Airway distensibility and volume recruitment with lung inflation in COPD

2010 ◽  
Vol 109 (4) ◽  
pp. 1019-1026 ◽  
Author(s):  
Simonetta Baldi ◽  
Raffaele Dellacà ◽  
Leonardo Govoni ◽  
Roberto Torchio ◽  
Andrea Aliverti ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Lung Volume ◽  
Muscle Tone ◽  
Forced Expiratory Volume ◽  
Chronic Obstructive ◽  
High Resolution Computed Tomography ◽  
Lung Inflation ◽  
Control Subjects ◽  
Airway Caliber

The effects of full lung inflation on respiratory conductance (Grs) and reactance (Xrs) were measured in 15 subjects with moderate to severe chronic obstructive pulmonary disease (COPD) and 11 matched healthy control subjects. Airway distensibility was estimated from the ratio of the difference of Grs between functional residual capacity and total lung capacity to the relevant changes in lung volume (ΔGrs/ΔVl) or transpulmonary pressure (ΔGrs/ΔPtp). Similar analysis was applied to Xrs to estimate lung volume recruitment (ΔXrs/ΔVl or ΔXrs/ΔPtp). The extent of emphysema in COPD subjects was estimated from the percentage of low attenuation area (LAA) at high-resolution computed tomography. At baseline, ΔGrs/ΔVl and ΔXrs/ΔVl were significantly less in COPD than control subjects, indicating less distensibility and volume recruitment in the former. In COPD, ΔGrs/ΔPtp and ΔXrs/ΔPtp were uncorrelated with LAA but correlated with 1-s forced expiratory volume and with each other. After albuterol, both ΔGrs/ΔPtp and ΔGrs/ΔVl became significantly and negatively correlated with LAA, while ΔXrs/ΔPtp and ΔXrs/ΔVl decreased significantly independently of LAA. Moreover, ΔGrs/ΔPtp and ΔXrs/ΔPtp with lung inflation were no longer correlated with each other, suggesting that airway distensibility and volume recruitment were affected differently by airway smooth muscle tone. Assuming that Grs mainly reflects airway caliber and Xrs the number of ventilated lung units, we conclude that airway smooth muscle contributes to airway stiffness and ventilation inhomogeneities in COPD subjects with prevailing bronchitis but only to the latter in those with more emphysema. We suggest that changes of airway distensibility and volume recruitment with a bronchodilator may be useful for disease phenotyping.

Mechanisms for isolated volume response to a bronchodilator in patients with COPD

2000 ◽  
Vol 88 (6) ◽  
pp. 1989-1995 ◽  
Author(s):  
Isa Cerveri ◽  
Riccardo Pellegrino ◽  
Roberto Dore ◽  
Angelo Corsico ◽  
Paola Fulgoni ◽  
...  
Keyword(s):  
Forced Expiratory Volume ◽  
Chronic Obstructive ◽  
Cube Root ◽  
High Resolution Computed Tomography ◽  
Obstructive Pulmonary Disease ◽  
Lung Inflation ◽  
Severe Emphysema ◽  
Airway Caliber ◽  
Volume Response ◽  
Residual Capacity

We hypothesized that an altered effect of lung inflation on airway caliber may in part explain the isolated volume response to bronchodilators, i.e., an increase of forced vital capacity (FVC) without change in 1-s forced expiratory volume (FEV1). Small-airway caliber was measured by high-resolution computed tomography at functional residual capacity and total lung capacity in five chronic obstructive pulmonary disease patients with an isolated increase of FVC (FVC responders) and five with an increase of both FVC and FEV1(FVC-FEV1 responders) after inhalation of salbutamol. In FVC-FEV1 responders, the airway diameter increased with the cube root of increase in lung volume but was unchanged or even decreased in four of five FVC responders. FVC responders had more severe emphysema, as inferred from lung function and imaging studies, than FVC-FEV1 responders. We speculate that longitudinal traction or space competition (Verbeken EK, Cauberghs M, and Van de Woestijne KP, J Appl Physiol 81: 2468–2480, 1996) are possible underlying mechanisms. We conclude that the isolated volume response to bronchodilators is associated with severe emphysema and likely results from an altered effect of lung inflation on airway caliber.

