Airway hysteresis in normal subjects and individuals with chronic airflow obstruction

Abstract

Specific conductance (sGaw) was measured without prior pharmacological induction of bronchoconstriction before and 5-10 s after a total lung capacity (TLC) volume history in normal subjects and in individuals with chronic airflow obstruction (CAO); increased sGaw after inspiration to TLC was considered evidence of airway hysteresis. Lung elastic recoil [Pst(L)] was also measured before and after inspiration to TLC. In the normal subjects 1) prebronchodilator sGaw increased significantly, whereas Pst(L) decreased significantly after inspiration to TLC; 2) modulators of cyclooxygenase activity had no significant effects on sGaw responses to deep inspiration; and 3) airway hysteresis diminished after inhalation of atropine or metaproterenol. In the CAO group 1) prebronchodilator sGaw and Pst(L) decreased significantly after inspiration to TLC, and 2) bronchoconstriction after deep inspiration diminished after inhalation of atropine or metaproterenol. This study demonstrates that normal airways exhibit hysteresis even without alteration of resting airway tone and that airway hysteresis is impaired in CAO.

Physiological techniques for detecting expiratory flow limitation during tidal breathing

“…In fact, there is not a single maximal flow-volume curve but rather a family of different curves, which depend on the time course of the inspiration preceding the FVC manoeuvre [35][36][37]. 4) Respiratory mechanics and time constant inequalities are different during the tidal and maximal expiratory efforts, again making comparisons of the two flow-volume curves problematic [38][39][40]. 5) Exercise may result in bronchodilation or bronchoconstriction and other changes of lung mechanics, which may also affect correct comparisons of the two flow-volume curves [41].…”

Interpretative strategies for lung function tests

“…Among them are the volume history effects of the deep breath preceding the forced expiratory manoeuvre on the bronchial tone and, thus, calibre [94][95][96][97][98], and the inability of these parameters to detect whether tidal breathing is flow limited or not [99][100][101][102]. The FEV1/VC ratio should not be used to determine the severity of an obstructive disorder, until new research data are available.…”

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

“…The reason for this discrepancy was unclear, but the effect of the deep inhalation to TLC on airway calibre when VC was measured as maximal expiration might have played a role. Indeed, it was recently shown that airway calibre is decreased after a full inflation in some patients with CAO [7]. Conversely, during induced bronchoconstriction, a full inflation increases airway calibre and reduces RV after a forced expiratory manoeuvre [11].…”

“…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].…”

“…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].…”