Outline the causes, consequences and management of intrinsic PEEP.

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College Answer

Causes: consider increased expiratory resistance (prolonged expiratory time constant: eg. bronchospasm,  narrow/kinked  ETT,  inspissated  secretions,  exhalation  valves/HME/filters), increased minute ventilation (inadequate expiratory time).

Consequences:  consider increased intra-thoracic  volume (with increased pressures for a given Vt and  risks  of  barotrauma),   increased   intra-thoracic   pressure   (decreasing   venous   return,   and increasing inspiratory work to trigger the ventilator).

Management:   consider  treatment   of  reversible   factors  (bronchospasm,   secretions,  expiratory devices), prolongation of expiratory time (decrease respiratory rate, increase inspiratory flow) or decrease  tidal  volumes,  application  of  exogenous  PEEP  (to  50  –  85%  of  accurately  measured intrinsic PEEP) to decrease inspiratory triggering work and improve distribution of inspired gas.

Discussion

This question is identical to Question 4 from the first paper of 2006.