Correction for nonlinearity of body flow plethysmograph

1981 ◽  
Vol 50 (3) ◽  
pp. 658-662 ◽  
Author(s):  
A. Harf ◽  
G. Atlan ◽  
H. Lorino ◽  
S. Deshayes ◽  
C. Morin ◽  
...  
Keyword(s):  
Vital Capacity ◽  
Normal Subjects ◽  
Forced Expiration ◽  
Wire Screen ◽  
Inertial Component ◽  
High Flows ◽  
Degree Equation ◽  
Drop Flow ◽  
Conventional Signal ◽  
Flow Element

A modification of conventional signal processing for the pressure-compensated flow plethysmograph is proposed to correct the nonlinearity of the flow element that appears for high flows as encountered during forced expiration. Woven screens behave as porous media with a viscous and an inertial component in the resistance; this explains the nonlinearity (23% at 15.1.s-1 with a 400-mesh wire screen area = 50 cm2). It was shown that the pressure drop-flow relationship can be described by a second-degree equation, which can be included in the computation of the thoracic signal from the box pressure. The need for such a correction is evidenced by testing the plethysmograph with a flow step input (0-15 l.s-1) equivalent both in amplitude and in frequency to the thoracic flow during a forced expiration. Such correction for nonlinearity avoids an overestimation of the thoracic forced vital capacity of up to 0.5 liter in normal subjects.

Sensitivity of forced expiration indices to induced changes in peripheral airway resistance

1981 ◽  
Vol 50 (1) ◽  
pp. 15-20 ◽  
Author(s):  
J. L. Racineux ◽  
R. Peslin ◽  
B. Hannhart
Keyword(s):  
Vital Capacity ◽  
Normal Subjects ◽  
Forced Expiration ◽  
Peripheral Airways ◽  
Maximal Expiratory Flow ◽  
Transit Times ◽  
Subject Variability ◽  
Peripheral Airway ◽  
Induced Changes ◽  
Within Subject Variability

To assess the actual sensitivity of forced expiration indices to changes in the resistance of peripheral airways, maximal expiratory flow-volume curves were obtained in 30 normal subjects breathing air and breathing an O2-Ne-SF6 gas mixture having the same density as air but a 45% larger viscosity. The measurements were made using a bag-in-box system to circumvent calibration problems, and the data were processed digitally. Besides the usual forced expiration indices, slope ratios, as described by Mead (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 156-165, 1978), and transit time indices were also computed. Breathing the viscous mixture, the largest changes were seen with the slope ratio measured at 60% forced vital capacity, followed by other slope ratios, the standard deviation of transit times, and maximal flows at low lung volumes. However, when the data were compared using the t test for paired measurements, the most significant changes were found with the forced expiratory volumes at 1 and 2 s, due to their low within-subject variability. These indices may therefore by considered as the most suitable for detecting changes in individuals.

Positive effort dependence of maximal expiratory flow

1987 ◽  
Vol 62 (2) ◽  
pp. 718-724 ◽  
Author(s):  
J. L. Allen ◽  
R. G. Castile ◽  
J. Mead
Keyword(s):  
Chest Wall ◽  
Conformational Changes ◽  
Vital Capacity ◽  
Transpulmonary Pressure ◽  
Normal Subjects ◽  
Forced Expiration ◽  
Respiratory Inductive Plethysmography ◽  
Maximal Expiratory Flow ◽  
Expiratory Flow ◽  
Normal Males

The maximal expiratory-flow volume (MEFV) curve in normal subjects is thought to be relatively effort independent over most of the vital capacity (VC). We studied seven normal males and found positive effort dependence of maximal expiratory flow between 50 and 80% VC in five of them, as demonstrated by standard isovolume pressure-flow (IVPF) curves. We then attempted to distinguish the effects of chest wall conformational changes from possible mechanisms intrinsic to the lungs as an explanation for positive effort dependence. IVPF curves were repeated in four of the subjects who had demonstrated positive effort dependence. Transpulmonary pressure was varied by introducing varied resistances at the mouth but effort, as defined by pleural pressure, was maintained constant. By this method, chest wall conformation at a given volume would be expected to remain the same despite changing transpulmonary pressures. When these four subjects were retested in this way, no increases in flow with increasing transpulmonary pressure were found. In further studies, voluntarily altering the chest wall pattern of emptying (as defined by respiratory inductive plethysmography) did however alter maximal expiratory flows, with transpulmonary pressure maintained constant. We conclude that maximal expiratory flow can increase with effort over a larger portion of the vital capacity than is commonly recognized, and this effort dependence may be the result of changes in central airway mechanical properties that occur in relation to changes in chest wall shape during forced expiration.

