21天头低位(-6°)卧床前后下体负压和头高位倾斜暴露时的心血管反应

Cardiovascular response to LBNP and HUT before and after 21 d HDTMegaloblastic anemiaCase report

目的探讨２１天头低位（ＨＤＴ）卧床对人体立位应激下心血管反应的影响，以及比较下体负压（ＬＢＮＰ）和头高位倾斜（ＨＵＴ）两种立位应激下心血管反应的差异。方法６名受试者在２１天ＨＤＴ前、后分别进行ＬＢＮＰ（－４．００ｋＰａ／３ｍｉｎ、－６．６７ｋＰａ／３ｍｉｎ及－９．３３ｋＰａ／３ｍｉｎ）和ＨＵＴ试验（３０°／３ｍｉｎ、４５°／３ｍｉｎ、６０°／３ｍｉｎ及７５°／３ｍｉｎ），以比较两种检测方法的血压（ＢＰ）和心率（ＨＲ）的变化情况。结果与ＬＢＮＰ（或ＨＵＴ）前相比：①ＬＢＮＰ（ＨＵＴ）时ＨＲ显著增加（Ｐ＜０．０１），ＳＢＰ显著降低（Ｐ＜０．０５）；卧床后相应的变化量增加。②ＬＢＮＰ时ＤＢＰ降低（卧床后达显著，Ｐ＜０．０５）；而ＨＵＴ时ＤＢＰ增加（卧床后达显著，Ｐ＜０．０５）。③ＬＢＮＰ时ＭＡＰ均显著降低（Ｐ＜０．０５）；而ＨＵＴ时在卧床前无变化（Ｐ＞０．０５），在卧床后显著增加（Ｐ＜０．０５）。结论ＬＢＮＰ和ＨＵＴ引起的ＣＶＳ反应并不相同。笔者认为，ＨＵＴ更能促进心血管系统对立位应激的调节作用。

Objective To investigate the effect of 21 days head down tilt (HDT) bed rest (BR) on cardiovascular response to lower body negative pressure (LBNP) and head up tilt (HUT), and the difference between cardiovascular responses to LBNP and HUT. Methods Six healthy male volunteers served as subjects. They underwent LBNP (-4.00 kPa/3 min, -6.67 kPa/3 min, -9.33 kPa/3min) and HUT tests (30/3 min, 45/3 min, 60/3 min and 75/3 min) before and after 21 days HDT bed rest. Blood pressure (BP) and heart rate (HR) during LBNP and HUT were compared. Results Compared with baseline values: HR increased significantly(P<0.01), whereas SBP decreased significantly (P<0.05) during LBNP(or HUT); the corresponding change of HR and SBP became more significant after 21 days HUT bed rest. DBP showed tendency of decrease before bed rest, and decreased significantly (P<0.05) after that during LBNP; whereas showed tendency of increase before bed rest (P>0.05), but increased significantly (P<0.05) after that during HUT. MAP decreased both before and after bed rest(P<0.05) during LBNP, while MAP remained unchange during HUT before bed rest and increased significantly after that (P<0.05). Conclusions The cardiovascular responses to LBNP and HUT are not identical. It is suggested that HUT can better reflect the ability of cardiovascular adjustment to orthostatic stress.