Helium and sulfur hexafluoride bolus washin in short-term microgravity

1999 ◽  
Vol 86 (5) ◽  
pp. 1594-1602 ◽  
Author(s):  
Brigitte Dutrieue ◽  
Anne-Marie Lauzon ◽  
Sylvia Verbanck ◽  
Ann R. Elliott ◽  
John B. West ◽  
...  
Keyword(s):  
Sulfur Hexafluoride ◽  
Vital Capacity ◽  
Parabolic Flight ◽  
Phase Iii ◽  
Lung Volumes ◽  
Single Breath ◽  
Close Proximity ◽  
Slope Difference ◽  
The Difference ◽  
Phase Iii Slope

We performed single-breath washout (SBW) tests in which He and sulfur hexafluoride (SF6) were inspired throughout the vital capacity inspirations or were inhaled as discrete boluses at different points in the inspiration. Tests were performed in normal gravity (1 G) and in up to 27 s of microgravity (μG) during parabolic flight. The phase III slope of the SBW could be accurately reconstructed from individual bolus tests when allowance for airways closure was made. Bolus tests showed that most of the SBW phase III slope results from events during inspiration at lung volumes below closing capacity and near total lung capacity, as does the SF6-He phase III slope difference. Similarly, the difference between 1 G and μG in phase III slopes for both gases was entirely accounted for by gravity-dependent events at high and low lung volumes. Phase IV height was always larger for SF6 than for He, suggesting at least some airway closure in close proximity to airways that remain open at residual volume. These results help explain previous studies in μG, which show large changes in gas mixing in vital capacity maneuvers but only small effects in tidal volume breaths.

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

2004 ◽  
Vol 97 (3) ◽  
pp. 827-834 ◽  
Author(s):  
I. Mark Olfert ◽  
G. Kim Prisk
Keyword(s):  
Sulfur Hexafluoride ◽  
Normal Gravity ◽  
Fluid Volume ◽  
Phase Iii ◽  
Single Breath ◽  
Multiple Breath Washout ◽  
Conductive Component ◽  
Slope Difference ◽  
Lung Periphery ◽  
Phase Iii Slope

The phase III slope of sulfur hexafluoride (SF6) in a single-breath washout (SBW) is greater than that of helium (He) under normal gravity (i.e., 1G), thus resulting in a positive SF6-He slope difference. In microgravity (μG), SF6-He slope difference is smaller because of a greater fall in the phase III slope of SF6 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 μG on phase III slopes of SF6 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 (SF6 1.050 ± 0.182%/l, He 0.670 ± 0.172%/l), the SBW phase III slopes for both SF6 and He tended to decrease during HDT, reaching nadir at 30 min (SF6 0.609 ± 0.211%/l, He 0.248 ± 0.138%/l; P = 0.08 and P = 0.06, respectively). In contrast to μG, the magnitude of the phase III slope decrease was similar for both SF6 and He; therefore, no change in SF6-He slope difference was observed. MBW analysis revealed a decrease in normalized phase III slopes at all time points during HDT, for both SF6 ( P < 0.01) and He ( P < 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 μG.

scholarly journals Paradoxical helium and sulfur hexafluoride single-breath washouts in short-term vs. sustained microgravity

1997 ◽  
Vol 82 (3) ◽  
pp. 859-865 ◽  
Author(s):  
Anne-Marie Lauzon ◽  
G. Kim Prisk ◽  
Ann R. Elliott ◽  
Sylvia Verbanck ◽  
Manuel Paiva ◽  
...  
Keyword(s):  
Sulfur Hexafluoride ◽  
Normal Gravity ◽  
Phase Iii ◽  
Homogeneous Distribution ◽  
Volume Distribution ◽  
Short Term ◽  
Single Breath ◽  
Slope Difference ◽  
Phase Iii Slope ◽  
Blood Volume Distribution

