Variability of the configuration of maximum expiratory flow-volume curves

With a computer technique variability of the configuration of maximum expiratory flow-volume (MEFV) curves was studied in terms of slope ratio, SR. SR = dV/dV divided by V/V, where V is the instantaneous flow and V is the volume increment above residual volume.) Approximately four SR-V curves, each based on three to five smoothed and averaged MEFV curves, were derived for each of 20 normal subjects (aged 23–55 yr) on a single occasion, and again at least 1 wk later. Individual curves were largely reproducible, the maximum difference in SR at most volumes being 0.3–1 U, but frequently showed substantial yet reproducible fluctuations with volume. These corresponeded to hitherto unrecognized irregularities of maximum expiratory flow that may reflect sudden changes in the location of flow limitation.

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Changes in flow-volume curve configuration with bronchoconstriction and bronchodilation

Journal of Applied Physiology ◽

10.1152/jappl.1986.61.6.2243 ◽

1986 ◽

Vol 61 (6) ◽

pp. 2243-2251 ◽

Cited By ~ 9

Author(s):

C. R. O'Donnell ◽

R. G. Castile ◽

J. Mead

Keyword(s):

Vital Capacity ◽

Normal Subjects ◽

Flow Volume ◽

Slope Ratio ◽

Lung Volumes ◽

Volume Curve ◽

Before And After ◽

Lower Lung ◽

Maximum Expiratory Flow ◽

Flow Volume Curve

Changes in the configuration of maximum expiratory flow-volume (MEFV) curves following mild degrees of bronchodilation or bronchoconstriction were studied in five normal and five asthmatic subjects. In a volume-displacement plethysmograph, MEFV curves were performed before and after inhalation of aerosolized isoproterenol (I) or histamine (H). Five filtered MEFV curves were averaged, and slope ratio vs. volume (SR-V) plots were obtained from averaged curves. Following I, maximal flows at 75% of the vital capacity (VC) were decreased in asthmatics but not in normal subjects. Flows at 50 and 25% of the VC increased in normal subjects and asthmatics, whereas VC′s were unchanged. In asthmatics, sudden large decreases in flow (bumps) occurred at lower lung volumes following I. H reduced flows over the entire VC, with greater reductions occurring in asthmatics than in normals, particularly at low lung volumes. In asthmatics, VC was slightly reduced, and bumps in MEFV curve configuration occurred at higher lung volumes or were abolished entirely following H. A reduction in the amount of configurational detail appreciable in MEFV curves following histamine in asthmatics was best seen in SR-V plots. Following H, SR′s decreased regularly with decreasing lung volume in all the asthmatics but in none of the normals. This was the single most striking finding of this study. Mild I- and H-induced perturbations of airway bronchomotor tone produced small but consistent changes in MEFV curve configuration.(ABSTRACT TRUNCATED AT 250 WORDS)

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Novel method for measuring effects of gas compression on expiratory flow

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00573.2003 ◽

2004 ◽

Vol 287 (2) ◽

pp. R479-R484 ◽

Cited By ~ 8

Author(s):

Amir Sharafkhaneh ◽

Todd M. Officer ◽

Sheila Goodnight-White ◽

Joseph R. Rodarte ◽

Aladin M. Boriek

Keyword(s):

Normal Subjects ◽

Chronic Obstructive ◽

Flow Limitation ◽

Flow Volume ◽

Expiratory Flow Limitation ◽

Obstructive Pulmonary Disease ◽

Flow Volume Loop ◽

Gas Compression ◽

Novel Method ◽

Expiratory Flow

During forced vital capacity maneuvers in subjects with expiratory flow limitation, lung volume decreases during expiration both by air flowing out of the lung (i.e., exhaled volume) and by compression of gas within the thorax. As a result, a flow-volume loop generated by using exhaled volume is not representative of the actual flow-volume relationship. We present a novel method to take into account the effects of gas compression on flow and volume in the first second of a forced expiratory maneuver (FEV1). In addition to oral and esophageal pressures, we measured flow and volume simultaneously using a volume-displacement plethysmograph and a pneumotachograph in normal subjects and patients with expiratory flow limitation. Expiratory flow vs. plethysmograph volume signals was used to generate a flow-volume loop. Specialized software was developed to estimate FEV1 corrected for gas compression (NFEV1). We measured reproducibility of NFEV1 in repeated maneuvers within the same session and over a 6-mo interval in patients with chronic obstructive pulmonary disease. Our results demonstrate that NFEV1 significantly correlated with FEV1, peak expiratory flow, lung expiratory resistance, and total lung capacity. During intrasession, maneuvers with the highest and lowest FEV1 showed significant statistical difference in mean FEV1 ( P < 0.005), whereas NFEV1 from the same maneuvers were not significantly different from each other ( P > 0.05). Furthermore, variability of NFEV1 measurements over 6 mo was <5%. We concluded that our method reliably measures the effect of gas compression on expiratory flow.

