Ventilator Add-On for Delivering PET Tracer Gases

bral blood flow, oxygen metabolism, and blood volume in critically ill patients has created a need for reliable technical solutions for delivering 15O-tracer gases to mechanically ventilated subjects. Our objective was to create such a solution. Methods: We designed a ventilator add-on unit that enables complex functional brain studies using labeled oxygen and carbon monoxide gases as tracers. The unit manages both steady-state and bolus inhalations, and the latter can be manually initiated using a remote trigger. All parts conduct-ing breathing gases can be sterilized. The unit can be oper-ated during both spontaneous pressure support breathing and volume-controlled ventilation. It supports the standard safety features and alarms of the ventilator and includes an overflow valve in the bolus reservoir. Results: The count rate curves obtained using the new unit were similar to those from the standard bag-inhalation method. Conclusion: The unit we describe offers an economical and easily operated solution for providing uninterrupted ventila-tor treatment while performing PET brain studies, and the provided treatment meets intensive care criteria. Key Words: PET; tracer; bolus; inhalation; ventilato