Expiratory Flow Limitation Definition, Mechanisms, Methods, and Significance

Department of Experimental and Clinical Sciences, University of Brescia, 1a Medicina, Spedali Civili, 25123 Brescia, Italy.
Pulmonary Medicine 03/2013; 2013(4):749860. DOI: 10.1155/2013/749860
Source: PubMed


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.

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    • "It is a phenomenon more frequent in females because of their reduced airway caliber.7,8 Even body position, aging, hyperpnea–tachypnea, exercise, low volume breathing, or airflow reduction, alone or more often combined, are the main elements involved in the development of EFL in humans.65 "
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    ABSTRACT: Respiratory disorders are often a cause of morbidity in top level endurance athletes, more often compromising their performance and rarely being a cause of death. Pathophysiological events occurring during exercise, such as bronchospasm, are sometimes followed by clear pathological symptoms represented by asthma related to physical exertion or rarely by pulmonary edema induced by a strenuous effort. Both bronchospasm and the onset of interstitial edema induced by exercise cannot be considered pathological per se, but are more likely findings that occur in several healthy subjects once physical exhaustion during exertion has been reached. Consequently, we get a vision of the respiratory system perfectly tailored to meet the body's metabolic demands under normal conditions but which is limited when challenged by strenuous exercise, in particular when it happens in an unfavorable environment. As extreme physical effort may elicit a pathological response in healthy subjects, due to the exceeding demand in a perfectly functional system, an overview of the main tools both enabling the diagnosis of respiratory impairment in endurance athletes in a clinical and preclinical phase has also been described.
    Open Access Journal of Sports Medicine 04/2014; 5:47-63. DOI:10.2147/OAJSM.S57828
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    ABSTRACT: Objective To determine the effects of endurance training on expiratory flow limitation (EFL) and dynamic hyperinflation in patients with stable COPD.Methods This was a prospective, single-blinded, non-randomized controlled 12-week study recruiting Chinese patients with stable COPD in an endurance training group (n=15) or a control group (n=13). Before and at the study end, we measured the EFL, pulmonary function, peak inspiratory flow (PIF) and maximum inspiratory pressure (MIP); moreover, the patients underwent a constant work rate exercise test in which Borg dyspnea scale, tidal breathing flow volume curves and inspiratory capacity (IC) were determined every other minute.ResultsExercise training significantly improved the exercise endurance time (7.00±3.05 vs 18.13±6.44 min, P<0.001), MIP (69.49±16.03 vs 80.18±15.97 cmH2O, P<0.001) and PIF (3.96±1.01 vs 4.51±1.13 L/sec, P=0.014), but not EFL (3.33 ± 0.49 vs 3.40 ± 0.51, P=0.334). Subjects on training had decreased breathing frequency (26.26±7.13 vs 23.15±5.34 breaths/min, P=0.002), minute ventilation (30.28±7.52 vs 26.85±4.17 L, P=0.013), tidal peak expiratory flow (1.53±0.22 vs 1.32±0.20 L/s, P=0.006), mean expiratory flow (0.87 ± 0.19 vs 0.68±0.15 L/s, P=0.011) and Borg dyspnea score (7.20±1.15 vs 3.93±1.39, P<0.001), as well as increased IC (1.50±0.34 vs 1.67±0.45 L, P=0.002), expiratory time (1.47±0.62 vs 1.72±0.62 sec, P=0.004) and inspiratory flow reserve (2.05 ± 1.10 vs 2.95 ± 1.19 L/s, P=0.002) at isotime. These changes were not observed in the control group.Conclusion Endurance training may benefit stable COPD patients in improving exercise endurance, inspiratory muscle strength, ventilatory requirements, exercise-induced hyperinflation, and exertional dyspnea.
    Internal Medicine Journal 05/2014; 44(8). DOI:10.1111/imj.12483 · 1.64 Impact Factor
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    ABSTRACT: The forced oscillation technique can identify expiratory flow limitation (EFL) when a large difference in inspiratory and expiratory reactance (ΔXrs) occurs. However, flow limitation can vary from breath to breath, and so we compared a multiple-breath ΔXrs approach to the traditional breath-by-breath assessment of EFL. We investigated the within- and between-day reproducibility and the factors that affect the size of ΔXrs when used as a continuous measurement over multiple breaths. In addition, we examined how multiple-breath ΔXrs relates to the sensation of breathlessness. 425 moderate to very severe chronic obstructive pulmonary disease (COPD) patients and 229 controls were included. Spirometry and impedance measurements were performed on a MasterScope CT Impulse Oscillation System. Median ΔXrs approached zero in healthy controls with little variation between measurements. COPD patients generally had higher ΔXrs and higher variability. The COPD patients with ΔXrs >0.1 kPa·L(-1)·s(-1) were prone to be more breathless and had a higher modified Medical Research Council dyspnoea scale score. In controls, the 95th percentile of ΔXrs was as low as 0.07 kPa·L(-1)·s(-1). We describe a new method to assess EFL at a patient level and propose a cut-off, mean ΔXrs >0.1 kPa·L(-1)·s(-1), as a way to identify COPD patients who are more likely to report dyspnoea.
    European Respiratory Journal 10/2014; 45(3). DOI:10.1183/09031936.00051214 · 7.64 Impact Factor

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