Tidal Volume (TV) post-process obtained with electrical impedance tomography on a group of chronic obstructive pulmonary disease (COPD) patients. Use of adjust equations

Equations used to estimate ventilation out of EIT images, validated on healthy volunteers show a significant bias and a larger variance when were applied on a COPD patients group. The differences in estimation values were found to be highly correlated with anthropometric parameters. Two groups of 13 and 4 COPD male patients (FEV1/FVC<70% and FVC ≥ 80%) were used in this study. We have measured different anthropometric parameters like age, weight, height and skinfolds. The EIT system (TIE4sys) and a pneumotach were simultaneously connected to monitor tidal volume. The main anthropometric parameters values of 13 COPD patients were: age: 67±9 years, height: 1.65±0.05 m, weight: 72±11 kg, BMI: 26.4±3.3; and the subscapular skinfold thickness was 23±9mm. The mean tidal volume estimated with TIE4sys and the pneumotach were: 0.580±0.212 L and 0.774±0.173 L r = 0.861 (p<0.01). The mean difference was 0.196±0.096 L (p<0.01). On this group we have found out an adjust equation and we have validated it on an independent group of 4 COPD patients. The equation was Diff=-1478+15.6(weight). The mean tidal volume values obtained with pneumotach and TIE4sys on the second group of COPD patients (M:4) were: 0.798±0.395 L and 0.732±0.327 L. The mean of the differences was 0.066±0.114L. The differences of determinations estimated with pneumotach and TIE4sys can be attributed to changes of anthropometric characteristics like subscapular skinfold.Peer ReviewedPostprint (author’s final draft

Charge Delocalization, Oxidation States, and Silver Mobility in the Mixed Silver-Copper Oxide AgCuO2

The electronic structure of AgCuO2, and more specifically the possible charge delocalization and its implications for the transport properties, has been the object of debate. Here the problem is faced by means of first-principles density functional theory calculations of the electron and phonon band structures as well as molecular dynamics simulations for different temperatures. It is found that both Cu and Ag exhibit noninteger oxidation states, in agreement with previous spectroscopic studies. The robust CuO2 chains impose a relatively short contact distance to the silver atoms, which are forced to partially use their dz2 orbitals to build a band. This band is partially emptied through overlap with a band of the CuO2 chain, which should be empty if copper were in a Cu3+ oxidation state. In that way, although structural correlations could roughly be consistent with an Ag+Cu3+O2 formulation, the appropriate oxidation states for the silver and copper atoms become Ag(1+δ)+ and Cu(3−δ)+, and as a consequence, the stoichiometric material should be metallic. The study of the electronic structure suggests that Ag atoms form relatively stable chains that can easily slide despite the linear coordination with oxygen atoms of the CuO2 chains. Phonon dispersion calculations and molecular dynamics simulations confirm the stability of the structure although pointing out that sliding of the silver chains is an easy motion that does not lead to substantial modifications of the electronic structure around the Fermi level and, thus, should not alter the good conductivity of the system. However, this sliding of the silver atoms from the equilibrium position explains the observed large thermal factors

Confiabilidade do teste da caminhada de seis minutos em pacientes com miastenia gravis generalizada

