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 Respiratory system reactance reflects communicating lung volume in chronic obstructive pulmonary disease

2019 ◽  
Vol 126 (5) ◽  
pp. 1223-1231 ◽  
Author(s):  
Stephen Milne ◽  
Kanika Jetmalani ◽  
David G. Chapman ◽  
Joseph M. Duncan ◽  
Claude S. Farah ◽  
...  
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Pulmonary Disease ◽  
Respiratory System ◽  
Lung Volume ◽  
Forced Oscillation ◽  
Chronic Obstructive ◽  
Forced Oscillation Technique ◽  
Obstructive Pulmonary Disease ◽  
Volume Relationship ◽  
Residual Capacity

Respiratory system reactance (Xrs) measured by the forced oscillation technique (FOT) is theoretically and experimentally related to lung volume. In chronic obstructive pulmonary disease (COPD), the absolute volume measured by body plethysmography includes a proportion that is inaccessible to pressure oscillations applied via the mouth, that is, a “noncommunicating” lung volume. We hypothesized that in COPD the presence of noncommunicating lung would disrupt the expected Xrs-volume relationship compared with plethysmographic functional residual capacity (FRCpleth). Instead, Xrs would relate to estimates of communicating volume, namely, expiratory reserve volume (ERV) and single-breath alveolar volume (VaSB). We examined FOT and lung function data from people with COPD ( n = 51) and from healthy volunteers ( n = 40). In healthy volunteers, we observed an expected inverse relationship between reactance at 5 Hz (X5) and FRCpleth. In contrast, there was no such relationship between X5 and FRCpleth in COPD subjects. However, there was an inverse relationship between X5 and both ERV and VaSB. Hence the theoretical Xrs-volume relationship is present in COPD but only when considering the communicating volume rather than the absolute lung volume. These findings confirm the role of reduced communicating lung volume as an important determinant of Xrs and therefore advance our understanding and interpretation of FOT measurements in COPD. NEW & NOTEWORTHY To investigate the determinants of respiratory system reactance (Xrs) measured by the forced oscillation technique (FOT) in chronic obstructive pulmonary disease (COPD), we examine the relationship between Xrs and lung volume. We show that Xrs does not relate to absolute lung volume (functional residual capacity) in COPD but instead relates only to the volume of lung in communication with the airway opening. This communicating volume may therefore be fundamental to our interpretation of FOT measurements in COPD and other pulmonary diseases.

Effect of airway smooth muscle tone on airway distensibility measured by the forced oscillation technique in adults with asthma

2012 ◽  
Vol 112 (9) ◽  
pp. 1494-1503 ◽  
Author(s):  
Vanessa J. Kelly ◽  
Nathan J. Brown ◽  
Scott A. Sands ◽  
Brigitte M. Borg ◽  
Gregory G. King ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Lung Volume ◽  
Forced Oscillation ◽  
Muscle Tone ◽  
Forced Oscillation Technique ◽  
Airway Closure ◽  
Lung Volumes ◽  
Volume Relationship ◽  
Residual Capacity

Airway distensibility appears to be unaffected by airway smooth muscle (ASM) tone, despite the influence of ASM tone on the airway diameter-pressure relationship. This discrepancy may be because the greatest effect of ASM tone on airway diameter-pressure behavior occurs at low transpulmonary pressures, i.e., low lung volumes, which has not been investigated. Our study aimed to determine the contribution of ASM tone to airway distensibility, as assessed via the forced oscillation technique (FOT), across all lung volumes with a specific focus on low lung volumes. We also investigated the accompanying influence of ASM tone on peripheral airway closure and heterogeneity inferred from the reactance versus lung volume relationship. Respiratory system conductance and reactance were measured using FOT across the entire lung volume range in 22 asthma subjects and 19 healthy controls before and after bronchodilator. Airway distensibility (slope of conductance vs. lung volume) was calculated at residual volume (RV), functional residual capacity (FRC), and total lung capacity. At baseline, airway distensibility was significantly lower in subjects with asthma at all lung volumes. After bronchodilator, distensibility significantly increased at RV (64.8%, P < 0.001) and at FRC (61.8%, P < 0.01) in subjects with asthma but not in control subjects. The increased distensibility at RV and FRC in asthma were not associated with the accompanying changes in the reactance versus lung volume relationship. Our findings demonstrate that, at low lung volumes, ASM tone reduces airway distensibility in adults with asthma, independent of changes in airway closure and heterogeneity.

scholarly journals Airway Closure during Surgical Pneumoperitoneum in Obese Patients

