Signal processing to remove spurious contributions to the assessment of respiratory mechanics.

Signal disruptions in small animals during the realization of the Forced Oscillation Technique are a well-known cause of data loss as it leads to non-reliable estimations of the respiratory impedance. In this work, we assessed the effects of removing the disrupted epoch when a 3-seconds input signal composed of one and a half 2-seconds full cycle is used.We tested our hypothesis in 25 SAMR1 mice under different levels of bronchoconstriction due to methacholine administration by iv bolus injections in different doses (15 animals) and by iv continuous infusion in different infusion rates (10 animals). Signal disruptions were computationally simulated as sharp drops in the pressure signal within a short timescale, and signal processing was performed using own developed algorithms.We found that the model goodness of fit worsens when averaging techniques to estimate the input respiratory impedance are not used. However, no statistically significant differences were observed in the comparison between Constant Phase Model parameters of the full 3-s signal and the 2-s non disrupted epoch in all doses or infusion rates for both methacholine delivery strategies.The proposed technique presents reliable outcomes that can reduce animal use in Forced Oscillation Technique realization.

Drug class effects on respiratory mechanics in animal models: access and applications.

Assessment of respiratory mechanics extends from basic research and animal modeling to clinical applications in humans. However, to employ the applications in human models, it is desirable and sometimes mandatory to study non-human animals first. To acquire further precise and controlled signals and parameters, the animals studied must be further distant from their spontaneous ventilation. The majority of respiratory mechanics studies use positive pressure ventilation to model the respiratory system. In this scenario, a few drug categories become relevant: anesthetics, muscle blockers, bronchoconstrictors, and bronchodilators. Hence, the main objective of this study is to briefly review and discuss each drug category, and the impact of a drug on the assessment of respiratory mechanics. Before and during the positive pressure ventilation, the experimental animal must be appropriately sedated and anesthetized. The sedation will lower the pain and distress of the studied animal and the plane of anesthesia will prevent the pain. With those drugs, a more controlled procedure is carried out; further, because many anesthetics depress the respiratory system activity, a minimum interference of the animal's respiration efforts are achieved. The latter phenomenon is related to muscle blockers, which aim to minimize respiratory artifacts that may interfere with forced oscillation techniques. Generally, the respiratory mechanics are studied under appropriate anesthesia and muscle blockage. The application of bronchoconstrictors is prevalent in respiratory mechanics studies. To verify the differences among studied groups, it is often necessary to challenge the respiratory system, for example, by pharmacologically inducing bronchoconstriction. However, the selected bronchoconstrictor, doses, and administration can affect the evaluation of respiratory mechanics. Although not prevalent, studies have applied bronchodilators to return (airway resistance) to the basal state after bronchoconstriction. The drug categories can influence the mathematical modeling of the respiratory system, systemic conditions, and respiratory mechanics outcomes.

Does the BODE index reflect the level of physical activity in daily life in patients with COPD?

OBJECTIVES: To study the relationship between the level of physical activity in daily life and disease severity assessed by the BODE index in patients with chronic obstructive pulmonary disease (COPD). METHODS: Sixty-seven patients with COPD (36 men) with forced expiratory volume in the first second (FEV(1)) of 39 (27-47)% predicted and age of 66 (61-72) years old were evaluated by spirometry, dyspnea levels (measured by the Medical Research Council scale, MRC) and by the 6-minute walking test (6MWT). The BODE index was calculated based on the body mass index (weight/height²), FEV(1), MRC and 6MWT, and then the patients were divided in four quartiles according to their scores (Quartile I: 0 to 2 points, n=15; Quartile II: 3 to 4 points, n=20; Quartile III: 5 to 6 points, n=23; Quartile IV: 7 to 10 points, n=9). Two activity monitors (DynaPort® and SenseWear®) were used to evaluate the level of physical activity in daily life. The Kruskal-Wallis test (Dunns's post-hoc test), the Mann-Whitney test and the Spearman Correlation Coefficient were used for statistical analysis. RESULTS: There were modest correlation between the BODE index and the time spent walking per day, the total daily energy expenditure and the time spent in moderate and vigorous activities per day (-0.32 ≤ r ≤ -0.47; p≤0.01 for all variables). When comparing the pooled quartiles I+II with III+IV, there were significant difference between the time spent walking per day, the total daily energy expenditure and the time spent in moderate activities per day (p≤0.05). CONCLUSION: The level of physical activity in daily life has a modest correlation with the classification of COPD severity assessed by the BODE index, reflecting only differences between patients with classified as mild-moderate and severe-very severe COPD.

