Curve-Modelling and Machine Learning for a Better COPD Diagnosis.

Background: Development of new tools in artificial intelligence has an outstanding performance in the recognition of multidimensional patterns, which is why they have proven to be useful in the diagnosis of Chronic Obstructive Pulmonary Disease (COPD). Methods: This was an observational analytical single-centre study in patients with spirometry performed in outpatient medical care. The segment that goes from the peak expiratory flow to the forced vital capacity was modelled with quadratic polynomials, the coefficients obtained were used to train and test neural networks in the task of classifying patients with COPD. Results: A total of 695 patient records were included in the analysis. The COPD group was significantly older than the No COPD group. The pre-bronchodilator (Pre BD) and post-bronchodilator (Post BD) spirometric curves were modelled with a quadratic polynomial, and the coefficients obtained were used to feed three neural networks (Pre BD, Post BD and all coefficients). The best neural network was the one that used the post-bronchodilator coefficients, which has an input layer of 3 neurons and three hidden layers with sigmoid activation function and two neurons in the output layer with softmax activation function. This system had an accuracy of 92.9% accuracy, a sensitivity of 88.2% and a specificity of 94.3% when assessed using expert judgment as the reference test. It also showed better performance than the current gold standard, especially in specificity and negative predictive value. Conclusion: Artificial Neural Networks fed with coefficients obtained from quadratic and cubic polynomials have interesting potential of emulating the clinical diagnostic process and can become an important aid in primary care to help diagnose COPD in an early stage.

Is EEG Entropy a Useful Measure for Alzheimer's Disease?

BACKGROUND: The number of individuals diagnosed with Alzheimer's disease (AD) has increased, and it is estimated to continue rising in the coming years. The diagnosis of this disease is challenging due to variations in onset and course, its diverse clinical manifestations, and the indications for measuring deposit biomarkers. Hence, there is a need to develop more precise and less invasive diagnostic tools. Multiple studies have considered using electroencephalography (EEG) entropy measures as an indicator of the onset and course of AD. Entropy is deemed suitable as a potential indicator based on the discovery that variations in its complexity can be associated with specific pathologies such as AD. METHODOLOGY: Following PRISMA guidelines, a literature search was conducted in 4 scientific databases, and 40 articles were analyzed after discarding and filtering. RESULTS: There is a diversity in entropy measures; however, Sample Entropy (SampEn) and Multiscale Entropy (MSE) are the most widely used (21/40). In general, it is found that when comparing patients with controls, patients exhibit lower entropy (20/40) in various areas. Findings of correlation with the level of cognitive decline are less consistent, and with neuropsychiatric symptoms (2/40) or treatment response less explored (2/40), although most studies show lower entropy with greater severity. Machine learning-based studies show good discrimination capacity. CONCLUSIONS: There is significant difficulty in comparing multiple studies due to their heterogeneity; however, changes in Multiscale Entropy (MSE) scales or a decrease in entropy levels are considered useful for determining the presence of AD and measuring its severity.

Cerebral rScO2 Measured by Near-Infrared Spectroscopy (NIRS) During Therapeutic Hypothermia in Neonates with Hypoxic-Ischemic Encephalopathy: A Systematic Review.

INTRODUCTION: Perinatal asphyxia, a leading cause of neonatal mortality and neurological sequelae, necessitates early detection of pathophysiological neurologic changes during hypoxic-ischaemic encephalopathy (HIE). This study aimed to review published data on rScO2 monitoring during hypothermia treatment in neonates with perinatal asphyxia to predict short- and long-term neurological injury. METHODS: A systematic review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Study identification was performed through a search between November and December 2021 in the electronic databases PubMed, Embase, Lilacs, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials (CENTRAL). The main outcome was short-term (Changes in brain magnetic resonating imaging) and long-term (In neurodevelopment) neurological injury. The study protocol was registered in PROSPERO (International Prospective Register of Systematic Reviews) with CRD42023395438. RESULTS: 380 articles were collected from databases in the initial search. Finally, 15 articles were selected for extraction and analysis of the information. An increase in rScO2 measured by NIRS (Near-infrared spectroscopy) at different moments of treatment predicts neurological injury. However, there exists a wide variability in the methods and outcomes of the studies. CONCLUSION: High rScO2 values were found to predict negative outcomes, with substantial discord among studies. NIRS is proposed as a real-time bedside tool for predicting brain injury in neonates with moderate to severe HIE.

