scholarly journals Reactance and elastance as measures of small airways response to bronchodilator in asthma

2019 ◽  
Vol 127 (6) ◽  
pp. 1772-1781 ◽  
Author(s):  
S. A. Bhatawadekar ◽  
D. Leary ◽  
V. de Lange ◽  
U. Peters ◽  
S. Fulton ◽  
...  
Keyword(s):  
Respiratory System ◽  
Healthy Subjects ◽  
Low Frequency ◽  
Upper Airway ◽  
Study Groups ◽  
Small Airways ◽  
Tree Model ◽  
Effective Measure ◽  
Bronchodilator Response ◽  
Airway Function

Bronchodilation alters both respiratory system resistance (Rrs) and reactance (Xrs) in asthma, but how changes in Rrs and Xrs compare, and respond differently in health and asthma, in reflecting the contributions from the large and small airways has not been assessed. We assessed reversibility using spirometry and oscillometry in healthy and asthma subjects. Using a multibranch airway-tree model with the mechanics of upper airway shunt, we compared the effects of airway dilation and small airways recruitment to explain the changes in Rrs and Xrs. Bronchodilator decreased Rrs by 23.0 (19.0)% in 18 asthma subjects and by 13.5 (19.5)% in 18 healthy subjects. Estimated respiratory system elastance (Ers) decreased by 23.2 (21.4)% in asthma, with no significant decrease in healthy subjects. With the use of the model, airway recruitment of 15% across a generation of the small airways could explain the changes in Ers in asthma with no recruitment in healthy subjects. In asthma, recruitment accounted for 40% of the changes in Rrs, with the remaining explained by airway dilation of 6.8% attributable largely to the central airways. Interestingly, the same dilation magnitude explained the changes in Rrs in healthy subjects. Shunt only affected Rrs of the model. Ers was unaltered in health and unaffected by shunt in both groups. In asthma, Ers changed comparably to Rrs and could be attributed to small airways, while the change in Rrs was split between large and small airways. This implies that in asthma Ers sensed through Xrs may be a more effective measure of small airways obstruction and recruitment than Rrs. NEW & NOTEWORTHY This is the first study to quantify to relative contributions of small and large airways to bronchodilator response in healthy subjects and patients with asthma. The response of the central airways to bronchodilator was similar in magnitude in both study groups, whereas the response of the small airways was significant among patients with asthma. These results suggest that low-frequency reactance and derived elastance are both sensitive measures of small airway function in asthma.

scholarly journals Bronchodilator Response Predicts Longitudinal Improvement in Small Airway Function in World Trade Center Dust Exposed Community Members

2019 ◽  
Vol 16 (8) ◽  
pp. 1421 ◽  
Author(s):  
Deepak Pradhan ◽  
Ning Xu ◽  
Joan Reibman ◽  
Roberta M. Goldring ◽  
Yongzhao Shao ◽  
...  
Keyword(s):  
World Trade ◽  
World Trade Center ◽  
Small Airway ◽  
Forced Oscillation Technique ◽  
Small Airways ◽  
Bronchodilator Response ◽  
Airway Injury ◽  
Airway Function ◽  
Trade Center ◽  
Over Time

The evolution of lung function, including assessment of small airways, was assessed in individuals enrolled in the World Trade Center Environmental Health Center (WTC-EHC). We hypothesized that a bronchodilator response at initial evaluation shown by spirometry or in small airways, as measured by forced oscillation technique (FOT), would be associated with improvement in large and small airway function over time. Standardized longitudinal assessment included pre and post bronchodilator (BD) spirometry (forced vital capacity, FVC; forced expiratory volume in 1 second, FEV1) and FOT (resistance at 5 Hz, R5; resistance at 5 minus 20 Hz, R5–20). Longitudinal changes were assessed using linear mixed-effects modelling with adjustment for potential confounders (median follow-up 2.86 years; 95% measurements within 4.9 years). Data demonstrated: (1) parallel improvement in airflow and volume measured by spirometry and small airway function (R5 and R5–20) measured by FOT; (2) the magnitude of longitudinal improvement was tightly linked to the initial BD response; and (3) longitudinal values for small airway function on FOT were similar to residual abnormality observed post BD at initial visit. These findings suggest presence of reversible and irreversible components of small airway injury that are identifiable at initial presentation. These results have implications for treatment of isolated small airway abnormalities that can be identified by non-invasive effort independent FOT particularly in symptomatic individuals with normal spirometry indices. This study underscores the need to study small airway function to understand physiologic changes over time following environmental and occupational lung injury.

