This study addresses the hypothesis that patients with obstructive sleep apnea, who exhibit recurrent episodes of oxygen desaturation at night, have higher hematocrit levels than nonapneic control subjects. We prospectively studied 624 patients referred to the sleep disorders center at St. Michael's Hospital because of suspicion of sleep apnea. All patients had nocturnal polysomnography and mea...

Equations of blood viscosity provide a prediction of the 'optimal' hematocrit' (hct) as the hct resulting in the highest value of the bell-shaped curve of hematocrit/viscosity ratio h/η. We investigated if overweight and obesity have an influence on these parameters. We compared 32 normal weight subjects, 40 overweight (BMI 25-30) and 38 obese subjects. There was no difference in the theoretica...

Most observers have found that when circulating red cell volume is deduced from measurement of plasma volume and venous hematocrit a higher value is obtained than when the red cell volume is measured directly. It is widely believed that this is because the proportion of red cells in the blood in large vessels is higher than that in the body as a whole and various correction factors have been pr...

The cut off for hemoglobin or hematocrit that indicates the need for an isotopic red cell mass study was investigated in 179 patients with a presumptive diagnosis of polycythemia vera or essential thrombocythemia. Hematocrit showed better diagnostic accuracy than hemoglobin. Hemoglobin over 18.5 g/dL in males or over 16.5 g/dL in females showed a high specificity indicating that red cell mass s...

Because of complicated rheological issues related with sickle cell blood, there exists a practical need to rationally determine critical hematocrit in transfusions for sickle cell patients. In this research, two major effects, i.e. oxygen concentration and hematocrit, are considered in a theoretical hydrodynamic model incorporating oxygen transport and lubrication theory. The pressure drop depe...

TO THE EDITOR: We appreciate the approach of Drs. Stark and Schuster (13) to elaborate a systematic foundation of the optimal hematocrit concept on physics. However, some corrections and additional information are necessary. It is important to note that the empirical description of Pries et al. (7)—in contrast to the theoretical approaches for bulk viscosity—is based on experiments for tube flo...