Signal processing and machine learning algorithm to classify anaesthesia depth.

BACKGROUND: Poor assessment of anaesthetic depth (AD) has led to overdosing or underdosing of the anaesthetic agent, which requires continuous monitoring to avoid complications. The evaluation of the central nervous system activity and autonomic nervous system could provide additional information on the monitoring of AD during surgical procedures. METHODS: Observational analytical single-centre study, information on biological signals was collected during a surgical procedure under general anaesthesia for signal preprocessing, processing and postprocessing to feed a pattern classifier and determine AD status of patients. The development of the electroencephalography index was carried out through data processing and algorithm development using MATLAB V.8.1. RESULTS: A total of 25 men and 35 women were included, with a total time of procedure average of 109.62 min. The results show a high Pearson correlation between the Complexity Brainwave Index and the indices of the entropy module. A greater dispersion is observed in the state entropy and response entropy indices, a partial overlap can also be seen in the boxes associated with deep anaesthesia and general anaesthesia in these indices. A high Pearson correlation might be explained by the coinciding values corresponding to the awake and general anaesthesia states. A high Pearson correlation might be explained by the coinciding values corresponding to the awake and general anaesthesia states. CONCLUSION: Biological signal filtering and a machine learning algorithm may be used to classify AD during a surgical procedure. Further studies will be needed to confirm these results and improve the decision-making of anaesthesiologists in general anaesthesia.

The Challenges of Spirometric Diagnosis of COPD.

Chronic obstructive pulmonary disease (COPD) is one of the top causes of morbidity and mortality worldwide. Although for many years its accurate diagnosis has been a focus of intense research, it is still challenging. Due to its simplicity, portability, and low cost, spirometry has been established as the main tool to detect this condition, but its flawed performance makes it an imperfect COPD diagnosis gold standard. This review aims to provide an up-to-date literature overview of recent studies regarding COPD diagnosis; we seek to identify their limitations and establish perspectives for spirometric diagnosis of COPD in the XXI century by combining deep clinical knowledge of the disease with advanced computer analysis techniques.

Descripción de la composición corporal en una cohorte de oficiales activos en el Ejército de Colombia

La composición corporal en población militar es indispensable en la caracterización del estado nutricional, lo cual representa la acumulación de grasa, huesos, agua y músculo total en el cuerpo. Objetivo: Describir y analizar variables de la composición corporal en datos recolectados de una muestra de oficiales del Ejército Nacional de Colombia. Metodología: Estudio descriptivo entre oficiales con la finalidad determinar la composición corporal y bioimpedancia con el estado nutricional como un indicador de riesgos sobre la salud, utilizando un tallímetro, báscula con precisión de 100 gramos, cinta antropométrica flexible, compás de pequeños diámetros y de pliegues cutáneos. Se consideró un valor de p estadísticamente significativo <0,05. Resultados: La muestra de oficiales recolectada está compuesta por un total de 96 sujetos, con una división de rangos militares de la siguiente manera: teniente (n= 28), capitán (n=23), mayor (n=15), teniente coronel (n=10), subteniente (n=4) y coronel (n=1). La diferencia de edad y peso entre el grupo de oficiales superiores y subalternos fue de 11,33 años (p=0,089) y 1,42 kilogramos (p=0,235), respectivamente. El valor esperado de la flexibilidad fue diferente entre grupos, siendo mayor en el grupo de oficiales subalternos (p=0,016). Conclusión: Las variables de composición corporal no presentaron diferencias estadísticamente significativas entre los grupos oficiales superiores y subalternos.

