Pulmonary capillary perfusion within a single alveolar wall continually switches among segments, even when large-vessel hemodynamics are constant. The mechanism is unknown. We hypothesize that the continually varying size of plasma gaps between individual red blood cells affects the likelihood of capillary segment closure and the probability of cells changing directions at the next capillary ju...

Adaptation takes place not only when going to high altitude, as generally accepted, but also when going down to sea level. Immediately upon ascent to high altitude, the carotid body senses the lowering of the arterial oxygen partial pressure due to a diminished barometric pressure. High altitude adaptation is defined as having three stages: 1) acute, first 72 hours, where acute mountain sicknes...

This study was undertaken in an effort to examine the effects of selective variations in systemic hematocrit on the preglomerular. glomerular. and postglomerular microcirculation in the rat. By isovolemic exchange transfusions, systemic hematocrit (control 51 ml/ 100 ml) was either reduced (21 ml/100 ml, N = 7 rats) or elevated (62 ml/100 ml, N = 7). Single nephron glomerular filtration rate va...

Since the original publications by Martini et al. (Dtsch. Arch. Klin. Med. 169: 212-222, 1930) and Fahraeus and Lindqvist (Am. J. Physiol. 96: 562-568, 1931), it has been known that the relative apparent viscosity of blood in tube flow depends on tube diameter. Quantitative descriptions of this effect and of the dependence of blood viscosity on hematocrit in the different diameter tubes are req...

Physiological studies on fetal blood in narrow glass tubes have suggested that fetal optimal hematocrit (hct) might be as high as 60%. A theoretical 'ideal' hct can also be predicted with a theoretical curve of hematocrit/viscosity (h/η) ratio vs hct constructed with Quemada's model. We used the database of one of our previous papers on fetal hemorheology to reinterpret its results with this co...

This study was undertaken in an effort to examine the effects of selective variations in systemic hematocrit on the preglomerular. glomerular. and postglomerular microcirculation in the rat. By isovolemic exchange transfusions, systemic hematocrit (control 51 ml/ 100 ml) was either reduced (21 ml/100 ml, N = 7 rats) or elevated (62 ml/100 ml, N = 7). Single nephron glomerular filtration rate va...