V. FORCED FLOW RATES

PEDIATRICS ◽  
1965 ◽  
Vol 35 (1) ◽  
pp. 200-210
Author(s):  
George R. DeMuth ◽  
William F. Howatt ◽  
Bruce Hill
Keyword(s):  
Flow Rate ◽  
Vital Capacity ◽  
Peak Flow ◽  
Normal Subjects ◽  
Forced Flow ◽  
Forced Expiration ◽  
Flow Rates ◽  
Multiple Units ◽  
Airway Conductance ◽  
Peak Inspiratory Flow Rate

1. Data from normal subjects on the peak expiratory flow rate, the peak inspiratory flow rate, and the flow rate at the point where half the vital capacity has been expired (E50), have been obtained as part of a longitudinal study of the growth of lung function in school children. 2. The peak flow rates grow in a manner similar to that of the lung volumes. 3. The E50, in contradistinction, grows in a manner similar to airway conductance (the reciprocal of airway resistance). 4. Longitudinal studies of the peak flow rates indicate that individuals tend to maintain their positions in relation to the group. 5. A theoretical postulation of the forced flow-volume relationship has been suggested. According to this postulation the lungs of the normal subject empty as a unit or nearly so. The flow (after the initial acceleration) at any point in time is dependent on his vital capacity and an emptying factor. This emptying factor decreases somewhat with increasing body size. This is more evident in the girls. 6. In the patient with airway obstructive disease (as asthma) the lung can be thought of as composed of multiple units in parallel with varying amounts of reduction in their emptying factor. 7. The theoretical advantages of clinical tests based upon flow in the mid or later portions of the forced expiration have been given.

The effect of conductive ventilation heterogeneity on diffusing capacity measurement

2008 ◽  
Vol 104 (4) ◽  
pp. 1094-1100 ◽  
Author(s):  
Sylvia Verbanck ◽  
Daniel Schuermans ◽  
Sophie Van Malderen ◽  
Walter Vincken ◽  
Bruce Thompson
Keyword(s):  
Carbon Monoxide ◽  
Vital Capacity ◽  
Experimental Situation ◽  
Normal Subjects ◽  
Diffusing Capacity ◽  
Capacity Measurement ◽  
Alveolar Volume ◽  
Estimation Errors ◽  
Single Breath ◽  
Ventilation Heterogeneity

It has long been assumed that the ventilation heterogeneity associated with lung disease could, in itself, affect the measurement of carbon monoxide transfer factor. The aim of this study was to investigate the potential estimation errors of carbon monoxide diffusing capacity (DlCO) measurement that are specifically due to conductive ventilation heterogeneity, i.e., due to a combination of ventilation heterogeneity and flow asynchrony between lung units larger than acini. We induced conductive airway ventilation heterogeneity in 35 never-smoker normal subjects by histamine provocation and related the resulting changes in conductive ventilation heterogeneity (derived from the multiple-breath washout test) to corresponding changes in diffusing capacity, alveolar volume, and inspired vital capacity (derived from the single-breath DlCO method). Average conductive ventilation heterogeneity doubled ( P < 0.001), whereas DlCO decreased by 6% ( P < 0.001), with no correlation between individual data ( P > 0.1). Average inspired vital capacity and alveolar volume both decreased significantly by, respectively, 6 and 3%, and the individual changes in alveolar volume and in conductive ventilation heterogeneity were correlated ( r = −0.46; P = 0.006). These findings can be brought in agreement with recent modeling work, where specific ventilation heterogeneity resulting from different distributions of either inspired volume or end-expiratory lung volume have been shown to affect DlCO estimation errors in opposite ways. Even in the presence of flow asynchrony, these errors appear to largely cancel out in our experimental situation of histamine-induced conductive ventilation heterogeneity. Finally, we also predicted which alternative combination of specific ventilation heterogeneity and flow asynchrony could affect DlCO estimate in a more substantial fashion in diseased lungs, irrespective of any diffusion-dependent effects.

Pattern and mechanism of airway response to hypocapnia in normal subjects

1979 ◽  
Vol 47 (1) ◽  
pp. 8-12 ◽  
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.

Deep breaths, methacholine, and airway narrowing in healthy and mild asthmatic subjects

2002 ◽  
Vol 93 (4) ◽  
pp. 1384-1390 ◽  
Author(s):  
Emanuele Crimi ◽  
Riccardo Pellegrino ◽  
Manlio Milanese ◽  
Vito Brusasco
Keyword(s):  
Forced Vital Capacity ◽  
Healthy Subjects ◽  
Vital Capacity ◽  
Forced Expiratory Volume ◽  
Forced Expiration ◽  
Airway Narrowing ◽  
Significant Difference ◽  
Mild Asthmatic ◽  
Residual Capacity ◽  
Airway Conductance