Background: Body composition in the military population is essential in the characterization of nutritional status, representing the accumulation of fat, bone, water, and total muscle in the body. Objective: Describe and analyze variables of the CP data collected from a sample of officers of the Colombian National Army. Methodology: Descriptive study among officers in order to determine body composition and bioimpedance with nutritional status as an indicator of health risks, using a height rod, a scale with a precision of 100 grams, a flexible anthropometric tape, a small diameter compass and skinfold compass. A statistically significant p value of <0.05 is considered. Results: The sample of officers collected is composed of a total of 96 subjects with a division of military ranks as follows: lieutenant (n= 28), captain (n=23), major (n=15), lieutenant colonel ( n=10), second lieutenant (n=4) and colonel (n=1). The difference in age and weight between the group of senior and junior officers was 11.33 years (p=0.089) and 1.42 kilograms (p=0.235), respectively. The expected value of flexibility is different between groups, being higher in the group of junior officers (p=0.016). Conclusion: The body composition variables did not present statistically significant differences between the superior and subordinate official groups.

Musicoterapia en pacientes con la COVID-19

Introducción: La musicoterapia puede ser utilizada para influenciar en el estado físico y emocional de pacientes diagnosticados con la COVID-19. Se realiza una revisión sistemática exploratoria que incluye estudios observacionales y ensayos clínicos; Pubmed y Scopus fueron las bases de datos empleadas para la realización de la búsqueda. Además, se incluyen registros de ensayos clínicos de la Plataforma de Registros Internacionales de Ensayos Clínicos de la Organización Mundial de la Salud. Objetivo: Explorar la literatura médica disponible, sobre el impacto clínico de la musicoterapia en pacientes diagnosticados con la COVID-19. Desarrollo: De 39 documentos encontrados se incluyen 2 artículos: un ensayo clínico y un reporte de caso, con una población total de 41 pacientes. Se encuentra evidencia médica que respalda el impacto clínico favorable sobre la saturación de oxígeno, rehabilitación física y síntomas asociados al estrés en pacientes con diagnóstico de la COVID-19 con y sin requerimiento de soporte ventilatorio. Conclusiones: La musicoterapia es una herramienta útil en el tratamiento y rehabilitación no farmacológica de pacientes con la COVID-19; sin embargo, son necesarios nuevos estudios clínicos con mayor número de poblaciones muestrales y mayor tiempo de seguimiento.

Background: Music therapy can be used to influence the physical and emotional state of patients diagnosed with COVID-19. An exploratory systematic review was carried out including observational studies and clinical trials, Pubmed and Scopus were the databases used to carry out the literature search. In addition, clinical trial registries from the World Health Organization International Clinical Trials Registry Platform are included. Objective: To explore the available medical literature on the clinical impact of music therapy in patients diagnosed with COVID-19. Development: Of 39 documents found in the search, two articles are included: a clinical trial and a case report, with a total population of 41 patients. Medical evidence is found to support the favorable clinical impact on oxygen saturation, physical rehabilitation and symptoms associated with stress in patients diagnosed with COVID-19 with and without the need for ventilatory support. Conclusions: Music therapy is a useful tool in the non-pharmacological treatment and rehabilitation of patients with COVID-19. However, new clinical studies with a larger number of sample populations and follow-up times using music therapy in this disease are necessary.

Lactato como marcador temprano de hipoxia cerebral en pacientes neurológicos bajo anestesia general: una revisión sistemática / Lactate as an early marker of cerebral hypoxia in neurological patients under general anesthesia: a systematic review

Resumen: Las complicaciones neurológicas perioperatorias secundarias a hipoxia durante procedimientos de sedación y anestesia general son frecuentes en cirugía cardiovascular y en pacientes con comorbilidades. Sin embargo, hasta el momento no existe un consenso para el diagnóstico de estas posibles complicaciones. En pacientes con trauma encefálico severo y/o hemorragia subaracnoidea el lactato cerebral no fue útil para predicción de hipoxia cerebral; pese a ello, la relación de lactato/piruvato podría ser una herramienta para diagnóstico intraoperatorio de hipoxia cerebral aguda. Los estudios sugieren que éste debe asociarse a otros marcadores y/o a monitoreo multimodal. Es necesario realizar estudios que evalúen su valor predictivo para hipoxia cerebral.

Abstract: Perioperative neurological complications secondary to hypoxia during sedation and general anesthesia procedures are frequent in cardiovascular surgery, and in patients with comorbidities. However, so far there is no consensus for the diagnosis of these possible complications. In patients with head trauma severe and/or subarachnoid hemorrhage cerebral lactate was not useful for predicting cerebral hypoxia, however the lactate/pyruvate ratio could be a tool for intraoperative diagnosis of acute cerebral hypoxia. Studies suggest that it must be associated with other markers or multimodal monitoring. Further studies are needed to evaluate lactate predictive value for the diagnosis of cerebral hypoxia.

