Influence of expiratory flow rate on "closing volume" measurement

1979 ◽  
Vol 46 (5) ◽  
pp. 1011-1015 ◽  
Author(s):  
D. P. Osmanliev ◽  
P. K. Popov
Keyword(s):  
Flow Rate ◽  
Normal Subjects ◽  
Volume Measurement ◽  
Closing Volume ◽  
Flow Limitation ◽  
Airway Closure ◽  
Dynamic Flow ◽  
Expiratory Flow ◽  
Phase Iv

The influence of expiratory flow rate (VE) on the onset of phase IV was studied in 15 normal subjects. VE was controlled voluntarily and varied between 0.2 and 2.5 l/s. All subjects showed significantly higher values for CV/VC, % at expiratory flow rate of 1.0 and 1.5 l/s, compared to those estimated at 0.2 l/s. The correlation between CV and volume of flow limitation (VFL) was also studied. For most of the subjects a considerable disagreement between the two values at very low VE was found. At higher flows, however, CV and VFL agreed well. Our results indicate that CV measurement is markedly influenced by VE in the range 0.2--1.5 l/s. This finding gives further support to the hypothesis that CV is determined in part by dynamic flow-limiting properties of the lung as well as by true airway closure.

Flow and age dependence of airway closure and dynamic compliance

1975 ◽  
Vol 38 (2) ◽  
pp. 199-207 ◽  
Author(s):  
R. Begin ◽  
A. D. Renzetti ◽  
A. H. Bigler ◽  
S. Watanabe
Keyword(s):  
Flow Rate ◽  
Normal Population ◽  
Dynamic Compliance ◽  
Normal Subjects ◽  
Closing Volume ◽  
Tolerance Interval ◽  
Flow Rates ◽  
Mean Values ◽  
Single Breath ◽  
Expiratory Flow

The influence of expiratory flow rate and age on the results of measurement of closing volume (CV) of the lung have been studied by a nitrogen single-breath method in 66 asymptomatic lifetime nonsmoking normal subjects between 20 and 82 yr of age. Normal was defined as having values for spirometric measurements within a 95% tolerance interval of reported predicted normal mean values. For the CV determination, inspiratory flow rate was held constant at 0.51/s and studies were carried out at expiratory flow rates of 0.25, 0.5, 1.0, and 1.5 1/s. Our results show that CV expressed as a percentage of vital capacity (VC) and the slope of the alveolar plateau increases with increasing flow rate and age. Dynamic compliance (Cdyn) at frequencies corresponding to peak flow rates of 0.5 and 1.5 1/s was also measured and correlated well with the CV results. Frequency dependence of compliance with aging was demonstrated. Nine smokers with normal spirometric measurements and abnormal CV %VC were also studied. Since the results of Cdyn measurement differentiated only two-thirds of the smokers from the normal population, we suggest that the CV method is probably more sensitive than the Cdyn method for the detection of small airway obstruction.

Influence of expiratory flow on closing capacity at low expiratory flow rates

1975 ◽  
Vol 39 (1) ◽  
pp. 60-65 ◽  
Author(s):  
J. R. Rodarte ◽  
R. E. Hyatt ◽  
D. A. Cortese
Keyword(s):  
Lung Volume ◽  
Normal Subjects ◽  
Closing Volume ◽  
Residual Volume ◽  
Dependent Lung ◽  
Flow Rates ◽  
Single Breath ◽  
Expiratory Flow ◽  
Expiratory Flow Rates ◽  
Phase Iv

Single-breath oxygen (SBO2) tests at expiratory flow rates of 0.2, 0.5, and 1.01/s were performed by 10 normal subjects in a body plethysmograph. Closing capacity (CC)--the absolute lung volume at which phase IV began--increased significantly with increases in flow. Five subjects were restudied with a 200-ml bolus of 100% N2 inspired from residual volume after N2 washout by breathing 100% O2 and similar results were obtained. An additional five subjects performed SBO2 tests in the standing, supine, and prone positions; closing volume (CV)--the lung volume above residual volume at which phase IV began--also increased with increases of expiratory flow. The observed increase in CC with increasing flow did not appear to result from dependent lung regions reaching some critical “closing volume” at a higher overall lung volume. In normal subjects, the phase IV increase in NI concentration may be caused by the asynchronous onset of flow limitation occurring initially in dependent regions.