Does the BODE index reflect the level of physical activity in daily life in patients with COPD? / O índice BODE reflete o nível de atividade física na vida diária de pacientes com DPOC?

OBJECTIVES: To study the relationship between the level of physical activity in daily life and disease severity assessed by the BODE index in patients with chronic obstructive pulmonary disease (COPD). METHODS: Sixty-seven patients with COPD (36 men) with forced expiratory volume in the first second (FEV1) of 39 (27-47) percent predicted and age of 66 (61-72) years old were evaluated by spirometry, dyspnea levels (measured by the Medical Research Council scale, MRC) and by the 6-minute walking test (6MWT). The BODE index was calculated based on the body mass index (weight/height²), FEV1, MRC and 6MWT, and then the patients were divided in four quartiles according to their scores (Quartile I: 0 to 2 points, n=15; Quartile II: 3 to 4 points, n=20; Quartile III: 5 to 6 points, n=23; Quartile IV: 7 to 10 points, n=9). Two activity monitors (DynaPort® and SenseWear®) were used to evaluate the level of physical activity in daily life. The Kruskal-Wallis test (Dunns's post-hoc test), the Mann-Whitney test and the Spearman Correlation Coefficient were used for statistical analysis. RESULTS: There were modest correlation between the BODE index and the time spent walking per day, the total daily energy expenditure and the time spent in moderate and vigorous activities per day (-0.32 < r <- 0.47; p<0.01 for all variables). When comparing the pooled quartiles I+II with III+IV, there were significant difference between the time spent walking per day, the total daily energy expenditure and the time spent in moderate activities per day (p<0.05). CONCLUSION: The level of physical activity in daily life has a modest correlation with the classification of COPD severity assessed by the BODE index, reflecting only differences between patients with classified as mild-moderate and severe-very severe COPD.

OBJETIVOS: Estudar a relação entre nível de atividade física na vida diária (AFVD) e gravidade da Doença Pulmonar Obstrutiva Crônica (DPOC) avaliada pelo índice BODE. MÉTODOS: Sessenta e sete pacientes com DPOC (36 homens), com volume expiratório forçado no primeiro segundo (VEF1) 39(27-47) por centoprevisto, e 66(61-72)anos foram submetidos a avaliações de espirometria, grau de dispneia (Medical Research Council scale, MRC) e teste de caminhada de 6 minutos (TC6). O índice BODE foi calculado com base no índice de massa corpórea (peso/estatura²), VEF1, MRC e TC6, e os pacientes foram subdivididos em quatro quartis de acordo com sua pontuação no BODE (quartil I: 0 a 2 pontos, n=15; quartil II: 3 a 4 pontos, n=20; quartil III: 5 a 6 pontos, n=23; quartil IV: 7 a 10 pontos, n=9). O nível de AFVD foi avaliado por dois monitores de atividade física (DynaPort® e SenseWear®). Os testes de Kruskal-Wallis (pós-teste Dunns), Mann-Whitney e Coeficiente de Correlação de Spearman foram utilizados na análise estatística. RESULTADOS: Houve correlação modesta entre os escores do índice BODE e o tempo gasto andando/dia, gasto energético total e tempo gasto/dia em atividades moderadas e vigorosas (-0,32< r <-0,47; p<0.01 para todos). Quando comparados os quartis agrupados I+II com III+IV, houve diferença significante entre o tempo gasto andando/dia, gasto energético total e tempo gasto em atividades moderadas (p<0,05). CONCLUSÃO: O nível de AFVD apresenta correlação modesta com a classificação da gravidade da DPOC dada pelo índice BODE, refletindo apenas diferenças entre pacientes com doença leve-moderada e grave-muito grave.