Quantifying tidal expiratory flow limitation using a vector-based analysis technique

2021 ◽  
Author(s):  
Ryan Welch ◽  
Alaina Francis ◽  
Thalia Babbage ◽  
Mandy Lardenoye ◽  
John Kolbe ◽  
...  
Keyword(s):  
Healthy Subjects ◽  
Tidal Flow ◽  
Airflow Obstruction ◽  
Peak Exercise ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Flow Reserve ◽  
Vector Difference ◽  
Expiratory Flow ◽  
The Difference

Abstract Objective: Tidal expiratory flow limitation (EFLT) is commonly identified by tidal breaths exceeding the forced vital capacity (FVC) loop. This technique, known as the Hyatt method, is limited by the difficulties in defining the FVC and tidal flow-volume (TV) loops. The vector-based analysis (VBA) technique described and piloted in this manuscript identifies and quantifies EFLT as tidal breaths that conform to the contour of the FVC loop. Approach: The FVC and TV loops are interpolated to generate uniformly spaced plots. VBA is performed to determine the smallest vector difference between each point on the FVC and TV curves, termed the flow reserve vector (FRV). From the FVC point yielding the lowest FRV, the tangential angles of the FVC and TV segments are recorded. If the TV and FVC loops become parallel, the difference between the tangential angles tends towards zero. We infer EFLT as parallel TV and FVC segments where the FRV is <0.1 and the tangential angle is within ±18 degrees for ≥5% of TV. EFLT is quantified by the percent of TV loop fulfilling these criteria. We compared the presence and degree of EFLT at rest and during peak exercise using the Hyatt method and our VBA technique in 25 healthy subjects and 20 subjects with moderate-severe airflow obstruction. Main results: Compared to the Hyatt method, our VBA technique reported a significantly lower degree of EFLT in healthy subjects during peak exercise, and in obstructed subjects at rest and during peak exercise. In contrast to the Hyatt method, our VBA technique re-classified five subjects (one in the healthy group and four in the obstructed group) as demonstrating EFLT. Significance: Our VBA technique provides an alternative approach to determine and quantify EFLT which may reduce the overestimation of the degree EFLT and more accurately identify subjects experiencing EFLT.

Expiratory flow limitation during exercise in competition cyclists

1999 ◽  
Vol 86 (2) ◽  
pp. 611-616 ◽  
Author(s):  
Susana Mota ◽  
Pere Casan ◽  
Franchek Drobnic ◽  
Jordi Giner ◽  
Olga Ruiz ◽  
...  
Keyword(s):  
Lung Volume ◽  
Exercise Test ◽  
Maximal Exercise ◽  
Peak Exercise ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Exercise Ventilation ◽  
Aerobic Exercise Capacity ◽  
Expiratory Flow ◽  
Maximal Voluntary Ventilation

In some trained athletes, maximal exercise ventilation is believed to be constrained by expiratory flow limitation (FL). Using the negative expiratory pressure method, we assessed whether FL was reached during a progressive maximal exercise test in 10 male competition cyclists. The cyclists reached an average maximal O2 consumption of 72 ml ⋅ kg−1 ⋅ min−1(range: 67–82 ml ⋅ kg−1 ⋅ min−1) and ventilation of 147 l/min (range: 122–180 l/min) (88% of preexercise maximal voluntary ventilation in 15 s). In nine subjects, FL was absent at all levels of exercise (i.e., expiratory flow increased with negative expiratory pressure over the entire tidal volume range). One subject, the oldest in the group, exhibited FL during peak exercise. The group end-expiratory lung volume (EELV) decreased during light-to-moderate exercise by 13% (range: 5–33%) of forced vital capacity but increased as maximal exercise was approached. EELV at peak exercise and at rest were not significantly different. The end-inspiratory lung volume increased progressively throughout the exercise test. The conclusions reached are as follows: 1) most well-trained young cyclists do not reach FL even during maximal exercise, and, hence, mechanical ventilatory constraint does not limit their aerobic exercise capacity, and 2) in absence of FL, EELV decreases initially but increases during heavy exercise.

