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The natural history of lung hyperinflation in patients with airway obstruction is unknown. In particular, little information exists about the extent of air trapping and its reversibility to bronchodilator therapy in those with mild airway obstruction. We completed a retrospective analysis of data from individuals with airway obstruction who attended our pulmonary function laboratory and had plethysmographic lung volume measurements pre- and post-bronchodilator (salbutamol). COPD was likely the predominant diagnosis but patients with asthma may have been included. We studied 2,265 subjects (61% male), age 65 ± 9 years (mean ± SD) with a post-bronchodilator FEV1/FVC <0.70. We examined relationships between indices of airway obstruction and lung hyperinflation, and measured responses to bronchodilation across subgroups stratified by GOLD criteria. In GOLD stage I, vital capacity (VC) and inspiratory capacity (IC) were in the normal range; pre-bronchodilator residual volume (RV), functional residual capacity (FRC) and specific airway resistance were increased to 135%, 119% and 250% of predicted, respectively. For the group as a whole, RV and FRC increased exponentially as FEV1 decreased, while VC and IC decreased linearly. Regardless of baseline FEV1, the most consistent improvement following bronchodilation was RV reduction, in terms of magnitude and responder rate. In conclusion, increases (above normal) in airway resistance and plethysmographic lung volumes were found in those with only minor airway obstruction. Indices of lung hyperinflation increased exponentially as airway obstruction worsened. Those with the greatest resting lung hyperinflation showed the largest bronchodilator-induced volume deflation effects. Reduced air trapping was the predominant response to acute bronchodilation across severity subgroups. [ABSTRACT FROM AUTHOR]

The article presents a study by the Respiratory Clinical Research Unit of the Montreal Chest Institute, McGill University Health Center in Canada which associated hyperpnea and hyperinflation as a contributor to energy demands in chronic obstructive pulmonary disease (COPD). The study compared the total-body energy demands of the internal and external work of cycling and delta mechanical efficiency with COPD while characterizing dynamic hyperinflation. Moreover , results of the study shows that bioenergetics of submaximal cycling is not compromised in moderately severe COPD despite tachypnea and dynamic hyperinflation.

The article focuses on the adequacy of the central and peripheral circulatory response of patients with chronic pulmonary disease to exercise. It has been suggested that ventricular filling may be impaired by dynamic hyperinflation and the resulting intra-thoracic pressure changes. Others propose that peripheral blood flow to exercising skeletal muscles may be limited due to a respiratory muscle steal phenomenon.