Inhomogeneity of pulmonary ventilation during sustained microgravity as determined by single-breath washouts

Guy, H. J.; Prisk, G. Kim; Elliott, A. R.; Deutschman, rd R. A.; West, John B.

doi:10.1152/jappl.1994.76.4.1719

Cited by 105 publications

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“…Their model is an electric circuit model consisting of three compartments without gravity effect. However, it is known that gravity effect is necessary for cardiogenic oscillation, as shown by Guy's microgravity experiments [21]. Our present simulation is consistent with their experiments because cardiogenic oscillation is generated by intrapulmonary inhomogeneity of the nitrogen concentration caused by gravity effect in our model.…”

Section: Validity Of the Lung Deformation Modelsupporting

confidence: 90%

A Novel Interpretation of Closing Volume Based on Single-Breath Nitrogen Washout Curve Simulation

Kitaoka¹,

Kawase²

2007

J. Physiol. Sci

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Abstract:Although closing volume is regarded as a clinical test for the early detection of peripheral airway closure, its grounds are not clear. There have been no simulation studies for phase IV in the single-breath nitrogen washout (SBNW) curve, even though several mathematical models for phase III have been proposed. We modeled the lung tissue deformation during slow expiration in which the tissue was regarded as a porous elastic body similar to a sponge. We assigned the maximum tissue density of lung parenchyma over which the lung tissue could not be contracted according to several experimental reports in literature. SBNW curves were then simulated by computing expired air volume and nitrogen concentration for respective acini in the lung model. The simulated SBNW curves well reproduced phase IV, cardiac oscillation, and its postural changes. We found that the higher lung compliance increased closing volume, but decreased residual volume. The smaller maximum tissue density generated larger closing volume and larger residual volume. It suggested that phase IV reflected the alveolar contractility, and the increase of closing volume in emphysema could be explained by an insufficient contraction of alveoli. We also found that the distribution of maximum tissue density affected the onset of Phase IV. A constant value of density generated a clear onset, but a wide distribution of it corresponding to peripheral airway closure obscured it. We suggest that the airway closure was not necessary for phase IV appearance in both normal and emphysematous lung.

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Section: Validity Of the Lung Deformation Modelsupporting

confidence: 90%

A Novel Interpretation of Closing Volume Based on Single-Breath Nitrogen Washout Curve Simulation

Kitaoka¹,

Kawase²

2007

J. Physiol. Sci

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“…All tests were performed on a system identical to that previously used to study ventilation inhomogeneity in G studies (20,25,40,43). Briefly, the system comprises of a bag-in-box system with separate bags for inspired and expired gases.…”

Section: Methodsmentioning

confidence: 99%

“…These data were converted to our standard laboratory format, by using a personal desktop computer, and analyzed with the same techniques applied to data previously obtained during G (20,38,40).…”

Section: Methodsmentioning

confidence: 99%

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Effect of 60° head-down tilt on peripheral gas mixing in the human lung

Olfert

Prisk

2004

Journal of Applied Physiology

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Olfert, I. Mark, and G. Kim Prisk. Effect of 60°head-down tilt on peripheral gas mixing in the human lung. J Appl Physiol 97: 827-834, 2004. First published April 16, 2004 10.1152/ japplphysiol.01379.2003The phase III slope of sulfur hexafluoride (SF 6) in a single-breath washout (SBW) is greater than that of helium (He) under normal gravity (i.e., 1G), thus resulting in a positive SF 6-He slope difference. In microgravity (G), SF6-He slope difference is smaller because of a greater fall in the phase III slope of SF 6 than He. We sought to determine whether increasing thoracic fluid volume using 60°head-down tilt (HDT) in 1G would produce a similar effect to G on phase III slopes of SF 6 and He. Single-breath vital capacity (SBW) and multiple-breath washout (MBW) tests were performed before, during, and 60 min after 1 h of HDT. Compared with baseline (SF 6 1.050 Ϯ 0.182%/l, He 0.670 Ϯ 0.172%/l), the SBW phase III slopes for both SF 6 and He tended to decrease during HDT, reaching nadir at 30 min (SF 6 0.609 Ϯ 0.211%/l, He 0.248 Ϯ 0.138%/l; P ϭ 0.08 and P ϭ 0.06, respectively). In contrast to G, the magnitude of the phase III slope decrease was similar for both SF 6 and He; therefore, no change in SF 6-He slope difference was observed. MBW analysis revealed a decrease in normalized phase III slopes at all time points during HDT, for both SF 6 (P Ͻ 0.01) and He (P Ͻ 0.01). This decrease was due to changes in the acinar, and not the conductive, component of the normalized phase III slope. These findings support the notion that changes in thoracic fluid volume alter ventilation distribution in the lung periphery but also demonstrate that the effect during HDT does not wholly mimic that observed in G.phase III slope; single-breath washout; multiple-breath washout; helium; sulfur hexafluoride NONUNIFORMITY OF PULMONARY ventilation results from inhomogeneities in both convective and diffusive gas transport, sometimes referred to as convective-dependent inhomogeneity (CDI) and diffusion-convection-dependent inhomogeneity (DCDI) (7). CDI effects may be induced by either gravitational mechanisms, such as topographic differences in pulmonary ventilation resulting from regional differences in pleural pressure (2, 27), or nongravitational mechanisms, such as differing mechanical properties (e.g., lung compliance) among regional lung units (7,37). DCDI effects involve a complex interaction between both convection and diffusion and are believed to occur in the branching structure of the lung when convective and diffusive transport mechanisms are similar in magnitude, which in humans is reported to be at or near the level of the entrance of the acinus (32). The effects of DCDI can be thought of as occurring on a small scale, i.e., intraregional, whereas CDI principally occurs between regions of the lung, i.e., interregional. Studies performed in microgravity (G) have shown that a substantial portion (ϳ75%) of ventilatory inhomogeneity (as evidenced by the phase III slope) is due to DCDI effects (20, 38 -40). However, there is...

