Tidal airway closure in asthma and COPD

<span style="font-family: 'Times','serif'; font-size: 12pt; mso-ansi-language: EN-US; mso-fareast-font-family: Times; mso-bidi-font-family: 'Times New Roman'; mso-fareast-language: IT; mso-bidi-language: AR-SA;" lang="EN-US">Functional closure of small airways can occur during tidal breathing above functional residual capacity (FRC) both in asthma and COPD patients, especially during exacerbations. Such event has several noxious consequences on gas exchange, airway hyperresponsiveness and mechanical stress and strain within lung tissue and airway wall, mostly due to increase in ventilation heterogeneity. The availability of simple functional tests based on sequential measurements of lung volumes (i.e.: FRC), by plethysmography and dilutional techniques may reveal and monitor easily tidal airway closure that can be and should be treated with the aim of abolishing or at least reducing this dangerous condition.

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Obesity and Asthma: Physiological Perspective

Journal of Allergy ◽

10.1155/2013/198068 ◽

2013 ◽

Vol 2013 ◽

pp. 1-11 ◽

Cited By ~ 4

Author(s):

Bill Brashier ◽

Sundeep Salvi

Keyword(s):

Airway Hyperresponsiveness ◽

Airway Resistance ◽

Smooth Muscle Contraction ◽

Small Airways ◽

Physiological Changes ◽

Tidal Breathing ◽

Expiratory Flow Limitation ◽

Lung Volumes ◽

Normal Breathing ◽

Residual Capacity

Obesity induces some pertinent physiological changes which are conducive to either development of asthma or cause of poorly controlled asthma state. Obesity related mechanical stress forces induced by abdominal and thoracic fat generate stiffening of the lungs and diaphragmatic movements to result in reduction of resting lung volumes such as functional residual capacity (FRC). Reduced FRC is primarily an outcome of decreased expiratory reserve volume, which pushes the tidal breathing more towards smaller high resistance airways, and consequentially results in expiratory flow limitation during normal breathing in obesity. Reduced FRC also induces plastic alteration in the small collapsible airways, which may generate smooth muscle contraction resulting in increased small airway resistance, which, however, is not picked up by spirometric lung volumes. There is also a possibility that chronically reduced FRC may generate permanent adaptation in the very small airways; therefore, the airway calibres may not change despite weight reduction. Obesity may also induce bronchodilator reversibility and diurnal lung functional variability. Obesity is also associated with airway hyperresponsiveness; however, the mechanism of this is not clear. Thus, obesity has effects on lung function that can generate respiratory distress similar to asthma and may also exaggerate the effects of preexisting asthma.

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Similar ventilation distribution in normal subjects prone and supine during tidal breathing

Journal of Applied Physiology ◽

10.1152/japplphysiol.00574.2001 ◽

2002 ◽

Vol 92 (2) ◽

pp. 622-626 ◽

Cited By ~ 18

Author(s):

M. J. Rodríguez-Nieto ◽

G. Peces-Barba ◽

N. González Mangado ◽

M. Paiva ◽

S. Verbanck

Keyword(s):

Normal Subjects ◽

Phase Iii ◽

Ventilation Distribution ◽

Tidal Breathing ◽

Ventilation Heterogeneity ◽

Multiple Breath Washout ◽

Residual Capacity ◽

Slope Difference ◽

The Difference ◽

Phase Iii Slope

Multiple-breath washout (MBW) tests, with end-expiratory lung volume at functional residual capacity (FRC) and 90% O2, 5% He, and 5% SF6as an inspired gas mixture, were performed in healthy volunteers in supine and prone postures. The semilog plot of MBW N2concentrations was evaluated in terms of its curvilinearity. The MBW N2normalized slope analysis yielded indexes of acinar and conductive ventilation heterogeneity (Verbanck S, Schuermans D, Van Muylem A, Paiva M, Noppen M, and Vincken W. J App Physiol 83: 1907–1916, 1997). Also, the difference between SF6and He normalized phase III slopes was computed in the first MBW expiration. Only MBW tests with similar FRC in the prone and supine postures ( P > 0.1; n= 8) were considered. Prone and supine postures did not reveal any significant differences in curvilinearity, N2normalized slope-derived indexes of conductive or acinar ventilation heterogeneity, nor SF6-He normalized phase III slope difference in the first MBW expiration ( P > 0.1 for all). The absence of significant changes in any of the MBW indexes suggests that ventilation heterogeneity is similar in the supine and prone postures of normal subjects breathing near FRC.

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Ventilation Heterogeneity in Asthma and COPD: The Value of the Poorly Communicating Fraction as the Ratio of Total Lung Capacity to Alveolar Volume

Respiration ◽

10.1159/000513954 ◽

2021 ◽

pp. 1-7

Author(s):

Roberta Pisi ◽

Marina Aiello ◽

Luigino Calzetta ◽

Annalisa Frizzelli ◽

Veronica Alfieri ◽

...

