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.

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.

Effect of breath-hold time on DLCO(SB) in patients with airway obstruction

1985 ◽  
Vol 58 (4) ◽  
pp. 1319-1325 ◽  
Author(s):  
B. L. Graham ◽  
J. T. Mink ◽  
D. J. Cotton
Keyword(s):  
Hold Time ◽  
Phase Iii ◽  
Breath Holding ◽  
Breath Hold ◽  
Single Breath ◽  
Incomplete Mixing ◽  
Capillary Membrane ◽  
Phase Iii Slope ◽  
Alveolar Capillary ◽  
Short Breath

The single-breath diffusing capacity of the lung for CO [DLCO(SB)] is considered a measure of the conductance of CO across the alveolar-capillary membrane and its binding with hemoglobin. Although incomplete mixing of inspired gas with alveolar gas could theoretically influence overall diffusion, conventional calculations of DLCO(SB) spuriously overestimate DLCO(SB) during short breath-holding periods when incomplete mixing of gas within the lung might have the greatest effect. Using the three-equation method to calculate DLCO(SB) which analytically accounts for changes in breath-hold time, we found that DLCO(SB) did not change with breath-hold time in control subjects but increased with increasing breath-hold time in both patients with asthma and patients with emphysema. The increase in DLCO(SB) with increasing breath-hold time correlated with the phase III slope of the single-breath N2 washout curve. We suggest that in patients with ventilation maldistribution, DLCO(SB) may be decreased for the shorter breath-hold maneuvers because overall diffusion is limited by the reduced transport of CO from the inspired gas through the alveolar gas prior to alveolar-capillary gas exchange.

Fast vs. slow exhalation before O2 inhalation alters subsequent phase III slope

1984 ◽  
Vol 56 (1) ◽  
pp. 52-56 ◽  
Author(s):  
T. S. Hurst ◽  
B. L. Graham ◽  
D. J. Cotton
Keyword(s):  
Total Lung Capacity ◽  
Normal Subjects ◽  
Phase Iii ◽  
Breath Holding ◽  
Small Airways ◽  
Residual Volume ◽  
Lung Capacity ◽  
Single Breath ◽  
Subsequent Phase ◽  
Phase Iii Slope

We studied 10 symptom-free lifetime non-smokers and 17 smokers all with normal pulmonary function studies. All subjects performed single-breath N2 washout tests by either exhaling slowly (“slow maneuver”) from end inspiration (EI) to residual volume (RV) or exhaling maximally (“fast maneuver”) from EI to RV. After either maneuver, subjects then slowly inhaled 100% O2 to total lung capacity (TLC) and without breath holding, exhaled slowly back to RV. In the nonsmokers seated upright phase III slope of single-breath N2 test (delta N2/l) was lower (P less than 0.01) for the fast vs. the slow maneuver, but this difference disappeared when the subjects repeated the maneuvers in the supine position. In contrast, delta N2/l was higher for the fast vs. the slow maneuver (P less than 0.01) in smokers seated upright. For the slow maneuver, delta N2/l was similar between smokers and nonsmokers but for the fast maneuvers delta N2/l was higher in smokers than nonsmokers (P less than 0.01). We suggest that the fast exhalation to RV decreases delta N2/l in normal subjects by decreasing apex-to-base differences in regional ratio of RV to TLC (RV/TLC) but increases delta N2/l in smokers, because regional RV/TLC increases distal to sites of small airways obstruction when the expiratory flow rate is increased.

Measurement of temporal changes in DLSBCO-3EQ from small alveolar samples in normal subjects

1994 ◽  
Vol 76 (4) ◽  
pp. 1494-1501 ◽  
Author(s):  
G. R. Soparkar ◽  
J. T. Mink ◽  
B. L. Graham ◽  
D. J. Cotton
Keyword(s):  
Hold Time ◽  
Normal Subjects ◽  
Gas Diffusion ◽  
Phase Iii ◽  
Mixing Efficiency ◽  
Breath Holding ◽  
Breath Hold ◽  
Inspiratory Capacity ◽  
Ventilation Inhomogeneity ◽  
Single Breath