Lauzon, Anne-Marie, G. Kim Prisk, Ann R. Elliott, Sylvia Verbanck, Manuel Paiva, and John B. West. Paradoxical helium and sulfur hexafluoride single-breath washouts in short-term vs. sustained microgravity. J. Appl. Physiol. 82(3): 859–865, 1997.—During single-breath washouts in normal gravity (1 G), the phase III slope of sulfur hexafluoride (SF6) is steeper than that of helium (He). Two mechanisms can account for this: 1) the higher diffusivity of He enhances its homogeneous distribution; and 2) the lower diffusivity of SF6 results in a more peripheral location of the diffusion front, where airway asymmetry is larger. These mechanisms were thought to be gravity independent. However, we showed during the Spacelab Life Sciences-2 spaceflight that in sustained microgravity (μG) the SF6-to-He slope difference is abolished. We repeated the protocol during short periods (27 s) of μG (parabolic flights). The subjects performed a vital-capacity inspiration and expiration of a gas containing 5% He-1.25% SF6-balance O2. As in sustained μG, the phase III slopes of He and SF6decreased. However, during short-term μG, the SF6-to-He slope difference increased from 0.17 ± 0.03%/l in 1 G to 0.29 ± 0.06%/l in μG, respectively. This is contrary to sustained μG, in which the SF6-to-He slope difference decreased from 0.25 ± 0.03%/l in 1 G to −0.01 ± 0.06%/l in μG. The increase in phase III slope difference in short-term μG was caused by a larger decrease of He phase III slope compared with that in sustained μG. This suggests that changes in peripheral gas mixing seen in sustained μG are mainly due to alterations in the diffusive-convective inhomogeneity of He that require >27 s of μG to occur. Changes in pulmonary blood volume distribution or cardiogenic mixing may explain the differences between the results found in short-term and sustained μG.

Single-breath washouts in a rotating stretcher

2001 ◽  
Vol 90 (4) ◽  
pp. 1415-1423 ◽  
Author(s):  
M. J. Rodríguez-Nieto ◽  
G. Peces-Barba ◽  
N. González Mangado ◽  
S. Verbanck ◽  
M. Paiva
Keyword(s):  
Vital Capacity ◽  
Phase Iii ◽  
Body Postures ◽  
Single Breath ◽  
Supine Posture ◽  
Or Groups ◽  
Slope Difference ◽  
Phase Iii Slope ◽  
Prone Posture ◽  
Phase Iv

Vital capacity single-breath washouts using 90% O2-5% He-5% SF6 as a test gas mixture were performed with subjects sitting on a stool (upright) or recumbent on a stretcher (prone, supine, lateral left, lateral right, with or without rotation at end of inhalation). On the basis of the combinations of supine and prone maneuvers, gravity-dependent contributions to N2 phase III slope and N2 phase IV height in the supine posture were estimated at 18% and 68%, respectively. Whereas both He and SF6 slope decreased from supine to prone, the SF6-He slope difference actually increased ( P = 0.015). N2 phase III slopes, phase IV heights, and cardiogenic oscillations were smallest in the prone posture, and we observed similarities between the modifications of He and SF6 slopes from upright to prone and from upright to short-term microgravity. These results suggest that phase III slope is partially due to emptying patterns of small units with different ventilation-to-volume ratios, corresponding to acini or groups of acini. Of all body postures under study, the prone position most reduces the inhomogeneities of ventilation during a vital capacity maneuver at both inter- and intraregional levels.

scholarly journals Tidal volume single-breath washin of SF6 and CH4 in transient microgravity

2003 ◽  
Vol 94 (1) ◽  
pp. 75-82 ◽  
Author(s):  
Brigitte Dutrieue ◽  
Manuel Paiva ◽  
Sylvia Verbanck ◽  
Marine Le Gouic ◽  
Chantal Darquenne ◽  
...  
Keyword(s):  
Tidal Volume ◽  
Conformational Changes ◽  
Functional Residual Capacity ◽  
Vital Capacity ◽  
Time Dependent ◽  
Phase Iii ◽  
Lung Volumes ◽  
Single Breath ◽  
Residual Capacity ◽  
Slope Difference

We performed tidal volume single-breath washins (SBW) by using tracers of different diffusivity and varied the time spent in microgravity (μG) before the start of the tests to look for time-dependent effects. SF6 and CH4 phase III slopes decreased by 35 and 26%, respectively, in μG compared with 1 G ( P < 0.05), and the slope difference between gases disappeared. There was no effect of time in μG, suggesting that neither the hypergravity period preceding μG nor the time spent in μG affected gas mixing at volumes near functional residual capacity. In previous studies using SF6 and He (Lauzon A-M, Prisk GK, Elliott AR, Verbanck S, Paiva M, and West JB. J Appl Physiol 82: 859–865, 1997), the vital capacity SBW showed an increase in slope difference between gases in transient μG, the opposite of the decrease in sustained μG. In contrast, tidal volume SBW showed a decrease in slope difference in both μG conditions. Because it is only the behavior of the more diffusive gas that differed between maneuvers and μG conditions, we speculate that, in the previous vital capacity SBW, the hypergravity period preceding the test in transient μG provoked conformational changes at low lung volumes near the acinar entrance.

