A clinical study of 114 subjects examined the relationship between blood viscosity and pulmonary circulation in smokers and nonsmokers. The study population was divided into 3 groups: former smokers, current heavy smokers and nonsmokers. Measures of pulmonary circulation included pulmonary blood flow rate, pulmonary artery pressure, and right ventricular systolic pressure using echocardiography. Blood viscosity was measured using a cone-and-plate viscometer. Spirometric assessments of pulmonary function were also performed. 

Systolic blood viscosity, measured at a high shear rate of 230 s-1, was demonstrated to be significantly lower in nonsmokers (4.04±0.31 cP) than in both former smokers (4.30±0.51 cP, p<0.001) and current heavy smokers (4.41±0.47 cP, p<0.01). In addition, pulmonary blood flow was observed to be significantly higher in nonsmokers (1.21±0.34 L/min) as compared with both former smokers (1.05±0.25 L/min, p<0.01) and current heavy smokers (1.00±0.16 L/min, p<0.001). 

The study authors highlighted a significant relationship between blood viscosity, hematocrit, smoking, age, urea, and spirometric parameters. Even after adjustment for hematocrit, blood viscosity was found to correlate with the following parameters (i) age, smoking, urea, cholesterol, and white blood cell count in former smokers; (ii) age, smoking, and urea in current heavy smokers; and (iii) only with urea in nonsmokers. 

The results of this study were consistent with many previous studies showing blood viscosity (BV) to be elevated in tobacco users. The authors stated increased BV and decreased pulmonary blood flow play an important role in the progression of pulmonary hypertension (PH). PH causes cor pulmonale in chronic obstructive pulmonary disease (COPD) patients and has a prognostic relevance in chronic obstructive pulmonary disease (COPD) patients in the progression of pulmonary hypertension (PH). PH causes cor pulmonale in chronic obstructive pund to lood viscositto, the stage prior to the development of PH.” 


Cakmak G, Alkan FA, Korkmaz K, et al. Blood viscosity as a forgotten factor and its effect on pulmonary flow. Translational Respiratory Medicine 2013; 1:1-5.