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.

Effect of lung volume on ventilation distribution

1989 ◽  
Vol 66 (6) ◽  
pp. 2502-2510 ◽  
Author(s):  
A. B. Crawford ◽  
D. J. Cotton ◽  
M. Paiva ◽  
L. A. Engel
Keyword(s):  
Lung Volume ◽  
Normal Subjects ◽  
Phase Iii ◽  
Mixing Efficiency ◽  
Ventilation Distribution ◽  
Single Breath ◽  
Wide Range ◽  
Residual Capacity ◽  
Phase Iii Slope ◽  
Volume Range

To examine the effect of preinspiratory lung volume (PILV) on ventilation distribution, we performed multiple-breath N2 washouts (MBNW) in seven normal subjects breathing 1-liter tidal volumes over a wide range of PILV above closing capacity. We measured the following two independent indexes of ventilation distribution from the MBNW: 1) the normalized phase III slope of the final breaths of the washout (Snf) and 2) the alveolar mixing efficiency during that portion of the washout where 80–90% of the lung N2 had been cleared. Three of the subjects also performed single-breath N2 washouts (SBNW) by inspiring 1-liter breaths and expiring to residual volume at PILV = functional residual capacity (FRC), FRC + 1.0, and FRC - 0.5, respectively. From the SBNW we measured the phase III slope over the expired volume ranges of 0.75–1.0, 1.0–1.6, and 1.6–2.2 liters (S0.75, S1.0, and S1.6, respectively). Between a PILV of 0.92 +/- 0.09 (SE) liter above FRC and a PILV of 1.17 +/- 0.43 liter below FRC, Snf decreased by 61% (P less than 0.001) and alveolar mixing efficiency increased from 80 to 85% (P = 0.05). In addition, Snf and alveolar mixing efficiency were negatively correlated (r = 0.74). In contrast, over a similar volume range, S1.0 and S1.6 were greater at lower PILV. We conclude that, during tidal breathing in normal subjects, ventilation distribution becomes progressively more inhomogeneous at higher lung volumes over a range of volumes above closing capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

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.

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)

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.

Multiple-breath washin of helium and sulfur hexafluoride in sustained microgravity

1998 ◽  
Vol 84 (1) ◽  
pp. 244-252 ◽  
Author(s):  
G. Kim Prisk ◽  
Ann R. Elliott ◽  
Harold J. B. Guy ◽  
Sylvia Verbanck ◽  
Manuel Paiva ◽  
...  
Keyword(s):  
Sulfur Hexafluoride ◽  
Normal Gravity ◽  
Normal Subjects ◽  
Standing Position ◽  
Primary Objective ◽  
Phase Iii ◽  
Gas Concentration ◽  
Residual Capacity ◽  
Diffusive Processes ◽  
Phase Iii Slope

Prisk, G. Kim, Ann R. Elliott, Harold J. B. Guy, Sylvia Verbanck, Manuel Paiva, and John B. West. Multiple-breath washin of helium and sulfur hexafluoride in sustained microgravity. J. Appl. Physiol. 84(1): 244–252, 1998.—We performed multiple-breath washouts of N2 and simultaneous washins of He and SF6 with fixed tidal volume (∼1,250 ml) and preinspiratory lung volume (approximately the subject’s functional residual capacity in the standing position) in four normal subjects (mean age 40 yr) standing and supine in normal gravity (1 G) and during exposure to sustained microgravity (μG). The primary objective was to examine the influence of diffusive processes on the residual, nongravitational ventilatory inhomogeneity in the lung in μG. We calculated several indexes of convective ventilatory inhomogeneity from each gas species. A normal degree of ventilatory inhomogeneity was seen in the standing position at 1 G that was largely unaltered in the supine position. When we compared the standing position in 1 G with μG, there were reductions in phase III slope in all gases, consistent with a reduction in convection-dependent inhomogeneity in the lung in μG, although considerable convective inhomogeneity persisted in μG. The reductions in the indexes of convection-dependent inhomogeneity were greater for He than for SF6, suggesting that the distances between remaining nonuniformly ventilated compartments in μG were short enough for diffusion of He to be an effective mechanism to reduce gas concentration differences between them.

