Age alters the cardiovascular response to direct passive heating
Age alters the cardiovascular response to direct passive heating
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DOI：
10.1152/jappl.1998.84.4.1323
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发表时间：
1998-04-01
影响因子：
3.3
通讯作者：
Kenney, WL
中科院分区：
文献类型：
--
作者：
Minson, CT;Wladkowski, SL;Kenney, WL
在年轻人的直接被动加热过程中，由于心输出量(（Q)除以点(c)）的增加以及内脏和肾脏血管床的血流重新分配，皮肤血流量急剧增加。为了检验年龄对这些反应的影响，7名年轻人（23 +/- 1岁）和7名老年人（70 +/- 3岁）被水灌注服被动加热到他们个人的热耐受极限。测量包括心率（HR）， (Q)过点(c)（通过乙炔再呼吸），中心静脉压（通过外周插入中心导管），血压（通过肱听诊），皮肤血流量（通过静脉闭塞容积描记术显示前臂血流量增加），内脏血流量（通过吲哚菁绿清除率），肾脏血流量（通过对氨基棘皮酸清除率），以及食管和平均皮肤温度。(Q) / dot(c)在老年人中明显低于年轻人（Y和O在热耐受极限分别为11.1 +/- 0.7和7.4 +/- 0.2 l/min, P < 0.05），尽管食管和平均皮肤温度以及达到热耐受极限的时间也有相似的增加。较低的搏气量（Y和O组分别为99 +/- 7和68 +/- 4 ml/次，P < 0.05），很可能是由于加热过程中肌力功能的减弱增加，这是老年男性中观察到的较低(Q) / dot(c)的主要因素。年轻男性和老年男性的HR增加相似；然而，当以最大HR的百分比表示时，老年男性依靠更大比例的变时储备来获得相同的HR反应（Y和0分别为最大HR的62 +/- 3%和75 +/- 4%，P < 0.05）。此外，老年男性在热耐受极限时，从脏腑和肾联合循环重新分配的血流量较少（Y和0分别为960 +/- 80和720 +/- 100 ml/min， P < 0.05）。由于这些综合的减弱反应，老年人流向皮肤的总血流量的增加明显较低。
During direct passive heating in young men, a dramatic increase in skin blood flow is achieved by a rise in cardiac output ((Q) over dot(c)) and redistribution of flow from the splanchnic and renal vascular beds. To examine the effect of age on these responses, seven young (Y; 23 +/- 1 yr) and seven older(0; 70 +/- 3 yr) men were passively heated with water-perfused suits to their individual limit of thermal tolerance. Measurements included heart rate (HR), (Q) over dot(c) (by acetylene rebreathing), central venous pressure (via peripherally inserted central catheter), blood pressures (by brachial auscultation), skin blood flow (from increases in forearm blood flow by venous occlusion plethysmography), splanchnic blood flow (by indocyanine green clearance), renal blood flow (by p-aminohippurate clearance), and esophageal and mean skin temperatures. (Q) over dot(c) was significantly lower in the older than in the young men (11.1 +/- 0.7 and 7.4 +/- 0.2 l/min in Y and O, respectively, at the limit of thermal tolerance; P < 0.05), despite similar increases in esophageal and mean skin temperatures and time to reach the Limit of thermal tolerance. A lower stroke volume (99 +/- 7 and 68 +/- 4 ml/beat in Y and O, respectively, P < 0.05), most likely due to an attenuated increase in inotropic function during heating, was the primary factor for the lower (Q) over dot(c) observed in the older men. Increases in HR were similar in the young and older men; however, when expressed as a percentage of maximal HR, the older men relied on a greater proportion of their chronotropic reserve to obtain the same HR response (62 +/- 3 and 75 +/- 4% maximal HR in Y and 0, respectively, P < 0.05). Furthermore, the older men redistributed less blood flow from the combined splanchnic and renal circulations at the limit of thermal tolerance (960 +/- 80 and 720 +/- 100 ml/min in Y and 0, respectively, P < 0.05). As a result of these combined attenuated responses, the older men had a significantly lower increase in total blood flow directed to the skin.