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

2002 ◽  
Vol 92 (3) ◽  
pp. 1232-1238 ◽  
Author(s):  
Christopher N. Mills ◽  
Chantal Darquenne ◽  
G. Kim Prisk
Keyword(s):  
Vital Capacity ◽  
Normal Subjects ◽  
Phase Iii ◽  
Mode Shift ◽  
Nitrogen Washout ◽  
Single Breath ◽  
Posture Change ◽  
Supine Posture ◽  
Residual Capacity ◽  
Phase Iii Slope

We studied the effects on aerosol bolus inhalations of small changes in convective inhomogeneity induced by posture change from upright to supine in nine normal subjects. Vital capacity single-breath nitrogen washout tests were used to determine ventilatory inhomogeneity change between postures. Relative to upright, supine phase III slope was increased 33 ± 11% (mean ± SE, P < 0.05) and phase IV height increased 25 ± 11% ( P < 0.05), consistent with an increase in convective inhomogeneity likely due to increases in flow sequencing. Subjects also performed 0.5-μm-particle bolus inhalations to penetration volumes (Vp) between 150 and 1,200 ml during a standardized inhalation from residual volume to 1 liter above upright functional residual capacity. Mode shift (MS) in supine posture was more mouthward than upright at all Vp, changing by 11.6 ml at Vp = 150 ml ( P < 0.05) and 38.4 ml at Vp = 1,200 ml ( P < 0.05). MS and phase III slope changes correlated positively at deeper Vp. Deposition did not change at any Vp, suggesting that deposition did not cause the MS change. We propose that the MS change results from increased sequencing in supine vs. upright posture.

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

1994 ◽  
Vol 76 (4) ◽  
pp. 1719-1729 ◽  
Author(s):  
H. J. Guy ◽  
G. K. Prisk ◽  
A. R. Elliott ◽  
R. A. Deutschman ◽  
J. B. West
Keyword(s):  
Vital Capacity ◽  
Normal Gravity ◽  
Parabolic Flight ◽  
Pulmonary Ventilation ◽  
Phase Iii ◽  
Single Breath ◽  
Relative Contribution ◽  
Cardiogenic Oscillations ◽  
Expiratory Flow Rates ◽  
Phase Iv

Gravity is known to cause inhomogeneity of ventilation. Nongravitational factors are also recognized, but their relative contribution is not understood. We therefore studied ventilatory inhomogeneity during sustained microgravity during the 9-day flight of Spacelab SLS-1. All seven crew members performed single-breath nitrogen washouts. They inspired a vital capacity breath of 100% oxygen with a bolus of argon at the start of inspiration, and the inspiratory and expiratory flow rates were controlled at 0.5 l/s. Control measurements in normal gravity (1 G) were made pre- and postflight in the standing and supine position. Compared with the standing 1-G measurements, there was a marked decrease in ventilatory inhomogeneity during microgravity, as evidenced by the significant reductions in cardiogenic oscillations, slope of phase III, and height of phase IV for nitrogen and argon. However, argon phase IV volume was not reduced, and considerable ventilatory inhomogeneity remained. For example, the heights of the cardiogenic oscillations during microgravity for nitrogen and argon were 44 and 24%, respectively, of their values at 1 G, whereas the slopes of phase III for nitrogen and argon were 78 and 29%, respectively, of those at 1 G. The presence of a phase IV in microgravity is strong evidence that airway closure still occurs in the absence of gravity. The results were qualitatively similar to those found previously during short periods of 0 G in parabolic flight.

Anomalous behavior of helium and sulfur hexafluoride during single-breath tests in sustained microgravity

1996 ◽  
Vol 80 (4) ◽  
pp. 1126-1132 ◽  
Author(s):  
G. K. Prisk ◽  
A. M. Lauzon ◽  
S. Verbanck ◽  
A. R. Elliot ◽  
H. J. Guy ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Sulfur Hexafluoride ◽  
Anomalous Behavior ◽  
Phase Iii ◽  
Breath Holding ◽  
Breath Hold ◽  
Breath Tests ◽  
Single Breath ◽  
Lung Periphery ◽  
Phase Iii Slope

We performed single-breath wash-in tests for He and SF6 in four subjects exposed to 14 days of microgravity (microG) during the Spacelab flight Spacelab Life Sciences-2. Subjects inspired a vital capacity breath of 5% He-1.25% SF6-balance O2 and then exhaled to residual volume at 0.5l/s. The tests were also performed with a 10-s breath hold at the end of inspiration. Measurements were also made with the subjects standing and supine in 1 G. Phase III slope was measured after the dead-space washout and before the onset of airway closure. In all subjects in 1 G, whether standing or supine, phase III slope for SF6 was significantly steeper than that for He. However, in microG, the slopes became the same. Furthermore, after breath holding in microG, the SF6 slopes were significantly flatter than those for He. On return to 1 G, the changes were reversed, and there was no difference between preflight and postflight values. Because most of the phase III slope reflects events occurring in the acinar regions of the lung, the results suggest that microG causes conformational changes in the acini or changes in cardiogenic mixing in the lung periphery, but in either case the mechanism is unclear.

