Objective To investigate the correlations of diaphragm function parameters, hypoalbuminemia, decoy receptor 3 (DcR3) and D-dimer (D-D) with disease severity and treatment outcomes of elderly patients with chronic obstructive pulmonary disease (COPD) complicated by respiratory failure.

Methods A total of 118 elderly COPD patients with respiratory failure were selected as study subjects. Patients were divided into mild (n=27), moderate (n=51) and severe (n=40) groups based on arterial oxygen partial pressurep_a(O₂). Diaphragm function parameters, DcR3, D-D and hypoalbuminemia were compared among the three groups. Based on the treatment outcomes at 28 days, patients were further divided into treatment success group (n=87) and treatment failure group (n=31). Univariate and multivariate analyses were performed to assess the correlations of diaphragm function parameters, hypoalbuminemia, DcR3, and D-D with adverse outcomes.

Results The diaphragm mobility and diaphragm movement area of patients in the severe group were significantly lower or smaller than those in the moderate group and the mild group(P < 0.05); the diaphragm mobility and diaphragm movement area of patients in the moderate group were significantly lower or smaller than those in the mild group (P < 0.05). The proportions of patients with DcR3, D-D and hypoproteinemia in the severe group were significantly higher than those in the moderate and mild groups, and the DcR3 and D-D in the moderate group were significantly higher than those in the mild group (P < 0.05). The age, Acute Physiological Function and Chronic Health Evaluation Ⅱ (APACHE Ⅱ) score, N-terminal pro-brain natriuretic peptide (NT-proBNP) and the proportion of patients with coronary heart disease in the treatment failure group were significantly higher than those in the treatment success group (P < 0.05). The diaphragm mobility in the treatment failure group was significantly lower than that in the treatment success group, and the diaphragm movement area was smaller than that in the treatment success group (P < 0.05). The proportions of patients with DcR3, D-D and hypoproteinemia in the treatment failure group were significantly higher than those in the treatment success group (P < 0.001). Older age, higher APACHE Ⅱ score, higher NT-proBNP, combined with coronary heart disease, higher DcR3, higher D-D level, hypoproteinemia, decreased diaphragm mobility and reduced diaphragm motor area were independent risk factors for adverse treatment outcomes in elderly patients with COPD complicated with respiratory failure (P < 0.05).

Conclusion In elderly COPD patients with respiratory failure, reduced diaphragm mobility, decreased diaphragm motion area, elevated DcR3 and D-D levels and the presence of hypoalbuminemia are associated with more severe disease conditions.