每日一题_2022.06.28

A 65-year-old man is admitted to the ICU with pneumonia and respiratory failure. He is mechanically ventialated, sedated with propofol and fentanyl (Richmond Agitation- Sedation Scale – 4). His settings are assist control/volume control with respiratory rate 18 breaths/min, tidal volume 450 mL, positive end-expiratory pressure (PEEP) 10 cm H2O, and fraction of inspired oxygen (FIO2) 50%, with oxygen saturation as measured by pulse oximetry (SpO2) 97%. Peak inspiratory pressure (PIP) is 23 cm H2O and plateau pressures are 20 cm H2O. After cleaning the patient, his SpO2 suddenly drops to 90%. The FIO2 is increased to 100%, and now the SpO2 has increased to 95%. The waveform shown below is seen on the ventilator.

What of the following is the most likely diagnosis?

A. Tension pneumothorax

B. Pulmonary embolism

C. Mucous plug

D. Migration of the tube (mainstem intubation) 

E. Air trapping (breath stacking)

答案解析：

吸气峰压(PIP)增加而平台压未显著增加，表明压力较基线的增加是由于气道阻力增加，而不是肺顺应性降低。由于在测量平台压时（吸气暂停期间）空气不移动，因此通过气道的气流阻力变化不会改变平台压。该患者患有肺炎，可能产生大量粘液和分泌物，由于镇静水平较深，无法咳出，导致气道阻塞和翻转后粘液堵塞。张力性气胸、插管移位（主干插管）和空气滞留（呼吸堆积）均有平台压升高以及PIP升高。预计肺栓塞不会对气道压力产生任何影响。

正确答案：C