为啥这么多逗号

Tension Pneumothorax

Occasionally, the defect in the lung or chest wall through which air gains entry to the pleural space forms a valve mechanism, and a tension pneumothorax occurs. During inspiration, air is sucked into the pleural space but cannot leave the pleura during expiration. A large pneumothorax develops, and increased respiratory effort reduces intra­ pleural pressure further, until the pressure in the affected hemithorax remains above atmospheric throughout almost the entire respiratory cycle, because air is only drawn into the pleura during peak inspiratory effort. Ventilation of the lung on the affected side ceases, the lung collapses, and ex­ tensive shunt and severe hypoxaemia occur. A more dra­ matic effect is the shift of the mediastinum away from the pneumothorax, which causes a sudden and catastrophic reduction in venous return and therefore cardiac output.Insertion of a cannula into the affected hemithorax relieves the pressure, creates an open pneumothorax and invariably saves the patient’s life.

张力性气胸

有时，肺或胸壁的破口形成一种只进不出的活瓣，空气经破口进入胸膜腔就会发生张力性气胸。吸气时，空气被吸入胸膜腔，但呼气时空气不能从胸膜腔排出。严重气胸时，会用力吸气而进一步降低胸膜腔内压，因为只有在最大吸气努力时空气才会被吸入胸膜腔，直到在几乎整个呼吸周期中患侧胸腔内压保持在大气压以上，用力吸气才无效。这时患侧肺停止通气，肺萎陷，出现大范围分流和严重低氧血症。更严重的影响是使纵隔向健侧移位，纵隔移位会导致静脉回流量突然且急剧的减少，从而导致心输出量减少。将导管插入患侧胸腔形成开放性气胸，可以减轻胸腔内压，从而挽救患者生命。

A large pneumothorax develops, and increased respiratory effort reduces intra­ pleural pressure further, until the pressure in the affected hemithorax remains above atmospheric throughout almost the entire respiratory cycle, because air is only drawn into the pleura during peak inspiratory effort.

严重气胸时，会用力吸气而进一步降低胸膜腔内压，因为只有在最大吸气努力时空气才会被吸入胸膜腔，直到在几乎整个呼吸周期中，患侧胸腔内压都在大气压以上，用力吸气才无效。

感觉是这个意思，为啥这么多逗号，按理两个逗号之间是插入语，如果and increased respiratory effort reduces intra­ pleural pressure further是插入语，那就更不能理解了？

and increased respiratory effort reduces intra­ pleural pressure further, until the pressure in the affected hemithorax remains above atmospheric throughout almost the entire respiratory cycle 这两个句子间就不应该有逗号