透過您的圖書館登入
IP:3.230.76.153
  • 期刊

抗G動作對負G轉換爲正G的防禦價值探討

The Protective Action of L-1 Maneuver during -Gz to +Gz Transitions

摘要


近年,美、英、加、德等國空軍相繼地發現先前的負G(-1~-2.5Gz)暴露,將會削減後續的正G耐力,此說明了感壓反射在正和負G的作用下,其消長趨勢並非如想像中的鏡像相稱。 本研究之目的爲以自行設計的垂直轉盤式負G的模擬器,探討-1Gz和+1Gz轉換間所導致的心臟血管反應,並商榷L-1動作的效益和適時性。實驗中,心跳率和動脈血壓的監測,分別利用指夾式氧脈計和指套式血壓計,皆屬於非侵害性的測量。 30名健康的受測者分爲空勤組(9男)和地勤組(19男,2女),先測量其直立5分鐘後(+1Gz)的動脈血壓和心跳率,旋即轉向倒懸的位置(-1Gz),及測量30秒後的相同生理參數,最後迅速回正至起始的位置,其間保持肌肉鬆懈。接著在適當的休息時間後,重複以上相同的步驟,惟在G力轉換的頃刻,或完成G力轉換時,要求受測者實施L-1動作,以比較之。 實驗結果顯示-1Gz誘導的心跳緩慢,在兩組受測者之中,皆因抗G動作而得以反轉,甚至在完成G力轉換時超過基準的心跳率,但抗G動作的實施時機並無顯著的影響。倒懸期間,兩組受測者的平均動脈血壓多呈現增加,此現象可能與血液容積的重新分佈有關。又自-1Gz轉換爲+1Gz時,若做L-1動作,可減少因迷走神經興奮所致的降血壓效應。實驗中亦見血氧飽和度於-1Gz的暴露,皆一致地降低。此外,臉浸冷水和負G誘導的心跳率降低值,兩者間呈現顯著的正相關(r=0.74)。 本研究的初步研究結果顯示,當-1Gz轉換至+1Gz時,抗G動作至少有兩種效益:(甲)提昇心跳率的基線,有利於未來高G暴露的生理和機械性防禦(乙)防止血液容積突然轉移到下肢,可藉以減少動脈血壓因靜水壓效應的降低。

關鍵字

負G G力轉換 L-1動作 臉浸冷水

並列摘要


Several Air Forces have noticed that peceded exposure to -Gz can reduce immediate +Gz tolerance since 1990. Experiments on-ground and in-flight also verified the fact that baroreceptor reflex was not what we expected to be a mirror image. The goal of this study was to test the hypothesis that -Gz to +Gz transitions significantly compromised the +Gz tolerance using a self-designed vertical rotating wheel. Thirty healthy volunteers was divided into two groups: aircrew (9 subjects) and ground personnel (21 subjects), depended upon their familiarity of L-1 maneuver. They were subjected to two sessions of gravitional stress which consisted of +1Gz to -1Gz and -Gz to +1Gz transitions with or without activating L-1 maneuver. At the beginning and end of each postural change, heart rate (HR) and arterial blood pressure (ABP) were recorded non-invasively by finger-cuff monitors. The results showed that negative G-induced bradycardia consistantly reversed and HR even exceeded its baseline level in both groups if L-1 maneuver was performed. During +Gz exposure, mean ABP increased possibly due to the redistribution of blood volume. On the other hand, L-1 maneuver could buffer the depression effect of vagal tone on ABP. Besides, decreases in HR resulted from -1Gz and facial immersion exhibited significant correlation (r=0.74). The preliminary data of this study implies that L-1 maneuver can offer at lest two physiological benefits as followed: (1) to elevate the background HR and prepare for the following +Gz exposure (2) to prevent further shift of blood volume to lower part of body and thereby reduce blood pooling.

延伸閱讀