Phase V of the single-breath washout test

1982 ◽  
Vol 52 (1) ◽  
pp. 34-43 ◽  
Author(s):  
G. M. Nichol ◽  
D. B. Michels ◽  
H. J. Guy
Keyword(s):  
Flow Rate ◽  
Flow Limitation ◽  
Tracer Gas ◽  
Flow Rates ◽  
Single Breath ◽  
Lower Lung ◽  
Expiratory Flow ◽  
The Difference ◽  
Expiratory Flow Rates ◽  
Phase Iv

A downward-deflecting phase V is often seen following the phase IV terminal rise in the single-breath N2 washout test (SB N2). This phase V was studied in eight normal nonsmoking subjects aged 27–41, using both the SB N2 test and single-breath washouts of boluses of inert tracer gas slowly inhaled from residual volume (RV). All of the subjects showed a distinct phase V in both tests. Expiratory flow rates between 0.1 and 2.0 1/s were used; at each flow rate phase V appeared shortly after expiration became flow limited. Thus the volume above RV at which phase V began increased with increasing expiratory flow rate. The difference between the exhaled volumes at which flow became limited and phase V appeared was shown to be approximately equal to the anatomic dead space. This behavior is predicted by a model of lung emptying in a gravitational field. As expiration proceeds, flow limitation occurs first in the (tracer-poor) lower lung regions and then progresses toward the (tracer-rich) upper lung regions causing phase IV. When all lung regions have finally become flow limited, the amount of flow from the upper regions decreases relative to that of the lower regions, thereby causing phase V.

Variability of the configuration of maximum expiratory flow-volume curves

1979 ◽  
Vol 46 (3) ◽  
pp. 565-570 ◽  
Author(s):  
Y. K. Tien ◽  
E. A. Elliott ◽  
J. Mead
Keyword(s):  
Normal Subjects ◽  
Flow Limitation ◽  
Residual Volume ◽  
Flow Volume ◽  
Maximum Difference ◽  
Slope Ratio ◽  
Computer Technique ◽  
Volume Increment ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow

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.

Lung and chest wall mechanics in patients with acute respiratory distress syndrome, expiratory flow limitation, and airway closure

2020 ◽  
Vol 128 (6) ◽  
pp. 1594-1603 ◽  
Author(s):  
Claude Guérin ◽  
Nicolas Terzi ◽  
Louis-Marie Galerneau ◽  
Mehdi Mezidi ◽  
Hodane Yonis ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Distress Syndrome ◽  
Flow Limitation ◽  
Airway Closure ◽  
Positive End Expiratory Pressure ◽  
Expiratory Flow Limitation ◽  
Lung Elastance ◽  
Chest Wall Mechanics ◽  
Expiratory Flow ◽  
Better Than

Expiratory flow limitation (EFL) and airway closure (AC) were observed in 32% and 52%, respectively, of 25 patients with ARDS investigated during mechanical ventilation in supine position with a positive end-expiratory pressure of 5 cmH2O. The performance of dynamic lung elastance to detect expiratory flow limitation was good and better than that to detect airway closure. The vast majority of patients with EFL also had AC; however, AC can occur in the absence of EFL.

Detection of expiratory flow limitation during exercise in COPD patients

1997 ◽  
Vol 82 (3) ◽  
pp. 723-731 ◽  
Author(s):  
Nickolaos G. Koulouris ◽  
Ioanna Dimopoulou ◽  
Päivi Valta ◽  
Richard Finkelstein ◽  
Manuel G. Cosio ◽  
...  
Keyword(s):  
Normal Subjects ◽  
Chronic Obstructive ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Obstructive Pulmonary Disease ◽  
Normal Limits ◽  
Volume Curve ◽  
Copd Patients ◽  
Flow Volume Curve ◽  
Expiratory Flow

Koulouris, Nickolaos G., Ioanna Dimopoulou, Päivi Valta, Richard Finkelstein, Manuel G. Cosio, and J. Milic-Emili.Detection of expiratory flow limitation during exercise in COPD patients. J. Appl. Physiol. 82(3): 723–731, 1997.—The negative expiratory pressure (NEP) method was used to detect expiratory flow limitation at rest and at different exercise levels in 4 normal subjects and 14 patients with chronic obstructive pulmonary disease (COPD). This method does not require performance of forced expirations, nor does it require use of body plethysmography. It consists in applying negative pressure (−5 cmH2O) at the mouth during early expiration and comparing the flow-volume curve of the ensuing expiration with that of the preceding control breath. Subjects in whom application of NEP does not elicit an increase in flow during part or all of the tidal expiration are considered flow limited. The four normal subjects were not flow limited up to 90% of maximal exercise power output (W˙max). Five COPD patients were flow limited at rest, 9 were flow limited at one-third W˙max, and 12 were flow limited at two-thirdsW˙max. Whereas in all patients who were flow limited at rest the maximal O2 uptake was below the normal limits, this was not the case in most of the other patients. In conclusion, NEP provides a rapid and reliable method to detect expiratory flow limitation at rest and during exercise.

