HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Orozco-Levi, M. Search for Related Content PubMed Articles by Orozco-Levi, M.

Structure and function of the respiratory muscles in patients with COPD: impairment or adaptation?

CORRESPONDENCE: M. Orozco-Levi, Muscle Research Unit, Servei de Pneumologia, Hospital del Mar, Institut Municipal d'Investigació Mèdica (IMIM), CEXS-Universitat Pompeu Fabra, Carrer Dr. Aiguader, 80, Barcelona, E-08003, Spain. Fax: 34 932213237. E-mail: morozco@imim.es

Keywords: adaptation, chronic obstructive pulmonary disease, function, impairment, respiratory muscles, structure

Received: June 30, 2003
Accepted June 30, 2003

Respiratory muscles are essential to alveolar ventilation. These muscles work against increased mechanical loads due to airflow limitation and geometrical changes of the thorax derived from pulmonary hyperinflation. Respiratory muscle fibres show several degrees of impairment in cellular and subcellular structures which, in many cases, are proportional to the severity of the disease and accompanying conditions (ageing, deconditioning, starvation, comorbidity). This structural impairment translates, from the functional point of view, to a loss of strength (capacity to generate tension) and an increased susceptibility to failure in the face of a particular load (early onset of fatigue).

On the other hand, there is accumulating evidence that the diaphragm and other respiratory muscles are also able to express adaptive changes in response to the chronic mechanical load imposed by the disease. In most cases, impairment and adaptation of the respiratory muscles reaches a balance that permits enough ventilation for patients' survival. However, this balance can be altered for additional increments of the mechanical or metabolic load on the muscles (e.g. abdominal or thoracic surgeries, pneumonia, pulmonary embolism, etc.). Moreover, loss of balance is not always associated with extreme situations. Many patients develop ventilatory failure and require hospital admission even if the cause of the exacerbation is less dramatic (bronchial infections, pain of any nature, electrolyte disturbances, etc.).

Although the physiopathology of chronic obstructive pulmonary disease exacerbations is multifactorial, the above-mentioned fragility suggests the existence of a "fragile balance" between respiratory muscle overload and respiratory muscle adaptations. Assessment of respiratory muscle function through specific tests evaluating the strength and endurance could offer valuable information about this particular susceptibility to muscle imbalance. Identification of patients possessing a fragile respiratory muscle balance could have important implications for the application of specific strategies such as respiratory muscle training, nutrition, or anabolic treatment.

This article has been cited by other articles:

				L. M. Fabbri, F. Luppi, B. Beghe, and K. F. Rabe Complex chronic comorbidities of COPD Eur. Respir. J., January 1, 2008; 31(1): 204 - 212. [Abstract] [Full Text] [PDF]

				M. Doucet, R. Debigare, D.R. Joanisse, C. Cote, P. LeBlanc, J. Gregoire, J. Deslauriers, R. Vaillancourt, and F. Maltais Adaptation of the diaphragm and the vastus lateralis in mild-to-moderate COPD Eur. Respir. J., December 1, 2004; 24(6): 971 - 979. [Abstract] [Full Text] [PDF]