scholarly journals Pitfalls in Expiratory Flow Limitation Assessment at Peak Exercise in Children

2020 ◽  
Vol Publish Ahead of Print ◽  
Author(s):  
Danielle Strozza ◽  
Daniel P. Wilhite ◽  
Tony G. Babb ◽  
Dharini M. Bhammar
Keyword(s):  
Peak Exercise ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Expiratory Flow

scholarly journals Increased prevalence of expiratory flow limitation during exercise in children with bronchopulmonary dysplasia

2018 ◽  
Vol 4 (4) ◽  
pp. 00048-2018 ◽  
Author(s):  
Christopher A. O'Dea ◽  
Karla Logie ◽  
Andrew Maiorana ◽  
Andrew C. Wilson ◽  
J. Jane Pillow ◽  
...  
Keyword(s):  
Bronchopulmonary Dysplasia ◽  
Gestational Age ◽  
Ventilatory Response ◽  
Peak Exercise ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Lower Tidal Volume ◽  
Preterm Children ◽  
Expiratory Flow ◽  
Response To Exercise

Evidence regarding the prevalence of expiratory flow limitation (EFL) during exercise and the ventilatory response to exercise in children born preterm is limited. This study aimed to determine the prevalence of EFL as well as contributing factors to EFL and the ventilatory response to exercise in preterm children with and without bronchopulmonary dysplasia (BPD).Preterm children (≤32 weeks gestational age) aged 9–12 years with (n=64) and without (n=42) BPD and term controls (n=43), performed an incremental treadmill exercise test with exercise tidal flow–volume loops.More preterm children with BPD (53%) had EFL compared with preterm children without BPD (26%) or term controls (28%) (p<0.05). The presence of EFL was independently associated with decreased forced expiratory volume in 1 s/forced vital capacity z-score and lower gestational age (p<0.05). There was no difference in peak oxygen uptake between preterm children with BPD and term controls (48.0 versus 48.4 mL·kg−1·min−1; p=0.063); however, children with BPD had a lower tidal volume at peak exercise (mean difference −27 mL·kg−1, 95% CI −49– −5; p<0.05). Children born preterm without BPD had ventilatory responses to exercise similar to term controls.Expiratory flow limitation is more prevalent in children born preterm with BPD and is associated with airway obstruction and a lower gestational age.

Respiratory effort sensation during exercise with induced expiratory-flow limitation in healthy humans

1997 ◽  
Vol 83 (3) ◽  
pp. 936-947 ◽  
Author(s):  
Bengt Kayser ◽  
Pawel Sliwinski ◽  
Sheng Yan ◽  
Mirek Tobiasz ◽  
Peter T. Macklem
Keyword(s):  
Healthy Subjects ◽  
Flow Limitation ◽  
Respiratory Effort ◽  
Expiratory Flow Limitation ◽  
Healthy Humans ◽  
Inspiratory Muscles ◽  
Expiratory Muscles ◽  
Expiratory Flow ◽  
End Tidal ◽  
Pressure Changes

Kayser, Bengt, Pawel Sliwinski, Sheng Yan, Mirek Tobiasz, and Peter T. Macklem. Respiratory effort sensation during exercise with induced expiratory-flow limitation in healthy humans. J. Appl. Physiol. 83(3): 936–947, 1997.—Nine healthy subjects (age 31 ± 4 yr) exercised with and without expiratory-flow limitation (maximal flow ∼1 l/s). We monitored flow, end-tidal [Formula: see text], esophageal (Pes) and gastric pressures, changes in end-expiratory lung volume, and perception (sensation) of difficulty in breathing. Subjects cycled at increasing intensity (+25 W/30 s) until symptom limitation. During the flow-limited run, exercise performance was limited in all subjects by maximum sensation. Sensation was equally determined by inspiratory and expiratory pressure changes. In both runs, 90% of the variance in sensation could be explained by the Pes swings (difference between peak inspiratory and peak expiratory Pes). End-tidal[Formula: see text] did not explain any variance in sensation in the control run and added only 3% to the explained variance in the flow-limited run. We conclude that in healthy subjects, during normal as well as expiratory flow-limited exercise, the pleural pressure generation of the expiratory muscles is equally related to the perception of difficulty in breathing as that of the inspiratory muscles.