Deep breaths taken before inhalation of methacholine attenuate the decrease in forced expiratory volume in 1 s and forced vital capacity in healthy but not in asthmatic subjects. We investigated whether this difference also exists by using measurements not preceded by full inflation, i.e., airway conductance, functional residual capacity, as well as flow and residual volume from partial forced expiration. We found that five deep breaths preceding a single dose of methacholine 1) transiently attenuated the decrements in forced expiratory volume in 1 s and forced vital capacity in healthy ( n = 8) but not in mild asthmatic ( n = 10) subjects and 2) increased the areas under the curve of changes in parameters not preceded by a full inflation over 40 min, during which further deep breaths were prohibited, without significant difference between healthy ( n = 6) and mild asthmatic ( n = 16) subjects. In conclusion, a series of deep breaths preceding methacholine inhalation significantly enhances bronchoconstrictor response similarly in mild asthmatic and healthy subjects but facilitates bronchodilatation on further full inflation in the latter.

Effect of Exertion on Vital Capacity of Normal Subjects

1938 ◽  
Vol 39 (3) ◽  
pp. 512-514 ◽  
Author(s):  
A. Iglauer ◽  
M. D. Altschule
Keyword(s):  
Vital Capacity ◽  
Normal Subjects

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.

Comparison of measures of forced expiration

1977 ◽  
Vol 42 (4) ◽  
pp. 607-613 ◽  
Author(s):  
J. R. Ligas ◽  
F. P. Primiano ◽  
G. M. Saidel ◽  
C. F. Doershuk
Keyword(s):  
Obstructive Lung Disease ◽  
Vital Capacity ◽  
Mean Transit Time ◽  
Forced Expiration ◽  
Flow Volume ◽  
Minimal Set ◽  
Average Flow ◽  
Maximal Expiratory Flow ◽  
The Mean ◽  
Independent Parameters

Theoretical relationships among a number of parameters were derived for idealized timed vital capacity (TVC) and maximal expiratory flow-volume (MEFV) curves to determine a minimal set of independent parameters. Normal pediatric subjects and those with cystic fibrosis were studied to verify these relationships experimentally. The average flow over the middle half (FEF25–75%) of the forced vital capacity (FVC) and flows at various exhaled percentages of the FVC (FEF50%, FEF75%), as well as moments of the TVC and MEFV curves were computed. From the TVC moments, a mean transit time (MTT) and an index of dispersion (ID) were also calculated. The minimum information needed to detect pulmonary mechanical changes associated with obstructive lung disease requires at least two reproducible measures: one related to the mean slope (e.g., FEF25–75%/FVC or MTT) and the other to the shape (e.g;, ID) of the effort-independent portion of the MEFV curve.

Evaluation of pulmonary resistance and maximal expiratory flow measurements during exercise in humans

1999 ◽  
Vol 86 (4) ◽  
pp. 1388-1395 ◽  
Author(s):  
Kenneth C. Beck ◽  
Robert E. Hyatt ◽  
Panagiotis Mpougas ◽  
Paul D. Scanlon
Keyword(s):  
Vital Capacity ◽  
Normal Subjects ◽  
Forced Expiratory Volume ◽  
Pulmonary Resistance ◽  
Tidal Breathing ◽  
Flow Measurements ◽  
Airway Function ◽  
Minor Influence ◽  
Exercise Induced ◽  
Exercise In Humans

To evaluate methods used to document changes in airway function during and after exercise, we studied nine subjects with exercise-induced asthma and five subjects without asthma. Airway function was assessed from measurements of pulmonary resistance (Rl) and forced expiratory vital capacity maneuvers. In the asthmatic subjects, forced expiratory volume in 1 s (FEV1) fell 24 ± 14% and Rl increased 176 ± 153% after exercise, whereas normal subjects experienced no change in airway function (Rl−3 ± 8% and FEV1−4 ± 5%). During exercise, there was a tendency for FEV1 to increase in the asthmatic subjects but not in the normal subjects. Rl, however, showed a slight increase during exercise in both groups. Changes in lung volumes encountered during exercise were small and had no consistent effect on Rl. The small increases in Rl during exercise could be explained by the nonlinearity of the pressure-flow relationship and the increased tidal breathing flows associated with exercise. In the asthmatic subjects, a deep inspiration (DI) caused a small, significant, transient decrease in Rl 15 min after exercise. There was no change in Rl in response to DI during exercise in either asthmatic or nonasthmatic subjects. When percent changes in Rl and FEV1 during and after exercise were compared, there was close agreement between the two measurements of change in airway function. In the groups of normal and mildly asthmatic subjects, we conclude that changes in lung volume and DIs had no influence on Rl during exercise. Increases in tidal breathing flows had only minor influence on measurements of Rl during exercise. Furthermore, changes in Rl and in FEV1 produce equivalent indexes of the variations in airway function during and after exercise.

Sign in / Sign up

Export Citation Format

Share Document