Questions: 

Chronic obstructive pulmonary disease (COPD) has recently been viewed as an inflammation-dependent systemic disease, which may affect erythrocyte integrity. Furthermore studies show changes in erythrocyte membrane caused by oxidative stress in COPD-patients. However, red cell deformability is an important parameter for passing the (lung) capillaries and thus for oxygen uptake is. The present study investigated, whether erythrocyte deformability is altered in COPD-patients under basal conditions and after acute exercise and whether an exercise intervention may influence erythrocyte flexibility of COPD-patients in the longterm. In addition, we measured oxidative and nitrosative stress.

Methods: 

11 non-oxygen dependent COPD patients (5 male, 6 female, age: 62.6±4.2 years, BMI: 25.4±6.8 kg/m², COPD-Stadium I-II) performed a bicycle ergometer test (WHO-scheme) until subjective exhaustion before and after a 3 months COPD-exercise intervention (1x/week weight training (60 minutes), 1x/week moderate cardiovascular training (90 min.)). Erythrocyte flexibility (laser assisted rotational optical analyser (LORCA®) were measured in erythrocytes isolated from venous blood samples (EDTA) taken before, directly after as well as 30 minutes after the bicycle ergometer test). 13 men without COPD (age: 53.7±4.2 yrs, BMI: 30.0±2.5 kg/m²) were tested for reference.

Results: 

COPD-patients reached a maximal workload of 59.1±32.2 W at a mean maximal heart frequency of 121±20 bpm before training (i.e. 47±26% of the age-adjusted workload at full cardiovascular load). Maximal lactate concentration was 3.98± 1.25 mM. In comparison the age adjusted reference group reached maximal workload of 165.4±24.0 W at a maximal lactate concentration of 5.7±2.2 mM. Erythrocyte elongation index was significantly increased at low and high shear stress in COPD patients before the exercise intervention compared to the values of the reference group. Shear stress sensitivity as measured by the pressure needed to achieve a 50% deformation was similar in both groups under all conditions. The COPD-training intervention did not significantly alter maximal workload (65.9±34.1 W) and maximal lactate concentration (3.7±1.5 mM) in COPD patients. However, elongation index was significantly decreased under low and high shear forces and reached similar values as measured in the reference group. Erythrocyte elongation index parameters did not change during acute exercise in the COPD- as well as the reference group before respectively after the exercise intervention.

Conclusions: 

The increased elongation index of the COPD patients before the training intervention may indicate a loss of erythrocyte shape stability. A COPD-exercise intervention may help to improve erythrocyte shape which may improve oxygen uptake and thus life quality in COPD.