| 1. |
- Kaminsky, DA, et al.
(författare)
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Oscillation mechanics of the human lung periphery in asthma
- 2004
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Ingår i: Journal of Applied Physiology. - : American Physiological Society. - 1522-1601 .- 8750-7587. ; 97:5, s. 1849-1858
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Tidskriftsartikel (refereegranskat)abstract
- To more precisely measure the mechanical properties of the lung periphery in asthma, we have developed a forced oscillation technique that applies a broad-band flow signal through a wedged bronchoscope. We interpreted the data from four healthy and eight mildly asthmatic subjects in terms of an anatomically accurate computer model of the wedged segment. There was substantial overlap in impedance between the two groups, with resistance ( R) showing minimal frequency dependence and elastance (E) showing positive and negative frequency dependence across subjects. After direct instillation of methacholine, R rose in both groups, but compared with healthy subjects, the asthmatic subjects displayed upward, parallel shifts in their dose-response curves. The baseline frequency-response patterns of E were enhanced after methacholine. Frequency dependencies of R and E were well reproduced in two normal subjects by a computational model that employed rigid airways connected to constant-phase tissue units but were better reproduced in the other two normal and three asthmatic subjects when the model employed heterogeneous, peripheral airway narrowing and compliant airways. To capture the frequency dependencies of R and E in the remaining five asthmatic subjects, the model was modified by increasing airway wall stiffness. These results indicate that the lung periphery of mildly asthmatic subjects is not well distinguished from that of healthy subjects by measurement of mechanical impedance at baseline, but group differences are seen after challenge with methacholine. Modeling of the response suggests that variable contributions of airway narrowing and wall compliance are operative in determining overall mechanical impedance of the lung periphery in humans with asthma, likely reflecting the functional consequences of airway inflammation and remodeling.
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| 2. |
- Wagers, S, et al.
(författare)
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Nonlinearity of respiratory mechanics during bronchoconstriction in mice with airway inflammation
- 2002
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Ingår i: Journal of Applied Physiology. - : American Physiological Society. - 1522-1601 .- 8750-7587. ; 92:5, s. 1802-1807
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Tidskriftsartikel (refereegranskat)abstract
- Respiratory system resistance (R) and elastance (E) are commonly estimated by fitting the linear equation of motion P = EV + R(V) over dot + P-0 (Eq. 1) to measurements of respiratory pressure (P), lung volume (V), and flow (V). However, the respiratory system is unlikely to behave linearly under many circumstances. We determined the importance of respiratory system nonlinearities in two groups of mechanically ventilated Balb/c mice [controls and mice with allergically inflamed airways (ova/ova)], by,g the impact of the addition of nonlinear terms (E2V2 assessing and R-2(V) over dot (V) over dot) on the goodness of model fit seen with Eq. 1. Significant improvement in fit (51.85 +/- 4.19%) was on seen in the ova/ova mice during bronchoconstriction when the E2V2 alone was added. An improvement was also observed with addition of the E2V2 term in mice with both low and high lung volumes ventilated at baseline, suggesting a volume-dependent nonlinearity of E. We speculate that airway closure in the constricted ova/ova mice accentuated the volume-dependent nonlinearity by decreasing lung volume and overdistending the remaining lung.
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