Expiratory flow limitation and regulation of end-expiratory lung volume during exercise

1993 ◽  
Vol 74 (5) ◽  
pp. 2552-2558 ◽  
Author(s):  
R. Pellegrino ◽  
V. Brusasco ◽  
J. R. Rodarte ◽  
T. G. Babb
Keyword(s):  
Lung Volume ◽  
Breathing Pattern ◽  
Airflow Obstruction ◽  
Forced Expiratory Volume ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Reflex Mechanism ◽  
Forced Expiratory Flow ◽  
Expiratory Flow ◽  
The Impact

To investigate the impact of expiratory flow limitation (FL) on breathing pattern and end-expiratory lung volume (EELV), we imposed a small expiratory threshold load for a few breaths during exercise in nine volunteers (29–62 yr): six were healthy and three had mild-to-moderate airflow obstruction (67–71% predicted forced expiratory volume in 1 s). Six subjects showed evidence of FL, i.e., tidal expiratory flow impinging on maximal forced expiratory flow, at one or more exercise levels. Whenever an expiratory threshold load was imposed, mean expiratory flow decreased (P < 0.02) in association with an increased expiratory time (TE; P < 0.05). When the load was imposed during non-FL conditions, TE increased less than expiratory flow decreased and EELV tended to increase. In contrast, during FL, with the load, TE increased more than expiratory flow decreased, subjects did not achieve maximal expiratory flow until a lower volume, and EELV decreased (P < 0.001). Under both FL and no-FL conditions, unloading reversed the changes associated with loading. These data indicate that the increase in EELV during exercise is linked to the occurrence of FL. We suggest that compression of airways downstream from the flow-limiting segment may elicit a reflex mechanism that influences breathing pattern by terminating expiration prematurely, thus increasing EELV.

Determinants of exercise performance in normal men with externally imposed expiratory flow limitation

2002 ◽  
Vol 92 (5) ◽  
pp. 1943-1952 ◽  
Author(s):  
Iacopo Iandelli ◽  
Andrea Aliverti ◽  
Bengt Kayser ◽  
Raffaele Dellacà ◽  
Stephen J. Cala ◽  
...  
Keyword(s):  
Exercise Performance ◽  
Valsalva Maneuver ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Optoelectronic Plethysmography ◽  
Expiratory Flow ◽  
The Difference ◽  
Blood Volume Shift ◽  
Normal Men ◽  
Gas Volume

To understand how externally applied expiratory flow limitation (EFL) leads to impaired exercise performance and dyspnea, we studied six healthy males during control incremental exercise to exhaustion (C) and with EFL at ∼1. We measured volume at the mouth (Vm), esophageal, gastric and transdiaphragmatic (Pdi) pressures, maximal exercise power (W˙max) and the difference (Δ) in Borg scale ratings of breathlessness between C and EFL exercise. Optoelectronic plethysmography measured chest wall and lung volume (Vl). From Campbell diagrams, we measured alveolar (Pa) and expiratory muscle (Pmus) pressures, and from Pdi and abdominal motion, an index of diaphragmatic power (W˙di). Four subjects hyperinflated and two did not. EFL limited performance equally to 65%W˙max with Borg = 9–10 in both. At EFLW˙max, inspiratory time (Ti) was 0.66s ± 0.08, expiratory time (Te) 2.12 ± 0.26 s, Pmus ∼40 cmH2O and ΔVl-ΔVm = 488.7 ± 74.1 ml. From Pa and Vl, we calculated compressed gas volume (Vc) = 163.0 ± 4.6 ml. The difference, ΔVl-ΔVm-Vc (estimated blood volume shift) was 326 ml ± 66 or 7.2 ml/cmH2O Pa. The high Pmus and long Te mimicked a Valsalva maneuver from which the short Ti did not allow recovery. Multiple stepwise linear regression revealed that the difference between C and EFL Pmus accounted for 70.3% of the variance in ΔBorg. ΔW˙di added 12.5%. We conclude that high expiratory pressures cause severe dyspnea and the possibility of adverse circulatory events, both of which would impair exercise performance.