2019 ◽  
Vol 131 (1) ◽  
pp. 58-73 ◽  
Author(s):  
Domenico Luca Grieco ◽  
Gian Marco Anzellotti ◽  
Andrea Russo ◽  
Filippo Bongiovanni ◽  
Barbara Costantini ◽  
...  
Keyword(s):  
Lung Volume ◽  
Respiratory Mechanics ◽  
Lung Mechanics ◽  
Control Group ◽  
Obese Patients ◽  
Airway Closure ◽  
Alveolar Pressure ◽  
Opening Pressure ◽  
Airway Opening ◽  
Pressure Controlled

AbstractEditor’s PerspectiveWhat We Already Know about This TopicWhat This Article Tells Us That Is NewBackgroundAirway closure causes lack of communication between proximal airways and alveoli, making tidal inflation start only after a critical airway opening pressure is overcome. The authors conducted a matched cohort study to report the existence of this phenomenon among obese patients undergoing general anesthesia.MethodsWithin the procedures of a clinical trial during gynecological surgery, obese patients underwent respiratory/lung mechanics and lung volume assessment both before and after pneumoperitoneum, in the supine and Trendelenburg positions, respectively. Among patients included in this study, those exhibiting airway closure were compared to a control group of subjects enrolled in the same trial and matched in 1:1 ratio according to body mass index.ResultsEleven of 50 patients (22%) showed airway closure after intubation, with a median (interquartile range) airway opening pressure of 9 cm H2O (6 to 12). With pneumoperitoneum, airway opening pressure increased up to 21 cm H2O (19 to 28) and end-expiratory lung volume remained unchanged (1,294 ml [1,154 to 1,363] vs. 1,160 ml [1,118 to 1,256], P = 0.155), because end-expiratory alveolar pressure increased consistently with airway opening pressure and counterbalanced pneumoperitoneum-induced increases in end-expiratory esophageal pressure (16 cm H2O [15 to 19] vs. 27 cm H2O [23 to 30], P = 0.005). Conversely, matched control subjects experienced a statistically significant greater reduction in end-expiratory lung volume due to pneumoperitoneum (1,113 ml [1,040 to 1,577] vs. 1,000 ml [821 to 1,061], P = 0.006). With airway closure, static/dynamic mechanics failed to measure actual lung/respiratory mechanics. When patients with airway closure underwent pressure-controlled ventilation, no tidal volume was inflated until inspiratory pressure overcame airway opening pressure.ConclusionsIn obese patients, complete airway closure is frequent during anesthesia and is worsened by Trendelenburg pneumoperitoneum, which increases airway opening pressure and alveolar pressure: besides preventing alveolar derecruitment, this yields misinterpretation of respiratory mechanics and generates a pressure threshold to inflate the lung that can reach high values, spreading concerns on the safety of pressure-controlled modes in this setting.

Long-term medical and psychosocial outcomes in congenital diaphragmatic hernia survivors

2019 ◽  
Vol 104 (8) ◽  
pp. 761-767 ◽  
Author(s):  
Jason K Tan ◽  
Georgia Banton ◽  
Corrado Minutillo ◽  
Graham L Hall ◽  
Andrew Wilson ◽  
...  
Keyword(s):  
Congenital Diaphragmatic Hernia ◽  
Diaphragmatic Hernia ◽  
Chest Ct ◽  
Lung Mechanics ◽  
Control Group ◽  
Architectural Distortion ◽  
Forced Oscillation Technique ◽  
Z Score

ObjectiveSurvival rates for congenital diaphragmatic hernia (CDH) are increasing. The long-term outcomes of CDH survivors were compared with a healthy control group to assess the morbidity for guidance of antenatal counselling and long-term follow-up programmes.Participants and designParticipants born with CDH in Western Australia 1993–2008 were eligible with matched controls from the general population. Participants had comprehensive lung function tests, echocardiogram, low-dose chest CT scan and completed a Strengths and Difficulties Questionnaire (SDQ) and quality of life (QOL) questionnaire.Results34 matched case–control pairs were recruited. Demographic data between groups were similar. Cases were smaller at follow-up (weight Z-score of −0.2vs0.3; p=0.03; height Z-score of −0.3vs0.6; p=0.01). Cases had lower mean Z-scores for forced expiratory volume in 1 s (FEV1) (−1.49 vs −0.01; p=0.004), FEV1/forced vital capacity (−1.92 vs −1.2; p=0.009) and forced expiratory flow at 25-75% (FEF25-75) (−1.18vs0.23; p=0.007). Cases had significantly worse respiratory mechanics using forced oscillation technique. Subpleural triangles architectural distortion, linear opacities and scoliosis on chest CT were significantly higher in cases. Prosthetic patch requirement was associated with worse lung mechanics and peak cough flow. Cases had significantly higher rates of gastro-oesophageal reflux disease (GORD) and GORD medication usage. Developmental delay was significantly higher in cases. More cases had a total difficulties score in the high to very high range (25% vs 0%, p=0.03) on the SDQ and reported lower objective QOL scores (70.2 vs 79.8, p=0.02).ConclusionSurvivors of CDH may have significant adverse long-term medical and psychosocial issues that would be better recognised and managed in a multidisciplinary clinic.

