scholarly journals Pulmonary function with expiratory resistive loading in healthy volunteers

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0252916
Author(s):  
Jyotika Erram ◽  
Monica Bari ◽  
Antoinette Domingo ◽  
Daniel T. Cannon
Keyword(s):  
Pulmonary Function ◽  
Model Comparison ◽  
Work Of Breathing ◽  
Lung Mechanics ◽  
Dynamic Hyperinflation ◽  
Flow Volume ◽  
Expiratory Flow Limitation ◽  
Volume Relationship ◽  
Expiratory Flow ◽  
Clinically Significant

Expiratory flow limitation is a key characteristic in obstructive pulmonary diseases. To study abnormal lung mechanics isolated from heterogeneities of obstructive disease, we measured pulmonary function in healthy adults with expiratory loading. Thirty-seven volunteers (25±5 yr) completed spirometry and body plethysmography under control and threshold expiratory loading of 7, 11 cmH2O, and a subset at 20 cmH2O (n = 11). We analyzed the shape of the flow-volume relationship with rectangular area ratio (RAR; Ma et al., Respir Med 2010). Airway resistance was increased (p<0.0001) with 7 and 11 cmH2O loading vs control (9.20±1.02 and 11.76±1.68 vs. 2.53± 0.80 cmH2O/L/s). RAR was reduced (p = 0.0319) in loading vs control (0.45±0.07 and 0.47±0.09L vs. 0.48±0.08). FEV1 was reduced (p<0.0001) in loading vs control (3.24±0.81 and 3.23±0.80 vs. 4.04±1.05 L). FVC was reduced (p<0.0001) in loading vs control (4.11±1.01 and 4.14±1.03 vs. 5.03±1.34 L). Peak expiratory flow (PEF) was reduced (p<0.0001) in loading vs control (6.03±1.67 and 6.02±1.84 vs. 8.50±2.81 L/s). FEV1/FVC (p<0.0068) was not clinically significant and FRC (p = 0.4) was not different in loading vs control. Supra-physiologic loading at 20 cmH2O did not result in further limitation. Expiratory loading reduced FEV1, FVC, PEF, but there were no clinically meaningful differences in FEV1/FVC, FRC, or RAR. Imposed expiratory loading likely leads to high airway pressures that resist dynamic airway compression. Thus, a concave expiratory flow-volume relationship was consistently absent–a key limitation for model comparison with pulmonary function in COPD. Threshold loading may be a useful strategy to increase work of breathing or induce dynamic hyperinflation.

scholarly journals Effect of nocturnal EPAP titration to abolish tidal expiratory flow limitation in COPD patients with chronic hypercapnia: a randomized, cross-over pilot study

2020 ◽  
Vol 21 (1) ◽  
Author(s):  
Emanuela Zannin ◽  
Ilaria Milesi ◽  
Roberto Porta ◽  
Simona Cacciatore ◽  
Luca Barbano ◽  
...  
Keyword(s):  
Oxygen Saturation ◽  
Work Of Breathing ◽  
Lung Mechanics ◽  
Intrinsic Peep ◽  
Chronic Obstructive ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Copd Patients ◽  
Ineffective Efforts ◽  
Expiratory Flow

