Pulmonary characteristics in COPD and mechanisms of increased work of breathing

J Appl Physiol (1985). 2009 Jul;107(1):309-14. doi: 10.1152/japplphysiol.00008.2009. Epub 2009 Apr 9.


Mechanical characteristics and gas exchange inefficiencies of the lungs contribute to increased work of ventilation in chronic obstructive pulmonary disease (COPD) at rest and exercise, and the energy cost of ventilation is increased in COPD at any external work level. Assuming typical ventilatory variables and respiratory characteristics, we estimated the relative contributions of inspiratory and expiratory resistance, dynamic elastance, intrinsic positive end-expiratory pressure, and gas exchange inefficiency to the work of breathing, finding that the last of these is likely to be of major importance. Dynamic hyperinflation can be seen as both an impediment to inspiratory muscle function and an essential component of adaptation to severe obstruction. Extrinsic restriction, in which the chest wall fails to achieve and maintain abnormally high lung volumes in COPD, can limit ventilatory function and contribute to disability.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Humans
  • Lung / physiopathology*
  • Pulmonary Disease, Chronic Obstructive / physiopathology*
  • Pulmonary Gas Exchange
  • Respiratory Mechanics*
  • Respiratory Muscles / physiopathology*
  • Thoracic Wall / physiopathology
  • Work of Breathing*