Effects of thoracic gas compression on maximal and partial flow-volume maneuvers

1989 ◽  
Vol 67 (2) ◽  
pp. 780-785 ◽  
Author(s):  
R. D. Fairshter ◽  
R. B. Berry ◽  
A. F. Wilson ◽  
T. Brideshead ◽  
D. Mukai
Keyword(s):  
Pulmonary Function ◽  
Normal Subjects ◽  
Flow Volume ◽  
Maximal Flow ◽  
Alveolar Pressure ◽  
Lung Volumes ◽  
Flow Rates ◽  
Gas Compression ◽  
Expiratory Flow ◽  
Compression Artifacts

Airway hysteresis can be evaluated by comparing maximal (MEFV) and partial (PEFV) expiratory flow-volume curves. The maneuvers are often obtained from pulmonary function systems that are subject to gas-compression artifacts. Because gas-compression artifacts might differentially affect PEFV vs. MEFV curves, we simultaneously obtained MEFV and PEFV curves by use of a spirometer and a volume-displacement plethysmograph (a method not subject to gas-compression artifacts) in normal and asthmatic subjects. Plethysmographic flow rates exceeded spirometric flow rates on all MEFV and PEFV maneuvers. When maximal flow exceeded partial flow (or vice versa) in the plethysmograph, the same result was virtually always observed for spirometric measurements. Alveolar pressure (PA) was higher on MEFV than on PEFV maneuvers in asthmatic subjects; comparisons between PA (on PEFV and MEFV maneuvers) in normal subjects varied at different lung volumes. Ratios of Vmax on PEFV maneuvers to Vmax on MEFV maneuvers (Vmax-p/Vmax-c) obtained from a volume-displacement plethysmograph differ quantitatively from ratios determined in systems subject to gas-compression artifacts; qualitatively, however, failure to account for thoracic gas compression ordinarily will not influence the ability to identify airway hysteresis (or lack thereof) by use of Vmax-p-to-Vmax-c ratios.

Dependence of maximal flow-volume curves on time course of preceding inspiration

1993 ◽  
Vol 75 (3) ◽  
pp. 1155-1159 ◽  
Author(s):  
E. D'Angelo ◽  
E. Prandi ◽  
J. Milic-Emili
Keyword(s):  
Time Course ◽  
Vital Capacity ◽  
Normal Subjects ◽  
Forced Expiratory Volume ◽  
Flow Volume ◽  
Maximal Flow ◽  
Lung Volumes ◽  
Residual Capacity ◽  
Expiratory Flow ◽  
Volume Range

Thirteen normal subjects, sitting in a body plethysmograph and breathing through a pneumotachograph, performed forced vital capacity maneuvers after a rapid inspiration without or with an end-inspiratory pause (maneuvers 1 and 2) and after a slow inspiration without or with an end-inspiratory pause (maneuvers 3 and 4), the pause lasting 4–6 s. Inspirations were initiated close to functional residual capacity. At all lung volumes, expiratory flow was larger with maneuver 1 than with any other maneuver and, over the upper volume range, larger with maneuver 3 than with maneuver 4, whereas it was similar for maneuvers 2 and 4. Relative to corresponding values with maneuver 4, peak expiratory flow was approximately 16 and approximately 4% larger with maneuvers 1 and 3, respectively, whereas forced expiratory volume in 1 s increased by approximately 5% only with maneuver 1. The time dependence of maximal flow-volume curves is consistent with the presence of viscoelastic elements within the respiratory system (D'Angelo et al. J. Appl. Physiol. 70: 2602–2610, 1991).

