Evaluación de la Saturación Venosa de Oxígeno (SvO2) desde la teoría de los sistemas dinámicos / Evaluation of SvO2 from the Theory of Dynamic Systems

Introducción: La evolución de un sistema dinámico se puede caracterizar a partir de la construcción de atractores caóticos. Objetivo: Desarrollar una metodología de evaluación de la saturación venosa de oxígeno, fundamentada en los sistemas dinámicos, para pacientes en Unidad de Cuidados Intensivos. Metodología: Se seleccionaron 10 pacientes con diferentes patologías de la Unidad de Cuidados Intensivos Postquirúrgicos, y registró la saturación venosa de oxígeno durante su tiempo de estancia. Con base en estos valores se construyeron atractores caóticos en el mapa de retardo y se evaluaron los valores mínimos y máximos ocupados por el atractor. Resultados: Se halló que la saturación venosa de oxígeno tiene un comportamiento caótico; los valores máximos y mínimos de los atractores en el mapa de retardo variaron entre 22,10 mmHg y 93,70 mmHg. Conclusiones: Se plantea una nueva metodología capaz de caracterizar el comportamiento de la variable monitorizada para la evaluación del paciente crítico(AU)

Introduction: The evolution of a dynamic system can be characterized from the construction of chaotic attractors. Objective: To develop a methodology based on dynamic systems, for the evaluation of venous oxygen saturation of patients in the Intensive Care Unit. Methodology: 10 patients with different pathologies of the Post-surgical Intensive Care Unit were selected, and recorded venous oxygen saturation during their time of stay. Based on these values, chaotic attractors were constructed on the delay map and the minimum and maximum values occupied by the attractor were evaluated. Results: It was found that venous oxygen saturation has a chaotic behavior; the maximum and minimum values of the attractors on the delay map varied between 22.10 mmHg and 93.70 mmHg. Conclusions: A new methodology is proposed capable of characterizing the behavior of this monitored variable for the evaluation of the critical patient(AU)

Effect of smoking habits on sleep

To evaluate the effect of smoking habits on sleep, data from 1492 adults referred to the Sleep Institute were accessed and divided into 3 categories of smoking status: current, former and non-smokers. Categories of pack-years (<15 and greater than or equal to 15) defined smoking severity. The association of smoking status and smoking severity with sleep was analyzed for sleep parameters, especially apnea and hypopnea index (AHI) greater than or equal to 5, more than 5 percent of total sleep time (TST) spent with oxyhemoglobin saturation (SaO2) <90 percent, and arousal index. The arousal index was higher among current (21 plus or minus 17) and former smokers (20 plus or minus 17) than non-smokers (17 plus or minus 15; P < 0.04). Former smokers had a higher percent of TST at SaO2 <90 percent than non-smokers (9 more less 18 vs 6 more less 13; P < 0.04). Former smokers with pack-years greater than or equal to 15 compared to <15 exhibited higher AHI (22 plus or minus 24 vs 16 plus or minus 21; P < 0.05) and arousal index (22 plus or minus 19 vs 18 plus or minus 15; P < 0.05). Current smokers with pack-years greater than or equal to 15 compared to <15 exhibited higher arousal index (23 plus or minus 18 vs 18 plus or minus 16; P < 0.05) and percent of TST at SaO2 <90 percent (11 plus or minus 17 vs 6 more less 13; P < 0.05). Smoking status and pack-years were not associated with AHI greater than or equal to 5 on logistic regression analysis, but current smokers with pack-years greater than or equal to 15 were 1.9 times more likely to spend more than 5 percent of TST at SaO2 <90 percent than non-smokers (95 percentCI = 1.21-2.97; P = 0.005). The variability of arousal index was influenced by gender, AHI and current smokers with pack-years greater than or equal to 15 (all P < 0.01). Smoking habits seem to be associated with arousal and oxyhemoglobin desaturation during sleep, but not with AHI. The effect was more pronounced in current than former smokers.

Interferência da coloração de esmaltes de unha e do tempo na oximetria de pulso em voluntários sadios / Interference of nail polish colors and time on pulse oximetry in healthy volunteers

INTRODUÇAO: A oximetria de pulso é um método não invasivo de mensuração da saturação periférica da oxiemoglobina (SpO2). É freqüentemente utilizado em unidades de emergência, de terapia intensiva e em centro cirúrgico. A leitura da oximetria de pulso tem acurácia limitada na presença de metaemoglobina, carboxiemoglobina, anemia, vasoconstrição periférica, esmalte de unha, luz fluorescente e movimentação. OBJETIVO: Avaliar a interferência da coloração de esmalte de unha e do tempo sobre a SpO2 em indivíduos sadios. MÉTODO: Participaram do estudo 61 voluntárias sadias, com idades entre 18 e 32 anos. Foi avaliada SpO2 nas seguintes colorações de esmaltes: base (dedo mínimo), rosa claro (dedo anular), rosa claro com cintilante (dedo médio) e vermelha (polegar). O indicador não recebeu esmalte. Foi analisado o tempo para cada coloração de esmalte, a cada minuto até completar cinco minutos. RESULTADOS: Quando comparadas as medidas da SpO2 com o controle, as colorações base (p = 0,56), rosa claro (p = 0,56) e rosa claro com cintilante (p = 0,37) não apresentaram diferença estatisticamente significante. A SpO2 apresentou variação significante na cor vermelha (p < 0,001), porém manteve-se dentro dos parâmetros de normalidade. Não houve variação significativa da SpO2 ao longo do tempo. CONCLUSAO: Apesar da diferença encontrada com o uso de esmalte vermelho, todas as medidas da SpO2 obtidas encontraram-se dentro do intervalo de normalidade, para indivíduos normais. A análise de cada cor de esmalte de unha em relação ao tempo mostrou que não houve variação na leitura da SpO2.

