Heterogeneity of bronchoconstriction does not distinguish mild asthmatic subjects from healthy controls when supine

2008 ◽  
Vol 104 (1) ◽  
pp. 10-19 ◽  
Author(s):  
David A. Kaminsky ◽  
Charles G. Irvin ◽  
Lennart K. A. Lundblad ◽  
John Thompson-Figueroa ◽  
Jeffrey Klein ◽  
...  
Keyword(s):  
Frequency Dependence ◽  
Computerized Tomography ◽  
Forced Oscillation ◽  
Fundamental Property ◽  
Lung Mechanics ◽  
Mild Asthma ◽  
Forced Oscillation Technique ◽  
Healthy Controls ◽  
Space Size ◽  
Air Space

Heterogeneity is a fundamental property of airway constriction; however, whether it is a distinguishing feature of mild asthma is not clear. We used computerized tomography and the forced oscillation technique to compare lung heterogeneity between 18 mildly asthmatic and 19 healthy control subjects at similar levels of bronchoconstriction while subjects were supine. We also assessed the effects of deep inhalation and albuterol on supine lung mechanics. Measures of heterogeneity included lung attenuation, from which we derived a novel index of air-space size, and the frequency dependence of respiratory system resistance between 1 and 20 Hz. We found that asthmatic subjects had airways hyperresponsiveness to methacholine in the sitting position compared with controls, but both groups had similar falls in forced expiratory volume in 1 s after inhaling methacholine while supine. There were no baseline differences between the groups in the frequency dependence of resistance, or lung attenuation, before methacholine, and both groups responded similarly with an increase in air-space size (+9.2% vs. +3.4%), air-space size heterogeneity (+9.8% vs. +4.2%), and frequency dependence of resistance (+76% vs. +86%) after methacholine. Deep inhalation did not affect resistance in either group, but albuterol significantly reduced resistance in both groups. We conclude that both computerized tomography and the forced oscillation technique demonstrate increased heterogeneity of airway narrowing during induced bronchoconstriction while supine and that this heterogeneity is equivalent between subjects with mild asthma and healthy controls when bronchoconstricted to the same degree. Thus heterogeneity appears to be a fundamental feature of bronchoconstriction and is not unique to mild asthma.

Effect of methacholine on peripheral lung mechanics and ventilation heterogeneity in asthma

2013 ◽  
Vol 114 (6) ◽  
pp. 770-777 ◽  
Author(s):  
Sue R. Downie ◽  
Cheryl M. Salome ◽  
Sylvia Verbanck ◽  
Bruce R. Thompson ◽  
Norbert Berend ◽  
...  
Keyword(s):  
Frequency Dependence ◽  
Forced Vital Capacity ◽  
Vital Capacity ◽  
Lung Mechanics ◽  
Forced Oscillation Technique ◽  
Airway Closure ◽  
Asthmatic Patients ◽  
Ventilation Heterogeneity ◽  
Trapped Gas ◽  
Lung Periphery

The forced oscillation technique (FOT) and multiple-breath nitrogen washout (MBNW) are noninvasive tests that are potentially sensitive to peripheral airways, with MBNW indexes being especially sensitive to heterogeneous changes in ventilation. The objective was to study methacholine-induced changes in the lung periphery of asthmatic patients and determine how changes in FOT variables of respiratory system reactance (Xrs) and resistance (Rrs) and frequency dependence of resistance (Rrs5-Rrs19) can be linked to changes in ventilation heterogeneity. The contributions of air trapping and airway closure, as extreme forms of heterogeneity, were also investigated. Xrs5, Rrs5, Rrs19, Rrs5-Rrs19, and inspiratory capacity (IC) were calculated from the FOT. Ventilation heterogeneity in acinar and conducting airways, and trapped gas (percent volume of trapped gas at functional residual capacity/vital capacity), were calculated from the MBNW. Measurements were repeated following methacholine. Methacholine-induced airway closure (percent change in forced vital capacity) and hyperinflation (change in IC) were also recorded. In 40 mild to moderate asthmatic patients, increase in Xrs5 after methacholine was predicted by increases in ventilation heterogeneity in acinar airways and forced vital capacity ( r2 = 0.37, P < 0.001), but had no correlation with ventilation heterogeneity in conducting airway increase or IC decrease. Increases in Rrs5 and Rrs5-Rrs19 after methacholine were not correlated with increases in ventilation heterogeneity, trapped gas, hyperinflation, or airway closure. Increased reactance in asthmatic patients after methacholine was indicative of heterogeneous changes in the lung periphery and airway closure. By contrast, increases in resistance and frequency dependence of resistance were not related to ventilation heterogeneity or airway closure and were more indicative of changes in central airway caliber than of heterogeneity.

