventilation. Then, all animals were studied in five body positions in a sequential order, 15 min each: Supine 1; Lateral Left; Supine 2; Lateral Right; Supine 3. The following functional images were analyzed by electrical impedance tomography: ventilation distributions and regional lung volumes, and perfusion distributions. The induction of the acute respiratory distress syndrome model resulted in a marked fall in oxygenation along with low regional ventilation and compliance of the dorsal half of the lung (gravitational-dependent in supine position). Both the regional ventilation and compliance of the dorsal half of the lung greatly increased along of the sequential lateral positioning strategy, and maximally at its end. In addition, a corresponding improvement of oxygenation occurred. In conclusion, our sequential lateral positioning strategy, with sufficient positive end-expiratory pressure to prevent collapse of the dependent lung units during lateral positioning, provided a relevant diminution of collapse in the dorsal lung in a porcine experimental model of early acute respiratory distress syndrome

Model mechanicke cinnosti srdecni

Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Mapping of electrical potentials from the chest surface - preprocessing and visualization

<div>The aim of the paper is to present current research activity in the area of computer supported ECG processing. Analysis of heart electric field based on standard 12lead system is at present the most frequently used method of heart diseasediagnostics. However body surface potential mapping (BSPM) that measures electric potentials from several tens to hundreds of electrodes placed on thorax surface has in certain cases higher diagnostic value given by data collection in areas that are inaccessible for standard 12lead ECG. For preprocessing, wavelet transform is used; it allows detect significant values on the ECG signal. Several types of maps, namely immediate potential, integral, isochronous, and differential.</div><br /

Acute Digital Ischemia Associated with Closed Injury

Injury of an artery has a significantly worse prognosis for the patient than a venous injury. Blunt injuries of lower limb digital arteries with the development of acute ischemia present a very rare phenomenon. A crush mechanism with a defect of the non-wetted surface of vessel’s inner part and the development of subsequent thromboischemic lesion is essential for the development of ischemia. We report a blunt injury of the right lower limb in a patient after incorrect stepping with subsequent lesion of digital arteries and the development of acute acral ischemia of the right toes

Validation of new marker of fluid responsiveness based on Doppler assessment of blood flow velocity in superior vena cava in mechanically ventilated pigs

Abstract Background We studied a novel approach for the evaluation and management of volemia: minimally invasive monitoring of respiratory blood flow variations in the superior vena cava (SVC). We performed an experiment with 10 crossbred (Landrace × large white) female pigs (Sus scrofa domestica). Methods Hypovolemia was induced by bleeding from a femoral artery, in six stages. This was followed by blood return and then an infusion of 1000 ml saline, resulting in hypervolemia. Flow in the SVC was measured by Flowire (Volcano corp., USA), located in a distal channel of a triple-lumen central venous catheter. The key parameters measured were venous return variation index (VRV)—a new index for fluid responsiveness, calculated from the maximal and minimal velocity time intervals during controlled ventilation—and systolic peak velocity (defined as peak velocity of a systolic wave using the final end-expiratory beat). A Swan–Ganz catheter (Edwards Lifesciences, USA) was introduced into the pulmonary artery to measure pulmonary arterial pressure, pulmonary capillary wedge pressure, and continuous cardiac output measurements, using the Vigilance monitor (Edwards Lifesciences, USA). Results We analyzed 44 VRV index measurements during defined hemodynamic status events. The curves of VRV indexes for volume responders and volume non-responders intersected at a VRV value of 27, with 10% false negativity and 2% false positivity. We compared the accuracy of VRV and pulse pressure variations (PPV) for separation of fluid responders and fluid non-responders using receiver operating characteristic (ROC) curves. VRV was better (AUCROC 0.96) than PPV (AUCROC 0.85) for identification of fluid responders. The VRV index exhibited the highest relative change during both hypovolemia and hypervolemia, compared to standard hemodynamic measurement. Conclusions The VRV index provides a real-time method for continuous assessment of fluid responsiveness. It combines the advantages of echocardiography-based methods with a direct and continuous assessment of right ventricular filling during mechanical ventilation

Acute Severe Heart Failure Reduces Heart Rate Variability: An Experimental Study in a Porcine Model

There are substantial differences in autonomic nervous system activation among heart (cardiac) failure (CF) patients. The effect of acute CF on autonomic function has not been well explored. The aim of our study was to assess the effect of experimental acute CF on heart rate variability (HRV). Twenty-four female pigs with a mean body weight of 45 kg were used. Acute severe CF was induced by global myocardial hypoxia. In each subject, two 5-min electrocardiogram segments were analyzed and compared: before the induction of myocardial hypoxia and >60 min after the development of severe CF. HRV was assessed by time-domain, frequency-domain and nonlinear analytic methods. The induction of acute CF led to a significant decrease in cardiac output, left ventricular ejection fraction and an increase in heart rate. The development of acute CF was associated with a significant reduction in the standard deviation of intervals between normal beats (50.8 [20.5–88.1] ms versus 5.9 [2.4–11.7] ms, p < 0.001). Uniform HRV reduction was also observed in other time-domain and major nonlinear analytic methods. Similarly, frequency-domain HRV parameters were significantly changed. Acute severe CF induced by global myocardial hypoxia is associated with a significant reduction in HRV

The Cortisol to Cortisone Ratio during Cardiac Catheterisation in Sows

A possible effect of mini-invasive heart intervention on a response of hypothalamo-pituitary-adrenal stress axis and conversion of cortisone to cortisol were studied. We have analysed two stress markers levels (cortisol, cortisone) and cortisol/cortisone ratio in 25 sows using minimally invasive heart catheterisation as the stress factor. The values of studied parameters were assessed in four periods of the experiment: (1) the baseline level on the day before intervention, (2) after the introduction of anaesthesia, (3) after conducting tissue stimulation or ablation, and (4) after the end of the catheterisation. For statistical analyses we used the non-parametric Friedman test for four dependent samples (including all four stages of the operation) or three dependent samples (influence of operation only, baseline level was excluded). Statistically significant differences in both Friedman tests were found for cortisol and for cortisone. We have found the highest level of cortisol/cortisone ratio in unstressed conditions, then it decreased to the minimal level at the end of the intervention. We have concluded that cortisol levels are blunted by the influence of anaesthesia after its administration, and therefore decrease back to the baseline at the end of the operation

Cortisol/cortisone Ratio in Sows during Heart Intervention The Cortisol to Cortisone Ratio during Cardiac Catheterisation in Sows

Abstract: A possible effect of mini-invasive heart intervention on a response of hypothalamo-pituitary-adrenal stress axis and conversion of cortisone to cortisol were studied. We have analysed two stress markers levels (cortisol, cortisone) and cortisol/cortisone ratio in 25 sows using minimally invasive heart catheterisation as the stress factor. The values of studied parameters were assessed in four periods of the experiment: (1) the baseline level on the day before intervention, (2) after the introduction of anaesthesia, (3) after conducting tissue stimulation or ablation, and (4) after the end of the catheterisation. For statistical analyses we used the nonparametric Friedman test for four dependent samples (including all four stages of the operation) or three dependent samples (influence of operation only, baseline level was excluded). Statistically significant differences in both Friedman tests were found for cortisol and for cortisone. We have found the highest level of cortisol/ cortisone ratio in unstressed conditions, then it decreased to the minimal level at http://d