El efecto del tipo de acondicionamiento físico sobre la insulina y glucosa en las distintas fases del ejercicio

Objetivo: Describir el comportamiento de la glucosa y la insulina durante las etapas del ejercicio en atletas acondicionados en ejercicio aeróbico y anaeróbico. Materiales y métodos: En un estudio cuasiexperimental de corte transversal se compararon la glucosa e insulina de 6 atletas anaeróbicos y 10 aeróbicos durante el reposo, ejercicio de moderada - alta intensidad y la recuperación. Se eligió un valor p de <0.05, se encontró distribución no-normal y se utilizaron pruebas no paramétricas y modelos de regresión linear. Resultados: El ejercicio moderado llevó a hipoinsulinemia, y el intenso a hiperinsulinemia e hiperglicemia. No encontramos diferencias entre los dos tipos de atletas. Conclusiones: El comportamiento del sistema nervioso autónomo afectaría el balance glucoenergético corporal durante el ejercicio aún más que la insulina, con variaciones dependiendo del tipo de entrenamiento, pero es necesario realizar estudios adicionales para evaluar esta relación.

Objective: Describe glucose and insulin behavior at the different phases of exercise in aerobic and anaerobic athletes. Materials and methods: Glucose and insulin from 6 anaerobic and 10 aerobic athletes were compared during rest, moderate-high intensity exercise, and recovery. Statistical analysis was performed to evaluate insulin and glucose behavior, and differences between aerobic aerobic and anaeribic-trained individuals. A p value of <0.05 was set. A non-normal distribution was found, non-parametric tests and multivariate analysis were performed. Results: Moderate exercise led to hypoinsulinemia, whereas intense exercise caused hyper-insulinemia and hyperglycemia. No differences were found between the 2 groups. Conclusions: Autonomic nervous system behavior may play a role in the glucoenergetic balance that could overcome insulin effect, and it could vary depeding on the type of exercise régimen but further evaluation is necessary to confirm these findings

Decisión Making, Stress Assessed by Physiological Response and Virtual Reality Stimuli / Toma de Decisiones, Estrés Valorado mediante la Respuesta Fisiológica y Estímulos en Realidad Virtual

Abstract Many decisions must be made under stress; therefore, stress and decision-making are intrinsically related not only at the behavioral level but also at the neural level. Additionally, virtual reality tools have been proposed as a method to induce stress in the laboratory. This review focuses on answering the following research question: Does stress assessed by physiological variables of a subject under virtual reality stimuli increase the chances of error in decision-making? The reviewed studies were consulted in the following databases: PubMed, IEEE Xplore, and Science Direct. The analysis of the consulted literature indicates that the stress induced in the laboratory using virtual reality tools and the physiological response of the central and autonomous nervous system are complementary subjects and allow the design of training and support systems for the decision-making process.

Resumen Muchas decisiones deben tomarse bajo estrés, por lo tanto, el estrés y la toma de decisiones están intrínsecamente relacionados, no solo a nivel conductual sino también a nivel neural. Además, las herramientas de realidad virtual se han propuesto como un método para inducir estrés en el laboratorio. El presente trabajo de revisión temática se centra en responder la siguiente pregunta de investigación: ¿El estrés evaluado mediante variables fisiológicas de un sujeto bajo estímulos de realidad virtual aumenta las posibilidades de error en la toma de decisiones? Los estudios revisados fueron consultados en las siguientes bases de datos: PubMed, IEEE Xplore y Science Direct. El análisis de la literatura consultada indica que el estrés inducido en el laboratorio, por medio de herramientas de realidad virtual, y la respuesta fisiológica del sistema nervioso central y autónomo son temas que se complementan y permiten el diseño de sistemas de soporte y entrenamiento para el proceso de toma de decisiones.