Mechanical properties of the upper airway

1983 ◽  
Vol 55 (2) ◽  
pp. 335-342 ◽  
Author(s):  
M. Cauberghs ◽  
K. P. Van de Woestijne
Keyword(s):  
Mechanical Properties ◽  
Lung Disease ◽  
Frequency Dependence ◽  
Respiratory System ◽  
Obstructive Lung Disease ◽  
Forced Oscillation ◽  
Valsalva Maneuver ◽  
Upper Airway ◽  
Forced Oscillations ◽  
Forced Oscillation Technique

The series and shunt components of the impedance of the upper airway (Zuaw) were evaluated from measurements obtained during a Valsalva maneuver by means of a modified forced oscillation technique. When the cheeks are supported, the upper airway can be represented by a single distributed transmission line. The homogeneity of this line was confirmed by measuring separately Zuaw and the impedance of the mouth. Correction of the impedance of the respiratory system, determined by means of the forced oscillations technique, for the shunt properties of Zuaw results in some modifications of the frequency dependence of resistance (Rrs) in healthy adults and in marked changes of the absolute values of Rrs in children and in patients with obstructive lung disease.

Assessing regional lung mechanics by combining electrical impedance tomography and forced oscillation technique

2018 ◽  
Vol 63 (6) ◽  
pp. 673-681 ◽  
Author(s):  
Chuong Ngo ◽  
Sarah Spagnesi ◽  
Carlos Munoz ◽  
Sylvia Lehmann ◽  
Thomas Vollmer ◽  
...  
Keyword(s):  
Pulmonary Function ◽  
Electrical Impedance Tomography ◽  
High Frequency ◽  
Electrical Impedance ◽  
Forced Oscillation ◽  
Pulmonary Function Tests ◽  
Lung Mechanics ◽  
Forced Oscillation Technique ◽  
Impedance Tomography ◽  
Regional Lung

Abstract There is a lack of noninvasive pulmonary function tests which can assess regional information of the lungs. Electrical impedance tomography (EIT) is a radiation-free, non-invasive real-time imaging that provides regional information of ventilation volume regarding the measurement of electrical impedance distribution. Forced oscillation technique (FOT) is a pulmonary function test which is based on the measurement of respiratory mechanical impedance over a frequency range. In this article, we introduce a new measurement approach by combining FOT and EIT, named the oscillatory electrical impedance tomography (oEIT). Our oEIT measurement system consists of a valve-based FOT device, an EIT device, pressure and flow sensors, and a computer fusing the data streams. Measurements were performed on five healthy volunteers at the frequencies 3, 4, 5, 6, 7, 8, 10, 15, and 20 Hz. The measurements suggest that the combination of FOT and EIT is a promising approach. High frequency responses are visible in the derivative of the global impedance index $\Delta {Z_{{\text{eit}}}}(t,{f_{{\text{os}}}}).$ The oEIT signals consist of three main components: forced oscillation, spontaneous breathing, and heart activity. The amplitude of the oscillation component decreases with increasing frequency. The band-pass filtered oEIT signal might be a new tool in regional lung function diagnostics, since local responses to high frequency perturbation could be distinguished between different lung regions.

scholarly journals Measurement duration impacts variability but not impedance measured by the forced oscillation technique in healthy, asthma and COPD subjects

2016 ◽  
Vol 2 (2) ◽  
pp. 00094-2015 ◽  
Author(s):  
Joanna C. Watts ◽  
Claude S. Farah ◽  
Leigh M. Seccombe ◽  
Blake M. Handley ◽  
Robin E. Schoeffel ◽  
...  
Keyword(s):  
Data Acquisition ◽  
Respiratory System ◽  
Forced Oscillation ◽  
Chronic Obstructive ◽  
Forced Oscillation Technique ◽  
Healthy Controls ◽  
Obstructive Pulmonary Disease ◽  
Acquisition Duration ◽  
Measurement Duration ◽  
Testing Protocols

The forced oscillation technique (FOT) is gaining clinical acceptance, facilitated by more commercial devices and clinical data. However, the effects of variations in testing protocols used in FOT data acquisition are unknown. We describe the effect of duration of data acquisition on FOT results in subjects with asthma, chronic obstructive pulmonary disease (COPD) and healthy controls.FOT data were acquired from 20 healthy, 22 asthmatic and 18 COPD subjects for 60 s in triplicate. The first 16, 30 and 60 s of each measurement were analysed to obtain total, inspiratory and expiratory resistance of respiratory system (Rrs) and respiratory system reactance (Xrs) at 5 and 19 Hz.With increasing duration, there was a decrease in total and expiratory Rrs for healthy controls, total and inspiratory Rrs for asthmatic subjects and magnitude of total and inspiratory Xrs for COPD subjects at 5 Hz. These decreases were small compared to the differences between clinical groups. Measuring for 16, 30 and 60 s provided ≥3 acceptable breaths in at least 90, 95 and 100% of subjects, respectively. The coefficient of variation for total Rrs and Xrs also decreased with duration. Similar results were found for Rrs and Xrs at 19 Hz.FOT results are statistically, but likely minimally, impacted by acquisition duration in healthy, asthmatic or COPD subjects.