Abstract Background Tidal expiratory flow limitation (EFLT) promotes intrinsic PEEP (PEEPi) in patients with chronic obstructive pulmonary disease (COPD). Applying non-invasive ventilation (NIV) with an expiratory positive airway pressure (EPAP) matching PEEPi improves gas exchange, reduces work of breathing and ineffective efforts. We aimed to evaluate the effects of a novel NIV mode that continuously adjusts EPAP to the minimum level that abolishes EFLT. Methods This prospective, cross-over, open-label study randomized patients to one night of fixed-EPAP and one night of EFLT-abolishing-EPAP. The primary outcome was transcutaneous carbon dioxide pressure (PtcCO2). Secondary outcomes were: peripheral oxygen saturation (SpO2), frequency of ineffective efforts, breathing patterns and oscillatory mechanics. Results We screened 36 patients and included 12 in the analysis (age 72 ± 8 years, FEV1 38 ± 14%Pred). The median EPAP did not differ between the EFLT-abolishing-EPAP and the fixed-EPAP night (median (IQR) = 7.0 (6.0, 8.8) cmH2O during night vs 7.5 (6.5, 10.5) cmH2O, p = 0.365). We found no differences in mean PtcCO2 (44.9 (41.6, 57.2) mmHg vs 54.5 (51.1, 59.0), p = 0.365), the percentage of night time with PtcCO2 > 45 mm Hg was lower (62(8,100)% vs 98(94,100)%, p = 0.031) and ineffective efforts were fewer (126(93,205) vs 261(205,351) events/hour, p = 0.003) during the EFLT-abolishing-EPAP than during the fixed-EPAP night. We found no differences in oxygen saturation and lung mechanics between nights. Conclusion An adaptive ventilation mode targeted to abolish EFLT has the potential to reduce hypercapnia and ineffective efforts in stable COPD patients receiving nocturnal NIV. Trial registration: ClicalTrials.gov, NCT04497090. Registered 29 July 2020—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04497090.

scholarly journals Expiratory Flow Limitation Definition, Mechanisms, Methods, and Significance

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Claudio Tantucci
Keyword(s):  
Work Of Breathing ◽  
Chronic Obstructive ◽  
Dynamic Hyperinflation ◽  
Flow Limitation ◽  
Negative Consequences ◽  
Expiratory Flow Limitation ◽  
Obstructive Pulmonary Disease ◽  
Inspiratory Muscles ◽  
Copd Patients ◽  
Expiratory Flow

When expiratory flow is maximal during tidal breathing and cannot be increased unless operative lung volumes move towards total lung capacity, tidal expiratory flow limitation (EFL) is said to occur. EFL represents a severe mechanical constraint caused by different mechanisms and observed in different conditions, but it is more relevant in terms of prevalence and negative consequences in obstructive lung diseases and particularly in chronic obstructive pulmonary disease (COPD). Although in COPD patients EFL more commonly develops during exercise, in more advanced disorder it can be present at rest, before in supine position, and then in seated-sitting position. In any circumstances EFL predisposes to pulmonary dynamic hyperinflation and its unfavorable effects such as increased elastic work of breathing, inspiratory muscles dysfunction, and progressive neuroventilatory dissociation, leading to reduced exercise tolerance, marked breathlessness during effort, and severe chronic dyspnea.

Relation of concavity in the expiratory flow-volume loop to dynamic hyperinflation during exercise in COPD

2016 ◽  
Vol 234 ◽  
pp. 79-84 ◽  
Author(s):  
Janos Varga ◽  
Richard Casaburi ◽  
Shuyi Ma ◽  
Ariel Hecht ◽  
David Hsia ◽  
...  
Keyword(s):  
Dynamic Hyperinflation ◽  
Flow Volume ◽  
Flow Volume Loop ◽  
Expiratory Flow

Inspiratory Muscle Training Improves Pulmonary Function And Reduces Expiratory Flow Limitation In Asthmatic Individuals.

2008 ◽  
Vol 40 (Supplement) ◽  
pp. S205
Author(s):  
Louise A. Turner ◽  
Timothy D. Mickleborough ◽  
Sandra Tecklenburg ◽  
Joel M. Stager ◽  
Martin R. Lindley ◽  
...  
Keyword(s):  
Pulmonary Function ◽  
Inspiratory Muscle ◽  
Inspiratory Muscle Training ◽  
Flow Limitation ◽  
Muscle Training ◽  
Expiratory Flow Limitation ◽  
Expiratory Flow