Variability of anesthetic depth in total intravenous anesthesia vs balanced anesthesia using entropy indices: a randomized, crossover, controlled clinical trial / Variabilidad de la profundidad anestésica en anestesia total intravenosa vs. anestesia general balanceada usando índices de entropía. Un ensayo clínico aleatorizado, cruzado y controlado

Abstract Introduction: Total intravenous anesthesia (TIVA) and balanced anesthesia (BA) are the most commonly used anesthetic techniques. The differences are the variability of the depth of anesthesia between these techniques that might predict which one is safer for patients and presents a lower risk of intraoperative awakening. Objective: To determine whether a difference exists in the variability of depth of anesthesia obtained by response entropy (RE). Methods: A crossover clinical trial was conducted on 20 healthy patients receiving upper or lower limb ambulatory orthopedic surgery. Patients were randomly assigned to (a) target-controlled infusion of propofol using the Schnider model at a target concentration of 2.5 µg/mL for 15 minutes and a 10-minute washout, followed by sevoflurane administration at 0.8 minimal alveolar concentration (MAC) for the reminder of the surgery, or (b) the reverse sequence. Differences in the variability of the depth of anesthesia using RE were evaluated using paired t-test. Results: The treatment effect showed no significant difference in the average values of RE, during TIVA = 97.23 vs BA 97.04 (P = 0.39). Carry Over (-4.98 vs 4.08) and Period (100.3 vs 94.68) effects were not significantly different. Conclusion: The present study suggests that both anesthetic techniques are equivalent in terms of the stability of the depth of anesthesia. It is important to keep testing the determinants of the efficacy of different populations because the individual behaviors of patients might ultimately tip the scale.

Resumen Introducción: La anestesia total intravenosa (TIVA, por sus siglas en inglés) y la anestesia balanceada (AB) son las técnicas anestésicas más comúnmente utilizadas. La diferencia está en la variabilidad de la profundidad de la anestesia entre estas dos técnicas, lo cual pudiera predecir cuál es más segura para los pacientes y representar un menor riesgo de despertar intraoperatorio. Objetivo: Determinar si existe alguna diferencia en la variabilidad de la profundidad de la anestesia obtenida según los índices de entropía de respuesta (ER). Métodos: Se llevó a cabo un estudio clínico cruzado en 20 pacientes sanos que se sometieron a cirugía ortopédica ambulatoria de miembros superiores o inferiores. Los pacientes se asignaron aleatoriamente así: a) infusión controlada por objetivo (TCI, por sus siglas en inglés) de propofol, utilizando el modelo Schnider a una concentración objetivo de 2,5 µg/mL durante 15 min y un período de lavado de 10 minutos, seguido de la administración de sevoflurano a 0,8 de concentración alveolar mínima (CAM) durante el tiempo restante de la cirugía; o b) la secuencia inversa. Las diferencias en la variabilidad de la profundidad de la anestesia utilizando entropía de respuesta se evaluaron utilizando la prueba t pareada. Resultados: El efecto del tratamiento no mostró ninguna diferencia significativa en los valores promedio de entropía de respuesta (ER) durante TIVA = 97,23 vs. AB 97,04 (P = 0,39). Los efectos de arrastre (-4,98 vs. 4,08) y período (100,3 vs. 94,68) no fueron significativamente diferentes. Conclusiones: El presente estudio sugiere que ambas técnicas anestésicas son equivalentes en términos de estabilidad de la profundidad de la anestesia. Es importante continuar probando los factores determinantes de eficacia en las distintas poblaciones, ya que el comportamiento individual de cada paciente pudiera finalmente inclinar la balanza.

CENTERS OF PHYSICAL ACTIVITIES AND HEALTH PROMOTION DURING THE COVID-19 PANDEMIC / CENTROS DE ATIVIDADES FÍSICAS E PROMOCÃO DE SAÚDE DURANTE A PANDEMIA DA COVID-19

Parece que esquemos que o mundo já enfrentara outras pandemias e, commaior ênfase, necessita combater outra pandemia, de natura diferente, representada pela inatividade física e hábito sedentário. De acordo com a OMS, somente no Brasil, doenças relacionadas ao sedentarismo matam 300 mil pessoas por ano e, no mundo, são aproximadamente 3,2 milhões de mortes anuais em decorrência desse comportamento prejudicial à saúde e qualidade de vida da população. Nesse sentido, questiona-se o porquê que, em alguns países do mundo, os centros de atividades físicas continuam fechados? Quando a própria OMS incentiva a manutenção da prática regular de atividades físicas como estratégia de promoção de saúde. Dessa forma, o referido ponto de vista tem como objetivo principal elucidar, através de evidências científicas, a importância e possibilidades de reabertura de centros de atividades físicas outdoor e indoor, visando à melhoria e manutenção da saúde e da qualidade de vida da população.