Modelling resistance and reactance with heterogeneous airway narrowing in mild to severe asthma

2015 ◽  
Vol 93 (3) ◽  
pp. 207-214 ◽  
Author(s):  
Swati A. Bhatawadekar ◽  
Del Leary ◽  
Geoffrey N. Maksym
Keyword(s):  
Frequency Dependence ◽  
Severe Asthma ◽  
Respiratory System ◽  
Upper Airway ◽  
Airway Disease ◽  
Small Airway ◽  
Small Airways ◽  
Airway Narrowing ◽  
Ventilation Heterogeneity

Ventilation heterogeneity is an important marker of small airway dysfunction in asthma. The frequency dependence of respiratory system resistance (Rrs) from oscillometry is used as a measure of this heterogeneity. However, this has not been quantitatively assessed or compared with other outcomes from oscillometry, including respiratory system reactance (Xrs) and the associated elastance (Ers). Here, we used a multibranch model of the human lung, including an upper airway shunt, to match previously reported respiratory mechanics in mild to severe asthma. We imposed heterogeneity by narrowing a proportion of the peripheral airways to account for patient Ers at 5 Hz, and then narrowed central airways to account for the remaining Rrs at 18 Hz. The model required >75% of the small airways to be occluded to reproduce severe asthma. While the model produced frequency dependence in Rrs, it was upward-shifted below 5 Hz compared with in-vivo results, indicating that other factors, including more distributed airway narrowing or central airway wall compliance, are required. However, Ers quantitatively reflected the imposed heterogeneity better than the frequency dependence of Rrs, independent of the frequency range for the estimation, and thus was a more robust measure of small-airway function. Thus, Ers appears to have greater potential as a clinical measure of early small-airway disease in asthma.

scholarly journals The Role of Airway Shunt Elastance on the Compartmentalization of Respiratory System Impedance

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Jason H. T. Bates
Keyword(s):  
Respiratory System ◽  
Upper Airway ◽  
Inverse Model ◽  
Tree Model ◽  
Upper Airways ◽  
Peripheral Airways ◽  
Pulmonary Airways ◽  
Peripheral Airway ◽  
In Series ◽  
Airway Tree

An inverse model consisting of two elastic compartments connected in series and served by two airway conduits has recently been fit to measurements of respiratory impedance in obese subjects. Increases in the resistance of the distal conduit of the model with increasing body mass index have been linked to peripheral airway compression by mass loading of the chest wall. Nevertheless, how the two compartments and conduits of this simple model map onto the vastly more complicated structure of an actual lung remain unclear. To investigate this issue, we developed a multiscale branching airway tree model of the respiratory system that predicts realistic input impedance spectra between 5 and 20 Hz with only four free parameters. We use this model to study how the finite elastances of the conducting airway tree and the proximal upper airways affect impedance between 5 and 20 Hz. We show that progressive constriction of the peripheral airways causes impedance to appear to arise from two compartments connected in series, with the proximal compartment being a reflection of the elastance of upper airway structures proximal to the tracheal entrance and the lower compartment reflecting the pulmonary airways and tissues. We thus conclude that while this simple inverse model allows evaluation of overall respiratory system impedance between 5 and 20 Hz in the presence of upper airway shunting, it does not allow the separate contributions of central versus peripheral pulmonary airways to be resolved.

scholarly journals Impulse Oscillometric Features and Respiratory System Models Track Small Airway Function in Children

10.5772/52579 ◽  
2013 ◽  
Author(s):  
Erika G. ◽  
Homer Nazeran ◽  
Carlos Ramos ◽  
Liza Rodriguez ◽  
Lidia Rascon ◽  
...  
Keyword(s):  
Respiratory System ◽  
Small Airway ◽  
System Models ◽  
Airway Function

Effects of activation frequency and force on low-frequency fatigue in human skeletal muscle

1999 ◽  
Vol 86 (4) ◽  
pp. 1337-1346 ◽  
Author(s):  
Stuart A. Binder-Macleod ◽  
David W. Russ
Keyword(s):  
Healthy Subjects ◽  
Human Skeletal Muscle ◽  
Low Frequency ◽  
Variable Frequency ◽  
Activation Pattern ◽  
Constant Frequency ◽  
Mean Frequency ◽  
Before And After ◽  
Low Frequency Fatigue ◽  
Force Time