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Maximum expiratory flow and transpulmonary pressure in the hamster

Journal of Applied Physiology ◽

10.1152/jappl.1978.45.6.840 ◽

1978 ◽

Vol 45 (6) ◽

pp. 840-845 ◽

Cited By ~ 10

Author(s):

E. C. Lucey ◽

B. R. Celli ◽

G. L. Snider

Keyword(s):

Vital Capacity ◽

Simple Technique ◽

Transpulmonary Pressure ◽

Esophageal Pressure ◽

Flow Limitation ◽

Flow Volume ◽

System Pressure ◽

Pleural Surface ◽

Maximum Expiratory Flow ◽

Expiratory Flow

Maximum expiratory flow was measured in 19 normal, anesthetized, tracheostomized, supine hamsters from records of forced deflation produced by the application of varying degrees of negative pressure to the tracheostomies of animals whose lungs had been previously inflated to a transpulmonary pressure (PL) of 25 cmH2O. Flow was measured with a pneumotachograph, volume with a constant-volume pressure plethysmograph and pleural surface pressure (Ppl) with a water-filled esophageal catheter. The esophageal pressure measurement overestimated Ppl and a simple technique was based on an estimate of the resting volume of the chest wall. This volume, at which the Ppl is zero, was calculated for anesthetized supine hamsters from the measurement of respiratory-system pressure and PL made independently of esophageal pressure and was found to be about 30% of vital capacity (VC). Flow limitation was present below 70% of VC with a tracheal deflation pressure of -30cmH2O. Negative effort dependence of flow was seen in small segments of the flow-volume curves. Mean +/- SD maximum expiratory flow at 50% VC was 52 +/- 9.5 ml/s or 9.1 VC/s. Upstream resistance was 0.09 +/- 0.03 cmH2O/ml per s.

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Maximum expiratory flow-volume curves during short periods of microgravity

Journal of Applied Physiology ◽

10.1152/jappl.1991.70.6.2587 ◽

1991 ◽

Vol 70 (6) ◽

pp. 2587-2596 ◽

Cited By ~ 10

Author(s):

H. J. Guy ◽

G. K. Prisk ◽

A. R. Elliott ◽

J. B. West

Keyword(s):

Vital Capacity ◽

Normal Subjects ◽

Flow Volume ◽

Elastic Recoil ◽

Microgravity Research ◽

Maximum Expiratory Flow ◽

Research Aircraft ◽

The Mean ◽

Expiratory Flow ◽

The Individual

To elucidate the effect of normal gravitation on the shape of the maximum expiratory flow-volume (MEFV) curve, we studied nine normal subjects in a National Aeronautics and Space Administration microgravity research aircraft. They performed multiple MEFV maneuvers at 0, 1, and approximately 2 G. The MEFV curves for each subject were filtered, aligned at residual volume, and ensemble averaged to produce an average MEFV curve for each state, allowing differences to be studied. Most subjects showed a decrease in the forced vital capacity at 0 G, which we attribute to an increased intrathoracic blood volume. In most of these subjects, the mean lung volume associated with a given flow was lower at 0 G over about the upper half of the vital capacity. This is similar to the change previously reported during headout immersion and is consistent with the known effect of engorgement of the lung with blood on elastic recoil. There were also consistent but highly individual changes in the position and magnitude of detailed features of the curve, the individual patterns being similar to those previously reported on transition from the erect to the supine position. This supports the idea that the location and motion of choke points that determine the detailed individual configuration of MEFV curves can be significantly influenced by gravitational forces, presumably via the effects of change in longitudinal tension on local airway pressure-diameter behavior and thus wave speed.