Inter- and intraregional ventilation inhomogeneity in hypergravity and after pressurization of an anti-G suit

2003 ◽  
Vol 94 (4) ◽  
pp. 1353-1364 ◽  
Author(s):  
Mikael Grönkvist ◽  
Eddie Bergsten ◽  
Ola Eiken ◽  
Per M. Gustafsson
Keyword(s):  
Functional Residual Capacity ◽  
Inert Gas ◽  
Phase Iii ◽  
Ventilation Distribution ◽  
Ventilation Inhomogeneity ◽  
Gas Trapping ◽  
Residual Capacity ◽  
Trapped Gas ◽  
Phase Iii Slope

This study assessed the effects of increased gravity in the head-to-foot direction (+Gz) and anti-G suit (AGS) pressurization on functional residual capacity (FRC), the volume of trapped gas (VTG), and ventilation distribution by using inert- gas washout. Normalized phase III slope ( SnIII) analysis was used to determine the effects on inter- and intraregional ventilation inhomogeneity. Twelve men performed multiple-breath washouts of SF6 and He in a human centrifuge at +1 to +3 Gzwearing an AGS pressurized to 0, 6, or 12 kPa. Hypergravity produced moderately increased FRC, VTG, and overall and inter- and intraregional inhomogeneities. In normogravity, AGS pressurization resulted in reduced FRC and increased VTG, overall, and inter- and intraregional inhomogeneities. Inflation of the AGS to 12 kPa at +3 Gz reduced FRC markedly and caused marked gas trapping and intraregional inhomogeneity, whereas interregional inhomogeneity decreased. In conclusion, increased +Gzimpairs ventilation distribution not only between widely separated lung regions, but also within small lung units. Pressurizing an AGS in hypergravity causes extensive gas trapping accompanied by reduced interregional inhomogeneity and, apparently, results in greater intraregional inhomogeneity.

scholarly journals Detection of Peripheral Ventilation Inhomogeneity in Smokers

1997 ◽  
Vol 4 (1) ◽  
pp. 27-33
Author(s):  
DJ Cotton ◽  
JT Mink ◽  
BL Graham
Keyword(s):  
Predictive Value ◽  
Vital Capacity ◽  
Phase Iii ◽  
Airflow Limitation ◽  
Mixing Efficiency ◽  
Breath Holding ◽  
Small Airways ◽  
Test Gas ◽  
Ventilation Inhomogeneity ◽  
Lung Periphery

BACKGROUND: In smokers, ‘small airways’ narrowing alters the conventional, vital capacity single breath washout (SBWVC). Although, in some studies, the test predicts smokers at risk of developing chronic airflow limitation, its wide variability partly explains its poor positive predictive value. An alternative explanation for the test’s poor predictive value is that it may not accurately reflect small airway narrowing in the lung periphery.OBJECTIVE: To determine whether smoke-induced increases in ventilation inhomogeneity differ between SBWVCmanoeuvres, which augment topographical (apex-to-base) ventilation inhomogeneity, and submaximal manoeuvres (SBWSM), which enhance peripheral ventilation inhomogeneity.STUDY GROUP AND DESIGN: Cross-sectional study of 21 current smokers and 21 nonsmokers with similar age and forced expiratory volumes in 1 s (FEV1).METHODS: Smokers and nonsmokers performed SBW with either slow vital capacity inhalation and exhalation of test gas without breath holding (SBWVC); or slow inhalation of test gas from functional residual capacity to one-half inspiratory capacity and, after 0 s or 10 s of breath holding, slow exhalation to residual volume (SBWSM). For all SBW the normalized phase III helium slope (Sn), closing capacity (CC) as a percentage of total lung capacity (TLC) and mixing efficiency (Emix) were measured.RESULTS: For SBWVC, smoking had no effect on Snor Emix. However, CC/TLC was increased in smokers (P<0.05), but did not correlate with pack years or age. For SBWSM, smoking had no effect on Emixor CC/TLC, but resulted in a steeper Sn(P <0.05), which decreased more with breath holding (P<0.01) and correlated with pack years (P<0.05) at 0 s but not 10 s of breath holding.CONCLUSIONS: In smokers with normal FEV1, SBWSM manoeuvres reveal increases in breath hold time-dependent ventilation inhomogeneity in the lung periphery, not detected by conventional SBWVC.

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.

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