Breathing at low lung volumes and chest strapping: a comparison of lung mechanics

1981 ◽  
Vol 50 (3) ◽  
pp. 650-657 ◽  
Author(s):  
N. J. Douglas ◽  
G. B. Drummond ◽  
M. F. Sudlow
Keyword(s):  
Lung Volume ◽  
Maximum Flow ◽  
Normal Subjects ◽  
Lung Mechanics ◽  
Lung Volumes ◽  
Flow Rates ◽  
Recoil Pressure ◽  
Forced Expiratory Flow ◽  
Expiratory Flow ◽  
Expiratory Flow Rates

In six normal subjects forced expiratory flow rates increased progressively with increasing degrees of chest strapping. In nine normal subjects forced expiratory flow rates increased with the time spent breathing with expiratory reserve volume 0.5 liters above residual volume, the increase being significant by 30 s (P less than 0.01), and flow rates were still increasing at 2 min, the longest time the subjects could breathe at this lung volume. The increase in flow after low lung volume breathing (LLVB) was similar to that produced by strapping. The effect of LLVB was diminished by the inhalation of the atropinelike drug ipratropium. Quasistatic recoil pressures were higher following strapping and LLVB than on partial or maximal expiration, but the rise in recoil pressure was insufficient to account for all the observed increased in maximum flow. We suggest that the effects of chest strapping are due to LLVB and that both cause bronchodilatation.

Novel method for measuring effects of gas compression on expiratory flow

2004 ◽  
Vol 287 (2) ◽  
pp. R479-R484 ◽  
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.

Effect of volume history on successive partial expiratory flow-volume maneuvers

1976 ◽  
Vol 41 (2) ◽  
pp. 153-158 ◽  
Author(s):  
J. J. Wellman ◽  
R. Brown ◽  
R. H. Ingram ◽  
J. Mead ◽  
E. R. McFadden
Keyword(s):  
Static Pressure ◽  
Normal Subjects ◽  
Flow Volume ◽  
Elastic Recoil ◽  
Flow Rates ◽  
Recoil Pressure ◽  
Maximal Expiratory Flow ◽  
Expiratory Flow ◽  
Expiratory Flow Rates ◽  
Volume History

In normal subjects, the second of two successive partial expiratory flow-volume (PEFV 2) curves often had higher isovolume maximal expiratory flow rates (Vmax) than the first (PEFV 1) (mean increase 30.2 +/- 13%). The higher Vmax on PEFV 2 was present only when there was a greater lung elastic recoil pressure (Pst(L)). In eight subjects the Pst(L) derived from sequential partial quasi-static pressure-volume curves, from interruption of the flow-volume maneuvers and at the start of the PEFV curves showed that isovolume upstream resistance increased although Vmax also increased after going to residual volume (RV). In four subjects the RV volume history did not change the pressure flow relationship across the upstream airways. If airways dimensions were the sole determinant of Vmax, then Vmax on PEFV 2 would be the same or smaller than on PEFV 1. That the opposite was observed in our study indicates that the increase in Pst(L), which results from parenchymal hysteresis, offsets any dimensional decrease in upstream airways due to airways hysteresis.

Pulmonary function

2013 ◽  
Author(s):  
Patricia A. Nixon
Keyword(s):  
Pulmonary Function ◽  
Lung Volumes ◽  
Flow Rates ◽  
Expiratory Flow ◽  
Expiratory Flow Rates

The focus of this chapter is the assessment and interpretation of pulmonary function during exercise in children, with emphasis on the parameters commonly measured in the paediatric setting. The measurements of resting pulmonary function (i.e. lung volumes and expiratory flow rates) are presented to provide the basic foundation for understanding changes that occur with exercise. Some measurements are more relevant to children with cardiopulmonary disorders, and examples of normal and abnormal responses are provided. In some instances, data on children are lacking, so responses of adults are presented.