scholarly journals Early onset of airway derecruitment assessed using the forced oscillation technique in subjects with asthma

2019 ◽  
Vol 126 (5) ◽  
pp. 1399-1408 ◽  
Author(s):  
Kris Nilsen ◽  
Francis Thien ◽  
Cindy Thamrin ◽  
Matt J. Ellis ◽  
G. Kim Prisk ◽  
...  
Keyword(s):  
Lung Volume ◽  
Forced Oscillation ◽  
Lung Mechanics ◽  
Control Group ◽  
Forced Oscillation Technique ◽  
Rapid Reduction ◽  
Control Subjects ◽  
Volume Curve ◽  
Volume Relationship ◽  
Highly Correlated

Derecruitment of air spaces in the lung occurs when airways close during exhalation and is related to ventilation heterogeneity and symptoms in asthma. The forced oscillation technique has been used to identify surrogate measures of airway closure via the reactance (Xrs) versus lung volume relationship. This study used a new algorithm to identify derecruitment from the Xrs versus lung volume relationship from a slow vital capacity maneuver. We aimed to compare two derecruitment markers on the Xrs versus volume curve, the onset reduction of Xrs (DR1vol) and the onset of more rapid reduction of Xrs (DR2vol), between control and asthmatic subjects. We hypothesized that the onset of DR1vol and DR2vol occurred at higher lung volume in asthmatic subjects. DR1vol and DR2vol were measured in 18 subjects with asthma and 18 healthy controls, and their relationships with age and height were examined using linear regression. In the control group, DR1vol and DR2vol increased with age ( r2 = 0.68, P < 0.001 and r2 = 0.71, P < 0.001, respectively). DR1vol and DR2vol in subjects with asthma [76.58% of total lung capacity (TLC) and 56.79%TLC, respectively] were at higher lung volume compared with control subjects (46.1 and 37.69%TLC, respectively) ( P < 0.001). DR2vol correlated with predicted values of closing capacity ( r = 0.94, P < 0.001). This study demonstrates that derecruitment occurs at two points along the Xrs-volume relationship. Both derecruitment points occurred at significantly higher lung volumes in subjects with asthma compared with healthy control subjects. This technique offers a novel way to measure the effects of changes in airways/lung mechanics. NEW & NOTEWORTHY This study demonstrates that the forced oscillation technique can be used to identify two lung volume points where lung derecruitment occurs: 1) where derecruitment is initiated and 2) where onset of rapid derecruitment commences. Measurements of derecruitment increase with age. The onset of rapid derecruitment was highly correlated with predicted closing capacity. Also, the initiation and rate of derecruitment are significantly altered in subjects with asthma.

scholarly journals Frequency dependence of forced oscillatory respiratory mechanics in horses with heaves

1997 ◽  
Vol 82 (3) ◽  
pp. 983-987 ◽  
Author(s):  
S. S. Young ◽  
D. Tesarowski ◽  
L. Viel
Keyword(s):  
Frequency Dependence ◽  
Respiratory Mechanics ◽  
Forced Oscillation ◽  
Element Model ◽  
Airway Disease ◽  
Allergic Airway Disease ◽  
Forced Oscillation Technique ◽  
Respiratory Impedance ◽  
Antigenic Challenge ◽  
Small Airway Obstruction

Young, S. S., D. Tesarowski, and L. Viel. Frequency dependence of forced oscillatory respiratory mechanics in horses with heaves. J. Appl. Physiol. 82(3): 983–987, 1997.—The effect of measurement frequency on respiratory mechanics was investigated in six horses with reversible allergic airway disease. Total respiratory impedance was measured at 1.5, 2.0, 3.0, and 5.0 Hz by using the forced oscillation technique with the horses in remission, after acute antigenic challenge producing clinical heaves, and with heaves but after the administration of 2 mg fenoterol by inhalation. The slopes of the magnitude (‖Zrs‖) and real part (R) of total respiratory impedance over the frequency range 1.5–3 Hz changed significantly after antigenic challenge and fenoterol. The ratio of R at 2 Hz to R at 3 Hz, however, discriminated better among the three conditions. Compliance and resonant frequency (calculated by using a three-element model) changed significantly after antigenic challenge and fenoterol, but inertance did not. We concluded that horses with heaves showed frequency dependence of R and ‖Zrs‖ at frequencies up to 3 Hz and that parameters derived from a three-element model were useful indicators of small airway obstruction in the horse.

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