Expiratory Flow Limitation and Its Relation to Dyspnea and Lung Hyperinflation in Patients with Chronic Obstructive Pulmonary Disease: Analysis Using the Forced Expiratory Flow-Volume Curve and Critique

Background: Tidal expiratory flow limitation (tEFL) is defined as absence of increase in air flow during forced expiration compared to tidal breathing and is related to dyspnea at rest and minimal exertion in patients with chronic airflow limitation (CAL). Tidal EFL has not been expressed as a continuous variable (0% - 100%) in previous analyses. Objective: To relate the magnitude of tEFL to spirometric values and Modified Medical Research Council (MMRC) score and Asthma Control Test (ACT). Methods: Tidal EFL was computed as percent of the tidal volume (0% - 100%) spanned (intersected) by the forced expiratory-volume curve. Results: Of 353 patients screened, 192 (114 M, 78 F) patients (136 with COPD, 56 with asthma) had CAL. Overall characteristics: (mean ± SD) age 59 ± 11 years, BMI 28 ± 7, FVC (% pred) 85 ± 20, FEV1 (% pred) 66 ± 21, FEV1/FVC 55% ± 10%, RV (% pred) 147 ± 42. Tidal EFL in patients with tEFL was 53% ± 39%. Using univariate analysis, strongest correlations were between tEFL and FVC and between tEFL and RV in patients with BMI < 30 kg/m2. In patients with nonreversible CAL, tEFL was positively associated with increasing MMRC, negatively with spirometric measurements, and positively with RV/TLC. In asthmatics, ACT scores were higher in patients with mean BMI ≥ 28 kg/m2 (p < 0.00014) and RV/TLC values > 40% (p < 0.03). Conclusions: Dyspnea is strongly associated with tEFL and lung function, particularly in patients with nonreversible CAL. Air trapping and BMI contribute to tEFL.

射流引风空调匀温性能及其影响因素的仿真研究

采用STAR CCM+软件对立式空调流场进行数值模拟,根据计算结果,分析讨论了射流引风的机理,并对其影响因素进行研究,对比了不同气流形态、风量以及引风通道宽度的引风性能。结果表明,双股气流形式的引风效果明显,提高风量可以提升引风量,但引风量占比在达到一定数值后反而会有所降低,引风通道宽度过大和过小都会减弱射流引风的匀温性能。

胸内型上气道阻塞的流速容量曲线改变

胸内型上气道阻塞性疾病通常缺乏特征性临床表现。回顾分析本院1990－1992年间肺功能检查共502例，发现其中有2例胸内型上气道阻塞的病例。其肺功能用力呼气流速容量曲线有特征性的呼气相平台，此法简便易行，具有较高诊断价值．

A new geometrical and mechanical relation in the respiratory system with airflow limitation—From the perspective of analytical respiratory mechanics

Classic respiratory mechanics is a branch of vectorial mechanics, which aims to recognize all forces acting on the respiratory system. Another branch of mechanics, analytical mechanics, has been used for analyzing the motions of complicated systems with constraints through equilibrium among scalar quantities such as kinetic energy and potential energy. However, until now, there have not been any studies concerning about analytical respiratory mechanics. In this paper, the author has obtained two types of motion equations (linear and nonlinear) for the airflow limitation from formulation of the analytical respiratory mechanics. Reconstructed flow-volume trajectories of the linear equation revealed a new relationship among the slope of the linear portion of trajectory, the coefficient of the dissipation function and the coefficient of the potential function. Reconstructed trajectories of the nonlinear equation suggested that a curved flow-volume trajectory would be caused by the emergence of regional hypoventilated clusters with airtrapped lobules. In conclusion, analytical respiratory mechanics will provide the basis for analyzing the mechanical properties of the respiratory system con cerning pulmonary functional images made by newly developed technologies.

Analysis on relationship of parameters such as R5 and MEFV with severity of chronic cough in 3 to 5 years old children by impulse oscillometry detection

Objective:The article aims to investigate the relationship of parameters such as airway vicosity resistance (R5) and maximal expiratory flow-volume curve (MEFV) with severity of chronic cough in 3 to 5 years old children by impulse oscillometry (IOS) detection when the oscillation frequency is 5Hz.Method: The article chooses eighty children with chronic cough who were diagnosed or treated in our hospital from March 2017 to March 2018 as the research group, and chooses 50 healthy children who had physical examination in our hospital as the control group. Children's asthma control test (C-ACT) is used to assess the disease severity of children. MEFV detection is carried out to the two groups of children to obtain the ratio of forced expiratory volume in one second and forced vital capacity (FEV1/FVC) and the peak expiratory flow (PEF). LsS inductance (X5) is detected by IOS when R5, the resonant frequency (Fres), and the oscillation frequency is 5Hz. The relationship of ACT score with MEFV and IOS indicators is analyzed by Pearson correlation. The receiver operating characteristic (ROC) curve is used to evaluate the diagnostic value of MEFV and IOS indicators to chronic cough. Results: The C-ACT score of the severe group is significantly lower than that of the control group (P<0.05). FEV1/FVC and PEF of the mild and severe groups are both lower than those of the control group, and FEV1/FVC and PEF of the severe group is lower than those of the mild group (P<0.05). Fres, R5 and X5 of the mild and severe groups are significantly higher than those of the control group, and Fres, R5 and X5 of the severe group are higher than the mild group (P<0.05). FEV1/FVC and PEF are positively correlated with C-ACT score (P<0.05), while Fres, R5 and X5 are negatively correlated with C-ACT score (P<0.05). FEV1/FVC and PEF respectively shows significant negative correlations with Fres, R5 and X5 (P<0.05). R5 has a self-high ROC value of 0.938, followed by Fres, which is 0.917. And the value of IOS diagnostic indicators is higher than MEFV indicators.Conclusion: FEV1 / FVC and PEF of children with chronic cough will decrease while Fres, R5 and X5 will increase, of which Fres, R5 and X5 have a higher correlation with the severity of cough symptoms, and ROC analysis results also show that R5 has the highest diagnostic value to 3~5 years old children with chronic cough.