HEMATOCRIT & BLOOD VOLUME--EFFECTS OF MAXIMAL 02 INTAKE

分血器

• 批准号: 2430783
• 负责人: ROBERT LEE JOHNSON
• 金额: $ 34.05万
• 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/2430783
• 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.

红细胞增多症是在高海拔地区慢性缺氧的正常反应， 疾病;然而，我们对疾病的程度或 红细胞增多症改善氧气输送的机制 缺氧不完全。 据推测，主要的好处是 提供更大的血液携氧能力以提高O2输送。 但最近的理论研究表明，红细胞增多症也 增强肺中肺泡空气和血液之间的扩散运输， 红细胞和线粒体之间的联系 兴趣也在发展 在运动员血液兴奋剂的潜在益处中（即，输血 诱导红细胞增多症）作为一种手段来提高运动表现， 没有缺氧。 后一种观点从动物身上得到了证实 狗和马通过脾脏自动输血的王国 收缩以在重负荷期间扩大血容量和血细胞比容两者 锻炼的 我们的目标是利用狗的这种自然能力， 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O2摄取，（2）如果扩散 运输是一个重要的来源，提高和（3）如果提高是 在模拟高海拔或模拟肺切除术后更大 疾病 我们计划在脾切除术前后进行以下比较， 正常的猎狐犬和肺切除术后的猎狐犬： 1. 最大摄氧量（VO 2 max）;静息时循环血浆容量和Hct 和剧烈运动。 2. 肺弥散量（DLCO）与心输出量的关系 锻炼时工作量增加。 3. 肺氧弥散量（DLO 2）和肺氧分布 用多种惰性气体研究通气/灌注比 呼吸空气和14%氧气的消除技术 载荷 4. 休息和运动时的肺和全身血流动力学。 5. 根据外周O2估算的组织中O2弥散量（DtO 2） 在运动高峰期提取。 在脾切除术后， 输血前后，使血容量恢复至脾切除前水平 峰值运动时的水平，（a）40%的血细胞比容（Hct）和（B）40%的Hct 的55-60%来分离Hct和体积的独立影响。 我们 假设脾切除术后VO 2 maz将部分减少， 通过（a）恢复和通过（B）完全恢复。 我们还预计VO 2 max 肺中的扩散转运将显著增强（DLCO较高 和DLO 2）和组织（更高的DtO 2），增强将更大， 模拟的海拔高度比在海平面，没有脾脏将 严重损害肺切除术的代偿反应。 这些研究 应有助于澄清赔偿机制和可能的赔偿范围， 红细胞增多症与高海拔和心肺疾病的关系。