高+Gz负荷下犬心血管系统反应特性

Cardiovascular Response to High Sustained +Gz Stress in Dogs.

目的探讨犬＋Ｇｚ负荷中、负荷后心电图、动脉血压反应特性。方法将压力传感器导管置于６只麻醉犬的升主动脉和髂总动脉，以测量犬暴露于＋１Ｇｚ、＋３Ｇｚ、＋５Ｇｚ、＋７Ｇｚ的血压，并采用Ａ导联持续监测心电图。结果（１）Ｐ波高度受＋Ｇｚ负荷的影响，负荷前、后１ｍｉｎ内差异显著（＋Ｇｚ负荷前Ｐ波２．３±０．２ｍＶ，＋３Ｇｚ后４．５±０．５ｍＶ，＋５Ｇｚ后４．８±０．３ｍＶ，＋７Ｇｚ后５．３±０．７ｍＶＰ＜０．０５）。（２）高＋Ｇｚ负荷时，髂总动脉血压表现为平均动脉压增高，脉压减低。（３）＋Ｇｚ终止后，升主动脉血压（ＡＰ）出现一过性增高（＋７Ｇｚ前ＡＰ１７．２９±５．５９／１１．３１±３．８６ｋＰａ，＋７Ｇｚ后第３０ｓ２７．５３±６．１２／２０．６２±１．８６ｋＰａ，Ｐ＜０．０１）。结论Ｐ波高度的变化反映心房移位，这可能是心律失常的原因。在高＋Ｇｚ负荷条件下，心血管功能不全，组织灌注压是一个重要的生理参数。＋Ｇｚ负荷终止后即刻，动脉血压极度增高。

Objective To investigate features of electrocardiography(ECG) and arterial pressure in dog during and after +Gz stress. Method Six anesthetized dogs were catheterized for the measurement of ascending aortic pressure(AP)and common iliac arterial pressure(CIAP).A lead of ECG was monitored continuously.Then, dogs were placed supine in rotatable plaform on one arm of an 1.7 m radius centrifuge.The animals were exposed serially to acceleration profiles of up to +7 Gz,consisting of a slow onset to peak acceleration,90 s peak G,and a rapid decline back to control.A recovery time of at least 20 min was allowed after each acceleration profile. Results (1) The amplitude of Pwave was influenced by the magnitude of the acceleration (2.30.2 mV at rest vs.4.50.5 mV at +3 Gz,4.80.3 mV at +5 Gz and 5.30.7 mV at +7 Gz, respectively P <0.05).(2)It appeared that arteria mean pressure increased and pusle pressure decreased in CIAP during high +Gz stress.(3)AP increased greatly after +Gz stress(17. 295.59/11.313.86 kPa at rest vs.27.536.12/20.621.86 kPa 30s after +7 Gz P <0.01). Conclusion (1)The change of the amplitude of Pwave reflected the atrial displacement which may be the reason of arrhythmia.(2)The perfusion pressure is an important physiological parameter to the cardiovascular dysfunction during high +Gz stress.(3)Greatly higher AP after +Gz stress could be a feature of vascular exhaustion.