Gas flow and mixing in the airways

Pedley, T. J.; Corieri, Patricia; Kamm, Roger D.; Grotberg, James B.; Hydon, Peter E.; Schroter, R. C.

doi:10.1097/00003246-199422091-00002

Cited by 61 publications

(64 citation statements)

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“…This dose is influenced by the average airway concentration of NO which is reflected by our measurements. Our finding that HFOV enhances airway concentrations and axial concentration profiles of both NO and COµ in healthy rabbits can be explained by the fact that the high frequency of flow alterations enhances longitudinal transport along the airways (Pedley et al 1994;Gavriely et al 1995). Qualitatively similar COµ profiles have been seen in HFOV-treated healthy dogs (Gavriely et al 1993).…”

Section: ------------------------------------------------------------supporting

confidence: 62%

Exhaled Nitric Oxide Increases During High Frequency Oscillatory Ventilation in Rabbits

Artlich¹,

Adding²,

Agvald³

et al. 1999

Exp. Physiol.

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summaryThis study compared the effects of high frequency oscillatory ventilation (HFOV) and intermittent mandatory ventilation (IMV) on the homeostasis of nitric oxide (NO) in the lower respiratory tract of healthy rabbits. The mechanisms underlying a putative stretch response of NO formation in the airways were further elucidated. Male New Zealand White rabbits were anaesthetized, tracheotomized and ventilated with IMV or HFOV in random order. Total NO excretion increased from 9·6 ± 0·8 nl min¢ (mean ± s.e.m.) during IMV to 22·6 ± 2·7 nl min¢ during HFOV (P < 0·001). This increase was not explained by changes of functional residual capacity (ÄFRC). A similar increase in NO excretion during HFOV was seen in isolated buffer-perfused lungs under constant circulatory conditions (P < 0·05, n = 4). Intratracheal mean COµ and NO concentrations, measured at 2·5, 5, 7·5 and 10 cm below tracheostomy, increased significantly with increasing distance into the lung during both IMV and HFOV (P < 0·001 for each comparison). At every intratracheal location of the sampling catheter, particularly low in the airways, both COµ and NO concentrations were significantly higher during HFOV than during IMV (P < 0·01 for each comparison). We conclude that HFOV increases pulmonary NO production in healthy rabbits. Increased stretch activation of the respiratory system during HFOV is suggested as a possible underlying mechanism. The increase in mean airway NO concentrations may have biological effects in the respiratory tract. Whether it can account for some of the benefits of HFOV treatment needs to be considered. introduction NO, which is continuously produced within the lower respiratory tract (Gustafsson et al. 1991;Persson et al. 1993), can be detected in the exhaled gas of most mammalian species, offering a unique possibility to study features of NO metabolism non-invasively (Gustafsson, 1997). However, the anatomic site and main cell type producing those NO molecules detected in exhaled gas is still a matter of debate (Gustafsson, 1997). Thus the extent to which the various biological functions of NO are reflected in the concentration of NO in exhaled gas merits further study. Moreover, factors influencing the amount of NO detected in exhaled gas are only beginning to evolve. We have recently shown in rabbits and guinea-pigs that lower airway NO formation is suppressed by high airway concentrations of COµ Str omberg et al. 1997;Adding et al. 1999). This rapid effect is also present in isolated buffer-perfused rabbit lungs and cannot be explained by either altered sympathetic outflow or changes of extracellular pH (Adding et al. 1999). Another mechanism to increase lower airway NO formation is revealed during increases of positive end-expiratory pressure (PEEP)

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Section: ------------------------------------------------------------supporting

confidence: 62%

Exhaled Nitric Oxide Increases During High Frequency Oscillatory Ventilation in Rabbits

Artlich¹,

Adding²,

Agvald³

et al. 1999

Exp. Physiol.

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“…However, after many years of debate on whether large or small airways are more responsible for airflow obstruction during asthma attacks, there remains little experimental evidence on which to base any conclusive answer. It is well accepted and known from morphometric models of WEIBEL [10], HORSFIELD and CUMMING [11,12], and others [13], that nearly all of the baseline airway resistance lies in the conducting airways w2 mm. With smooth muscle contraction, this partitioning can surely change, but this situation has not been extensively modelled.…”

Section: Which Airways Cause the Problem In Asthma?mentioning

confidence: 95%

Radiofrequency ablation of airway smooth muscle for sustained treatment of asthma: preliminary investigations

Cox

Miller

Mitzner

et al. 2004

European Respiratory Journal

128

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“…Table 1 provides the values of the foregoing dimensionless parameters calculated for three particle sizes at different locations along the acinar tree. The breathing period of T ¼ 4 s was assumed and velocity values are quoted from Pedley et al [36] for inhalation rate of 0.5 liters/s along the acinar tree.…”

Section: Introductionmentioning

confidence: 99%

The Simultaneous Role of an Alveolus as Flow Mixer and Flow Feeder for the Deposition of Inhaled Submicron Particles

Henry¹,

Haber

Haberthür

et al. 2012

Journal of Biomechanical Engineering

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In an effort to understand the fate of inhaled submicron particles in the small sacs, or alveoli, comprising the gas-exchange region of the lung, we calculated the flow in threedimensional (3D) rhythmically expanding models of alveolated ducts. Since convection toward the alveolar walls is a precursor to particle deposition, it was the goal of this paper to investigate the streamline maps' dependence upon alveoli location along the acinar tree. On the alveolar midplane, the recirculating flow pattern exhibited closed streamlines with a stagnation saddle point. Off the midplane we found no closed streamlines but nested, funnel-like, spiral, structures (reminiscent of Russian nesting dolls) that were directed towards the expanding walls in inspiration, and away from the contracting walls in expiration. These nested, funnel-like, structures were surrounded by air that flowed into the cavity from the central channel over inspiration and flowed from the cavity to the central channel over expiration. We also found that fluid particle tracks exhibited similar nested funnel-like spiral structures. We conclude that these unique alveolar flow structures may be of importance in enhancing deposition. In addition, due to inertia, the nested, funnel-like, structures change shape and position slightly during a breathing cycle, resulting in flow mixing. Also, each inspiration feeds a fresh supply of particleladen air from the central channel to the region surrounding the mixing region. Thus, this combination of flow mixer and flow feeder makes each individual alveolus an effective mixing unit, which is likely to play an important role in determining the overall efficiency of convective mixing in the acinus.

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Gas flow and mixing in the airways

Cited by 61 publications

References 0 publications

Exhaled Nitric Oxide Increases During High Frequency Oscillatory Ventilation in Rabbits

Exhaled Nitric Oxide Increases During High Frequency Oscillatory Ventilation in Rabbits

Radiofrequency ablation of airway smooth muscle for sustained treatment of asthma: preliminary investigations

The Simultaneous Role of an Alveolus as Flow Mixer and Flow Feeder for the Deposition of Inhaled Submicron Particles

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