Effects of arterial oxygen tension and cardiac output on venous saturation: a mathematical modeling approach

OBJECTIVES: Hemodynamic support is aimed at providing adequate O-2 delivery to the tissues; most interventions target O-2 delivery increase. Mixed venous O-2 saturation is a frequently used parameter to evaluate the adequacy of O-2 delivery. METHODS: We describe a mathematical model to compare the effects of increasing O-2 delivery on venous oxygen saturation through increases in the inspired O-2 fraction versus increases in cardiac output. The model was created based on the lungs, which were divided into shunted and non-shunted areas, and on seven peripheral compartments, each with normal values of perfusion, optimal oxygen consumption, and critical O-2 extraction rate. O-2 delivery was increased by changing the inspired fraction of oxygen from 0.21 to 1.0 in steps of 0.1 under conditions of low (2.0 L.min(-1)) or normal (6.5 L.min(-1)) cardiac output. The same O-2 delivery values were also obtained by maintaining a fixed O-2 inspired fraction value of 0.21 while changing cardiac output. RESULTS: Venous oxygen saturation was higher when produced through increases in inspired O-2 fraction versus increases in cardiac output, even at the same O-2 delivery and consumption values. Specifically, at high inspired O-2 fractions, the measured O-2 saturation values failed to detect conditions of low oxygen supply. CONCLUSIONS: The mode of O-2 delivery optimization, specifically increases in the fraction of inspired oxygen versus increases in cardiac output, can compromise the capability of the "venous O-2 saturation" parameter to measure the adequacy of oxygen supply. Consequently, venous saturation at high inspired O-2 fractions should be interpreted with caution.

JOB SATISFACTION: A QUALITY INDICATOR IN NURSING HUMAN RESOURCE MANAGEMENT

This descriptive study addresses the job satisfaction of nurse managers and clinical nurses working at the Hematology and Hemotherapy Services of a public hospital in Sao Paulo. The study objectives were to identify the factors that caused job satisfaction among nurse managers and clinical nurses, and support the results in the development of indicators to evaluate the quality of nursing human resource management. The components of the study were: autonomy, interaction, professional status, job requirements, organizational norms and remuneration. Participants were 44 nurses. Data were collected using a Job Satisfaction Index (JSI) questionnaire. In conclusion, this study permitted the identification of the clinical nurse group, which was the most satisfied, with a JSI of 10.5; the managerial group scored 10.0. Regarding the satisfaction levels in regards to the current activity, 88.9% of the nurse managers reported feeling satisfied, as did 90.9% of clinical nurses. For both groups, autonomy was the component with the highest level of professional satisfaction.

Job satisfaction among control room operators of electrical systems

Shift workers from control centers of electrical systems are a group that has received little attention in Brazil. This study aimed to compare workers' job satisfaction at five control centers of a Brazilian company electrical system, and according to their job titles. Method: The Organization Satisfaction Index (OSI) questionnaire to assess job satisfaction was used. ANOVA was used to compare OSI means, according to job title and control center. The results showed that there is no difference in job satisfaction among job titles, but a significant difference was found according to the control center. A single organizational culture cannot be applied to several branches. It is required to implement actions that would result in job satisfaction improvements among workers of all studied control rooms centers. The high level of education of operators working in all centers might have contributed to the similar values of perceived satisfaction among distinct job titles.

A non-cross-bridge, static tension is present in permeabilized skeletal muscle fibers after active force inhibition or actin extraction

Cornachione AS, Rassier DE. A non-cross-bridge, static tension is present in permeabilized skeletal muscle fibers after active force inhibition or actin extraction. Am J Physiol Cell Physiol 302: C566-C574, 2012. First published November 16, 2011; doi: 10.1152/ajpcell.00355.2011.-When activated muscle fibers are stretched, there is a long-lasting increase in the force. This phenomenon, referred to as "residual force enhancement," has characteristics similar to those of the " static tension," a long-lasting increase in force observed when muscles are stretched in the presence of Ca2+ but in the absence of myosin-actin interaction. Independent studies have suggested that these two phenomena have a common mechanism and are caused either by 1) a Ca2+-induced stiffening of titin or by 2) promoting titin binding to actin. In this study, we performed two sets of experiments in which activated fibers (pCa(2+) 4.5) treated with the myosin inhibitor blebbistatin were stretched from 2.7 to 2.8 mu m at a speed of 40 L-o/s, first, after partial extraction of TnC, which inhibits myosin-actin interactions, or, second, after treatment with gelsolin, which leads to the depletion of thin (actin) filaments. We observed that the static tension, directly related with the residual force enhancement, was not changed after treatments that inhibit myosin-actin interactions or that deplete fibers from troponin C and actin filaments. The results suggest that the residual force enhancement is caused by a stiffening of titin upon muscle activation but not with titin binding to actin. This finding indicates the existence of a Ca2+-regulated, titin-based stiffness in skeletal muscles.

