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通常情况下肺通气是通过呼吸肌收缩、肺及胸廓的扩张,使空气进入肺而实现的。呼吸肌衰竭则导致气体交换障碍。此时可应用机械呼吸器维持肺泡通气、肺容量及其弹性。常用的有间歇正压呼吸(IPPB,亦称吸气期正压呼吸)、呼气末正压呼吸(PEEP)和连续气道正压呼吸(CAPA)3种。本文旨在阐述各种机械呼吸器实现肺泡通气的方法,以及机械呼吸和气道正压对肺、心及全身的影响。【机械呼吸和气道正压的生理学】为便于理解机械呼吸的作用,先对正常自主呼吸作一简要复习。正常自主呼吸是由延髓呼吸中枢发动的。其神经冲动经膈神经及传出神经传出,引起膈肌及肋间外肌收缩使胸腔扩张,胸腔内负压增大,产生跨肺正压(跨肺压(P_(tP))=口腔内压(P_m)—胸腔内压(P_(pl)),此压
Usually, pulmonary ventilation is achieved through the contraction of the respiratory muscles, the expansion of the lungs and thorax, and the passage of air into the lungs. Respiratory muscle failure results in gas exchange disorders. Mechanical respirators may be used to maintain alveolar ventilation, lung capacity, and elasticity. Commonly used intermittent positive pressure breathing (IPPB, also known as breathing positive pressure breathing), positive end expiratory pressure (PEEP) and continuous positive airway pressure (CAPA) 3 kinds. The purpose of this article is to describe the ways in which various mechanical ventilators can achieve alveolar ventilation and the effects of mechanical respiration and positive airway pressure on the lung, heart and body. Physiological Mechanisms of Mechanical Breathing and Positive Airway Pressure To facilitate understanding of the effects of mechanical respiration, a brief review of normal spontaneous breathing was performed. Normal spontaneous breathing is initiated by the medullary respiratory center. The nerve impulse by the phrenic nerve and the outgoing nerve, causing diaphragm and intercostal muscle contraction so that the chest dilatation, increased intrathoracic negative pressure, resulting in transpiratory pulmonary pressure (P_ (tP)) = intraoral Pressure (P_m) - Thoracic pressure (P_ (pl)), this pressure