Keyword(s):

Total Lung Capacity ◽

Airflow Obstruction ◽

Diffusing Capacity ◽

Body Plethysmography ◽

Alveolar Volume ◽

Asthmatic Patients ◽

Lung Capacity ◽

Copd Patients ◽

Ventilation Heterogeneity ◽

Patient Groups

Background: The ventilation heterogeneity (VH) is reliably assessed by the multiple-breath nitrogen washout (MBNW), which provides indices of conductive (Scond) and acinar (Sacin) VH as well as the lung clearance index (LCI), an index of global VH. VH can be alternatively measured by the poorly communicating fraction (PCF), that is, the ratio of total lung capacity by body plethysmography to alveolar volume from the single-breath lung diffusing capacity measurement. Objectives: Our objective was to assess VH by PCF and MBNW in patients with asthma and with COPD and to compare PCF and MBNW parameters in both patient groups. Method: We studied 35 asthmatic patients and 45 patients with COPD. Each patient performed spirometry, body plethysmography, diffusing capacity, and MBNW test. Results: Compared to COPD patients, asthmatics showed a significantly lesser degree of airflow obstruction and lung hyperinflation. In asthmatic patients, both PCF and LCI and Sacin values were significantly lower than the corresponding ones of COPD patients. In addition, in both patient groups, PCF showed a positive correlation with LCI (p < 0.05) and Sacin (p < 0.05), but not with Scond. Lastly, COPD patients with PCF >30% were highly likely to have a value ≥2 of the mMRC dyspnea scale. Conclusions: These results showed that PCF, a readily measure derived from routine pulmonary function testing, can provide a comprehensive measure of both global and acinar VH in asthma and in COPD patients and can be considered as a comparable tool to the well-established MBNW technique.

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Assessment of the influence of lung inflation state on the quantitative parameters derived from hyperpolarized gas lung ventilation MRI in healthy volunteers

Journal of Applied Physiology ◽

10.1152/japplphysiol.00464.2018 ◽

2019 ◽

Vol 126 (1) ◽

pp. 183-192 ◽

Cited By ~ 7

Author(s):

Paul J. C. Hughes ◽

Laurie Smith ◽

Ho-Fung Chan ◽

Bilal A. Tahir ◽

Graham Norquay ◽

...

Keyword(s):

Healthy Volunteers ◽

Lung Volume ◽

Lung Ventilation ◽

Lung Volumes ◽

Lung Inflation ◽

Longitudinal Measurements ◽

Anatomical Images ◽

Lower Lung ◽

Ventilation Heterogeneity ◽

Residual Capacity

In this study, the effect of lung volume on quantitative measures of lung ventilation was investigated using MRI with hyperpolarized 3He and 129Xe. Six volunteers were imaged with hyperpolarized 3He at five different lung volumes [residual volume (RV), RV + 1 liter (1L), functional residual capacity (FRC), FRC + 1L, and total lung capacity (TLC)], and three were also imaged with hyperpolarized 129Xe. Imaging at each of the lung volumes was repeated twice on the same day with corresponding 1H lung anatomical images. Percent lung ventilated volume (%VV) and variation of signal intensity [heterogeneity score (Hscore)] were evaluated. Increased ventilation heterogeneity, quantified by reduced %VV and increased Hscore, was observed at lower lung volumes with the least ventilation heterogeneity observed at TLC. For 3He MRI data, the coefficient of variation of %VV was <1.5% and <5.5% for Hscore at all lung volumes, while for 129Xe data the values were 4 and 10%, respectively. Generally, %VV generated from 129Xe images was lower than that seen from 3He images. The good repeatability of 3He %VV found here supports prior publications showing that percent lung-ventilated volume is a robust method for assessing global lung ventilation. The greater ventilation heterogeneity observed at lower lung volumes indicates that there may be partial airway closure in healthy lungs and that lung volume should be carefully considered for reliable longitudinal measurements of %VV and Hscore. The results suggest that imaging patients at different lung volumes may help to elucidate obstructive disease pathophysiology and progression. NEW & NOTEWORTHY We present repeatability data of quantitative metrics of lung function derived from hyperpolarized helium-3, xenon-129, and proton anatomical images acquired at five lung volumes in volunteers. Increased regional ventilation heterogeneity at lower lung inflation levels was observed in the lungs of healthy volunteers.

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Effects of body position change on thoracoabdominal motion

Journal of Applied Physiology ◽

10.1152/jappl.1978.45.4.581 ◽

1978 ◽

Vol 45 (4) ◽

pp. 581-589 ◽

Cited By ~ 51

Author(s):

V. P. Vellody ◽

M. Nassery ◽

W. S. Druz ◽

J. T. Sharp

Keyword(s):