The purpose of this study was to assess the reliability of the six minutes walking test (6MWT) as a functional capacity test for patients with generalized myasthenia gravis (MG). Eleven patients with generalized MG (5 men, six women), aged 55±9 years, were first assessed as to pulmonary function and then submitted to three 6MWT in different days. Heart rate and oxygen saturation were measured (by means of portable oxymeter) during, and dyspnea (by the Borg scale) and distance walked were measured after, each test. At the three tests distances walked were 498 m, 517 m and 520 m (respectively 99%, 103%, and 104% of predicted values). Mean heart rate, oxygen saturation, and dyspnea values showed constant behaviour through the three tests. A high relative reliability was found between the tests, with interclass coefficient correlation over 0.90 (6MWT1-6MWT2, 0.960; 6MWT1-6MWT3, 0.945; and 6MWT2-6MWT3, 0.970); absolute reliability of 4%, 3.5% and 4.8%, as well as good repeatability of 11%, 9.8% and 13.4% were found for respectively the first, second, and third tests. Upper and lower agreement limits, as well as bias mean values by the Bland-Altman test show clinically acceptability. It may hence be said that the 6MWT proved safe, reliable and reproducible, and may be used for exercise tolerance assessment and follow up of patients with generalized myasthenia gravis.Este estudo objetivou determinar a confiabilidade do teste da caminhada de seis minutos (TC6M) como um teste de capacidade funcional em pacientes com miastenia gravis generalizada (MG). Foram selecionados 11 pacientes com MG - 5 homens, 6 mulheres - com idade de 55±9 anos, avaliados inicialmente quanto à função fulmonar, que se submeteram a três TC6M em dias diferentes. Durante e/ou após cada teste foram medidas freqüência cardíaca e saturação de oxigênio (por oxímetro portátil), sensação de dispnéia (pela escala de Borg) e distância percorrida. Nos três testes as distâncias percorridas foram 498 m, 517 m e 520 m (respectivamente 99%, 103% e 104% do valor predito). Em média, a freqüência cardíaca, dispnéia e saturação de oxigênio mostraram comportamento constante nos três testes. Foram encontradas alta confiabilidade relativa, com coeficiente de correlação interclasse maior que 0,90 entre os testes (TC6M1-TC6M2, 0,960; TC6M1-TC6M3, 0,945; e TC6M2-TC6M3, 0,970) e confiabilidade absoluta de 4%, 3,5% e 4,8%, com reprodutibilidade de 11%, 9,8% e 13,4%, respectivamente para o primeiro, segundo e terceiro testes. Os limites superiores e inferiores de concordância e o valor médio das médias das diferenças (bias) calculados pelo teste de Bland-Altman mostraram-se clinicamente aceitáveis. Conclui-se que o TC6M se mostrou seguro, confiável e reprodutível, podendo ser aplicado para avaliação e seguimento da tolerância ao exercício em pacientes com MG generalizada

Determinación de la pulsioximetría y de la capnografía en el laboratorio de función pulmonar

Objetivo: Comparar los valores de oxihemoglobina, obtenidos mediante un pulsioxímetro, y de presión arterial de anhídrido carbónico (PaCO2) al final de la espiración, medida con un capnógrafo, con los obtenidos a partir de una muestra de sangre arterial (oxihemoglobina y PaCO2). Pacientes y métodos: El estudio se realizó en 57 pacientes consecutivos --16 de ellos fumadores-- que acudieron para un estudio de la función pulmonar, de entre 34 y 83 años años de edad. Resultados: El valor medio (± desviación estándar) de la oxihemoglobina por pulsioximetría fue del 95 ± 2,4% y en sangre arterial del 95,1 ± 2,3% (p = NS). El valor medio de la PaCO2 al final de la espiración, medida por el capnógrafo, fue de 37,9 ± 5,3 mmHg y el de la PaCO2 en sangre arterial de 40,6 ± 5,4 mmHg (p < 0,0001). El coeficiente de correlación entre las 2 determinaciones de oxihemoglobina fue de 0,806 (p < 0,0001) y entre la PaCO2 al final de la espiración y la PaCO2 en sangre arterial fue de 0,845 (p < 0,0001). La media de las diferencias entre ambos valores de oxihemoglobina fue del 0,08 ± 1,46%, y entre la PaCO2 al final de la espiración y la PaCO2 fue de 2,7 ± 2,9 mmHg. Conclusión: Ambos equipos de lectura (pulsioxímetro y capnógrafo) han demostrado ser correctos para su uso en el laboratorio de función pulmonar. Deben tenerse en cuenta las diferencias apreciadas entre la PaCO2 al final de la espiración y la PaCO2 arterial