Factors Related to Cardiopulmonary Endurance of Hospitalized Older Adults With Chronic Obstructive Pulmonary Disease

Background: Chronic Obstructive Pulmonary Disease (COPD) is characteristic with chronic airway inflammation and airflow obstruction, which presents as dyspnea and, chronic cough with sputum. Severe COPD with acute exacerbation needs hospitalization. Progressive and irreversible airway obstruction of COPD may result in dyspnea aggravation, malnutrition, sarcopenia, and decreased exercise capacity. Patients with COPD have not only impaired social activities but quality of life as well. The impact on family and carers for taking caregivers of COPD is substantial. Studies have shown that medical treatment, pulmonary rehabilitation, muscle training, and self-management can improve COPD symptoms and exercise capacity. However, studies investigating causes and predictor factors of cardiopulmonary endurance for COPD patients are scant.

Purpose: To explore whether and how cardiopulmonary endurance is related to age, body composition, dyspnea, respiratory muscle strength, lower limb muscle strength and endurance. In addition, we evaluated predictor factors, explanatory power and models in a sample of the elderly hospitalized with COPD.

Methods: This is a cross-sectional study design by using a random sampling in the elderly hospitalized with COPD. A total of 83 participants admitted to a chest specialist hospital with a diagnosis of COPD were enrolled in this study. We evaluated 6-minute walk distance (6MWD) for cardiopulmonary endurance, while age, sex, COPD severity, body composition, dyspnea, respiratory muscle strength, lower limb muscle strength and enduranceparameters were collected as well. We measured COPD severity by Global Initiative for Chronic Obstructive Lung Disease guideline (GOLD), body composition by body mass index (BMI), dyspnea by modified Medical Research Council dyspnea scale (mMRC), respiratory muscle strength by measuring the maximal inspiratory pressure (PImax) and the maximal expiratory pressure (PEmax), lower limb muscle strength by measuring quadriceps, and lower limb muscle endurance by measuringthe 30-s chair stand test. T test, one-way ANOVA, correlation, and multivariate regression analyses were used to evaluate association between variables and predictor factors. The study received approval from the Ethics Committee and informed consent was obtained from all study participants.

Results: A total of 83 participants participated in the study. The study patients were aged 74.01±6.93years, were male (90.63%), body composition abnormalities > 60.25%, with stage 3 mMRC (57.83%). The Cardiopulmonary endurance was significantly associated with age (r =-0.27, p = .013), respiratory muscle strength including PImax ( r = 0.54 , p ＜.001) and PEmax(r = 0.49， p ＜.001), lower limb muscle strength (r = 0.34，p = .002), lower limb muscle endurance (r = 0.64, p ＜.001), COPD severity (F =10.28, p ＜.001), and dypnesa (F =11.16, p＜.001). Mulitvariate analyses showed that cardiopulmonary endurance was associated with the severity of disease (extremely severe reference group mild) (β = ﹣42.12, p ＝.011), dypnesa (level 2 reference group level 4) (β =58.16, p ＝.001) and with lower limb muscle endurance (β = 17.35, p ＜.001). These variables can explain 53% (Adj R ²=0.53， p ＜.001) of variance in the cardiopulmonary endurance of older adults with COPD. COPD severity, dypnesa and lower limb muscle endurance were main predictive factors that explained 41% of variance (R² = 0.41, p ＜.001).

Conclusion: This study indicated that cardiopulmonary endurance was associated with age, respiratory muscle strength, lower limb muscle strength, lower limb muscle endurance, COPD severity and dypnesa. Our results may provide caregiver information to improve cardiopulmonary endurance in the elderly with COPD.

Key words: Chronic Obstructive Pulmonary Disease, the elderly, Cardiopulmonary Endurance