每日一题_2022.06.19

A 65-year-old woman with a history of chronic obstrutive pulmonary disease is intubated for respiratory failure after several days of increasing symptoms. After initial stabilization on the ventilator, her oxygen saturation suddenly decreases to 80% despite a fraction of inspired oxygen of 100%. With the help of an inspiratory hold maneuver, the clinician is able to ascertain the following parameters: peak inspiratory pressure 45 cm H2O, plateau pressure 20 cm H2O, positive end-expiratory pressure 5 cm H2O.

 Which of the following is the most likely reason for her sudden hypoxia?

A. Decreased dynamic lung compliance, suggesting pneumothorax 

B. Decreased static lung compliance, suggesting bronchospasm 

C. Increased dynamic lung compliance, suggesting pneumothorax 

D. Increased static lung compliance, suggesting pneumothorax

E. Decreased dynamic lung compliance, suggesting bronchospasm

答案解析：

静态肺顺应性定义为给定施加压力下的容量变化：静态顺应性(Cstat)= 潮气量/（平台压[PPlat]-呼气末正压[PEEP]）。静态肺顺应性降低（“肺僵硬”）的常见原因包括限制性肺部疾病、气胸、胸腔积液和急性呼吸窘迫综合征。

动态肺顺应性是指肺在空气运动过程中的顺应性：动态顺应性(Cdyn)= 潮气量/（吸气峰压[PIP]-PEEP）。更直接地受阻塞性生理的影响，如气管插管堵塞、支气管分泌物或支气管痉挛等。

该患者的动态肺顺应性降低，表现为PIP增加，但静态肺顺应性不变。这提示阻塞性过程，如支气管痉挛。

正确答案：E