scholarly journals Attenuation of induced bronchoconstriction in healthy subjects: effects of breathing depth

2005 ◽  
Vol 98 (3) ◽  
pp. 817-821 ◽  
Author(s):  
Francesco G. Salerno ◽  
Riccardo Pellegrino ◽  
Gianluca Trocchio ◽  
Antonio Spanevello ◽  
Vito Brusasco ◽  
...  
Keyword(s):  
Healthy Subjects ◽  
Vital Capacity ◽  
Total Lung Capacity ◽  
Flow Limitation ◽  
Residual Volume ◽  
Expiratory Flow Limitation ◽  
Lung Volumes ◽  
Lung Capacity ◽  
Forced Expiratory Flow ◽  
Expiratory Flow

The effects of breathing depth in attenuating induced bronchoconstriction were studied in 12 healthy subjects. On four separate, randomized occasions, the depth of a series of five breaths taken soon (∼1 min) after methacholine (MCh) inhalation was varied from spontaneous tidal volume to lung volumes terminating at ∼80, ∼90, and 100% of total lung capacity (TLC). Partial forced expiratory flow at 40% of control forced vital capacity (V̇part) and residual volume (RV) were measured at control and again at 2, 7, and 11 min after MCh. The decrease in V̇part and the increase in RV were significantly less when the depth of the five-breath series was progressively increased ( P < 0.001), with a linear relationship. The attenuating effects of deep breaths of any amplitude were significantly greater on RV than V̇part ( P < 0.01) and lasted as long as 11 min, despite a slight decrease with time when the end-inspiratory lung volume was 100% of TLC. In conclusion, in healthy subjects exposed to MCh, a series of breaths of different depth up to TLC caused a progressive and sustained attenuation of bronchoconstriction. The effects of the depth of the five-breath series were more evident on the RV than on V̇part, likely due to the different mechanisms that regulate airway closure and expiratory flow limitation.

Regional expiratory flow limitation studied with Technegas in asthma

2001 ◽  
Vol 91 (5) ◽  
pp. 2190-2198 ◽  
Author(s):  
Riccardo Pellegrino ◽  
Alberto Biggi ◽  
Alberto Papaleo ◽  
Gianfranco Camuzzini ◽  
Joseph R. Rodarte ◽  
...  
Keyword(s):  
Flow Limitation ◽  
Airway Wall ◽  
Tidal Breathing ◽  
Expiratory Flow Limitation ◽  
Flow Measurements ◽  
Time Activity ◽  
Flow Reserve ◽  
Forced Expiratory Flow ◽  
Residual Capacity ◽  
Expiratory Flow

Regional expiratory flow limitation (EFL) may occur during tidal breathing without being detected by measurements of flow at the mouth. We tested this hypothesis by using Technegas to reveal sites of EFL. A first study ( study 1) was undertaken to determine whether deposition of Technegas during tidal breathing reveals the occurrence of regional EFL in induced bronchoconstriction. Time-activity curves of Technegas inhaled during 12 tidal breaths were measured in four asthmatic subjects at control conditions and after exposure to inhaled methacholine at a dose sufficient to abolish expiratory flow reserve near functional residual capacity. A second study ( study 2) was conducted in seven asthmatic subjects at control and after three increasing doses of methacholine to compare the pattern of Technegas deposition in the lung with the occurrence of EFL. The latter was assessed at the mouth by comparing tidal with forced expiratory flow or with the flow generated on application of a negative pressure. Study 1 documented enhanced and spotty deposition of Technegas in the central lung regions with increasing radioactivity during tidal expiration. This is consistent with increased impaction of Technegas on the airway wall downstream from the flow-limiting segment. Study 2 showed that both methods based on analysis of flow at the mouth failed to detect EFL at the time spotty deposition of Technegas occurred. We conclude that regional EFL occurs asynchronously across the lung and that methods based on mouth flow measurements are insensitive to it.

