The ‘Dark Side' of Chronic Obstructive Pulmonary Disease

contraction, either thickness or flattening or motion, could provide relevant information on respiratory mechanics and functional capacity to improve diagnosis formulation and evaluate the progression of COPD. Traditional respiratory functional tests mainly assess downstream airflow limitations in COPD patients. By contrast, the diaphragm represents the less explored ‘side’ of the COPD, being affected by the upstream effects of airway obstruction (local overload), other than systemic imbalance. In this issue of Respiration , Smargiassi et al. [3] propose ultrasonography (US) in detecting diaphragm thickness and thickening at different lung volumes in a consecutive series of patients with COPD. The relationship between US measurements and parameters of respiratory function and body composition is computed. All diaphragm thickness measures are found positively related to fat-free mass. As regards lung volumes, diaphragm thickness at total lung capacity is found to be closely related to the inspiratory capacity. Moreover, there is a significant negative association between the values for diaphragm thickening and the air trapping indices. The authors propose that the assessment of the diaphragm is a useful tool to study the progression of the disease in COPD patients in terms of lung hyperinflation and loss of fat-free mass. The utility of US in the evaluation of diaphragm function in COPD has previously been established, and it will Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide, accounting for a major healthcare problem. It is characterized by incompletely reversible airway obstruction with airway inflammation and remodeling as initial pathological lesions. Accordingly, functional and anatomical changes in different compartments of the lungs occur, leading to air trapping and pulmonary hyperinflation and imposing an excessive load on the respiratory muscles. Other than these complex mechanical lung changes, increasing evidence indicates that COPD results in important systemic manifestations due to inflammation, gas exchange abnormalities, nutritional imbalance, comorbidity and chronic steroid administration, which might affect skeletal muscle performance, including diaphragm function [1] . Spirometry has universally been recognized as the gold standard for the diagnosis of COPD. However, it is accepted that a single measurement of FEV 1 incompletely represents the complex clinical picture of COPD. Therefore, the evaluation of additional parameters is recommended in order to assess the respiratory and systemic consequences of COPD [2] . The diaphragm is the principal generator of tidal volume in normal subjects at rest. A reduction in diaphragm mobility has been identified in patients with COPD and has been associated with a decline in pulmonary function parameters. Therefore, the assessment of diaphragmatic Published online: April 11, 2014