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“…Unfortunately, the classical SBW manoeuvre involved inspiration of the test gases over a vital capacity (VC) manoeuvre, and microgravity experiments performed in the meantime have confirmed that the phase-III slope resulting from the classical SBW test is in fact a mixture of small-and large-scale ventilation inhomogeneities, partly dependent on gravity and airway closure [26,27]. By contrast, a modified SBW test starting the inspiration from functional residual capacity (FRC) has been shown to be less affected by confounding effects, such as gravity [28].…”

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confidence: 99%

Peripheral airway involvement in asthma assessed by single-breath SF₆and He washout

Gustafsson¹,

Ljungberg²,

Kjellman³

2003

Eur Respir J

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The aim of the study was to assess how deep into the acinar region the airway response to cold dry-air hyperventilation challenge (CACh) reaches in subjects with asthma of different severity.Peripheral airway function was measured using a single-breath sulphur hexafluoride (SF 6 ) and helium (He) washout test and overall airway function by forced expiratory volume in one second (FEV1) at rest, after CACh and b 2 -therapy in 55 adults with a history of asthma. The normalised phase-III slopes (Sn III ) for SF 6 and He were used to assess peripheral airway obstruction and the (SF 6 -He) Sn III difference to indicate where obstruction occurred. While a greater He versus SF 6 slope increase indicates a response close to the acinar entrance, the reverse indicates a response deeper into the acinar airspaces.Twelve subjects had a major fall in FEV1 (o20%) after CACh, 16 a minor fall (10-19%), and 27 did not react. Resting He and SF 6 Sn III were significantly greater in major responders with respect to minor and nonresponders, while resting FEV1 did not differ between the three groups. The major responders showed marked increases of He and SF 6 Sn III after CACh, with greater increase for He resulting in a negative (SF 6 -He) Sn III difference.To conclude, airways close to the acinar entrance participate in the overall airway response to cold-air challenge in asthmatic adults with marked airway hyperresponsiveness to cold, dry air. There is growing awareness that the inflammatory cell infiltration and airway wall thickening characteristic of bronchial asthma engage not only the large and the mediumsized airways but the entire airway tree [1][2][3]. The peripheral airways are usually defined as those airways with a diameter of v2 mm and correspond approximately to airway generations 8-23 of WEIBEL9S [4] model of lung architecture. Direct and indirect evidence of peripheral airway involvement in asthma have come from post mortem studies [5][6], tissue specimens obtained in vivo using bronchoscopic biopsy techniques [7], bronchoscopic airflow resistance studies in distal lung units [8][9][10], and inert-gas washout studies [11][12][13]. In a previous nitrogen (N 2 ) multiple-breath washout (MBW) study, STROM-BERG and GUSTAFSSON [13] assessed the peripheral airway effects of cold dry-air hyperventilation challenge (CACh) on asthma patients and controls [13]. After the challenge the asthmatic subjects demonstrated not only a fall in FEV1 but also increased overall ventilation inhomogeneity and gas trapping, indicating peripheral airway obstruction [14].Exercise-induced bronchoconstriction (EIB) is a common problem in children and adults with asthma [15,16]. The underlying mechanism of EIB is drying and cooling of the airways due to the increased ventilation necessary during physical exercise [17,18]. Evaporation of water from the thin airway surface liquid layer is thought to result in a hyperosmolar stimulus to inflammatory cells in the airway mucosa of asthmatic subjects and the subsequent production and release...

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Inhomogeneity of pulmonary ventilation during sustained microgravity as determined by single-breath washouts

Cited by 105 publications

References 0 publications

A Novel Interpretation of Closing Volume Based on Single-Breath Nitrogen Washout Curve Simulation

A Novel Interpretation of Closing Volume Based on Single-Breath Nitrogen Washout Curve Simulation

Effect of 60° head-down tilt on peripheral gas mixing in the human lung

Peripheral airway involvement in asthma assessed by single-breath SF₆and He washout

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Inhomogeneity of pulmonary ventilation during sustained microgravity as determined by single-breath washouts

Cited by 105 publications

References 0 publications

A Novel Interpretation of Closing Volume Based on Single-Breath Nitrogen Washout Curve Simulation

A Novel Interpretation of Closing Volume Based on Single-Breath Nitrogen Washout Curve Simulation

Effect of 60° head-down tilt on peripheral gas mixing in the human lung

Peripheral airway involvement in asthma assessed by single-breath SF6and He washout

Contact Info

Product

Resources

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Peripheral airway involvement in asthma assessed by single-breath SF₆and He washout