Decay of inspiratory muscle pressure during expiration in conscious humans

Shee, C. D.; Ploysongsang, Yongyudh; Milic–Emili, J.

doi:10.1152/jappl.1985.58.6.1859

Cited by 59 publications

(45 citation statements)

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“…Firstly, during spontaneous breathing there is postinspiratory activity (PIA) of the inspiratory muscles during the initial part of expiration, which counterbalances the elastic recoil pressure stored in the respiratory system during the preceding inspiration; and, hence, exerts an expiratory braking action [19][20][21]. As a result, the flow during spontaneous expiration increases slowly to its peak value, whereas during relaxed (passive) expiration it peaks very rapidly [22,23].…”

Section: Discussionmentioning

confidence: 99%

A simple method to detect expiratory flow limitation during spontaneous breathing

Koulouris¹,

Valta²,

Lavoie³

et al. 1995

Eur Respir J

220

225

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A A s si im mp pl le e m me et th ho od d t to o d de et te ec ct t e ex xp pi ir ra at to or ry y f fl lo ow w l li im mi it ta at ti io on n d du ur ri in ng g s sp po on nt ta an ne eo ou us s b br re ea at th hi in ng g N.G. Koulouris*, P. Valta*, A. Lavoie*, C. Corbeil**, M. Chassé**, J. Braidy**, J. Milic-Emili*A simple method to detect expiratory flow limitation during spontaneous breathing. N.G. Koulouris, P. Valta, A. Lavoie, C. Corbeil, M. Chassé, J. Braidy, J. Milic-Emili. ERS Journals Ltd 1995. ABSTRACT: Patients with severe chronic obstructive pulmonary disease (COPD) often exhale along the same flow-volume curve during quiet breathing as during a forced expiratory vital capacity manoeuvre, and this has been taken as indicating flow limitation at rest. To obtain such curves, a body plethysmograph and the patient's co-operation are required. We propose a simple technique which does not entail these requirements. It consists in applying negative pressure at the mouth during a tidal expiration (NEP). Patients in whom NEP elicits an increase in flow throughout the expiration are not flow-limited. In contrast, patients in whom application of NEP does not elicit an increase in flow during most or part of the tidal expiration are considered as flowlimited. Using this technique, 26 stable COPD patients were studied sitting and supine.Eleven patients were flow-limited both seated and supine, eight were flow-limited only when supine, and seven were not flow-limited either seated or supine. Only 5 of 19 patients who were flow-limited seated and/or supine had severe ventilatory impairment (forced expiratory volume in one second (FEV 1 ) <40% predicted).We conclude that the NEP technique provides a simple, rapid, and reliable method for detection of expiratory flow limitation in spontaneously breathing subjects, which does not require the patient's co-operation, and can be applied in different body positions both at rest and during muscular exercise. Our results also indicate a high prevalence of flow limitation in COPD patients at rest, particularly when supine. Eur Respir J., 1995, 8, 306-313 It has long been suggested that patients with severe chronic obstructive pulmonary disease (COPD) may exhibit expiratory flow limitation at rest, as reflected by the fact that they breathe tidally along or above their maximum expiratory flow-volume curves [1][2][3]. The effects of expiratory flow limitation may be partly compensated by breathing at lung volumes higher than the relaxation volume of the respiratory system [3]. The latter condition, which is termed dynamic pulmonary hyperinflation, is associated with intrinsic positive endexpiratory pressure (PEEPi) [4]. The combined effects of increased flow resistance, dynamic hyperinflation and PEEPi place a severe burden on the inspiratory muscles of COPD patients [5][6][7], and may also contribute to dyspnoea [8].Though dynamic hyperinflation is the hallmark of expiratory flow limitation, the prevalence and clinical significance of this phenomenon have not been adequa...

