Infection Probability Index: Implementation of an Automated Chronic Wound Infection Marker.

The number of people suffering from chronic wounds is increasing due to demographic changes and the global epidemics of obesity and diabetes. Innovative imaging techniques within the field of chronic wound diagnostics are required to improve wound care by predicting and detecting wound infections to accelerate the application of treatments. For this reason, the infection probability index (IPI) is introduced as a novel infection marker based on thermal wound imaging. To improve usability, the IPI was implemented to automate scoring. Visual and thermal image pairs of 60 wounds were acquired to test the implemented algorithms on clinical data. The proposed process consists of (1) determining various parameters of the IPI based on medical hypotheses, (2) acquiring data, (3) extracting camera distortions using camera calibration, and (4) preprocessing and (5) automating segmentation of the wound to calculate (6) the IPI. Wound segmentation is reviewed by user input, whereas the segmented area can be refined manually. Furthermore, in addition to proof of concept, IPIs' correlation with C-reactive protein (CRP) levels as a clinical infection marker was evaluated. Based on average CRP levels, the patients were clustered into two groups, on the basis of the separation value of an averaged CRP level of 100. We calculated the IPIs of the 60 wound images based on automated wound segmentation. Average runtime was less than a minute. In the group with lower average CRP, a correlation between IPI and CRP was evident.

Inhaled Argon Impedes Hepatic Regeneration after Ischemia/Reperfusion Injury in Rats.

Organoprotective effects of noble gases are subject of current research. One important field of interest is the effect of noble gases on hepatic regenerative capacity. For the noble gas argon, promising studies demonstrated remarkable experimental effects in neuronal and renal cells. The aim of this study was to investigate the effects of argon on the regenerative capacity of the liver after ischemia/reperfusion injury (IRI). Male, Sprague-Dawley rats underwent hepatic IRI by clamping of the hepatic artery. Expression of hepatoproliferative genes (HGF, IL-1ß, IL-6, TNF), cell cycle markers (BrdU, TUNEL, Ki-67), and liver enzymes (ALT, AST, Bilirubin, LDH) were assessed 3, 36, and 96 h after IRI. Expression of IL-1ß and IL-6 was significantly higher after argon inhalation after 36 h (IL-1ß 5.0 vs. 8.7 fold, p = 0.001; IL-6 9.6 vs. 19.1 fold, p = 0.05). Ki-67 was higher in the control group compared to the argon group after 36 h (214.0 vs. 38.7 positive cells/1000 hepatocytes, p = 0.045). Serum levels of AST and ALT did not differ significantly between groups. Our data indicate that argon inhalation has detrimental effects on liver regeneration after IRI as measured by elevated levels of the proinflammatory cytokines IL-1ß and IL-6 after 36 h. In line with these results, Ki-67 is decreased in the argon group, indicating a negative effect on liver regeneration in argon inhalation.

Contactless monitoring of heart and respiratory rate in anesthetized pigs using infrared thermography.

Pig experiments have played an important role in medical breakthroughs during the last century. In fact, pigs are one of the major animal species used in translational research, surgical models and procedural training due to their anatomical and physiological similarities to humans. To ensure high bioethical standards in animal trials, new directives have been implemented, among others, to refine the procedures and minimize animals' stress and pain. This paper presents a contactless motion-based approach for monitoring cardiorespiratory signals (heart rate and respiratory rate) in anesthetized pigs using infrared thermography. Heart rate monitoring is estimated by measuring the vibrations (precordial motion) of the chest caused by the heartbeat. Respiratory rate, in turn, is computed by measuring the mechanical chest movements that accompany the respiratory cycle. To test the feasibility of this approach, thermal videos of 17 anesthetized pigs were acquired and analyzed. A high agreement between infrared thermography and a gold standard (electrocardiography and capnography-derived respiratory rate) was achieved. The mean absolute error averaged 3.43 ± 3.05 bpm and 0.27 ± 0.48 breaths/min for heart rate and respiratory rate, respectively. In sum, infrared thermography is capable of assessing cardiorespiratory signals in pigs. Future work should be conducted to evaluate infared thermography capability of capturing information for long term monitoring of research animals in a diverse set of facilities.

Comparison of two experimental ARDS models in pigs using electrical impedance tomography.