Soluble interleukin-6 receptor in young adults and its relationship with body composition and autonomic nervous system.

BACKGROUND: The immune system generates inflammatory responses through cytokines like Interleukin 6 (IL-6) and the Tumor Necrosis Factor alpha (TNF α); these cytokines mediate cellular responses aided by the presence of soluble receptors such as: Soluble Interleukin 6 Receptor (sIL6R) and Soluble Tumor Necrosis Factor Receptors Type 1 and 2 (sTNFR1, sTNFR2); the literature is limited about the relationship between this cytokines and the role of its soluble receptors. OBJECTIVES: This study is to determine a possible relationship between specific inflammatory markers and their soluble receptors with the autonomic nervous system's activity and body composition. METHODS: 27 subjects (13 men of 19.3 ± 1.6 years old and 14 women of 19.1 ± 1.7 years old) were evaluated. Body composition, autonomic nervous system activity and plasma concentration of inflammatory markers IL-6, TNF α, sIL6R, sTNFR1 and sTNFR2 were measured using bio-impedance, heart rate variability and ELISA respectively. RESULTS: A positive association between body-fat percentage and the sIL6R (0.47, p = .013) as well as inverse relationship between muscular mass and the sIL6R (-0.45, p = .019) were found. The sIL6R was also positively correlated with sympathetic activity markers: Relation LF/HF (0.52, p = .006), cardiac sympathetic index (0.45, p = .008), and cardiac vagal index (-0.44, p = .022). CONCLUSION: This study suggested that the IL-6 trans-signaling involving both the soluble receptor, sIL6R, and gp130 membrane co-receptor could produce inflammatory responses that generate an impact on the autonomic nervous system, possibly due to its direct action on the hypothalamus, the solitary tract nucleus, or the heart.

Revisión sistemática de "miocinas y regulación metabólica" / A systematic review of "myokines and metabolic regulation"

Malos hábitos como el sedentarismo, obesidad o sobrealimentación, se relacionan a la evolución de estados pro-inflamatorios crónicos, principal factor de riesgo para el desarrollo de enfermedades crónicas no transmisibles (ECNT). Sin embargo, modificar únicamente el peso corporal no reduce el riesgo, es necesario también aumentar la masa muscular, dando a entender que existe una relación benéfica asociada a este tejido que no está totalmente dilucidada. Durante los últimos años, las explicaciones celulares más interesantes se han enfocado en la producción de citokinas musculares denominadas miokinas, dentro de las que se destacan la interleucina 6, el factor inhibidor de la leucemia, entre otras recientemente estudiadas como lo son la mionectina y la musclina. Debido a los múltiples avances, se realiza una revisión que pretende: presentar los hallazgos más recientes y representativos acerca de las miokinas, corregir conceptos y demostrar su aplicabilidad en la prescripción del ejercicio físico para la salud

Bad habits such as sedentary lifestyle, obesity or overfeeding, are related to the production of chronic pro-inflammatory states, the main risk factor for the development of chronic noncommunicable diseases (CNCD). However, modifying only the body weight does not reduce the risk, it is necessary to increase muscle mass, this implies there is a beneficial relationship associated with the muscle tissue that is not fully elucidated. During the last years, the most interesting cellular explanations have focused on the production of muscle cytokines called myokines, among which stand out interleukin 6, the inhibitory factor of leukemia, with others recently studied such as mionectine and muscline. Due to the multiple advances, this intends to present the most recent and representative findings about myokines, correct concepts and demonstrate their applicability in the prescription of physical exercise for health

Respuesta carta al Editor / Reply to Letter to the Editor

Reply to Letter to the Editor

Heart rate variability and body composition as vo2max determinants / Variabilidade da frequência cardíaca e composição corporal como determinantes do vo2máx / Variabilidad de la frecuencia cardiaca y composición corporal como determinantes del vo2max