The bimodal quasi-static and dynamic elastance of the murine lung

2008 ◽  
Vol 105 (2) ◽  
pp. 685-692 ◽  
Author(s):  
Graeme R. Zosky ◽  
Tibor Z. Janosi ◽  
Ágnes Adamicza ◽  
Elizabeth M. Bozanich ◽  
Vincenzo Cannizzaro ◽  
...  
Keyword(s):  
Lung Volume ◽  
Lung Mechanics ◽  
Mouse Lung ◽  
Forced Oscillation Technique ◽  
Mechanically Ventilated ◽  
Thoracic Gas Volume ◽  
Residual Capacity ◽  
Gas Volume ◽  
Tissue Elastance

The double sigmoidal nature of the mouse pressure-volume (PV) curve is well recognized but largely ignored. This study systematically examined the effect of inflating the mouse lung to 40 cm H2O transrespiratory pressure (Prs) in vivo. Adult BALB/c mice were anesthetized, tracheostomized, and mechanically ventilated. Thoracic gas volume was calculated using plethysmography and electrical stimulation of the intercostal muscles. Lung mechanics were tracked during inflation-deflation maneuvers using a modification of the forced oscillation technique. Inflation beyond 20 cm H2O caused a shift in subsequent PV curves with an increase in slope of the inflation limb and an increase in lung volume at 20 cm H2O. There was an overall decrease in tissue elastance and a fundamental change in its volume dependence. This apparent “softening” of the lung could be recovered by partial degassing of the lung or applying a negative transrespiratory pressure such that lung volume decreased below functional residual capacity. Allowing the lung to spontaneously recover revealed that the lung required ∼1 h of mechanical ventilation to return to the original state. We propose a number of possible mechanisms for these observations and suggest that they are most likely explained by the unfolding of alveolar septa and the subsequent redistribution of the fluid lining the alveoli at high transrespiratory pressure.

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.

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.

scholarly journals Respiratory mechanics during initial lung aeration at birth in the preterm lamb

2020 ◽  
Vol 318 (3) ◽  
pp. L525-L532 ◽  
Author(s):  
Chiara Veneroni ◽  
David G. Tingay ◽  
Karen E. McCall ◽  
Prue M. Pereira-Fantini ◽  
Elizabeth J. Perkins ◽  
...  
Keyword(s):  
Lung Volume ◽  
Lung Mechanics ◽  
Forced Oscillation Technique ◽  
Volume Changes ◽  
Impedance Tomography ◽  
Lung Aeration ◽  
Sustained Inflation ◽  
Airway Opening ◽  
Respiratory System Resistance ◽  
Direct Reflection

Despite recent insights into the dynamic processes during lung aeration at birth, several aspects remain poorly understood. We aimed to characterize changes in lung mechanics during the first inflation at birth and their relationship to changes in lung volume. Intubated preterm lambs (gestational age, 124–127 days; n = 17) were studied at birth. Lung volume changes were measured by electrical impedance tomography (VL EIT). Respiratory system resistance (R5) and oscillatory compliance (Cx5) were monitored with the forced oscillation technique at 5 Hz. Lambs received 3–7 s of 8 cmH2O of continuous distending pressure (CDP) before delivery of a sustained inflation (SI) of 40 cmH2O. The SI was then applied until either Cx5 or the VL EIT or the airway opening volume was stable. CDP was resumed for 3–7 s before commencement of mechanical ventilation. The exponential increases with time of Cx5 and VL EIT from commencement of the SI were characterized by estimating their time constants (τCx5 and τVL EIT, respectively). During SI, a fast decrease in R5 and an exponential increase in Cx5 and VL EIT were observed. Cx5 and VL EIT provided comparable information on the dynamics of lung aeration in all lambs, with τCx5 and τVL EIT being highly linearly correlated ( r2 = 0.87, P < 0.001). Cx5 and VL EIT decreased immediately after SI. Despite the standardization of the animal model, changes in Cx5 and R5 both during and after SI were highly variable. Lung aeration at birth is characterized by a fast reduction in resistance and a slower increase in oscillatory compliance, the latter being a direct reflection of the amount of lung aeration.

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