BACKGROUND: Animal trials contribute to major achievements in medical science. The so-called lavage model is frequently used to evaluate ventilation strategies in acute respiratory distress syndrome (ARDS) using electrical impedance tomography (EIT). But, the lavage model itself might have systematic impacts on EIT parameters. Therefore, we established an additional experimental model, in which ARDS is caused by intravenously administered lipopolysaccharide (LPS). In this study, we want to examine if EIT measurements provide consistent results in both experimental models or whether the pathophysiology of the model influences the findings. Overall, we want to compare both experimental models regarding clinical parameters and EIT-derived indices, namely the global inhomogeneity (GI) index and the regional ventilation delay (RVD) index. METHODS: Nineteen pigs were included in this study, allocated to the control group (CO; n = 5), lavage group (LAV; n = 7) and LPS group (LPS; n = 7). After baseline measurements and the establishment of ARDS, assessment of respiratory mechanics, hemodynamics, gas exchange and EIT recordings were performed hourly over eight hours. RESULTS: In both experimental ARDS models, EIT measurements provided reliable results. But, the GI and the RVD index did not show consistent results as compared to the CO group. Initially, GI and RVD index were higher in the LAV group but not in the LPS group as compared to the CO group. This effect disappeared during the study. Furthermore, the GI index and the RVD index were higher in the LAV group compared to the LPS group in the beginning as well. This, once again, disappeared. Clinical lung injury parameters remained more stable when using LPS. CONCLUSION: The two models showed quite different influences on the GI and RVD index. This implies, that the underlying pathophysiology affects EIT parameters and thus the findings. Hence, translation to EIT-guided clinical therapy in humans suffering from ARDS might be limited.

Monitoring of cardiac output and lung ventilation by Electrical Impedance Tomography in a porcine model of acute lung injury.

Adequate medical treatment of the Acute Respiratory Distress Syndrome is still challenging since patient-individual aspects have to be taken into account. Lung protective ventilation and hemodynamic stability have always been two of the most crucial aims of intensive care therapy. For both aspects, a continuous - preferably non-invasive - monitoring is desirable that is available at the bedside. Unfortunately, there is no technique clinically established yet, that provides both measurement of cardiac stroke volume and ventilation dynamics in real-time. Electrical Impedance Tomography (EIT) is a promising technique to close this gap. The aim of the study was to investigate if stroke volume can be estimated by a self-developed software using EIT-based image analysis. In addition, two EIT-derived parameters, namely Global Inhomogeneity Index (GII) and Impedance Ratio (IR), were calculated to evaluate homogeneity of air distribution. Experimental acute lung injury (ALI) was provoked in seven female pigs (German Landrace) by lipopolysaccharide (LPS). All animals suffered from experimental ALI 3 to 4 hours after LPS infusion. At defined time points, respiratory and hemodynamic parameters, blood gas analyses and EIT-recordings were performed. Eight hours after ALI, animals were euthanized. Stroke volume, derived from pulmonary artery catheter (PAC), decreased continuously up to four hours after ALI. Then, stroke volume increased slightly. Stroke volume, derived from the self-developed tool, showed the same characteristics (p=0.047, r = 0.365). In addition to the GII and IR individually, both classified scores showed a high correlation with the Horowitz Index, defined as paO2/FiO2. To conclude, EIT-derived measures enabled a reliable estimation of cardiac stroke volume and regional distribution of ventilation.

Argon Delays Initiation of Liver Regeneration after Partial Hepatectomy in Rats.

BACKGROUND: The liver can heal up to restitutio ad integrum following damage resulting from various causes. Different studies have demonstrated the protective effect of argon on various cells and organs. To the best of our knowledge, the organ-protective effects of the noble gas argon on the liver have not yet been investigated, although argon appears to influence signal paths that are well-known mediators of liver regeneration. We hypothesized that argon inhalation prior to partial hepatectomy (70%) has a positive effect on the initiation of liver regeneration in rats. METHODS: Partial hepatectomy (70%) with or without inhaled argon (50 vol%) was performed for 1 h. Liver tissue was harvested after 3, 36, and 96 h to analyze the mRNA and protein expression of hepatocyte growth factor (HGF), interleukin-6 (IL-6), tumor necrosis factor-α, and extracellular signal-regulated kinase 1/2. Histological tissue samples were prepared for immunohistochemistry (bromodeoxyuridine [BrdU], Ki-67, and TUNEL) and blood was analyzed regarding the effects of argon on liver function. Statistical analyses were performed using 1-way ANOVA followed by the post hoc Tukey-Kramer test. RESULTS: After 3 h, the primary outcome parameter of hepatocyte proliferation was significantly reduced with argon 50 vol% inhalation in comparison to nitrogen inhalation (BrdU: 15.7 ± 9.7 vs. 7.7 ± 3.1 positive cells/1,000 hepatocytes, p = 0.013; Ki-67: 17.6 ± 13.3 vs. 4.7 ± 5.4 positive cells/1,000 hepatocytes, p = 0.006). This was most likely mediated by significant downregulation of HGF (after 3 h: 5.2 ± 3.2 vs. 2.3 ± 1.0 fold, p = 0.032; after 96 h: 2.1 ± 0.5 vs. 1.3 ± 0.3 fold, p = 0.029) and IL-6 (after 3 h: 43.7 ± 39.6 vs. 8.5 ± 9.2 fold, p = 0.032). Nevertheless, we could detect no significant effect on the weight of the residual liver, liver-body weight ratio, or liver blood test results after argon inhalation. CONCLUSION: Impairment of liver regeneration was apparent after argon 50 vol% inhalation that was most probably mediated by downregulation of HGF and IL-6 in the initial phase. However, the present study was not adequately powered to prove that argon has detrimental effects on the liver. Further studies are needed to evaluate the effects of argon on livers with preexisting conditions as well as on ischemia-reperfusion models.