ABSTRACT Introduction: The maximum oxygen consumption (VO2max) is the gold standard in the cardiorespiratory endurance assessment. Objective: This study aimed to develop a mathematical model that contains variables to determine the VO2max of sedentary people. Methods: Twenty participants (10 men and 10 women) with a mean age of 19.8±1.77 years were included. For each participant, body composition (percentage of fat and muscle), heart rate variability (HRV) at rest (supine and standing), and VO2max were evaluated through an indirect test on a cycloergometer. A multivariate linear regression model was developed from the data obtained, and the model assumptions were verified. Results: Using the data obtained, including percentage of fat (F), percentage of muscle (M), percentage of power at very low frequency (VLF), α-value of the detrended fluctuation analysis (DFAα1), heart rate (HR) in the resting standing position, and age of the participants, a model was established for men, which was expressed as VO2max = 4.216 + (Age*0.153) + (F*0.110) - (M*0.053) - (VLF*0.649) - (DFAα1*2.441) - (HR*0.014), with R2 = 0.965 and standard error = 0.146 L/min. For women, the model was expressed as VO2max = 1.947 - (Age*0.047) + (F*0.024) + (M*0.054) + (VLF*1.949) - (DFAα1*0.424) - (HR*0.019), with R2 = 0.987 and standard error = 0.077 L/min. Conclusion: The obtained model demonstrated the influence exerted by body composition, the autonomic nervous system, and age in the prediction of VO2max.

RESUMO Introdução: O consumo máximo de oxigênio (VO2máx) é o padrão-ouro na avaliação da resistência cardiorrespiratória. Objetivo: Este estudo visou desenvolver um modelo matemático com as variáveis usadas na determinação do VO2máx em indivíduos sedentários. Método: Vinte indivíduos (10 homens e 10 mulheres) com média de idade 19,8±1,77 anos foram incluídos. Para cada participante, foram avaliados composição corporal (percentual de gordura e de músculo), variabilidade da frequência cardíaca (VFC) em repouso (em decúbito dorsal e em pé) e o VO2máx, empregando-se o protocolo em cicloergômetro, método indireto. A partir dos dados obtidos, desenvolveu-se um modelo de regressão linear multivariado e os pressupostos do modelo foram verificados. Resultados: Usando os dados obtidos, incluindo percentual de gordura (G), porcentagem de músculos (M), porcentagem de energia em frequência muito baixa (FMB), valor de α da análise de flutuação sem tendências (DFAα1), frequência cardíaca (FC) em repouso na posição em pé e a idade dos participantes, estabeleceu-se um modelo para homens, expresso como: VO2máx = 4,216 + (Idade*0,153) + (G*0,110) - (M*0,053) - (FMB0,649*) - (DFAα1*2,441) - (FC*0,014) com R2 = 0,965 e erro padrão = 0,146 L/min. Para as mulheres, o modelo foi expresso como: VO2máx = 1,947 - (Idade*0,047) + (G*0,024) + (M*0,054) + (FMB*1,949) - (DFAα1*0,424) - (FC*0,019) com R2 = 0,987 e erro padrão de 0,077 L/min. Conclusão: O modelo desenvolvido demonstrou a influência exercida pela composição corporal, pelo sistema nervoso autônomo e pela idade na predição do VO2máx.

