Impact of anaemia on lung function and exercise capacity in patients with stable severe chronic obstructive pulmonary disease

OBJECTIVE This study intended to search for potential correlations between anaemia in patients with severe chronic obstructive pulmonary disease (COPD; GOLD stage III) and pulmonary function at rest, exercise capacity as well as ventilatory efficiency, using pulmonary function test (PFT) and cardiopulmonary exercise testing (CPET). SETTING The study was undertaken at Shanghai Pulmonary Hospital, a tertiary-level centre affiliated to Tongji University. It caters to a large population base within Shanghai and referrals from centres in other cities as well. PARTICIPANTS 157 Chinese patients with stable severe COPD were divided into 2 groups: the anaemia group (haemoglobin (Hb) <12.0 g/dL for males, and <11 g/dL for females (n=48)) and the non-anaemia group (n=109). PRIMARY AND SECONDARY OUTCOME MEASURES Arterial blood gas, PFT and CPET were tested in all patients. RESULTS (1) Diffusing capacity for carbon monoxide (DLCO) corrected by Hb was significantly lower in the anaemia group ((15.3±1.9) mL/min/mm Hg) than in the non-anaemia group ((17.1±2.1) mL/min/mm Hg) (p<0.05). A significant difference did not exist in the level of forced expiratory volume in 1 s (FEV1), FEV1%pred, FEV1/forced vital capacity (FVC), inspiratory capacity (IC), residual volume (RV), total lung capacity (TLC) and RV/TLC (p>0.05). (2) Peak Load, Peak oxygen uptake (VO2), Peak VO2%pred, Peak VO2/kg, Peak O2 pulse and the ratio of VO2 increase to WR increase (ΔVO2/ΔWR) were significantly lower in the anaemia group (p<0.05); however, Peak minute ventilation (VE), Lowest VE/carbon dioxide output (VCO2) and Peak dead space/tidal volume ratio (VD/VT) were similar between the 2 groups (p>0.05). (3) A strong positive correlation was found between Hb concentration and Peak VO2 in patients with anaemia (r=0.702, p<0.01). CONCLUSIONS Anaemia has a negative impact on gas exchange and exercise tolerance during exercise in patients with severe COPD. The decrease in amplitude of Hb levels is related to the quantity of oxygen uptake.