HEMATOCRIT & BLOOD VOLUME--EFFECTS OF MAXIMAL 02 INTAKE

分血器

• 批准号: 2714088
• 负责人: ROBERT LEE JOHNSON
• 金额: $ 41.71万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-06-01 至 2000-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2714088
• 关键词: aerobic exercise; blood cell count; blood circulation; blood volume; capillary; cardiac output; cardiopulmonary disease; dogs; hemodynamics; mathematical model; model design /development; oxygen transport; pneumonectomy; polycythemia; pulmonary diffusion; pulmonary respiration; respiratory circulation; respiratory oxygenation; rest; spleen; splenectomy

Polycythemia is a normal response to chronic hypoxia at high altitude or from disease; however our understanding of the extent to which or mechanisms by which polycythemia improves oxygen delivery in response to hypoxia is incomplete. It has been assumed that the major benefit is to provide greater oxygen carrying capacity of blood to raise O2 delivery. But recent theoretical considerations suggest that polycythemia also enhances diffusive transport between alveolar air and blood in the lung and between red cells and mitochondria in tissues. Interest also has developed in potential benefits of blood doping in athletes (i.e., blood transfusion to induce polycythemia) as a means to improve athletic performance even in the absence of hypoxia. The latter idea gains credence from the animal kingdom where dogs and horses auto-transfuse themselves by splenic contraction to expand both blood volume and hematocrit during heavy exercise. Our objective is to exploit this natural ability in dogs to determine (1) if spontaneous increases of blood volume and hematocrit (Hct) by splenic contraction enhances maximal O2 uptake, (2) if diffusive transport is an important source of enhancement and (3) if enhancement is greater at simulated high altitude or after pneumonectomy to simulate lung disease. We plan the following comparisons pre and post splenectomy in normal foxhounds and foxhounds after pneumonectomy: 1. Maximal O2 uptake (VO2max); circulating plasma volume and Hct at rest and heavy exercise. 2. Relationships of lung diffusing capacity (DLCO) to cardiac output as workload increases during exercise. 3. O2 diffusing capacity of the lung (DLO2) and distribution of ventilation/perfusion ratios studied with the multiple inert gas elimination technique breathing air and 14% oxygen at increasing work loads. 4. Pulmonary and systemic hemodynamics at rest and exercise. 5. O2 diffusing capacity in tissues (DtO2) estimated from peripheral O2 extraction at peak exercise. After splenectomy comparisons will be made before and after transfusion to restore blood volume to pre-splenectomy levels at peak exercise, (a) at a hematocrit (Hct) of 40% and (b) at a Hct of 55-60% to separate independent effects of Hct and volume. We hypothesize that VO2maz will be reduced after splenectomy, partially restored by (a) and completely restored by (b). We also expect that VO2max will be significantly enhanced by diffusive transport in lung (higher DLCO and DLO2) and tissues (higher DtO2), that enhancement will be greater at simulated altitude than at sea level and that the absence of a spleen will severely impair the compensatory response to pneumonectomy. These studies should help clarify mechanisms and potential extent of compensation by polycythemia to high altitude and cardiopulmonary disease.

红细胞增多症是对高原或高原慢性缺氧的正常反应 远离疾病；然而，我们对疾病程度的理解 红细胞增多症改善氧输送的机制 缺氧是不完全的。人们一直认为这样做的主要好处是 提供更大的血液携氧能力，提高氧气输送。 但最近的理论考虑表明，红细胞增多症也 增强肺泡空气和血液在肺内的扩散传输 在组织中的红细胞和线粒体之间。人们的兴趣也在增长 在运动员中使用血液兴奋剂的潜在好处(即输血 诱发红细胞增多症)作为提高运动成绩的一种手段，即使在 没有缺氧。后一种想法得到了动物的信任 狗和马通过脾自动输血的王国 重型时收缩以扩大血容量和红细胞压积 锻炼身体。我们的目标是利用狗的这种天生能力 确定(1)血容量和红细胞压积(Hct)是否自发增加 通过脾收缩增强最大氧气摄取量，(2)如果是扩散的 运输是增强的重要来源；以及(3)如果增强是 在模拟高原或全肺切除后模拟肺 疾病。我们计划在脾切除前后进行以下比较 正常的猎狐犬和全肺切除后的猎狐犬： 1.最大吸氧量(VO2max)；循环血浆容量和静息时Hct 和繁重的运动。 2.肺弥散量(DLCO)与心输出量的关系 在运动过程中，工作量增加。 3.肺组织氧扩散量(DLO2)及其分布 多次惰性气体通气/灌流比的研究 在增加工作时呼吸空气和14%氧气的消除技术 大把的。 4.安静和运动时的肺和全身血流动力学。 5.根据外周氧气估算组织内氧气弥散量(DtO2) 运动高峰期拔牙。脾切除后将进行比较 输血前后恢复脾切除术前血容量 运动高峰时的水平，(A)在红细胞压积(Hct)为40%时和(B)在Hct时 55-60%来分离Hct和容量的独立效应。我们 假设部分脾切除后VO2 maz会减少 由(A)恢复，并由(B)完全恢复。我们还预计VO2max 在肺内的弥散传输将显著增强(较高的DLCO 和组织(较高的DtO2)，这种增强在 模拟海拔比海平面高，没有脾的话 严重损害全肺切除术后的代偿反应。这些研究 应有助于澄清补偿机制和潜在的补偿范围 高原红细胞增多症和心肺疾病。