Airway closure and closing volume

1979 ◽  
Vol 46 (1) ◽  
pp. 24-30 ◽  
Author(s):  
L. Forkert ◽  
S. Dhingra ◽  
N. R. Anthonisen
Keyword(s):  
Blood Flow ◽  
Lung Volume ◽  
Regional Perfusion ◽  
Phase Iii ◽  
Breath Hold ◽  
Closing Volume ◽  
Residual Volume ◽  
Airway Closure ◽  
Lung Volumes ◽  
Phase Iv

Using boluses of radioactive Xe we compared regional N2O uptake with regional perfusion distribution during open glottis breath hold in five seated men. Measurements were made near residual volume, at closing volume (CV), above CV and when possible, between CV and residual volume (RV). At low lung volumes basal N2O uptake was small whereas basal blood flow was not. This discrepancy was interpreted as evidence of airway closure and was quantitated. All subjects showed extensive basal closure near RV. At closing volume four of five subjects demonstrated closure and some closure was evident in these subjects at volumes in excess of CV. The increase in airway closure with decreasing lung volume was much greater below CV than above it. Conventional CV tracings were obtained using helium boluses; the height of phase IV was positively correlated with the change in airway closure between CV and RV as assessed by the N2O technique. The slope of phase III did not correlate with the amount of airway closure measured at CV. We concluded that the conventionally measured CV is not the volume at which airway closure begins but that the onset of phase IV reflects an increase in basal airway closure and the height of phase IV reflects the amount of basal closure between CV and RV.

scholarly journals Effect of manually assisted cough and mechanical insufflation on cough flow of normal subjects, patients with chronic obstructive pulmonary disease (COPD), and patients with respiratory muscle weakness

Thorax ◽  
2001 ◽  
Vol 56 (6) ◽  
pp. 438-444
Author(s):  
P Sivasothy ◽  
L Brown ◽  
I E Smith ◽  
J M Shneerson
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Pulmonary Disease ◽  
Flow Rate ◽  
Peak Expiratory Flow Rate ◽  
Respiratory Muscle ◽  
Normal Subjects ◽  
Chronic Obstructive ◽  
Respiratory Muscle Weakness ◽  
Obstructive Pulmonary Disease ◽  
Expiratory Flow

BACKGROUNDIt has been suggested that cough effectiveness can be improved by assisted techniques. The effects of manually assisted cough and mechanical insufflation on cough flow physiology are reported in this study.METHODSThe physiological actions and patient self-assessment of manually assisted cough and mechanical insufflation were investigated in 29 subjects (nine normal subjects, eight patients with chronic obstructive pulmonary disease (COPD), four subjects with respiratory muscle weakness (RMW) with scoliosis, and eight subjects with RMW without scoliosis).RESULTSThe peak cough expiratory flow rate and cough expiratory volume were not improved by manually assisted cough and mechanical insufflation alone or in combination in normal subjects. The median increase in peak cough expiratory flow in subjects with RMW without scoliosis with manually assisted cough alone or in combination with mechanical insufflation of 84 l/min (95% confidence interval (CI) 19 to 122) and 144 l/min (95% CI 14 to 195), respectively, reflects improvement in the expulsive phase of coughing by these techniques. Manually assisted cough and mechanical insufflation in combination raised peak expiratory flow rate more than either technique alone in this group. The abnormal chest shape in scoliotic subjects and the fixed inspiratory pressure used made effective manually assisted cough and mechanical insufflation difficult in this group and no improvements were found. In patients with COPD manually assisted cough alone and in combination with mechanical insufflation decreased peak expiratory flow rate by 144 l/min (95% CI 25 to 259) and 135 l/min (95% CI 30 to 312), respectively.CONCLUSIONSManually assisted cough and mechanical insufflation should be considered to assist expectoration of secretions in patients with RMW without scoliosis but not in those with scoliosis.

Peak flowmeter resistance decreases peak expiratory flow in subjects with COPD

2000 ◽  
Vol 89 (1) ◽  
pp. 283-290 ◽  
Author(s):  
Martin R. Miller ◽  
Ole F. Pedersen
Keyword(s):  
Peak Expiratory Flow ◽  
Healthy Subjects ◽  
Normal Subjects ◽  
Chronic Obstructive ◽  
Flow Limitation ◽  
Added Resistance ◽  
Elastic Recoil ◽  
Obstructive Pulmonary Disease ◽  
Thoracic Gas Volume ◽  
Expiratory Flow

Previous studies have shown that the added resistance of a mini-Wright peak expiratory flow (PEF) meter reduced PEF by ∼8% in normal subjects because of gas compression reducing thoracic gas volume at PEF and thus driving elastic recoil pressure. We undertook a body plethysmographic study in 15 patients with chronic obstructive pulmonary disease (COPD), age 65.9 ± 6.3 yr (mean ± SD, range 53–75 yr), to examine whether their recorded PEF was also limited by the added resistance of a PEF meter. The PEF meter increased alveolar pressure at PEF (Ppeak) from 3.7 ± 1.4 to 4.7 ± 1.5 kPa ( P = 0.01), and PEF was reduced from 3.6 ± 1.3 l/s to 3.2 ± 0.9 l/s ( P = 0.01). The influence of flow limitation on PEF and Ppeak was evaluated by a simple four-parameter model based on the wave-speed concept. We conclude that added external resistance in patients with COPD reduced PEF by the same mechanisms as in healthy subjects. Furthermore, the much lower Ppeak in COPD patients is a consequence of more severe flow limitation than in healthy subjects and not of deficient muscle strength.

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.

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