From the Naval Medical Research Center (NMRC) (A.H.S., A.H., L.T.V.T.H., B.H., B.K.S., S.J.C., C.R.A., P.F.M.-M., R.M.M., C.D.L.M.), Silver Spring; Department of Surgery (A.H.S., R.M.M.), Uniformed Services University (USU), Bethesda; Veterinary Services-Diagnostic Pathology (M.A.J.), Walter Reed Army Institute of Research, Silver Spring; and Walter Reed National Military Medical Center (S.J.C., C.D.L.M.), Bethesda, Maryland.
J Trauma Acute Care Surg. 2019 Jan;86(1):116-122. doi: 10.1097/TA.0000000000002014.
Aeromedical evacuation to definitive care is standard in current military conflicts. However, there is minimal knowledge on the effects of hypobaria (HYPO) on either the flight crew or patients. The effects of HYPO were investigated using healthy swine.
Anesthetized Yorkshire swine underwent a simulated 4 h "transport" to an altitude of 2,441 m (8,000 feet.; HYPO, N = 6) or at normobaric conditions (NORMO, N = 6). Physiologic and biochemical data were collected. Organ damage was assessed for hemorrhage, inflammation, edema, necrosis, and for lungs only, microatelectasis.
All parameters were similar prior to and after "transport" with no significant effects of HYPO on hemodynamic, neurologic, or oxygen transport parameters, nor on blood gas, chemistry, or complete blood count data. However, the overall Lung Injury Score was significantly worse in the HYPO than the NORMO group (10.78 ± 1.22 vs. 2.31 ± 0.71, respectively) with more edema/fibrin/hemorrhage in the subpleural, interlobular and alveolar space, more congestion in alveolar septa, and evidence of microatelectasis (vs. no microatelectasis in the NORMO group). There was also increased severity of pulmonary neutrophilic (1.69 ± 0.20 vs. 0.19 ± 0.13) and histiocytic inflammation (1.83 ± 0.23 vs. 0.47 ± 0.17) for HYPO versus NORMO, respectively. On the other hand, there was increased renal inflammation in NORMO compared with HYPO (1.00 ± 0.13 vs. 0.33 ± 0.17, respectively). There were no histopathological differences in brain (whole or individual regions), liver, pancreas, or adrenals.
Hypobaria, itself, may have an adverse effect on the respiratory system, even in healthy individuals, and this may be superimposed on combat casualties where there may be preexisting lung injury. The additional effects of anesthesia and controlled ventilation on these results are unknown, and further studies are indicated using awake models to better characterize the mechanisms for this pathology and the factors that influence its severity.
在当前的军事冲突中，将伤员空运到确定性治疗是标准做法。然而，对于低气压（HYPO）对飞行机组人员或患者的影响，我们知之甚少。我们使用健康的猪来研究 HYPO 的影响。
麻醉的约克夏猪接受了模拟的 4 小时“运输”，将其运往海拔 2441 米（8000 英尺）的高空（HYPO，N=6）或在常压条件下（NORMO，N=6）。收集生理和生化数据。评估器官损伤是否有出血、炎症、水肿、坏死，仅对肺进行微肺不张评估。
在“运输”前后，所有参数均相似，HYPO 对血流动力学、神经或氧气转运参数均无显著影响，对血气、化学或全血细胞计数数据也无显著影响。然而，HYPO 组的整体肺损伤评分明显高于 NORMO 组（分别为 10.78±1.22 和 2.31±0.71），在胸膜下、小叶间和肺泡空间有更多的水肿/纤维蛋白/出血，肺泡隔充血更多，并且有微肺不张的证据（而 NORMO 组没有微肺不张）。HYPO 组的肺中性粒细胞（1.69±0.20 与 0.19±0.13）和组织细胞炎症（1.83±0.23 与 0.47±0.17）的严重程度也分别增加。另一方面，NORMO 组的肾炎症程度比 HYPO 组增加（1.00±0.13 与 0.33±0.17）。脑（整体或各区域）、肝、胰腺或肾上腺无组织病理学差异。
低气压本身可能对呼吸系统造成不良影响，即使是在健康个体中，并且这可能会加重已经存在的肺部损伤的战斗伤亡。关于麻醉和控制通气对这些结果的影响，我们知之甚少，还需要进一步的研究，使用清醒的模型来更好地描述这种病理学的机制以及影响其严重程度的因素。
