Vital capacities in acute and chronic airway obstruction: dependence on flow and volume histories

Abstract

Vital capacities in acute and chronic airway obstruction: dependence on flow and volume histories. V. Brusasco, R. Pellegrino, J.R. Rodarte. ©ERS Journals Ltd 1997. ABSTRACT: The aim of this study was to investigate whether measurements of vital capacity (VC) are affected by the direction of the manoeuvre (inspiratory vs expiratory) and by the rate of expiratory flow.The study was performed on 25 individuals with chronic airway obstruction (CAO) and a forced expiratory volume in one second (FEV1) (expressed in standardized residuals (SR)) of -2.0±1.4 SD (CAO group), and 10 asthmatic subjects with methacholine (MCh)-induced bronchoconstriction (FEV1 -2.3±1.02 SR) (MCh group). VCs were measured during fast inspiration following both slow (FIVCse) and forced (FIVCfe) expiration from end-tidal inspiration to residual volume (RV), and during slow (EVC) or forced (FVC) expiration from total lung capacity (TLC).In the CAO group, FVC was the smallest volume These data suggest that both flow and volume histories contribute to decreased vital capacities during bronchoconstriction. However, whereas increasing expiratory flow always tends to decrease vital capacity, the volume history of full inflation has different effects in chronic and acute bronchoconstriction, probably due to different effects on airway calibre. These results stress the importance of using standardized manoeuvres in order to obtain comparable values of vital capacity. Eur Respir J 1997; 10: 1320-1320 Vital capacity (VC) is defined as the maximum amount of air that can be mobilized with a single expiratory or inspiratory manoeuvre, i.e. the difference between total lung capacity (TLC) and residual volume (RV) [1, 2]. Hence, the size of VC depends on the determinants both of TLC and RV. In patients with airway obstruction, dynamic factors (flow limitation, airway closure) are determinants of RV [3,4]. Therefore, it can be hypothesized that factors influencing airway calibre may also influence RV and, by inference, VC.A previous volume history of deep inhalation may cause changes in airway calibre, the direction and magnitude of which depend on the site and the mechanism of airway obstruction [5][6][7][8][9][10]. Moreover, the RV attained after a forced expiration changes according to the direction and the magnitude of the bronchomotor effect of deep inhalation [11,12]. Based on these data, it may be expected that the size of VC measured from expiratory or inspiratory manoeuvres would differ. Furthermore, under conditions where RV is determined by dynamic factors occurring in the airways, it might be expected that changing expiratory flow would also affect the measurement of VC.The aim of this study was to investigate the extent to which flow and volume histories may affect VC measurements. To this end, VC values obtained with expiratory or inspiratory manoeuvres and with inspiratory manoeuvres preceded by forced or slow exhalations to RV were compared. Methods SubjectsTwo groups of subjects, whose anthropometric and pulmonary function data are presented ...

Interpretative strategies for lung function tests

“…This committee feels that the advantage of using VC in place of FVC is that the ratio of FEV1 to VC is capable of accurately identifying more obstructive patterns than its ratio to FVC, because FVC is more dependent on flow and volume histories [61]. In contrast with a fixed value of 0.7, the use of the 5th percentile does not lead to an overestimation of the ventilatory defect in older people with no history of exposure to noxious particles or gases [62].…”

“…The effects of anatomical or functional lesions on maximum flows depend on the site of the obstruction, kind of lesion (variable or fixed) and the extent of anatomical obstruction [61,127,130]. Typical cases of extra-and intrathoracic central or upper airway obstruction are reported in figures 3 and 4.…”

“…FVC). The FVC is usually reduced more than IVC or SVC in airflow obstruction [61]. The FEV6 may be substituted for VC if the appropriate LLN for the FEV1/FEV6 is used (from the NHANES III equations) [12,63].…”

Standardisation of spirometry

“…IVC) and expiratory (i.e. EVC) manoeuvres may be observed in patients with airways obstruction [43,44].…”

Airway inflammation in COPD: physiological outcome measures and induced sputum

“…Two-thirds of the patients responded with changes in V9p30 or IC. Flow and volume history in VC manoeuvres can alter airway calibre and FEV1 contributes to the performance of these measurements [34,35]. Of the two, IC appears to be the best available choice because it can be measured easily with most laboratory spirometers.…”