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Analysis of Maximum Expiratory Flow Volume Curves Using Canonical Correlation Analysis

Methods of Information in Medicine ◽

10.1055/s-0038-1635359 ◽

1985 ◽

Vol 24 (02) ◽

pp. 91-100 ◽

Cited By ~ 3

Author(s):

W. van Pelt ◽

Ph. H. Quanjer ◽

M. E. Wise ◽

E. van der Burg ◽

R. van der Lende

Keyword(s):

Correlation Analysis ◽

Canonical Correlation Analysis ◽

Canonical Correlation ◽

Flow Volume ◽

Non Linear ◽

Maximum Expiratory Flow ◽

Expiratory Flow ◽

Relationship Of ◽

The Relationship ◽

Age And Sex

SummaryAs part of a population study on chronic lung disease in the Netherlands, an investigation is made of the relationship of both age and sex with indices describing the maximum expiratory flow-volume (MEFV) curve. To determine the relationship, non-linear canonical correlation was used as realized in the computer program CANALS, a combination of ordinary canonical correlation analysis (CCA) and non-linear transformations of the variables. This method enhances the generality of the relationship to be found and has the advantage of showing the relative importance of categories or ranges within a variable with respect to that relationship. The above is exemplified by describing the relationship of age and sex with variables concerning respiratory symptoms and smoking habits. The analysis of age and sex with MEFV curve indices shows that non-linear canonical correlation analysis is an efficient tool in analysing size and shape of the MEFV curve and can be used to derive parameters concerning the whole curve.

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Pattern and mechanism of airway response to hypocapnia in normal subjects

Journal of Applied Physiology ◽

10.1152/jappl.1979.47.1.8 ◽

1979 ◽

Vol 47 (1) ◽

pp. 8-12 ◽

Cited By ~ 35

Author(s):

C. F. O'Cain ◽

M. J. Hensley ◽

E. R. McFadden ◽

R. H. Ingram

Keyword(s):

Vital Capacity ◽

Normal Subjects ◽

Oxygen Mixture ◽

Flow Volume ◽

Mixture Density ◽

Lung Capacity ◽

Airway Constriction ◽

Maximal Expiratory Flow ◽

Airway Response ◽

Expiratory Flow

We examined the bronchoconstriction produced by airway hypocapnia in normal subjects. Maximal expiratory flow at 25% vital capacity on partial expiratory flow-volume (PEFV) curves fell during hypocapnia both on air and on an 80% helium- 20% oxygen mixture. Density dependence also fell, suggesting predominantly small airway constriction. The changes seen on PEFV curves were not found on maximal expiratory flow-volume curves, indicating the inhalation to total lung capacity substantially reversed the constriction. Pretreatment with a beta-sympathomimetic agent blocked the response, whereas atropine pretreatment did not, suggesting that hypocapnia affects airway smooth muscle directly, not via cholinergic efferents.

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Mechanism of reduced maximum expiratory flow in dogs with compensatory lung growth

Journal of Applied Physiology ◽

10.1152/jappl.1986.60.2.441 ◽

1986 ◽

Vol 60 (2) ◽

pp. 441-448 ◽

Cited By ~ 12

Author(s):

H. W. Greville ◽

M. E. Arnup ◽

S. N. Mink ◽

L. Oppenheimer ◽

N. R. Anthonisen

Keyword(s):

Control Flow ◽

Sham Operation ◽

Forced Expiration ◽

Flow Limitation ◽

Lung Growth ◽

Lung Volumes ◽

Flow Rates ◽

Compensatory Lung Growth ◽

Maximum Expiratory Flow ◽

Expiratory Flow

We examined the mechanism of the reduced maximum expiratory flow rates (Vmax) in a dog model of postpneumonectomy compensatory lung growth. During forced expiration, a Pitot-static tube was used to locate the airway site of flow limitation, or choke point, and to measure dynamic intrabronchial pressures. The factors determining Vmax were calculated and the results analyzed in terms of the wave-speed theory of flow limitation. Measurements were made at multiple lung volumes and during ventilation both with air and with HeO2. Five of the puppies had undergone a left pneumonectomy at 10 wk of age, and 5 littermate controls had undergone a sham operation. All dogs were studied at 26 wk of age, at which time compensatory lung growth had occurred in the postpneumonectomy group. Vmax was markedly decreased in the postpneumonectomy group compared with control, averaging 42% of the control flow rates from 58 to 35% of the vital capacity (VC). At 23% of the VC, Vmax was 15% less than control. Choke points were more peripheral in the postpneumonectomy dogs compared with controls at all volumes. The total airway pressure was the same at the choke-point airway in the postpneumonectomy dogs as that in the same airway in the control dogs, suggesting that the airways of the postpneumonectomy dogs displayed different bronchial area-pressure behavior from the control dogs. Despite the decreased Vmax on both air and HeO2, the density dependence of flow was high in the postpneumonectomy dogs and the same as controls at all lung volumes examined.

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