Flow-Volume Relationship at Low Lung Volumes in Healthy Term Newborn Infants

PEDIATRICS ◽  
1978 ◽  
Vol 61 (4) ◽  
pp. 636-640
Author(s):  
Saul M. Adler ◽  
Mary Ellen B. Wohl
Keyword(s):  
Newborn Infants ◽  
Chamber Pressure ◽  
Positive Pressure ◽  
Forced Expiration ◽  
Flow Volume ◽  
Convex Shape ◽  
Lung Volumes ◽  
Volume Relationship ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow

To describe the maximum expiratory flow-volume relationship in newborn infants, we simulated forced expiration by transiently applying positive pressure in a chamber surrounding the infant's body. Maximum expiratory flows were reached at any given lung volume when increases in chamber pressure failed to produce increases in flow. Maximum expiratory flows were achieved in seven of nine healthy newborn infants at lung volumes equal to functional residual capacity (FRC) and in all infants at lung volumes below FRC. The volume expired below FRC (6.4 ml/kg) was roughly equivalent to previously calculated values of expiratory reserve volume in newborn infants (7 ml/kg). The maximum expiratory flow volume curves showed that the infants were able to increase expiratory flow rates well above those achieved during tidal breathing. The convex shape of the curves at low lung volumes is compatible with flow limitation occurring in peripheral airways.

Expiratory flow limitation and dynamic pulmonary hyperinflation during high-frequency ventilation

1986 ◽  
Vol 60 (6) ◽  
pp. 2071-2078 ◽  
Author(s):  
J. Solway ◽  
T. H. Rossing ◽  
A. F. Saari ◽  
J. M. Drazen
Keyword(s):  
High Frequency ◽  
Progressive Increase ◽  
High Frequency Ventilation ◽  
Dynamic Hyperinflation ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Pulmonary Hyperinflation ◽  
Residual Capacity ◽  
Frequency Ventilation ◽  
Expiratory Flow

Dynamic hyperinflation of the lungs occurs during high-frequency oscillatory ventilation (HFOV) and has been attributed to asymmetry of inspiratory and expiratory impedances. To identify the nature of this asymmetry, we compared changes in lung volume (VL) observed during HFOV in ventilator-dependent patients with predictions of VL changes from electrical analogs of three potential modes of impedance asymmetry. In the patients, when a fixed oscillatory tidal volume was applied at a low mean airway opening pressure (Pao), which resulted in little increase in functional residual capacity, progressively greater dynamic hyperinflation was observed as HFOV frequency, (f) was increased. When mean Pao was raised so that resting VL increased, VL remained at this level during HFOV as f was increased until a critical f was reached; above this value, VL increased further with f in a fashion nearly parallel to that observed when low mean Pao was used. Three modes of asymmetric inspiratory and expiratory impedance were modeled as electrical circuits: 1) fixed asymmetric resistance [Rexp greater than Rinsp]; 2) variable asymmetric resistance [Rexp(VL) greater than Rinsp, with Rexp(VL) decreasing as VL increased]; and 3) equal Rinsp and Rexp, but with superimposed expiratory flow limitation, the latter simulated using a bipolar transistor as a descriptive model of this phenomenon. The fixed and the variable asymmetric resistance models displayed a progressive increase of mean VL with f at either low or high mean Pao. Only the expiratory flow limitation model displayed a dependence of dynamic hyperinflation on mean Pao and f similar to that observed in our patients. We conclude that expiratory flow limitation can account for dynamic pulmonary hyperinflation during HFOV.

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.

scholarly journals Effect of bronchodilation on expiratory flow limitation and resting lung mechanics in COPD

2009 ◽  
Vol 33 (6) ◽  
pp. 1329-1337 ◽  
Author(s):  
R. L. Dellaca ◽  
P. P. Pompilio ◽  
P. P. Walker ◽  
N. Duffy ◽  
A. Pedotti ◽  
...  
Keyword(s):  
Lung Mechanics ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Expiratory Flow
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