Critical Care Medicine-Neurologic Disorders>>>>>Mechanical Ventilation
Question 6#

A 54-year-old man with ischemic cardiomyopathy is admitted to ICU for respiratory failure due to decompensated heart failure and cardiogenic pulmonary edema. On the day of admission, he requires intubation and mechanical ventilation, and aggressive diuresis is initiated. On day 3 of his ICU stay, his ventilator is set on:

He is fully awake and breathing comfortably. He is placed on a spontaneous breathing trial with pressure support settings of:

Within minutes, he experiences oxygen desaturation, tachypnea, and respiratory distress.

Which among the following in the MOST LIKELY cause for failure of his spontaneous breathing trial?

A. Atelectrauma from collapse of alveoli with tidal breathing
B. Mucous plugging from lower airway pressure
C. Increased preload and decreased afterload
D. Decreased preload and increased afterload
E. Increased preload and increased afterload

Correct Answer is E


Correct Answer: E

The application of PEEP in both noninvasive and invasive positive pressure ventilation serves to decrease cardiac preload, through decreased venous return and decrease cardiac afterload as a result of decreased ventricular volume (and therefore radius) and transmural cardiac wall tension. In patients with baseline cardiac dysfunction, weaning-induced cardiac dysfunction may be observed when the absence of PEEP leads to an acute increase in cardiac preload and afterload (answer E is correct; answers C and D are incorrect). 

Atelectrauma is a form of lung injury most common in ARDS, in which loss of surfactant and alveolar flooding result in alveolar instability and cyclic opening and closing of lung units with ventilation. Although atelectrauma can occur in other types of respiratory failure, it is less likely to result in such a rapid decompensation (answer A is incorrect). Mucous plugging can occur on any PEEP and is less likely to explain this increased respiratory distress associated with the reduction in positive pressure (answer B is incorrect). 


  1. Cherpanath TG, Lagrand WK, Schultz MJ, Groeneveld AB. Cardiopulmonary interactions during mechanical ventilation in critically ill patients. Neth Heart J. 2013;21(4):166-172.