Effect of salbutamol on dynamic hyperinflation in chronic obstructive pulmonary disease patients

Abstract

Bronchodilating agents are commonly used in patients with chronic obstructive pulmonary disease (COPD) to reduce airway obstruction [1]. Although many COPD patients may obtain substantial increase in airflow after inhalation of bronchodilators [2], one-third of them do not show significant acute spirometric changes [3]. It is a common tenet, however, that improvements in symptoms and exercise capacity may occur even in the absence of spirometric improvement [4]. Such findings are frequent in patients with relatively severe COPD (forced expiratory volume in one second (FEV1) <50% pred), who often exhibit expiratory flow limitation (EFL) during resting breathing, i.e. their tidal expiratory flow is maximal under the prevailing condition [5].In the presence of EFL, the expiratory flow can increase only by breathing at higher lung volume. Thus, EFL promotes dynamic pulmonary hyperinflation, a condition where the end-expiratory lung volume (EELV) is greater than the relaxation or elastic equilibrium volume (Vr). As a result, there is a positive end-expiratory pressure (PEEP) in the alveoli which is called intrinsic PEEP (PEEPi) and acts as an inspiratory threshold load [6]. Dynamic hyperinflation is associated not only with increased inspiratory work due to PEEPi [7] but also with impaired inspiratory muscle function [8]. This, together with flow-limiting dynamic compression during tidal breathing, may contribute to dyspnoea in flow-limited COPD patients [9,10]. Indeed, in a study by ELTAYARA et al. [9], the severity of chronic dyspnoea was found to correlate much more closely with flow limitation than with usual spirometric indices.The aim of this study was to assess whether, in patients with moderate-to-severe COPD, the administration of a bronchodilator (short-acting β 2 -agonist) abolished EFL and/or reduced the EELV during tidal breathing. EFL was assessed with the negative expiratory pressure (NEP) method [5,11]. Tidal EFL was also assessed with the conventional method based on comparison of tidal with maximal flow-volume (V '-V) curves obtained with body plethysmography [12]. Methods SubjectsEighteen patients (14 males and four females, aged 65±2 yrs (mean±SEM), range 48-77 yrs) suffering from COPD according to the American Thoracic Society (ATS) guidelines [1] were studied when in a stable condition.Effect of salbutamol on dynamic hyperinflation in chronic obstructive pulmonary disease patients. C. Tantucci, A. Duguet, T. Similowski, M. Zelter, J-P. Derenne, J. Milic-Emili. ©ERS Journals Ltd 1998. ABSTRACT: Expiratory flow limitation (EFL), which promotes dynamic hyperinflation and increased work of breathing, often occurs in chronic obstructive pulmonary disease (COPD). The purpose of this study was to assess the effect of bronchodilators on EFL and end-expiratory lung volume in patients with moderate-to-severe COPD.EFL was assessed by applying negative expiratory pressure (NEP) at the mouth during tidal expiration. EFL was present when expiratory flow did not increase or increased only in the early phase ...

Role of inspiratory capacity on exercise tolerance in COPD patients with and without tidal expiratory flow limitation at rest

“…This provides a reasonable mechanistic explanation for the close association between resting IC and exercise tolerance in FL patients. Assessment of IC has already been shown to provide useful information on the effects of surgical treatment [25] and bronchodilators [26] on hyperinflation in COPD patients. Recently, it has also been shown that in COPD patients the increase in IC after anticholinergic therapy best reflected the improvements in exercise endurance and dyspnoea [27].…”

“…Assessment of FL may also provide a useful guide for rehabilitation in COPD patients: in patients without FL, rehabilitation based on exercise should be particularly beneficial, while in patients with FL administration of bronchodilators and inspiratory muscle training should be preferable in order to decrease the prevailing hyperinflation [26,27] and to increase the working capacity of the inspiratory muscles [28,29].…”

Tidal expiratory flow limitation and chronic dyspnoea in patients with cystic fibrosis

“…Assessment of tidal FL was made using: 1) the NEP technique [2,4] and 2) the "conventional" method of superimposition of tidal with maximal expiratory flow/volume (V9/V) curves [11]. In this case, volume was measured with the body plethysmograph to avoid errors due to thoracic gas compression [18].…”

“…Using the negative expiratory pressure (NEP) technique, it has been shown that in patients with chronic obstructive pulmonary disease (COPD) there is a high prevalence of expiratory flow limitation (FL) during resting breathing [1][2][3][4]. The presence of tidal FL promotes dynamic pulmonary hyperinflation (DH) and intrinsic positive end-expiratory pressure, with a concomitant increase of inspiratory work, impairment of inspiratory muscle function, and adverse effects on haemodynamics [5].…”

Reversibilidad espirométrica en la enfermedad pulmonar obstructiva crónica: Efecto diferencial del salbutamol sobre el volumen espiratorio forzado del primer segundo y el volumen pulmonar

“…La evaluación de los cambios de volumen pulmonar no requiere de equipos sofisticados, ya que con un simple espirómetro es posible medir la capacidad vital lenta (CVL), la capacidad vital forzada (CVF) y la capacidad inspiratoria. Se desconoce cuál es la magnitud de los cambios de volumen y cuántos pacientes podrían ser catalogados como respondedores frente a los broncodilatadores, basados sólo en los cambios de volumen, ya que los trabajos que han explorado esta aproximación adolecen de limitaciones entre las que destacan: el carácter retrospectivo de un estudio 10 , no existiendo la certeza de que los pacientes estudiados fueran todos portadores de EPOC; el empleo de dosis muy elevadas de salbutamol (5 mg) 11 , lo que no permite establecer si los resultados son aplicables a la práctica diaria; la exclusión de pacientes que mejoran los flujos espiratorios (VEF 1 ) frente a los broncodilatadores 12 ; y el análisis de grupos pequeños de pacientes 13,14 . De acuerdo con estos antecedentes, el propósito del presente trabajo fue estudiar si la administración de 200 µg de salbutamol, dosis que se emplea habitualmente para evaluar la reversibilidad en la prueba espirométrica, produce mayores cambios de volumen pulmonar que del VEF 1 en pacientes portadores de EPOC con distinto grado de severidad de la obstrucción y en etapa estable de la enfermedad.…”