Job satisfaction and discrepancies between social and biological timing

The discrepancies between social and biological timing are reflected in shift workers' well-being. The aim of this study was to verify the association between job satisfaction and chronotype among day and night nursing personnel. Several variables, including seniority at the hospital and, in the same shift, sleep duration, quality of sleep, sleepiness and willingness to change sleep timing were also analyzed. Chronotype was calculated by using the morningness-eveningness questionnaire. We studied 514 nursing professionals from a public university hospital. Among the day workers, the higher the morningness, the more the workers were satisfied with their job. In contrast, among night workers, job satisfaction was associated with sleep quality and seniority at the hospital but not with chronotype. Our results suggest that an agreement between work schedule and chronotype may help to increase job satisfaction among diurnal workers.

Voice disorders related to job stress in teaching: a case-control study

This case-control study aimed to test the association between voice disorders and job stress among public schoolteachers in Sao Paulo, Brazil. The groups consisted of teachers with (n = 165) and without (n = 105) voice-related complaints. Both groups answered the questionnaires Conditions of Vocal Production and Job Stress Scale. Analysis of cases and controls showed comparable samples, differing only by vocal symptoms. There was a statistically significant difference between cases and controls in relation to job stress involving high strain (OR = 2.1;95%CI: 1.1-3.9), which places high demands combined with low job control. High strain in cases in this study represents the highest risk of physical and mental disorders for teachers. Loss of voice prevents teachers from continuing in their professional role, eliminates their professional identity, and jeopardizes their career.

Um modelo de projeto de layout para ambientes job shop com alta variedade de peças baseado nos conceitos da produção enxuta

Segundo Canem e Williamson (1998), o planejamento do layout é importante, pois normalmente representa os maiores e mais caros recursos da organização. Além disso, a localização e disposição física dos equipamentos no chão de fábrica têm impacto em diversos fatores como nível de estoque em processo, tamanho dos lotes de transferência, dificuldade no gerenciamento das atividades, movimentação de pessoas e produtos, entre outros. Portanto, o estudo de conceitos de arranjo físico e o desenvolvimento de modelos de projeto do layout, que visem a otimização dos recursos de produção, são de vital importância na busca pela melhoria dos sistemas produtivos. Neste contexto, este artigo apresenta um novo modelo de projeto de layout, para ambientes job shop com ampla variedade de peças. O modelo foi desenvolvido durante uma pesquisa de doutorado e foi aplicado em algumas empresas do setor metal mecânico. Os resultados obtidos comprovaram a eficiência do modelo projetado. O objetivo do modelo consiste em conduzir a equipe de projeto de layout a desenvolver alternativas de arranjo físico que estejam em consonância com conceitos e princípios da filosofia de produção enxuta. Vale ressaltar novamente que o modelo foi desenvolvido para ambientes com alta variedade de peças, ambientes esses em que, devido à dificuldade em se projetar o arranjo físico, as empresas terminam por adotar o layout funcional, conceito esse de arranjo físico que apresenta sérios problemas como excesso de transporte, altos níveis de estoques em processo, etc.

Induced tooth movement: standardization of terms to describe the effects of forces on the periodontal ligament: compression/Traction instead of Pressure/Tension

There is no reason for Dentistry to use different terms for phenomena defined in Physics, the specific field in which concepts associated with forces are established and adapted. In place of pressure/tension, the compression/traction pair should be used. This study defines each one of these terms and justifies their use. Our contemporary world demands standardized criteria, methods, measures, concepts and terms to ensure that study protocols, results and applications are used in the same way in any country or area of human action.