Muscle wasting occurs rapidly in the ICU setting. Ultrasonography is a useful surrogate measure for identifying future impairment. Vastus intermedius may be an important muscle to monitor in the future because it demonstrated the greatest change in muscle quality and had the strongest relationship to volitional measures.

Extracellular matrix (ECM) composition has an important role in determining airway structure. We postulated that ECM lung composition of chronic obstructive pulmonary disease (COPD) patients differs from that observed in smoking and nonsmoking subjects without airflow obstruction.We determined the fractional areas of elastic fibres, type-I, -III and -IV collagen, versican, decorin, biglycan, lumican, fibronectin and tenascin in different compartments of the large and small airways and lung parenchyma in 26 COPD patients, 26 smokers without COPD and 16 nonsmoking control subjects.The fractional area of elastic fibres was higher in non-obstructed smokers than in COPD and nonsmoking controls, in all lung compartments. Type-I collagen fractional area was lower in the large and small airways of COPD patients and in the small airways of non-obstructed smokers than in nonsmokers. Compared with nonsmokers, COPD patients had lower versican fractional area in the parenchyma, higher fibronectin fractional area in small airways and higher tenascin fractional area in large and small airways compartments. In COPD patients, significant correlations were found between elastic fibres and fibronectin and lung function parameters.Alterations of the major ECM components are widespread in all lung compartments of patients with COPD and may contribute to persistent airflow obstruction.

The importance of the adaptive immune response, specifically the role of regulatory T (Treg) cells in controlling the obstruction progression in smokers, has been highlighted. To quantify the adaptive immune cells in different lung compartments, we used lung tissues from 21 never-smokers without lung disease, 22 current and/or ex-smokers without lung disease (NOS) and 13 current and/or ex-smokers with chronic obstructive pulmonary disease (COPD) for histological analysis. We observed increased T, B, IL-17 and BAFF cells in small and large airways of COPD individuals; however, in the NOS, we only observed increase in T and IL-17 cells only in small airways. A decrease in the density of Treg, TGF-β and IL-10 in small and large airways was observed only in COPD individuals. In the lymphoid tissues, Treg, T,B-cells and BAFF cells were also increased in COPD; however, changes in Treg inhibitory associated cytokines were not observed in this compartment. Therefore, our results suggest that difference in Treg cell distributions in lung compartments and the decrease in TGF-β and IL-10 cells in the airways may lead to the obstruction in smokers.

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In asthma, ECM in ASM is related to the dynamics of airway function in the absence of differences in ECM expression between asthma and controls. This indicates that the ASM layer in its full composition is a major structural component in determining variable airways obstruction in asthma.