The dynamic changes in CO concentration [CO] during a single breath could be influenced by topographic inhomogeneity in the lung or by peripheral inhomogeneity due to a gas mixing resistance in the gas phase of the lung or to serial gradients in gas diffusion. Ten healthy subjects performed single-breath maneuvers by slowly inhaling test gas from functional residual capacity to one-half inspiratory capacity and slowly exhaling to residual volume with target breath-hold times of 0, 1.5, 3, 6, and 9 s. We calculated the three-equation single-breath diffusing capacity of the lung for CO (DLSBCO-3EQ) from the mean [CO] in both the entire alveolar gas sample and in four successive equal alveolar gas samples. DLSBCO-3EQ from the entire alveolar gas sample was independent of breath-hold time. However, with 0 s of breath holding, from early alveolar gas samples DLSBCO-3EQ was reduced and from late alveolar gas samples it was increased. With increasing breath-hold time, DLSBCO-3EQ from the earliest alveolar gas sample rapidly increased, whereas from the last alveolar gas sample it rapidly decreased such that all values from the small alveolar gas samples approached DLSBCO-3EQ from the entire alveolar sample. These changes correlated with ventilation inhomogeneity, as measured by the phase III He concentration slope and the mixing efficiency, and were larger for maneuvers with inspired volumes to one-half inspiratory capacity vs. total lung capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Effect of airway closure on ventilation distribution

1989 ◽  
Vol 66 (6) ◽  
pp. 2511-2515 ◽  
Author(s):  
A. B. Crawford ◽  
D. J. Cotton ◽  
M. Paiva ◽  
L. A. Engel
Keyword(s):  
Normal Subjects ◽  
Phase Iii ◽  
Mixing Efficiency ◽  
Breath Holding ◽  
Airway Closure ◽  
Ventilation Distribution ◽  
Residual Capacity ◽  
Lung Periphery ◽  
Phase Iii Slope ◽  
Volume Range

We examined the effect of airway closure on ventilation distribution during tidal breathing in six normal subjects. Each subject performed multiple-breath N2 washouts (MBNW) at tidal volumes of 1 liter over a range of preinspiratory lung volumes (PILV) from functional residual capacity (FRC) to just above residual volume. All subjects performed washouts at PILV below their measured closing capacity. In addition five of the subjects performed MBNW at PILV below closing capacity with end-inspiratory breath holds of 2 or 5 s. We measured the following two independent indexes of ventilation maldistribution: 1) the normalized phase III slope of the final breaths of the washout (Snf) and 2) the alveolar mixing efficiency of those breaths of the washout where 80–90% of the initial N2 had been cleared. Between a mean PILV of 0.28 liter above closing capacity and that 0.31 liter below closing capacity, mean Snf increased by 132% (P less than 0.005). Over the same volume range, mean alveolar mixing efficiency decreased by 3.3% (P less than 0.05). Breath holding at PILV below closing capacity resulted in marked and consistent decreases in Snf and increases in alveolar mixing efficiency. Whereas inhomogeneity of ventilation decreases with lung volume when all airways are patent (J. Appl. Physiol. 66: 2502–2510, 1989), airway closure increases ventilation inequality, and this is substantially reduced by short end-inspiratory breath holds. These findings suggest that the predominant determinant of ventilation distribution below closing capacity is the inhomogeneous closure of airways subtending regions in the lung periphery that are close together.

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.

scholarly journals Nonuniformity of Diffusing Capacity From Small Alveolar Gas Samples Is Increased in Smokers

1998 ◽  
Vol 5 (2) ◽  
pp. 101-108 ◽  
Author(s):  
DJ Cotton ◽  
JT Mink ◽  
BL Graham
Keyword(s):  
Vital Capacity ◽  
Phase Iii ◽  
Mixing Efficiency ◽  
Breath Holding ◽  
Diffusing Capacity ◽  
Test Gas ◽  
Ventilation Inhomogeneity ◽  
Single Breath ◽  
Lung Periphery ◽  
Physiological Tests