Persistent small-airways dysfunction after exposure to hyperoxia

1995 ◽  
Vol 78 (4) ◽  
pp. 1421-1424 ◽  
Author(s):  
E. Thorsen ◽  
B. K. Kambestad
Keyword(s):  
Pulmonary Function ◽  
Complete Recovery ◽  
Small Airways ◽  
Lung Volumes ◽  
Flow Rates ◽  
Maximal Expiratory Flow ◽  
Hyperoxic Exposure ◽  
Expiratory Flow ◽  
Expiratory Flow Rates

To assess the contribution of hyperoxia to reduced pulmonary function after a deep saturation dive, a shallow saturation dive to a pressure of 0.25 MPa with the same profile of hyperoxic exposure as in a deep saturation dive to 3.7 MPa was conducted. The PO2 was 40 kPa, with periods of 75 kPa for 2 h every 2nd day during the first 14 days, 50 kPa the next 12 days, and a gradual fall to 21 kPa over the last 2 days in decompression. Seven submariners and one professional diver aged 22–27 yr participated. Pulmonary function, including static and dynamic lung volumes and flows and transfer factor for carbon monoxide (TLCO), were measured twice before, immediately after, 1 mo after, and 1 and 3 yr after the dive. As reported previously, there was a significant reduction in TLCO and in maximal expiratory flow rates at low lung volumes immediately after the dive. At the follow-up examinations 1 and 3 yr after, there was no recovery of the maximal expiratory flow rates. Forced midexpiratory flow rate was still reduced by 8.7 +/- 5.6% (P < 0.05) and 9.3 +/- 7.1% (P < 0.01), respectively. Forced expired volume in 1 s and forced vital capacity were not significantly reduced. There was a complete recovery of the TLCO. The findings are consistent with the studies indicating development of airway obstruction in divers, and the findings indicate that exposure to hyperoxia contributes to this effect.

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.

Simulation of the effects of mechanical nonhomogeneities on expiratory flow from human lungs

1990 ◽  
Vol 68 (6) ◽  
pp. 2550-2563 ◽  
Author(s):  
R. K. Lambert
Keyword(s):  
Fluid Mechanics ◽  
Left Lung ◽  
Flow Volume ◽  
Alveolar Pressure ◽  
Peripheral Airways ◽  
Volume Curve ◽  
Human Lungs ◽  
Flow Volume Curve ◽  
Expired Gas ◽  
Expiratory Flow

A computational model for expiration from lungs with mechanical nonhomogeneities was used to investigate the effect of such nonhomogeneities on the distribution of expiratory flow and the development of alveolar pressure differences between regions. The nonhomogeneities used were a modest constriction of the peripheral airways and a 50% difference in compliance between regions. The model contains only two mechanically different regions but allows these to be as grossly distributed as left lung-right lung or to be distributed as a set of identical pairs of parallel nonhomogeneous regions with flows from each merging in a specified bronchial generation. The site of flow merging had no effect on the flow-volume curve but had a significant effect on the development of alveolar pressure differences (delta PA). With the peripheral constriction, greater values of delta PA developed when flows were merged peripherally rather than centrally. The opposite was true in the case of a compliance nonhomogeneity. The delta PA values were smaller at submaximal flows. Plots of delta PA vs. lung volume were similar to those obtained experimentally. These results were interpreted in terms of the expression used for the fluid mechanics of the merging flows. delta PA was greater when the viscosity of the expired gas was increased or when its density was reduced. Partial forced expirations were shown to indicate the presence of mechanical nonhomogeneity.

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

1986 ◽  
Vol 60 (2) ◽  
pp. 441-448 ◽  
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.

scholarly journals Post-Operative Flow-Volume Loops

1977 ◽  
Vol 5 (2) ◽  
pp. 146-148 ◽  
Author(s):  
A. Morton ◽  
P. Hansen ◽  
A. B. Baker
Keyword(s):  
Flow Volume ◽  
Lung Volumes ◽  
Flow Rates ◽  
Lower Flow

A study of flow-volume curves pre- and post-operatively demonstrated a marked difference between bronchitic and non-bronchitic patients. All bronchitic patients showed lower flow rates at low lung volumes post-operatively, when compared with their pre-operative values. Non-bronchitic patients all had higher flow rates for the same comparison.

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