Supine Position ◽

Muscle Force ◽

Body Position ◽

Tidal Breathing ◽

Position Change ◽

Rib Cage ◽

Inspiratory Muscles ◽

Residual Capacity ◽

Lateral Decubitus ◽

Local Compliance

With a linearized respiratory magnetometer, measurements of anteroposterior and lateral diameters of both the rib cage and the abdomen were made at functional residual capacity and continuously during tidal breathing. Twenty-five subjects with normal respiratory systems were studied in the sitting, supine, lateral decubitus, and prone body positions. When subjects changed from sitting to supine position anteroposterior diameters of both rib cage and abdomen decreased while their lateral diameters increased. Both anteroposterior and lateral tidal excursions of the rib cage decreased; those of the abdomen increased. When subjects turned from supine to lateral decubitus position both anteroposterior diameters increased and the lateral diameters decreased. This was associated with an increase in both lateral excursions and a decrease in the abdominal anteroposterior excursions. Diameters and tidal excursions in the prone position resembled those in the supine position. Diameter changes could be explained by gravitational effects. Differences in tidal excursions accompanying body position change were probably related to 1) differences in the distribution of respiratory muscle force, 2) differences in the activity or mechanical advantage of various inspiratory muscles, and 3) local compliance changes in parts of the rib cage and abdomen.

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Airway surface liquid thickness as a function of lung volume in small airways of the guinea pig

Journal of Applied Physiology ◽

10.1152/jappl.1994.77.5.2333 ◽

1994 ◽

Vol 77 (5) ◽

pp. 2333-2340 ◽

Cited By ~ 39

Author(s):

D. Yager ◽

T. Cloutier ◽

H. Feldman ◽

J. Bastacky ◽

J. M. Drazen ◽

...

Keyword(s):

Surface Tension ◽

Epithelial Cells ◽

Guinea Pig ◽

Cross Sections ◽

Lung Volume ◽

Longitudinal Direction ◽

Small Airways ◽

Airway Surface Liquid ◽

Residual Capacity ◽

Surface Liquid

The average thickness and distribution of airway surface liquid (ASL) on the luminal surface of peripheral airways were measured in normal guinea pig lungs frozen at functional residual capacity (FRC) and total lung capacity (TLC). Tissue blocks containing cross sections of airways of internal perimeter 0.188–3.342 mm were cut from frozen lungs and imaged by low-temperature scanning electron microscopy (LTSEM). Measurements made from LTSEM images were found to be independent of freezing rate by comparison of measurements at rapid and slow freezing rates. At both lung volumes, the ASL was not uniformly distributed in either the circumferential or longitudinal direction; there were regions of ASL where its thickness was < 0.1 micron, whereas in other regions ASL collected in pools. Discernible liquid on the surfaces of airways frozen at FRC followed the contours of epithelial cells and collected in pockets formed by neighboring cells, a geometry consistent with a low value of surface tension at the air-liquid interface. At TLC airway liquid collected to cover epithelial cells and to form a liquid meniscus, a geometry consistent with a higher value of surface tension. The average ASL thickness (h) was approximately proportional to the square root of airway internal perimeter, regardless of lung volume. For airways of internal perimeter 250 and 1,800 microns, h was 0.9 and 1.8 microns at FRC and 1.7 and 3.7 microns at TLC, respectively. For a given airway internal perimeter, h was 1.99 times thicker at TLC than at FRC; the difference was statistically significant (P < 0.01; 95% confidence interval 1.29–3.08).(ABSTRACT TRUNCATED AT 250 WORDS)

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Respiratory parameter estimation using forced oscillatory impedance data

Journal of Applied Physiology ◽

10.1152/jappl.1977.43.2.322 ◽

1977 ◽

Vol 43 (2) ◽

pp. 322-330 ◽

Cited By ~ 22

Author(s):

M. J. Tsai ◽

R. L. Pimmel ◽

E. J. Stiff ◽

P. A. Bromberg ◽

R. L. Hamlin

Keyword(s):

Respiratory Symptoms ◽

Forced Oscillation ◽

Respiratory Resistance ◽

Added Resistance ◽

Tidal Breathing ◽

Frequency Dependency ◽

Respiratory Parameter ◽

Clinically Normal ◽

Impedance Data ◽

Residual Capacity

The frequency dependency of the magnitude and phase angle of total respiratory impedance was measured in apneic dogs at functional residual capacity during forced oscillation by a special electronics unit. Regression analysis of these data yielded estimates of total respiratory resistance (RFO), inertance (IFO), and compliance (CFO). After correcting for the effects of the endotracheal tube, mean control values (+/-SE) of RFO, IFO, and CFO for the clinically normal dogs were 1.30+/-0.10 cmH2O–1–1-s, 0.0114+/-0.0022 cmH2O–1–1-s2, and 0.0306+/-0.0009 1-cm H2O–1, respectively. Estimates obtained with added resistance, a less dense gas, and abdominal weighting were consistent with predicted effects. In four dogs with mild respiratory symptoms, mean RFO was significantly elevated with no change in IFO or CFO. Independent measurements of resistance and compliance during tidal ventilation correlated well with RFO (r=0.87) and CFO (r=0.80), but RFO and CFO were, on the average, 71% of the tidal breathing values. Thus, the method provides precise estimates of RFO, IFO, and CFO, and allows detection of small changes in these parameters.

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