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Section: Discussionmentioning

confidence: 99%

A simple method to detect expiratory flow limitation during spontaneous breathing

Koulouris¹,

Valta²,

Lavoie³

et al. 1995

Eur Respir J

220

225

View full text Add to dashboard Cite

show abstract

“…For clinical use, Rint methods have to rely upon the collection of Pmo(t) curves during quiet breathing. Inevitably, effects due to respiratory muscle activity [25,26] and to upper airway compliance [27] can distort the pressure signal. Uncontrollable movement of the tongue or variations in the size of the glottic aperture could all have had a substantial influence on the upper airway geometry and, hence, led to measurement variability.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of a new interrupter device for measuring bronchial responsiveness and the response to bronchodilator in 3 year old children

Phagoo¹,

Wilson²,

Silverman³

1996

European Respiratory Journal

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“…In eight normal subjects, it has been shown that such relaxation occurs during the last 20% tE (mean), ranging between the last 55% and the last 4% of tE [16].…”

Section: Determination Of Tidal Breathing Indicesmentioning

confidence: 97%

“…In normal subjects, evidence points to full relaxation only occurring towards the end of expiration, inspiratory muscle activity continuing well This study shows that there is a relationship between these measurements made from analysis of tidal breathing and recognized measurements of airflow obstruction and overinflation. Eur Respir J 1998;12: 1113-1117 into expiration [11,[16][17][18][19]. Our hypothesis has been that if the relaxed part of tidal expiration can be identified, analysis of this portion of the flow-time or flow-volume relationships will be informative about the presence and severity of airflow obstruction.…”

Section: Analysis Of Expiratory Tidal Flow Patterns As a Diagnostic Tmentioning

confidence: 99%

Analysis of expiratory tidal flow patterns as a diagnostic tool in airflow obstruction

Morris

Madgwick²,

Collyer³

et al. 1998

Eur Respir J

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In 1981, we made the observation that tidal flow versus time has a distinctive pattern in patients with airflow obstruction that is different from the sinusoidal appearance seen in normal subjects. To quantify this difference, we described timing indices derived from the analysis of tidal expiratory flow [1]. These indices, volume expired when the peak tidal expiratory flow reached (VPTEF)/tidal volume (VT) and (time to peak expiratory tidal flow (tPTEF)/ expiratory time (tE) closely correlated with each other and correlated significantly with other indices of airflow obstruction [1]. The index tPTEF/tE, has been demonstrated to be useful in predicting wheezy illness in the new-born [2], in discriminating between asthmatic and nonasthmatic children [3][4][5] and between healthy control subjects and children with cystic fibrosis [5] and showing response to histamine [5,6], methacholine [7] and bronchodilator [3][4][5] in asthmatic children, though recently has not been found to be useful in the diagnosis of narrowed airways in infants [8][9][10].In our original description of the typical flow time pattern of tidal expiration in patients with airflow obstruction, we described three parts to the curve: 1) a rapid rise to maximum flow; 2) a slow decline in flow over most of expiration, followed by; 3) an abrupt fall of flow to zero as the next inspiration is triggered while there is still a measurable expiratory flow. In contrast, in normal subjects, expiratory flow rises more slowly to a maximum, and then decreases gradually to zero, resulting in a smoother appearance of the tidal expiratory flow-time curve.The index tPTEF/tE uses only information from the first part of the expiratory flow-time curve, based on a single point. We have described two further indices [11,12] in an attempt to use the information contained in the period of declining expiratory flow after the maximum flow has been reached (figs. 1 and 2). These indices are: 1) the time constant of the respiratory system (Trs); and 2) extrapolated volume (EV) (the volume of dynamic overinflation), i.e. the extra volume that would have been expired if expiration had continued to the elastic equilibrium volume.The theoretical basis of this analysis is that if expiration is relaxed the decay of flow against time reflects the compliance and resistance of the respiratory system. OTIS et al.[13] described a simple model of the respiratory system consisting of a single compartment of constant elastance served by a pathway of constant resistance. When, in this model, expiratory flow is driven by the relaxation pressures of the lung and chest wall, there is a linear volumeflow relationship. This slope is the time constant of relaxed expiration and by analogy with an electrical model Trs is equal to resistance×compliance of the total respiratory system (lungs+ chest wall). COMROE et al. [14] suggested that volume-flow curves of passive expiration could be used to assess the mechanical properties of the lung and chest wall.In patients with airflow obstruction, there ...

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Decay of inspiratory muscle pressure during expiration in conscious humans

Cited by 59 publications

References 0 publications

A simple method to detect expiratory flow limitation during spontaneous breathing

A simple method to detect expiratory flow limitation during spontaneous breathing

Evaluation of a new interrupter device for measuring bronchial responsiveness and the response to bronchodilator in 3 year old children

Analysis of expiratory tidal flow patterns as a diagnostic tool in airflow obstruction

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