Effects of lung volume, bronchoconstriction, and cigarette smoke on morphometric airway dimensions

1988 ◽  
Vol 64 (3) ◽  
pp. 913-919 ◽  
Author(s):  
A. L. James ◽  
P. D. Pare ◽  
J. C. Hogg
Keyword(s):  
Smooth Muscle ◽  
Cigarette Smoke ◽  
Lung Volume ◽  
Muscle Tone ◽  
Cigarette Smoke Exposure ◽  
Wall Thickening ◽  
Airway Wall ◽  
Lung Inflation ◽  
Wall Area ◽  
Airway Dimensions

To examine the role of airway wall thickening in the bronchial hyperresponsiveness observed after exposure to cigarette smoke, we compared the airway dimensions of guinea pigs exposed to smoke (n = 7) or air (n = 7). After exposure the animals were anesthetized with urethan, pulmonary resistance was measured, and the lungs were removed, distended with Formalin, and fixed near functional residual capacity. The effects of lung inflation and bronchoconstriction on airway dimensions were studied separately by distending and fixing lungs with Formalin at total lung capacity (TLC) (n = 3), 50% TLC (n = 3), and 25% TLC (n = 3) or near residual volume after bronchoconstriction (n = 3). On transverse sections of extraparenchymal and intraparenchymal airways the following dimensions were measured: the internal area (Ai) and internal perimeter (Pi), defined by the epithelium, and the external area (Ae) and external perimeter (Pe), defined by the outer border of smooth muscle. Airway wall area (WA) was then calculated, WA = Ae - Ai. Ai, Pe, and Ae decreased with decreasing lung volume and after bronchoconstriction. However, WA and Pi did not change significantly with lung volume or after bronchoconstriction. After cigarette smoke exposure airway resistance was increased (P less than 0.05); however, there was no difference in WA between the smoke- and air-exposed groups when the airways were matched by Pi. We conclude that Pi and WA are constant despite changes in lung volume and smooth muscle tone and that airway hyperresponsiveness induced by cigarette smoke is not mediated by increased airway wall thickness.

Reflex regulation of airway smooth muscle tone

2006 ◽  
Vol 101 (3) ◽  
pp. 971-985 ◽  
Author(s):  
Brendan J. Canning
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Mammalian Species ◽  
Autonomic Nerve ◽  
Autonomic Nerves ◽  
Parasympathetic Nerves ◽  
Afferent Nerves ◽  
Airway Caliber ◽  
Efferent Pathways

Autonomic nerves in most mammalian species mediate both contractions and relaxations of airway smooth muscle. Cholinergic-parasympathetic nerves mediate contractions, whereas adrenergic-sympathetic and/or noncholinergic parasympathetic nerves mediate relaxations. Sympathetic-adrenergic innervation of human airway smooth muscle is sparse or nonexistent based on histological analyses and plays little or no role in regulating airway caliber. Rather, in humans and in many other species, postganglionic noncholinergic parasympathetic nerves provide the only relaxant innervation of airway smooth muscle. These noncholinergic nerves are anatomically and physiologically distinct from the postganglionic cholinergic parasympathetic nerves and differentially regulated by reflexes. Although bronchopulmonary vagal afferent nerves provide the primary afferent input regulating airway autonomic nerve activity, extrapulmonary afferent nerves, both vagal and nonvagal, can also reflexively regulate autonomic tone in airway smooth muscle. Reflexes result in either an enhanced activity in one or more of the autonomic efferent pathways, or a withdrawal of baseline cholinergic tone. These parallel excitatory and inhibitory afferent and efferent pathways add complexity to autonomic control of airway caliber. Dysfunction or dysregulation of these afferent and efferent nerves likely contributes to the pathogenesis of obstructive airways diseases and may account for the pulmonary symptoms associated with extrapulmonary disorders, including gastroesophageal reflux disease, cardiovascular disease, and rhinosinusitis.

Chest wall distortion and discharge of pulmonary slowly adapting receptors

1992 ◽  
Vol 73 (4) ◽  
pp. 1619-1625 ◽  
Author(s):  
S. Iscoe ◽  
S. P. Gordon
Keyword(s):  
Smooth Muscle ◽  
Chest Wall ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Respiratory Neurons ◽  
Lung Inflation ◽  
Smooth Muscle Tone ◽  
Residual Capacity ◽  
Discharge Patterns ◽  
Spontaneously Breathing

We assessed the effects of chest wall distortion, changes in lung volume, and abolition of airway smooth muscle tone on the discharge patterns of 92 pulmonary slowly adapting receptors (SAR) in decerebrate, spontaneously breathing cats. Distortion resulted from their inspiratory efforts against an occluded airway at functional residual capacity and at increased end-expiratory lung volumes. Approximately 40% of SAR increased discharge frequencies during occlusions. Modulation of SAR discharge during occlusions persisted after administration of atropine to eliminate airway smooth muscle tone. Phasic modulation of SAR discharge was eliminated during no-inflation tests after paralyzing the cats and ventilating them on a cycle-triggered pump. We conclude 1) parasympathetic modulation of airway smooth muscle tone makes no obvious contribution to SAR discharge in spontaneously breathing cats; 2) the no-inflation test (withholding of lung inflation during neural inspiration) in paralyzed and ventilated cats is a valid test for the presence of projections from SAR to medullary respiratory neurons; and 3) in the absence of tidal volume changes, distortion stimulates some SAR. Sensory feedback from receptors in the lung, not just those in the chest wall, may therefore provide information about abnormal chest wall configurations.

