Effect of Preceding Inspiratory Speed and End-Inspiratory Pause on Forced Expiratory Manoeuvre in Healthy Subjects and Chronic Obstructive Pulmonary Disease Patients

Abstract

Background: Lower peak expiratory flow (PEF) and forced expiratory volume in 1 s (FEV₁) have been consistently found after slow inspiration with end-inspiratory pause (EIP). Objectives: It was the aim of this study to establish the respective influence of the speed of preceding inspiration (SPI) and EIP on the parameters obtained from the following expiratory forced vital capacity (FVC) manoeuvre. Methods: In 8 healthy subjects and 12 patients with chronic obstructive pulmonary disease (COPD), a number of inspirations with different SPI and EIP were performed. In the subsequent FVC manoeuvre, maximal expiratory flows, including PEF, and maximal expired volumes at different times, including FEV₁, were measured. For each FVC manoeuvre, peak expiratory time, expired volume at PEF (as % of FVC), flow limitation by the negative expiratory pressure technique and FVC were checked to be sure of achieving a similar expiratory effort and starting inflation lung volume. Results: The highest values of PEF and FEV₁ were found in normal subjects and COPD patients after fastest SPI without EIP (p < 0.001). In normal subjects, no significant PEF and FEV₁ changes during FVC manoeuvre were observed with different SPI, in the absence of EIP. In contrast, inspirations with slower SPI (inspiratory time >2 s) without EIP were followed by lower PEF in COPD patients (p < 0.05). As compared with inspirations without EIP, those with a presence of EIP were invariably followed by lower PEF and FEV₁, both in normal subjects and in COPD patients (p < 0.05). Conclusions: The effect of SPI on subsequent PEF and FEV₁ is irrelevant in healthy subjects as well as in COPD patients, unless SPI is too slow (inspiratory time >2 s), while any EIP decreases these indices in all individuals.