近年来，关于急性呼吸窘迫综合征（ ARDS） 机械通气患者是否应该保留自主呼吸存在着广泛的争议。有研究认为重度ARDS 患者机械通气中也应保留自主呼吸；而有研究认为完全肌松具有肺保护作用。鉴于目前 ARDS 机械通气中保留自主呼吸存在利和弊的争论，本课题在ARDS动物模型中，通过硬膜外麻醉松弛呼气肌肉和膈神经封闭方法松弛吸气肌肉，分别形成保留膈肌（吸气肌肉）活动模型和保留腹肌（呼气肌肉）活动模型。在上述模型上探索吸气和呼气肌肉活动对肺的氧合、肺容量、肺损伤和炎症介质的影响，从而阐明自主呼吸中吸气和呼气肌肉对ARDS机械通气的效果影响及其相关机制。探讨改变既往呼吸肌肉“全”或“无”方式，在ARDS机械通气中采用单独麻痹吸气或呼气肌肉，从而保留自主呼吸的优点，避免其缺点， 达到肺保护性通气目的，减少临床大剂量镇静肌松药物的应用。本课题为ARDS机械通气相关性肺损伤防治提供新思路。

Abstract(limited to 800 words)：. In recent years, whether spontaneous breathing (SB) should be preserved in the early phase of ARDS has been intensively debated. It has been proved that SB with the activity of diaphragm during mechanical ventilation is associated with beneficial effects in better aeration and less atelectasis in lung dependent zones, as well as less hyperinflation in nondependent lung zones in ARDS; Improving gas exchange，global hemodynamics and organ perfusion ；Preventing ventilator-induced diaphragmatic dysfunction(VIDD)；Decreasing ventilator-associated lung injury (VALI). Thus, some researchers have claimed that SB should be preserved even in the most severe cases of ARDS.Expiration in mechanical ventilation is a passive phenomenon produced due to the lung elastic recoil forces. However, in the presence of increased respiratory driving, expiratory muscles, especially the abdominal muscles may actively participate in breath and increase intra-abdominal pressure (IAP). It has been proved that the increase of IAP even 10 cmH2O may have injurious impacts on organ functions and aggravate lung damage. Caironi et al has recently proved that the amount of lung cyclically recruitment and decruitment leads to the increase of mortality in ARDS patients. In view of the advantages and disadvantages of spontaneous breathing during mechanical ventilation in patients with ARDS, we hypothesized that activity of inspiratory muscles (diaphragm) had beneficial effects, while activity of expiratory muscles (abdominal muscle) had adverse effect. So, in animal model, we paralyzed the expiratory muscle by epidural anesthesia and paralyzed inspiratory muscle by phrenic nerve paralysis to established preserving diaphragm (inspiratory muscle) activity model and preserving abdominal muscles (expiratory muscle) model respectively. So as to explore the impacts and mechanism of inspiratory and expiratory muscles activities during mechanical ventilation in ARDS animal model and to test the hypothesis that deep sedation or paralysis might be replaced by the strategy of expiratory muscles paralysis through epidural anesthesia.