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.

Invited Review: Complexity of factors modulating airway narrowing in vivo: relevance to assessment of airway hyperresponsiveness

2003 ◽  
Vol 95 (3) ◽  
pp. 1305-1313 ◽  
Author(s):  
Vito Brusasco ◽  
Riccardo Pellegrino
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Muscle Activation ◽  
Muscle Tone ◽  
Clinical Settings ◽  
Airway Narrowing ◽  
Geometric Factors ◽  
Airway Caliber ◽  
Airway Response

In vivo, the airway response to constrictor stimuli is the net result of a complex array of factors, some facilitating and some opposing airway narrowing, which makes the interpretation of bronchial challenges far from being straightforward. This review begins with a short description of the complex mechanisms of airway smooth muscle activation and force generation as the starting events for airway narrowing. It then focuses on gain factors modulating airway smooth muscle shortening and on the geometric factors determining the magnitude of reduction in airway caliber in vivo. Finally, in light of the evidence that mechanical modulation of airway smooth muscle tone and airway narrowing is at least as important as the inflammatory contractile mediators in the pathogenesis of airway hyper-responsiveness, the implications for the interpretation of bronchial challenges in clinical settings are discussed.

Effect of lung inflation and airway muscle tone on airway diameter in vivo

1996 ◽  
Vol 80 (5) ◽  
pp. 1581-1588 ◽  
Author(s):  
R. H. Brown ◽  
W. Mitzner
Keyword(s):  
Smooth Muscle ◽  
Basement Membrane ◽  
Muscle Contraction ◽  
Lung Volume ◽  
Airway Pressure ◽  
Muscle Tone ◽  
Smooth Muscle Contraction ◽  
Lung Inflation ◽  
Highly Nonlinear

How normal airway dimensions change with lung volume is of great importance in determining flow limitation during the normal forced vital capacity maneuver as well as in the manifestation of obstructive lung disease. The literature presents a confusing picture, with some results suggesting that airway diameter increases linearly with the cube root of lung volume and others showing a highly nonlinear relation. The effect of smooth muscle contraction on lung-airway interdependence is even less well understood. Recent morphological work explicitly assumes that airway basement membrane is nondistensible, although the lung volume at which this maximal airway size is reached is unknown. With smooth muscle contraction, folding of the epithelium and basement membrane accounts for the changes in luminal area. In this study, we measured the effect of lung inflation on relaxed and contracted airway areas by using high-resolution computed tomography at different transpulmonary pressures, each held for 2 min. We found that fully relaxed airways are quite distensible up to a pressure of 5-7 cmH2O (P < 0.001), where they reach a maximal size with no further distension up to an airway pressure of 30 cmH2O (P = 0.49). Thus relaxed airways clearly do not expand isotropically with the lung. With smooth muscle tone, the airways in different animals responded differently to lung inflation, with some animals showing minimal airway dilation up to an airway pressure of 20 cmH2O and others showing airways that were more easily dilated with lung expansion. However, maximal diameter of these moderately constricted airways was not usually achieved even up to an airway pressure of 30 cmH2O. Thus a transient deep inspiration in vivo would be expected to have only a small effect on contracted airways.

Inhibition of dihydropyridine-sensitive calcium entry in hypoxic relaxation of airway smooth muscle

1995 ◽  
Vol 268 (2) ◽  
pp. L201-L206 ◽  
Author(s):  
C. Vannier ◽  
T. L. Croxton ◽  
L. S. Farley ◽  
C. A. Hirshman
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Bay K 8644 ◽  
O2 Concentration ◽  
Voltage Dependent ◽  
Progressive Hypoxia ◽  
Carbamyl Choline

Hypoxia dilates airways in vivo and reduces active tension of airway smooth muscle in vitro. To determine whether hypoxia impairs Ca2+ entry through voltage-dependent channels (VDC), we tested the ability of dihydropyridines to modulate hypoxia-induced relaxation of KCl- and carbamyl choline (carbachol)-contracted porcine bronchi. Carbachol- or KCl-contracted bronchial rings were exposed to progressive hypoxia in the presence or absence of 1 microM BAY K 8644 (an L-type-channel agonist). In separate experiments, rings were contracted with carbachol or KCl, treated with nifedipine (a VDC antagonist), and finally exposed to hypoxia. BAY K 8644 prevented hypoxia-induced relaxation in KCl-contracted bronchi. Nifedipine (10(-5) M) totally relaxed KCl- contracted bronchi. Carbachol-contracted bronchi were only partially relaxed by nifedipine but were completely relaxed when the O2 concentration of the gas was reduced from 95 to 0%. These data indicate that hypoxia can reduce airway smooth muscle tone by limiting entry of Ca2+ through a dihydropyridine-sensitive pathway, but that other mechanisms also contribute to hypoxia-induced relaxation of carbachol-contracted bronchi.

