Phenomenological characterization of blood's intermediate shear rate: a new concept for hemorheology.

The phenomena of aggregation, breakdown, and disaggregation of the rouleaux of red blood cells (RBCs) in addition to deformability affect the human blood viscosity at different shear rates. In this study, the intermediate shear rate is introduced and defined when the effect of aggregation on the change of blood viscosity is diminished; and afterwards, the alteration in the blood viscosity is dominantly affected by the deformation of RBCs. With this respect, modeling the effective parameters on the blood shear-thinning behavior including hematocrit and plasma viscosity was performed for the two different shear regions discriminated by the proposed intermediate shear rates. The presented rheological model reflects a phenomenological approach to assess the human blood viscosity with an average error of ± 5% compared to experimental data for hematocrits between 0.299 and 0.702, subjected to various shear rates from 0.2 to 680 1/s. The temperature changes as well as biochemical effects on whole blood viscosity are characterized by the introduced plasma viscosity-dependent model. The presented comprehensive model could be used for better understanding of blood flow hemodynamics and analyzing the shear dependence of aggregation and deformability behaviors of RBCs.

Total pulmonary artery atresia associated with abnormal pulmonary venous drainage as a rare presentation of scimitar syndrome.

Scimitar syndrome or pulmonary venolobar syndrome is a rare, complex, and variable malformation of the right lung characterized by an abnormal right sided pulmonary drainage into the inferior vena cava, malformation of the right lung, abnormal arterial supply, and sometimes cardiac malformation. Despite the varying degrees of pulmonary hypoplasia and pulmonary artery hypertension, about half of the patients with scimitar syndrome are asymptomatic or mildly symptomatic when the diagnosis is made. Neonates have severe symptoms and worse prognosis while older children come to light because of recurrent respiratory infections, heart murmur, or an abnormal chest radiograph.