BACKGROUND: Although centrilobular emphysema, and small airway, interstitial and alveoli inflammation can be detected pathologically in the lungs of smokers with relatively well preserved lung function, these changes are difficult to assess using available physiological tests. Because submaximal single breath washout (SBWSM) manoeuvres improve the detection of abnormalities in ventilation inhomogeneity in the lung periphery in smokers compared with traditional vital capacity manoeuvres, SBWSMmanoeuvres were used in this study to measure temporal differences in diffusing capacity using a rapid response carbon monoxide analyzer.OBJECTIVE: To determine whether abnormalities in the lung periphery can be detected in smokers with normal forced expired volumes in 1 s using the three-equation diffusing capacity (DLcoSB-3EQ) among small alveolar gas samples and whether the abnormalities correlate with increases in peripheral ventilation inhomogeneity.PARTICIPANTS AND DESIGN: Cross-sectional study in 21 smokers and 21 nonsmokers all with normal forced exhaled flow rates.METHODS: Both smokers and nonsmokers performed SBWSMmanoeuvres consisting of slow inhalation of test gas from functional residual capacity to one-half inspiratory capacity with either 0 or 10 s of breath holding and slow exhalation to residual volume (RV). They also performed conventional vital capacity single breath (SBWVC) manoeuvres consisting of slow inhalation of test gas from RV to total lung capacity and, without breath holding, slow exhalation to RV. DLcoSB-3EQ was calculated from the total alveolar gas sample. DLcoSB-3EQ was also calculated from four equal sequential, simulated aliquots of the total alveolar gas sample. DLcoSB-3EQ values from the four alveolar samples were normalized by expressing each as a percentge of DLcoSB-3EQ from the entire alveolar gas sample. An index of variation (DI) among the small-sample DLcoSB-3EQ values was correlated with the normalized phase III helium slope (Sn) and the mixing efficiency (Emix).RESULTS: For SBWSM, DIwas increased in smokers at 0 s of breath holding compared with nonsmokers, and correlated with age, smoking pack-years and Sn. The decrease in DIwith breath holding was greater in smokers and correlated with the change in Sn with breath holding. For SBWVCmanoeuvres, there were no differences due to smoking in Sn or Emix, but DIwas increased in smokers and correlated with age and smoking pack-years, but not with Sn.CONCLUSIONS: For SBWSMmanoeuvres the increase in DIin smokers correlated with breath hold time-dependent increases in Sn, suggesting that the changes in DIreflected the same structural alterations that caused increases in peripheral ventilation inhomogeneity. For SBWVCmanoeuvres, the increase in DIin smokers was not associated with changes in ventilation inhomogeneity, suggesting that the effect of smoking on DIduring this manoeuvre was due to smoke-related changes in alveolar capillary diffusion, rather than due solely to alterations in the distribution of ventilation.

Changing effect of lung volume on respiratory drive in man

1975 ◽  
Vol 38 (5) ◽  
pp. 768-773 ◽  
Author(s):  
N. N. Stanley ◽  
M. D. Altose ◽  
S. G. Kelsen ◽  
C. F. Ward ◽  
N. S. Cherniack
Keyword(s):  
Human Subjects ◽  
Inhibitory Effect ◽  
Breath Holding ◽  
Breath Hold ◽  
Respiratory Drive ◽  
Lung Inflation ◽  
Single Breath ◽  
Single Breath Hold ◽  
Sustained Effect ◽  
Residual Capacity

Experiments were conducted on human subjects to study the effect of lung inflation during breath holding on respiratory drive. Two series of experiments were performed: the first to examine respiratory drive during a single breath hold, the second designed to examine the sustained effect of lung inflation on subsequent breath holds. The experiments involved breath holding begun either at the end of a normal expiration or after a maximum inspiration. When breath holding was repeated at 10-min intervals, the increase in BHT produced by lung inflation was greater in short breath holds (after CO2 rebreathing) than in long breath holds (after hyperventilation). If breath holds were made in rapid succession, the first breath hold was much longer when made at total lung capacity than at functional residual capacity, but this effect of lung inflation diminished in subsequent breath holds. It is concluded that the inhibitory effect of lung inflation decays during breath holding and is regained remarkably slowly during the period of breathing immediately after breath holding.

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.

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