RESUMEN Introducción: El consumo máximo de oxígeno (VO2max) es el patrón áureo en la evaluación de la resistencia cardiorrespiratoria. Objetivo: Este estudio tuvo como objetivo desarrollar un modelo matemático con las variables que participan en la determinación del VO2max en individuos sedentarios. Método: Veinte sujetos (10 hombres y 10 mujeres) con edad promedio de 19,8 ± 1,77 años se han incluido. Para cada participante, se evaluó la composición corporal (porcentaje de grasa y músculo), variabilidad de la frecuencia cardiaca (VFC) en reposo (decúbito supino y en pie) y VO2max mediante un test indirecto en cicloergómetro. A partir de los datos obtenidos se desarrolló un modelo de regresión lineal multivariado y se comprobaron los supuestos del modelo. Resultados: Usando los datos obtenidos, incluyendo porcentaje de grasa (G), porcentaje de músculos (M), porcentaje de energía en frecuencia muy baja (FMB), valor de α del análisis de fluctuación sin tendencias (DFAα1), frecuencia cardiaca (FC) en reposo en la posición en pie y la edad de los participantes, se estableció un modelo para hombres que se expresa como VO2max = 4,216 + (Edad*0,153) + (G*0,110) - (M*0,053) - (FMB*0,649) - (DFAα1*2,441) - (FC*0,014) con R2 = 0,965 y error típico = 0,146 L/min. Para las mujeres el modelo se expresó como VO2max = 1,947 - (Edad*0,047) + (G*0,024) + (M*0,054) + (FMB*1,949) - (DFAα1*0,424) - (FC*0,019) con R2 = 0,987 y error típico de 0,077 L/min. Conclusión: El modelo desarrollado demostró la influencia ejercida por la composición corporal, el sistema nervioso autónomo y la edad en la predicción del VO2max.

Carta al Editor / Letter to the Editor

Letter to the Editor

Ensayo clínico cruzado y aleatorizado para comparar dos modelos farmacocinéticos de propofol usando índices de entropía / Randomized cross-over clinical trial comparing two pharmacokinetic models of propofol using entropy indices

Introduction: There are two different pharmacokinetic models (Marsh and Schnider) for the administration of total intravenous anesthesia with propofol, the parameter differences could have some impact over the depth of anesthesia. Objective: To determine if there is a significant difference in the variability of depth of anesthesia suggesting that one model is superior in achieving a more stable and predictable depth of anesthesia during surgery. Methods: A cross-over clinical trial was conducted on 16 healthy patients programmed for upper or lower limb ambulatory orthopedic surgery. Patients were randomly assigned to (i) effect site target controlled infusion of propofol with Marsh model at a target concentration of 2.5 μg/ml for 20 min, a 20 min washout, then propofol was administered with Schnider model at the same effect site target for the reminder of the surgery, or (ii) the reverse sequence. Differences in variability of depth of anesthesia, were assessed by comparing records of spectral entropy indices during surgery through an unpaired t-test. Results: There was no evidence of significant difference in the mean variances of either spectral entropy indices between the two models (p-value: 0.57 for State Entropy, p-value: 0.51 for Response Entropy). Conclusion: The study suggests that both pharmacokinetic models are equivalent in terms of stability of depth of anesthesia. It is important to keep testing determinants of the efficacy of the models in different types of population because their behavior according to individual characteristics of patients or variables such as cost-effectiveness could end up tilting the scale.

Introducción: Hay dos modelos farmacocinéticos diferentes para la administración de la anestesia total intravenosa con propofol (Marsh y Schnider), las diferencias entre los parámetros podrían tener algún impacto sobre la profundidad anestésica. Objetivo: Comparar la variabilidad de la profundidad anestésica durante administración de infusión de propofol con los modelos de Marsh y Schnider para determinar si hay diferencias significativas que sugieran que uno de los modelos es superior en lograr una profundidad anestésica más estable y predecible. Métodos: Estudio clínico cruzado, controlado y aleatorizado llevado a cabo en 16 pacientes programados para cirugía ambulatoria de ortopedia. Los pacientes fueron asignados aleatoriamente a i) infusión controlada por objetivo de propofol con el modelo de Marsh a una concentración objetivo en sitio de efecto de 2.5μg/ml durante 20 minutos, 20 minutos de periodo de lavado, seguido de infusión de propofol con modelo de Schnider a la misma concentración objetivo; o ii) la secuencia inversa. La diferencia en variabilidad de profundidad anestésica fue evaluada mediante la comparación de registros de índices de entropía con una prueba t no pareada. Resultados: No se encontró evidencia de diferencias significativas de la varianza media en los índices de entropía espectral asociada a los modelos (valor-p: 0.57 para entropía de estado, valor-p: 0.51 para entropía de respuesta). Conclusión: El estudio sugiere que ambos modelos son equivalentes en términos de estabilidad de profundidad anestésica. Es importante continuar estudiando la eficacia de los modelos en diferentes tipos de población, dado que su comportamiento según características individuales de los pacientes o variables cómo costo-efectividad podrían inclinar la balanza.