No comparison of the amount of low-frequency fatigue (LFF) produced by different activation frequencies exists, although frequencies ranging from 10 to 100 Hz have been used to induce LFF. The quadriceps femoris of 11 healthy subjects were tested in 5 separate sessions. In each session, the force-generating ability of the muscle was tested before and after fatigue and at 2, ∼13, and ∼38 min of recovery. Brief (6-pulse), constant-frequency trains of 9.1, 14.3, 33.3, and 100 Hz and a 6-pulse, variable-frequency train with a mean frequency of 14.3 Hz were delivered at 1 train/s to induce fatigue. Immediately postfatigue, there was a significant effect of fatiguing protocol frequency. Muscles exhibited greater LFF after stimulation with the 9.1-, 14.3-, and variable-frequency trains. These three trains also produced the greatest mean force-time integrals during the fatigue test. At 2, ∼13, and ∼38 min of recovery, however, the LFF produced was independent of the fatiguing protocol frequency. The findings are consistent with theories suggesting two independent mechanisms behind LFF and may help identify the optimal activation pattern when functional electrical stimulation is used.

scholarly journals Effect of Acupuncture on Heart Rate Variability: A Systematic Review

2014 ◽  
Vol 2014 ◽  
pp. 1-19 ◽  
Author(s):  
Joanne W. Y. Chung ◽  
Vincent C. M. Yan ◽  
Hongwei Zhang
Keyword(s):  
Systematic Review ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
High Frequency ◽  
Healthy Subjects ◽  
Keyword Search ◽  
Data Extraction ◽  
Meta Analysis ◽  
Low Frequency ◽  
Control Group

Aim.To summarize all relevant trials and critically evaluate the effect of acupuncture on heart rate variability (HRV).Method.This was a systematic review with meta-analysis. Keyword search was conducted in 7 databases for randomized controlled trials (RCTs). Data extraction and risk of bias were done.Results.Fourteen included studies showed a decreasing effect of acupuncture on low frequency (LF) and low frequency to high frequency ratio (LF/HF ratio) of HRV for nonhealthy subjects and on normalized low frequency (LF norm) for healthy subjects. The overall effect was in favour of the sham/control group for high frequency (HF) in nonhealthy subjects and for normalized high frequency (HF norm) in healthy subjects. Significant decreasing effect on HF and LF/HF ratio of HRV when acupuncture was performed on ST36 among healthy subjects and PC6 among both healthy and nonhealthy subjects, respectively.Discussion.This study partially supports the possible effect of acupuncture in modulating the LF of HRV in both healthy and nonhealthy subjects, while previous review reported that acupuncture did not have any convincing effect on HRV in healthy subjects. More published work is needed in this area to determine if HRV can be an indicator of the therapeutic effect of acupuncture.

Comparative studies of the functioning of the respiratory system in children in conditions of health institutions

2021 ◽  
pp. 66-72
Author(s):  
Alena Anatolievna Antonova ◽  
Galina Aleksandrovna Yamanova
Keyword(s):  
Children And Adolescents ◽  
Respiratory System ◽  
Minute Volume ◽  
Control Measures ◽  
Functional Study ◽  
Time Of Arrival ◽  
Effective Measure ◽  
Child Population ◽  
Respiratory Minute Volume ◽  
Student’S T

Summer health camp is a seasonal preventive institution for recreation, preservation and strengthening of the health of children and adolescents, which allows you to cover a large contingent of the child population with health-improving activities. The article presents the dynamics of the functional indicators of the respiratory system in children and adolescents who were in a summer health camp. On the basis of the children’s health camp «Young railroad worker» and the camp on the basis of a secondary educational school, research was carried out, in which children aged 7–10 years took part. Respiratory function was measured using a spirometer. The data obtained were analyzed using generally accepted methods of mathematical statistics. To identify the level of significance of differences, we used Student’s t-test.In children with round-the-clock stay in the camp, there is a statistically significant increase in Lung Capacity by 101.97 ml and a daytime stay — by 80.55 ml. At the end of the shift, summer health-improving recreation led to an increase in the indicators of the Respiratory Minute Volume (at the time of arrival, the Respiratory Minute Volume indicator in children 7–10 years old was 3,71 ± 1,03 l/min, and at the end 4,31 ± 1,88 l/min with round-the-clock stay; 3,65 ± 1,04 l/min and 4,1 ± 1,54 l/min with a daytime stay) due to an increase in Tidal Volume, which indicates a favorable respiratory response.The results of the functional study revealed an increase in the reserve capacity of the respiratory organs, which indicates the positive effect of the camp on the child’s body.The results obtained in the study of the functional state of respiration will make it possible to determine the directions and forms of organization of medical care in order to prevent deviations in the state of health. These results can serve as a basis for further in-depth research in summer camps of various types and the development of control measures and means of strengthening and maintaining the health of children. Thus, summer health camps are an effective measure of recreation and preservation, strengthening the health of the child population.

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