Mode shift of an inhaled aerosol bolus is correlated  with flow sequencing in the human lung

Mills, Christopher N.; Darquenne, Chantal; Prisk, G. Kim

doi:10.1152/japplphysiol.00655.2001

Cited by 7 publications

(6 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Data presented in this study were collected using the same technique as in previous studies by our group in which 3 of the 11 subjects also participated. (5,7,10) Data from the present study that were obtained in these three subjects agreed well with that obtained previously. (7) In both studies, data were obtained with air at a flow rate of ϳ0.5 L/sec and with 1 m-diameter particles.…”

Section: Heliox and Regional Aerosol Deposition 163supporting

confidence: 91%

“…(5,7) PETERSON ET AL. Data were grouped on the basis of four categorical variables: carrier gas (air or heliox), particle size (1 or 2 m), subject number (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11), and penetration volume (150, 300, 500, 800, and 1200). A oneway ANOVA for two correlated samples was performed to test for differences between the chosen categorical variables.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Aerosol Deposition in the Human Lung Periphery Is Increased by Reduced-Density Gas Breathing

Peterson

Prisk

Darquenne

2008

Journal of Aerosol Medicine and Pulmonary Drug Delivery

Self Cite

View full text Add to dashboard Cite

Aerosol mixing resulting from turbulent flows is thought to be a major mechanism of deposition in the upper respiratory tract (URT). Because turbulence levels are a function of gas density, the use of a low-density carrier gas should reduce deposition in the URT allowing the aerosol to reach more peripheral airways of the lung. We performed aerosol bolus tests on 11 healthy subjects to investigate the effect of reduced gas density on regional aerosol deposition in the human lung. Using both air and heliox (80% helium, 20% oxygen) as carrier gas, boluses of 1 and 2 microm-diameter particles were inhaled to five volumetric lung depths (V(p)) between 150 and 1200 mL during an inspiration from residual volume (RV) to 1 liter above functional residual capacity at a constant flow rate of approximately 0.50 L/sec, which was immediately followed by an expiration to RV at the same flow rate. Aerosol deposition and axial dispersion were calculated from aerosol concentration and flow rate measured at the mouth. For 1 microm-diameter particles, deposition was significantly reduced by 29 +/- 28% (mean +/- SD, p < 0.05) when breathing heliox instead of air at shallow V(p) (150 mL) and significantly increased by 11 +/- 9% at deep V(p) (1200 mL). For 2 microm-diameter particles, deposition was significantly higher at V(p) = 500 mL by 6 +/- 7% and the predicted V(p) to achieve 100% deposition was significantly lower with heliox (834 +/- 146 mL) compared to air (912 +/- 128 mL) (p < 0.05). Despite a decrease in deposition at shallow V(p), there was no change in axial dispersion, suggesting that other factors such as radial turbulent mixing result in decreased aerosol deposition. Our results suggested that heliox reduces upper airway deposition of 1 and 2 microm-diameter particles allowing more particles to penetrate and subsequently deposit in the peripheral lung.

show abstract

Section: Heliox and Regional Aerosol Deposition 163supporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Aerosol Deposition in the Human Lung Periphery Is Increased by Reduced-Density Gas Breathing

Peterson

Prisk

Darquenne

2008

Journal of Aerosol Medicine and Pulmonary Drug Delivery

Self Cite

View full text Add to dashboard Cite

show abstract

“…The lack of SF 6 -He difference indicates that either 1) changes occurring in the phase III slope as a result of HDT were upstream of DCDI effects and thus primarily involved CDI mechanisms, or 2) changes in the lung periphery occurred in a manner that affected He and SF 6 similarly. In contrast to HDT, overall ventilatory inhomogeneity is increased in the supine position (18,19,29). The increase in ventilatory inhomogeneity in the supine position appears to be largely, if not solely, related to CDI transport mechanisms (18,19).…”

Section: Discussionmentioning

confidence: 96%

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

Olfert

Prisk

2004

Journal of Applied Physiology

Self Cite

View full text Add to dashboard Cite

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...

show abstract

“…The occurrence of sequential emptying, together with these differences in gas concentrations, is a prerequisite for the appearance of phase IV phenomena: if all pulmonary units should empty at the same time, differences in gas concentrations would not appear in the expirate because of gas mixing between the different units. In the presence of the pleural pressure gradients induced by gravity, basal regions of the lung are relatively more deflated at the end of expiration due to the overlying weight of the rest of the lung (37). As a consequence, airway closure is not homogeneous in the lung; the highest (least negative) pleural pressures being in the dependent parts, a basal-to-apical sequential emptying occurs.…”

Section: Origin and Significance Of Phase IV Phenomenamentioning

confidence: 99%

Residual heterogeneity of intra- and interregional pulmonary perfusion in short-term microgravity

Montmerle¹,

Sundblad²,

Linnarsson³

2005

Journal of Applied Physiology

View full text Add to dashboard Cite

We hypothesized that the perfusion heterogeneity in the human, upright lung is determined by nongravitational more than gravitational factors. Twelve and six subjects were studied during two series of parabolic flights. We used cardiogenic oscillations of O(2)/SF(6) as an indirect estimate of intraregional perfusion heterogeneity (series 1) and phase IV amplitude (P(4)) as a indirect estimate of interregional perfusion heterogeneity (series 2). A rebreathing-breath holding-expiration maneuver was performed. In flight, breath holding and expiration were performed either in microgravity (0 G) or in hypergravity. Controls were performed at normal gravity (1 G). In series 1, expiration was performed at 0 G. Cardiogenic oscillations of O(2)/SF(6) were 19% lower when breath holding was performed at 0 G than when breath holding was performed at 1 G [means (SD): 1.7 (0.3) and 2.3 (0.6)% units] (P = 0.044). When breath holding was performed at 1.8 G, values did not differ from 1-G control [2.6 (0.8)% units, P = 0.15], but they were 17% larger at 1.8 G than at 1 G. In series 2, expiration was performed at 1.7 G. P(4) changed with gravity (P < 0.001). When breath holding was performed at 0 G, P(4) values were 45 (46)% of control. When breath holding was performed at 1.7 G, P(4) values were 183 (101)% of control. We conclude that more than one-half of indexes of perfusion heterogeneity at 1 G are caused by nongravitational mechanisms.

show abstract

Mode shift of an inhaled aerosol bolus is correlated with flow sequencing in the human lung

Cited by 7 publications

References 21 publications

Aerosol Deposition in the Human Lung Periphery Is Increased by Reduced-Density Gas Breathing

Aerosol Deposition in the Human Lung Periphery Is Increased by Reduced-Density Gas Breathing

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

Residual heterogeneity of intra- and interregional pulmonary perfusion in short-term microgravity

Contact Info

Product

Resources

About