Oximetria de pulso: algoritmos de cálculo / Pulse oximetry: algorithms of calculation

Este trabalho apresenta os fundamentos do método de cálculo da SpO2 e discute dois diferentes algoritmos. As vantagens e desvantagens de cada uma deles são ressaltadas. Através de alguns resultados comprova-se que a eliminação do componente DC do sinal não afeta o cálculo da SpO2 e simplifica o tratamento analógico, proporcionando uma maior confiabilidade ao sistema.

Excessive polycythaemia of high altitude. Pulmonary function studies including carbon monoxide diffusion capacity.

Pulmonary function studies were done in 21 soldiers (low landers) posted at high altitude (average height 4773 metres) for prolonged periods (average 77.09 months), who had developed excessive polycythaemia, mean haemoglobin concentration being 23.06 g/dl. Studies revealed significant reduction in diffusion capacity of lungs which gradually returned to normal on sojourn at low altitudes for 70 days. Both the degree of polycythaemia and reduction in lung diffusion capacity were much more pronounced in smokers than in non-smokers. Vital capacity did not show any difference in these subjects while forced expiratory volume in 1 sec and ratio of forced expiratory volume to vital capacity (FEV1/VC) revealed only obstructive features in smokers.

Adaptative features of amazon fishes: hemoglobins of Brycon cf cephalus and Brycon cf erythropterum (PISCES)

Os padröes eletroforéticos de hemoglobinas, os fosfatos intraeritrocitários e o efeito Bohr de sangue e hemoglobinas de Brycon cf cephalus e Brycon cf erythropterum, capturados no rio Negro, foram estudados. Foram detectadas dez fraçöes hemoglobínicas (oito anódicas e duas catódicas) em B. cf cephalus e oito fraçöes anódicas em B. cf erythropterum, através de eletroforese em gel de amido. ATP e GTP foram detectados no sangue das duas espécies, e ambos têm influência no efeito Bohr de hemoglobinas. O efeito Bohr de sangue apresentou-se similar para as duas espécies estudadas

Further evidence of dimer-tetramer transition in hemoglobin from Liophis miliaris

Liophis miliaris hemoglobins in the stripped form exhibit a high oxigen affinity, a small alkaline Bohr effect, a pronounce organic polyphosphate effect and a pH-dependent Hill coefficient, close to 2 below pH 7.5 and near 1 at higher pHs. Molecular weight determinations indicate 2 forms, a dimeric form of MW 32000 d. and a tetrameric form of about 64000 d. The deoxyhemoglobin is tetrameric. Ion-exchange chromatography shows two components which may bind to each other being eluted as a single component of MW 32000 d. The osygen alkaline Bohr effect observed for the stripped hemoglobin may be explained by the transition from the tetramer to the dimer during oxygen addition experiments. The phenomenon appears to be unique among animals. ß-Chain sequencing determinations show that abnormal human hemoglobin with similar properties has a glutamic acid residue substituted at the alfa1-ß2 interface by valine in snake hemoglobin

Enzymatic activation of the carcinogens 2 phenylethylhydrazine and 1,2 dimethylhydrazine to carbon centered radicals

Spin-trapping experiments demonstrate that oxidation of 1,2-dimethylhydrazine and 2-phenylethylgydrazine generates a comparable yield of carbon-centered radicals when catalyzed by horseradish peroxidase-H2O2. Using oxyhemoglobin as the catalyst, 2-phenylethylgydrazine oxidation generates ten times carbon-centered radicals than 1,2-dimethylhidrazine oxidation. This results is in agreement with oxygen consumption studies from which the apparent KM values of 8.0 mM and 72 mM were calculated for the oxyhemoglobin-catalyzed oxidation of 2-phenylethylhydrazine and 1,2-dimethylhydrazine, respectively. These differences in metabolic activation of mono- and disubstituted hydrazines may be of importance regarding the carcinogenic properties of these derivatives

Consideraçöes sobre a dissociabilidade da oxiemoglobina / Dissociability of oxyhemoglobin

O suprimento de oxigênio para a célula é muito dependente da reaçäo em que o O2 e a hemoglobina se ligam reversivelmente. O equilíbrio desta reaçäo pode ser modificado por vários fatores. Por exemplo: CO2, H+, 2-3 DPG e temperatura diminuem a afinidade entre as duas moléculas, ou seja, aumentam a dissociabilidade da oxiemoglobina. O efeito nos dois níveis capilares seria oposto: em nível pulmonar, maléfico e em nível tecidual, benéfico. A análise teórica da reaçäo mostra que prevalece a ocorrência tecidual, sendo a pulmonar desprezível. Mostra, também, que em graves comprometimentos respiratórios com pO2 muito abaixo do limite de saturaçäo, o aumento da dissociabilidade pode ser prejudicial