The spleen may release pooled erythrocytes to the general circulation during strenuous conditions such as heavy exercise. Most of our knowledge of this reservoir function of the spleen derives from animal studies, and the splenic contribution to the circulating blood volume in humans has been regarded as unimportant. We recorded the erythrocyte content in the human spleen during graded bicycle exercise to maximal working capacity. In five normal adults 99mTc-labeled autologous erythrocytes were injected intravenously, and the subjects were placed on bicycles with the back against a gamma camera focusing on the spleen. During increasing exercise the splenic erythrocyte content decreased linearly, and at maximal work load it had been reduced to a mean of 34.2% (range 44-26%) of the initial count rate at supine rest. Concomitantly norepinephrine and epinephrine in plasma increased gradually, whereas neuropeptide Y increased only at maximal exercise. A rise in hematocrit from a mean of 44.6 to 48 was observed, but the autotransfusion of erythrocytes from the spleen only partly explains the rise in hematocrit during physical activity.

No abstract

Home mechanical ventilation (HMV) is increasingly used as a therapeutic option to patients with symptomatic chronic hypoventilation. There is, however, a paucity of solid data on factors that could affect prognosis in patients on home ventilation. In the present study, our aim was to study several factors in these patients with potential influence on survival. We examined 1526 adult patients from a nationwide HMV register to which data had been reported prospectively for 10 years. The patients constituted a broad diagnostic spectrum and the primary outcome in this study was death. We found by far the poorest survival rate in the ALS patients with only 5% alive after 5 years. Among the other patient groups the survival pattern was more uniform and the scoliosis, polio and Pickwick patients presented the best survival rate, after 5 years being around 75%. No factors were associated with a greater hazard for death in the ALS patients; in the non-ALS patients, however, negative predictors for survival were age, concomitant use of oxygen therapy, tracheostomy ventilation and start of ventilatory support in an acute clinical setting. Center size or county specific home ventilation treatment prevalence did not affect survival. In conclusion, in a large material of patients on HMV we found by far the poorest survival in the ALS patients. In the non-ALS patients a number of patient-related factors affected survival, while the size of the treating center or the regional treatment prevalence did not.