Outline the causes, consequences and management of intrinsic PEEP.
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.
This question is identical to Question 4 from the first paper of 2006.