scholarly journals Prevalence of tidal expiratory flow limitation in preschool children with and without respiratory symptoms: application of the negative expiratory pressure (NEP) method

2009 ◽  
pp. 373-382
Author(s):  
A Jiřičková ◽  
J Šulc ◽  
P Pohunek ◽  
O Kittnar ◽  
A Dohnalová ◽  
...  
Keyword(s):  
Preschool Children ◽  
High Frequency ◽  
Respiratory Symptoms ◽  
Tidal Flow ◽  
Upper Airway ◽  
Limited Range ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Reasonable Approach ◽  
Expiratory Flow

Negative expiratory pressure (NEP) applied at the mouth during tidal expiration provides a non-invasive method for detecting expiratory flow limitation. Forty-two children were studied, i.e. 25 children with different respiratory symptoms (R) and 17 without any respiratory symptoms (NR). Children were examined without any sedation. A preset NEP of -5 cm H2O was applied; its duration did not exceed duration of tidal expiration. A significance of FL was judged by determining of a flow-limited range (in % of tidal volume). FL was found in 48 % children of R group. No patient of the NR group elicited FL (P<0.001 R vs. NR). The frequency of upper airway collapses was higher in R group (12 children) than in NR group (5 children). In conclusion, a high frequency of tidal FL in the R group was found, while it was not present in NR group. A relatively high frequency of expiratory upper airway collapses was found in both groups, but it did not differ significantly. NEP method represents a reasonable approach for tidal flow limitation testing in non-sedated preschool children.

Modeling expiratory flow from excised tracheal tube laws

1999 ◽  
Vol 87 (5) ◽  
pp. 1973-1980 ◽  
Author(s):  
Nikolai Aljuri ◽  
Lutz Freitag ◽  
José G. Venegas
Keyword(s):  
Static Pressure ◽  
Pressure Recovery ◽  
High Frequency Ventilation ◽  
Flow Limitation ◽  
Flow Conditions ◽  
Expiratory Flow Limitation ◽  
Elastic Tubes ◽  
Viscous Losses ◽  
Forced Expiratory Flow ◽  
Expiratory Flow

Flow limitation during forced exhalation and gas trapping during high-frequency ventilation are affected by upstream viscous losses and by the relationship between transmural pressure (Ptm) and cross-sectional area ( A tr) of the airways, i.e., tube law (TL). Our objective was to test the validity of a simple lumped-parameter model of expiratory flow limitation, including the measured TL, static pressure recovery, and upstream viscous losses. To accomplish this objective, we assessed the TLs of various excised animal tracheae in controlled conditions of quasi-static (no flow) and steady forced expiratory flow. A tr was measured from digitized images of inner tracheal walls delineated by transillumination at an axial location defining the minimal area during forced expiratory flow. Tracheal TLs followed closely the exponential form proposed by Shapiro (A. H. Shapiro. J. Biomech. Eng. 99: 126–147, 1977) for elastic tubes: Ptm = K p[( A tr/ A tr0)− n − 1], where A tr0 is A tr at Ptm = 0 and K p is a parametric factor related to the stiffness of the tube wall. Using these TLs, we found that the simple model of expiratory flow limitation described well the experimental data. Independent of upstream resistance, all tracheae with an exponent n < 2 experienced flow limitation, whereas a trachea with n > 2 did not. Upstream viscous losses, as expected, reduced maximal expiratory flow. The TL measured under steady-flow conditions was stiffer than that measured under expiratory no-flow conditions, only if a significant static pressure recovery from the choke point to atmosphere was assumed in the measurement.

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