Effect of inspiratory flow rate on regional distribution of inspired gas.

Bake, Björn; Wood, Lindsay; Murphy, Brian G; Macklem, Peter T.; Milic–Emili, J.

doi:10.1152/jappl.1974.37.1.8

Cited by 102 publications

(32 citation statements)

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“…Our present study focuses largely on the influences of fluid inertia upon the distribution of ventilation, and demonstrates that fluid inertia may be manifested in two ways, unsteady acceleration and convective momentum flux. This idea adds some insights to the results of Bake et al (12), in which the effect of increasing inspiratory flow rate upon the distribution of ventilation was shown to favor the lung apex. However, careful examination of their data reveals that after the initial increment of flow, in only three of seven subjects did further increases of flow rate increasingly favor the apex, while in three of the seven the opposite tendency was true.…”

Section: Resultssupporting

confidence: 56%

“…In such circumstances, regional lung distension might be controlled, at least in part, by the distribution of nonlinear (i.e., amplitude-dependent) features, such as the pressure-volume elastic characteristic of lung parenchyma, flow-dependent changes in airways resistances, convective momentum flux per unit area (pu2)-also known as dynamic head-and by associated fluidic factors, such as airway branching angles, distal airway pressures, and Reynolds numbers. Flow-dependent changes in flow distribution have been observed in in vitro airway models (7)(8)(9)(10)(11) and in humans (12)(13)(14)(15). Computational models that predict flowdependent alterations in the distribution of inspired gas have incorporated nonlinearities of flow resistance and tissue elasticity, but as yet have not dealt with nonlinear manifestations of fluid inertia (16,17).…”

mentioning

confidence: 99%

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Regional alveolar pressure during periodic flow. Dual manifestations of gas inertia.

Allen¹,

Frantz²,

Fredberg³

1985

J. Clin. Invest.

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We measured pressure excursions at the airway opening and at the alveoli (PA) as well as measured the regional distribution of PA during forced oscillations of six excised dog lungs while frequency (f12-32 Hzj), tidal volume (VT 15-80 ml]), and mean transpulmonary pressure (PL 125, 10, and 6 cm H20) were varied. PA'S were measured in four alveolar capsules glued to the pleura of different lobes. The apex-to-base ratio of PA'S was used as an index of the distribution of dynamic lung distension. At low ; there was slight preferential distension of the lung base which was independent of VT, but at higher f, preferential distension of the lung apex was found when VT's were small, whereas preferential distension of the lung base was found when VT's approached or exceeded dead space. These V1-related changes in distribution at high frequencies seem to depend upon the branching geometry of the central airways and the relative importance of convective momentum flux vs. unsteady inertia of gas residing therein, which, in this study, we showed to be proportional to the ratio VT/VD*, where VD* is an index of dead space. Furthermore, they imply substantial alteration in the distribution of ventilation during high frequency ventilation as f VT, and PL vary. The data also indicate that alveolar and airway opening pressure costs per unit flow delivered at the airway opening exhibit weakly nonlinear behavior and that resonant amplification of PA's, which has been described previously for the case of very small

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Section: Resultssupporting

confidence: 56%

mentioning

confidence: 99%

Regional alveolar pressure during periodic flow. Dual manifestations of gas inertia.

Allen¹,

Frantz²,

Fredberg³

1985

J. Clin. Invest.

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show abstract

“…However, during moderate, heavy, and forced breathing, these changes may not be negligible and may have significant effects on airway gas flow and lung functions. For example, by assuming that the viscous pressure drop in a tube at a given flow rate is proportional to 1/D 4 , where D is the diameter, the pressure drop can decrease by five times with a 50% increase in the diameter.…”

Section: Accounting For Tissue Expansion and Airway Deformationmentioning

confidence: 99%

“…The regional distribution of ventilation in the human lungs depends upon the balance of airway resistance and tissue compliance (4). During resting breathing in the healthy lung, it is predominantly the regional tissue compliance that determines the distribution of air.…”

Section: Introductionmentioning

confidence: 99%

Airway Gas Flow

Tawhai

Lin

2011

Comprehensive Physiology

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Local characteristics of airflow and its global distribution in the lung are determined by interaction between resistance to flow through the airways and the compliance of the tissue, with tissue compliance dominating flow distribution in the healthy lung. Current understanding is that conceptualizing the airways of the lung as a system of smooth adjoined cylinders through which air traverses laminarly is insufficient for understanding flow and energy dissipation and is particularly poor for predicting physiologically realistic transport of particles by the airflow. With rapid advances in medical imaging, computer technologies, and computational techniques, computational fluid dynamics is now becoming a viable tool for providing detailed information on the mechanics of airflow in the human respiratory tract. Studies using such techniques have shown that the upper airway (specifically its development of a turbulent laryngeal jet in the trachea), airway geometry, branching and rotation angle, and the pattern of joining of successive bifurcations are important in determining airflow structures. It is now possible to compute airflow in physical domains that are anatomically accurate and subject specific, enabling comparisons among intersubjects, that among subjects of different ages, and that among different species.

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“…The less expanded basal lung tissue has a greater compliance and, consequently, greater relative ventilation, when inspiration starts from FRC with measurements made under static conditions. When, instead, the distribution of inspired gas was studied during inspiratory flow, especially high flows, regional differences were less than those seen with static or low flow inspiration (Bake et al, 1974). Studies in humans by Rehder and colleagues showed that ventilation was more uniform in the prone than previously found in the supine position.…”

Section: Ventilation Heterogeneitymentioning

confidence: 96%

Gas Exchange in the Normal Lung : Experimental studies on the effects of positive end-expiratory pressure and body position

Johansson¹

2014

Linköping University Medical Dissertations

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BACKGROUND:The principal function of the lung is gas exchange requiring adequate ventilation and perfusion at the level of the alveoli. The efficiency of gas exchange is depending on the distributions of regional ventilation (V) and pulmonary blood flow (Q) and their correlation. AIMS:To validate a high-resolution method to quantify regional V and to investigate the Radioactive microspheres, 15 m in diameter, were used for determining regional Q. Nitric oxide synthase (NOS) was inhibited with Nω-nitro-L-arginine methyl ester (L-NAME) to evaluate the role of NO on regional V/Q matching. The right lung was dried at total lung capacity and diced in approx. 1000 regions tracking the spatial location of each region. CONCLUSION: There were marked differences in redistribution of regional ventilation and regional pulmonary blood flow between prone and supine position when PEEP was applied. RESULTS:NO was not an active mechanism for V/Q matching in normal sheep lungs. VII List of original papershis thesis is based on the following four papers, which will be referred to by their Roman numerals: I.Positive end-expiratory pressure affects regional redistribution of ventilation differently in prone and supine sheep.

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Effect of inspiratory flow rate on regional distribution of inspired gas.

Cited by 102 publications

References 0 publications

Regional alveolar pressure during periodic flow. Dual manifestations of gas inertia.

Regional alveolar pressure during periodic flow. Dual manifestations of gas inertia.

Airway Gas Flow

Gas Exchange in the Normal Lung : Experimental studies on the effects of positive end-expiratory pressure and body position

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