Expiratory flow-limitation and heliox breathing in resting and exercising COPD patients

D’Angelo, Edgardo; Santus, Pierachille; Civitillo, Marco F.; Centanni, Stefano; Pecchiari, Matteo

doi:10.1016/j.resp.2009.09.009

Cited by 17 publications

(19 citation statements)

References 27 publications

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“…A potential confounding factor is the eventual presence of tidal expiratory flow-limitation [18], which has been investigated, using the negative expiratory pressure technique [51], only in one instance [32]. This study assessed, in 26 stable COPD patients, tidal expiratory flow-limitation, inspiratory capacity, breathing pattern, and dyspnea sensation during air and heliox 21 breathing at rest and during exercise at 1/3 and 2/3 of the maximal work rate.…”

Section: Heliox Breathing During Exercise In Copd Patientsmentioning

confidence: 99%

“…In this connection, it should be underlined that dyspnea is not necessarily related to dynamic hyperinflation, in fact, in normal subjects, dyspnea may not change with heliox 21 even if dynamic hyperinflation decreases [26], and, in COPD patients, dyspnea can decrease even in the absence of dynamic hyperinflation [32, 44]. The reduction of dyspnea documented by D'Angelo et al [32] could thus be related to a decrease of the inspiratory work, which, depending on the extent of turbulence in the airways, can amount up to 50%–60% [6, 52]. …”

Section: Heliox Breathing During Exercise In Copd Patientsmentioning

confidence: 99%

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Effects of Heliox in Stable COPD Patients at Rest and during Exercise

Pecchiari

2012

Pulmonary Medicine

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Heliox has been administered to stable chronic obstructive pulmonary disease (COPD) patients at rest and during exercise on the assumption that this low density mixture would have reduced work of breathing, dynamic hyperinflation, and, consequently, dyspnea sensation. Contrary to these expectations, beneficial effects of heliox in these patients at rest have been reported only sporadically, and the majority of the studies performed until now suggests that heliox is not a therapeutic option in spontaneously breathing resting COPD patients. On the other hand, when it is administered to COPD patients exercising at a constant work rate, heliox systematically decreases dyspnea sensation, and, often but not always, increases exercise tolerance. For these reasons, heliox has been evaluated as a non pharmacological tool to power rehabilitation programs. The conflicting results provided by the published trials probably point at a substantial heterogeneity of the COPD patients population in terms of respiratory mechanics and gas exchange. Therefore, further studies, aimed to the identification of mechanisms conditioning the response of exercising COPD patients to heliox, are warranted, before heliox administration, which is costly and cumbersome, can be routinely used in rehabilitation programs.

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Section: Heliox Breathing During Exercise In Copd Patientsmentioning

confidence: 99%

Section: Heliox Breathing During Exercise In Copd Patientsmentioning

confidence: 99%

Effects of Heliox in Stable COPD Patients at Rest and during Exercise

Pecchiari

2012

Pulmonary Medicine

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“…The location of expiratory flow limitation is considered to be in the central airways (4th–7th generation) and move to the periphery during forced expiratory manoeuvres. It is located beyond the 7th (i.e., from the 8th onwards) generation during tidal breathing [2–4]. …”

Section: Introductionmentioning

confidence: 99%

“…Initially, the latter is histologically characterized by denuded epithelium, rupture of alveolar-airway attachments, and increased number of polymorphonuclear leucocytes [5–7]. Studies in which heliox (80% He/20% O 2 ) was administered in COPD patients provided also corroborative evidence that EFL T was located in the peripheral airways [2–4]. EFL T promotes dynamic pulmonary hyperinflation and PEEPi with concurrent dyspnoea and exercise limitation [8].…”