ATP stimulates Ca2+oscillations and contraction in airway smooth muscle cells of mouse lung slices

2002 ◽  
Vol 283 (6) ◽  
pp. L1271-L1279 ◽  
Author(s):  
Albrecht Bergner ◽  
Michael J. Sanderson
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Phospholipase C ◽  
Airway Smooth Muscle ◽  
Muscle Cells ◽  
Mouse Lung ◽  
Airway Smooth Muscle Cells ◽  
Airway Caliber ◽  
Inositol 1,4,5 Trisphosphate ◽  
Trisphosphate Receptor

In airway smooth muscle cells (SMCs) from mouse lung slices, ≥10 μM ATP induced Ca2+oscillations that were accompanied by airway contraction. After ∼1 min, the Ca2+oscillations subsided and the airway relaxed. By contrast, ≥0.5 μM adenosine 5′- O-(3-thiotriphosphate) (nonhydrolyzable) induced Ca2+oscillations in the SMCs and an associated airway contraction that persisted for >2 min. Adenosine 5′- O-(3-thiotriphosphate)-induced Ca2+oscillations occurred in the absence of external Ca2+but were abolished by the phospholipase C inhibitor U-73122 and the inositol 1,4,5-trisphosphate receptor inhibitor xestospongin. Adenosine, AMP, and α,β-methylene ATP had no effect on airway caliber, and the magnitude of the contractile response induced by a variety of nucleotides could be ranked in the following order: ATP = UTP > ADP. These results suggest that the SMC response to ATP is impaired by ATP hydrolysis and mediated via P2Y2or P2Y4receptors, activating phospholipase C to release Ca2+via the inositol 1,4,5-trisphosphate receptor. We conclude that ATP can serve as a spasmogen of airway SMCs and that Ca2+oscillations in SMCs are required to sustain airway contraction.

scholarly journals Angiogenesis-related factors in skeletal muscles of COPD patients: roles of angiopoietin-2

2013 ◽  
Vol 114 (9) ◽  
pp. 1309-1318 ◽  
Author(s):  
Mahroo Mofarrahi ◽  
Ioanna Sigala ◽  
Theodoros Vassilokopoulos ◽  
Sharon Harel ◽  
Yeting Guo ◽  
...  
Keyword(s):  
Vastus Lateralis ◽  
Interferon Γ ◽  
Forced Expiratory Volume ◽  
Chronic Obstructive ◽  
Mrna Levels ◽  
Gene Expressions ◽  
Related Factors ◽  
Control Subjects ◽  
Copd Patients ◽  
Angiopoietin 2

The role of angiogenesis factors in skeletal muscle dysfunction in patients with chronic obstructive pulmonary disease (COPD) is unknown. The first objective of this study was to assess various pro- and antiangiogenic factor and receptor expressions in the vastus lateralis muscles of control subjects and COPD patients. Preliminary inquiries revealed that angiopoietin-2 (ANGPT2) is overexpressed in limb muscles of COPD patients. ANGPT2 promotes skeletal satellite cell survival and differentiation. Factors that are involved in regulating muscle ANGPT2 production are unknown. The second objective of this study was to evaluate how oxidants and proinflammatory cytokines influence muscle-derived ANGPT2 expression. Angiogenic gene expressions in human vastus lateralis biopsies were quantified with low-density real-time PCR arrays. ANGPT2 mRNA expressions in cultured skeletal myoblasts were quantified in response to proinflammatory cytokine and H2O2 exposure. Ten proangiogenesis genes, including ANGPT2, were significantly upregulated in the vastus lateralis muscles of COPD patients. ANGPT2 mRNA levels correlated negatively with forced expiratory volume in 1 s and positively with muscle wasting. Immunoblotting confirmed that ANGPT2 protein levels were significantly greater in muscles of COPD patients compared with control subjects. ANGPT2 expression was induced by interferon-γ and -β and by hydrogen peroxide, but not by tumor necrosis factor. We conclude that upregulation of ANGPT2 expression in vastus lateralis muscles of COPD patients is likely due to oxidative stress and represents a positive adaptive response aimed at facilitating myogenesis and angiogenesis.

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