Acute changes of lung volumes and lung mechanics in asthma and in normal subjects.

Abstract

(1978). Thorax, 33,[394][395][396][397][398][399][400] Acute changes of lung volumes and lung mechanics in asthma and in normal subjects. Lung volumes, pulmonary mechanics, and specific airway conductance (sGaw) were studied before and 15 minutes after 200 ,ug of aerosol salbutamol in nine asthmatics undergoing mild spontaneous exacerbations of their disease and in five normal subjects. In addition, three of the normal subjects were studied after voluntarily breathing at high lung volumes for one minute.The normal subjects and four of the asthmatics showed no overall changes in lung volumes or pressure-volume (PV) curves after salbutamol, even though airway dilatation was produced in the asthmatic subjects. In another five asthmatics, salbutamol induced a significant fall in the total lung capacity (TLC) in three, and in the residual volume and functional residual capacity in all five. There was a significant displacement of the PV curve downwards and to the right in all five, with increased lung compliance (Cl stat) in two.The fall in TLC could be accounted for by the increase in lung elasticity. There is reason to believe that this change in lung mechanics could be due to the reversal of asthma-induced stress relaxation.Sustained breathing at high lung volume is known to cause stress relaxation of the lung. However, this breathing pattern did not alter the PV curve or TLC in two of three normal subjects, which is consistent with stress relaxation being rapidly reversible. The other normal subject had an acute shift of the PV curve upwards and to the left after breathing at high lung volume. It has been concluded that stress relaxation is usually rapidly reversed but that in some individuals it may only be slowly reversed. This more persistent form of stress relaxation may contribute to the acute changes of TLC found in some asthmatics.

Assessing the effect of deep inhalation on airway calibre: a novel approach to lung function in bronchial asthma and COPD

“…Yet, the absolute starting lung volume for the partial expiratory manoeuvre may still be kept constant if the IC is measur-ed approximately 2 min before the partial manoeuvre in order to calculate the new volume between EELV and the desired percentage of control FVC. This technique as-sumes that TLC does not change systematically during a bronchoconstrictor or bronchodilator challenge, which is a reasonable assumption [45,46]. Both curves should have sharp peak expiratory flow (PEF), to indicate that the effort was maximal and possibly that gas compression was similar during the two manoeuvres.…”

Response of Lung Volumes to Inhaled Salbutamol in a Large Population of Patients With Severe Hyperinflation

“…On the other hand, one small series of asthmatic subjects demonstrated a reduction of TLC after bronchodilator administration. 13 An understanding of the effects of bronchodilators on lung volumes is important, as hyperinflation is responsible for much of the increased work of breathing and dyspnea seen in patients with obstructive lung diseases.…”

Lung elastic recoil during breathing at increased lung volume

“…We are unaware of any previous study reporting elastic recoil during voluntary increases in mean lung volume. In a previous study of static deflation P-V curves from TLC after subjects breathed for 45-60 s at very high mean lung volumes, one of three normal subjects showed a decrease in the static lung recoil pressure, but the other two did not (8). Several studies have shown decreases in TLC and increases in static deflation elastic recoil at constant lung volume after relief of bronchoconstriction with beta agonist (4, 7).…”