Rapid and complete occlusion of a heat and moisture exchange filter by pulmonary edema (clinical report).

Purpose: A case of near fatal obstruction of a breathing system is described, due to occlusion of a heat and moisture exchange filter in a patient with pulmonary edema. Previous reports have described cases of mechanical obstruction to fresh gas flow due to an accumulation of a bolus of fluid within the filter housing. However, in this case, the cause of occlusion was due to the protein and cell debris contained in a small amount of pulmonary edema fluid interacting with the filter membrane.

Clinical Features: Obstruction occurred rapidly and without warning, and was difficult to differentiate from the more common diagnoses of bronchospasm or tension pneumothorax. Outwardly the filter appeared normal, and routine protocol for emergency management of suspected breathing system obstruction initially failed to identify the site of occlusion.

Conclusion: Minimal contamination by proteinaceous fluid may cause rapid and complete occlusion of a breathing system filter. Blockage of the breathing system filter and catheter mount should be considered in cases of unexplained breathing system occlusion. The use of a fresh breathing system without a filter for each patient, as recommended by The American Center for Disease Control and the American Society of Anesthesiologists, would have prevented this scenario from occurring.