Section: Introductionmentioning

confidence: 99%

Methods for Assessing Expiratory Flow Limitation during Tidal Breathing in COPD Patients

et al. 2012

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Patients with severe COPD often exhale along the same flow-volume curve during quite breathing as during forced expiratory vital capacity manoeuvre, and this has been taken as indicating expiratory flow limitation at rest (EFLT). Therefore, EFLT, namely, attainment of maximal expiratory flow during tidal expiration, occurs when an increase in transpulmonary pressure causes no increase in expiratory flow. EFLT leads to small airway injury and promotes dynamic pulmonary hyperinflation with concurrent dyspnoea and exercise limitation. In fact, EFLT occurs commonly in COPD patients (mainly in GOLD III and IV stage) in whom the latter symptoms are common. The existing up-to-date physiological methods for assessing expiratory flow limitation (EFLT) are reviewed in the present work. Among the currently available techniques, the negative expiratory pressure (NEP) has been validated in a wide variety of settings and disorders. Consequently, it should be regarded as a simple, non invasive, most practical, and accurate new technique.

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“…Previous studies have explored the hypothesis that breathing low-density helium/oxygen (He/O 2 ) mixtures improves lung emptying in patients with obstructive lung disease [5-9]. From these investigations, coupled with analysis of the underlying respiratory fluid mechanics, it may be gathered that the potential for He/O 2 to influence expiratory flow rates is highly dependent on the location of obstruction [5,6]. Moving from the upper airways to the peripheral lung, as the gas Reynolds number decreases by several orders of magnitude, airway resistance becomes less influenced by flow inertia (which depends in turn on gas density) and more influenced by viscous effects [5,10,11].…”

Section: Introductionmentioning

confidence: 99%

Bench and mathematical modeling of the effects of breathing a helium/oxygen mixture on expiratory time constants in the presence of heterogeneous airway obstructions

Katz

Terzibachi

Gouinaud

et al. 2012

BioMedical Engineering OnLine

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BackgroundExpiratory time constants are used to quantify emptying of the lung as a whole, and emptying of individual lung compartments. Breathing low-density helium/oxygen mixtures may modify regional time constants so as to redistribute ventilation, potentially reducing gas trapping and hyperinflation for patients with obstructive lung disease. In the present work, bench and mathematical models of the lung were used to study the influence of heterogeneous patterns of obstruction on compartmental and whole-lung time constants.MethodsA two-compartment mechanical test lung was used with the resistance in one compartment held constant, and a series of increasing resistances placed in the opposite compartment. Measurements were made over a range of lung compliances during ventilation with air or with a 78/22% mixture of helium/oxygen. The resistance imposed by the breathing circuit was assessed for both gases. Experimental results were compared with predictions of a mathematical model applied to the test lung and breathing circuit. In addition, compartmental and whole-lung time constants were compared with those reported by the ventilator.ResultsTime constants were greater for larger minute ventilation, and were reduced by substituting helium/oxygen in place of air. Notably, where time constants were long due to high lung compliance (i.e. low elasticity), helium/oxygen improved expiratory flow even for a low level of resistance representative of healthy, adult airways. In such circumstances, the resistance imposed by the external breathing circuit was significant. Mathematical predictions were in agreement with experimental results. Time constants reported by the ventilator were well-correlated with those determined for the whole-lung and for the low-resistance compartment, but poorly correlated with time constants determined for the high-resistance compartment.ConclusionsIt was concluded that breathing a low-density gas mixture, such as helium/oxygen, can improve expiratory flow from an obstructed lung compartment, but that such improvements will not necessarily affect time constants measured by the ventilator. Further research is required to determine if alternative measurements made at the ventilator level are predictive of regional changes in ventilation. It is anticipated that such efforts will be aided by continued development of mathematical models to include pertinent physiological and pathophysiological phenomena that are difficult to reproduce in mechanical test systems.

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Expiratory flow-limitation and heliox breathing in resting and exercising COPD patients

Cited by 17 publications

References 27 publications

Effects of Heliox in Stable COPD Patients at Rest and during Exercise

Effects of Heliox in Stable COPD Patients at Rest and during Exercise

Methods for Assessing Expiratory Flow Limitation during Tidal Breathing in COPD Patients

Bench and mathematical modeling of the effects of breathing a helium/oxygen mixture on expiratory time constants in the presence of heterogeneous airway obstructions

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