Similar ventilation distribution in normal subjects prone and supine during tidal breathing

2002 ◽  
Vol 92 (2) ◽  
pp. 622-626 ◽  
Author(s):  
M. J. Rodríguez-Nieto ◽  
G. Peces-Barba ◽  
N. González Mangado ◽  
M. Paiva ◽  
S. Verbanck
Keyword(s):  
Normal Subjects ◽  
Phase Iii ◽  
Ventilation Distribution ◽  
Tidal Breathing ◽  
Ventilation Heterogeneity ◽  
Multiple Breath Washout ◽  
Residual Capacity ◽  
Slope Difference ◽  
The Difference ◽  
Phase Iii Slope

Multiple-breath washout (MBW) tests, with end-expiratory lung volume at functional residual capacity (FRC) and 90% O2, 5% He, and 5% SF6as an inspired gas mixture, were performed in healthy volunteers in supine and prone postures. The semilog plot of MBW N2concentrations was evaluated in terms of its curvilinearity. The MBW N2normalized slope analysis yielded indexes of acinar and conductive ventilation heterogeneity (Verbanck S, Schuermans D, Van Muylem A, Paiva M, Noppen M, and Vincken W. J App Physiol 83: 1907–1916, 1997). Also, the difference between SF6and He normalized phase III slopes was computed in the first MBW expiration. Only MBW tests with similar FRC in the prone and supine postures ( P > 0.1; n= 8) were considered. Prone and supine postures did not reveal any significant differences in curvilinearity, N2normalized slope-derived indexes of conductive or acinar ventilation heterogeneity, nor SF6-He normalized phase III slope difference in the first MBW expiration ( P > 0.1 for all). The absence of significant changes in any of the MBW indexes suggests that ventilation heterogeneity is similar in the supine and prone postures of normal subjects breathing near FRC.

Postural effects on lung volumes and asynchronous ventilation in anesthetized horses

1980 ◽  
Vol 48 (1) ◽  
pp. 97-103 ◽  
Author(s):  
P. R. Sorenson ◽  
N. E. Robinson
Keyword(s):  
Lung Volume ◽  
Phase Iii ◽  
Lung Volumes ◽  
Lung Capacity ◽  
Single Breath ◽  
Supine Posture ◽  
Residual Capacity ◽  
Phase Iii Slope ◽  
Average Body ◽  
Prone Posture

Quasi-static pressure-volume curves and single-breath nitrogen washouts were performed simultaneously on eight anesthetized horses (average body wt = 485 kg) in left lateral, right lateral, prone, and supine postures (sequence randomized). The shift from prone to lateral or supine posture decreased expiratory reserve volume (ERV), vital capacity (VC), residual volume (RV), functional residual capacity (FRC), and total lung capacity (TLC); RV and FRC expressed as %TLC were unchanged, suggesting that in the lateral and supine postures a significant portion of the lung volume was not recruited by VC maneuvers. Phase III slope increased from 0.13 %N2/l in prone horses to 0.34 %N2/l in the lateral and supine positions. The onset of phase IV was not significantly different from FRC in the prone or laterally recombent animal, but exceeded FRC in the supine horse. The sequence of body positions had no effect on any of our results indicating that all changes in lung volumes and regional asynchronous ventilation c;n be reversed by placing the horse in the prone posture. The reduction in lung volume and increased asynchronous ventilation in the lateral and supine horse suggests that impaired gas exchange in anesthetized horses is predominantly related to posture, and not general anesthesia.

Inflection point on transpulmonary pressure-volume curves and closing volume

1975 ◽  
Vol 38 (2) ◽  
pp. 228-235 ◽  
Author(s):  
M. Demedts ◽  
J. Clement ◽  
D. C. Stanescu ◽  
K. P. van de Woestijne
Keyword(s):  
Inflection Point ◽  
Vital Capacity ◽  
Transpulmonary Pressure ◽  
Bronchial Obstruction ◽  
Closing Volume ◽  
Lung Volumes ◽  
Nitrogen Washout ◽  
Single Breath ◽  
Space Effect ◽  
Washout Curves

In 20 healthy subjects and 18 patients with bronchial obstruction, closing volume (CV) on single-breath nitrogen washout curves and inflection point (IP) on transpulmonary pressure-volume curves were recorded simultaneously during slow expiratory vital capacity maneuvers. IP and CV did not occur at identical lung volumes, IP being systematically larger than CV for small CV values. This discrepancy could not be attributed to an esophageal or mediastinal artifact. It is suggested that, though CV and IP both express “airway closure,” their sensitivity to closure may differ: CV underestimates closure because of a dead space effect; the latter may vary individually. On the other hand, IP may not reflect the true beginning of closure, particularly when it occurs at higher lung volumes.

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