Chronic obstructive pulmonary disease and severe pneumonia

In the present issue of the Journal, Fujii et al. report the difficulty of weaning elderly patients who have been diagnosed with community-acquired pneumonia with emphysematous changes in thoracic computed-tomography (CT) scans of the chest and/or a low concentration of serum albumin from mechanical ventilation.1 As the authors mentioned in the article, the proportion and number of elderly adults ≥65 years-of-age is increasing in Japan. Pneumonia is the fourth most common cause of death in Japan, and the majority of deaths as a result of pneumonia are among people aged ≥65 years. Fukuchi et al. reported a high prevalence of chronic obstructive pulmonary disease (COPD) in older male smokers, and that 15.7% of people aged 60–69 years and 24.4% of people aged ≥70 years were estimated to have airflow limitation.2 They also predicted further increases in the number of COPD patients over the next decade, suggesting that the number of elderly pneumonia patients who experience complications from COPD might increase in the near future. Holguin et al. have shown that the prevalence and in-hospital mortality for pneumonia, congestive heart failure, ischemic heart disease, thoracic malignancies and respiratory failure were higher in hospital discharges of patients with COPD when compared with those of patients without a diagnosis of COPD.3 That report showed that COPD is associated with higher hospitalization prevalence and in-hospital mortality from other comorbidities, and that COPD has a significant impact not only on pneumonia, but also on other conditions in terms of mortality. From this point of view, an early diagnosis and adequate treatment of COPD might be important for reducing the number of deaths as a result of pneumonia and other conditions. Several reports have shown that airway and lung infection by bacteria, including Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae, exacerbates COPD in 40–60% of cases.4–6 Bacterial infection causes severe exacerbations of COPD, requiring mechanical ventilation,6 as shown in this article.1 Infection by viruses, such as influenza in the lung, also induces secondary bacterial infection, including bacterial bronchitis and pneumonia. Mortality among COPD patients increased with the frequency of severe exacerbations, and patients with the greatest mortality risk were those with three or more acute COPD exacerbations.7 Among COPD patients with three or more exacerbations, the 5-year survival rate was less than 30%.7 Bacterial infection induces various inflammatory factors, such as interleukin-8, in airways. These factors can accumulate and stimulate neutrophils in airways to release elastase, and induce mucosal epithelial damage, mucus hypersecretion and smooth muscle contraction, thus limiting airflow.8 Bacterial infection in alveoli might also cause injury of epithelial cells and affect barrier functions between the alveolar epithelial cells. Injury of the alveolar wall by bacterial infection might induce fluid accumulation and plasma exudation in the alveolar space. These pathological mechanisms might cause COPD exacerbations,8 and severe hypoxia and/or hypercapnea in COPD patients, requiring mechanical ventilation. Thus, severe respiratory failure in COPD might be related to difficulty in weaning from mechanical ventilation. Malnutrition status in COPD patients has been reported in patients with decreased body mass index (BMI), fat-free mass (FFM) and serum albumin concentrations.9,10 FFM was correlated with forced expiratory volume in 1 s, and forced vital capacity and distance walked in 6 min. The number of days of hospitalization was inversely related to FFM, muscle mass, BMI, serum albumin concentrations10 and bodyweight.11 In contrast, severe COPD and aging were independent and concurrent conditions leading to malnutrition.12 COPD severity was also negatively correlated with increases in mobility, patient's perception of their own nutritional and health status, and arm and calf circumferences.12 Furthermore, Ranieri et al. showed that malnutrition, severity of exacerbation and disability status could be identified as risk factors associated with mortality in elderly patients admitted for COPD exacerbations.13 These findings suggest that malnutrition, including low serum albumin levels, might be associated with length of hospitalization, mortality and difficulty of weaning from mechanical ventilation in COPD exacerbations, as shown by the authors.1 Increased levels of nutritional status, such as serum albumin, improve immunological function,14 and appropriate nutritional management improves the survival rate in patients after surgical treatment,15 as the authors mentioned. These findings also suggest that nutritional status is an important predictor of the efficacy of treatment for pneumonia and respiratory failure using antibiotics and mechanical ventilation in patients with COPD. Recent studies have shown that pneumococcal vaccination reduces the mortality rate in elderly people16 and frequency of pneumonia in COPD patients.17 Furumoto et al. showed an additive effect of pneumococcal vaccine and influenza vaccine on acute exacerbation in patients with chronic lung disease, including COPD.18 We also showed that pneumococcal vaccination reduces the frequency of fever, exacerbations, pneumonia and hospitalization in COPD patients with repetitive pneumonia and exacerbations.19 We reported that more than 50% of elderly adults with pneumonia were shown to have cerebral infarction using CT scans and magnetic resonance of their brains.20 The swallowing reflex and cough reflex were shown to be altered in pneumonia patients with cerebral infarction, and administration of an angiotensin-converting enzyme (ACE) inhibitor improved the swallowing reflex.21 When an ACE inhibitor, imidapril, either amantadine or cilostazol, was given, the incidence of pneumonia was reduced.22–24 COPD has been reported to be a risk factor for stroke,25 as well as cardiovascular disease. Therefore, these agents, including imidapril, amantadine and cilostazol, might also be effective in the prevention of pneumonia in COPD patients with cerebral infarction. Because the number of COPD patients who experience complications from pneumonia might increase in the near future, prevention of pneumonia in COPD patients might be important for decreasing the number of pneumonia-related deaths in elderly adults in Japan. Pneumococcal and influenza vaccination, as well as smoking cessation and treatment of COPD, might prevent not only pneumonia, but also COPD exacerbations, and might ultimately reduce the number of deaths as a result of pneumonia in elderly people, especially in male smokers.