Hamilton Medical AG Breathing Set MRI

Certain lots of the expiratory valve set pre-assembled to the breathing circuit set, coaxial (see FSN) do not perform as intended. In some cases, the expiratory valve membrane adhered to the expiratory valve body's sealing ring, thereby impairing valve opening and expiratory gas flow. The issue is not detected during the pre-operative test of the ventilator unless a test lung is actively ventilated. In case of an adhering expiratory valve membrane, the malfunction appears within the first breaths after ventilation is initiated. 

When the expiratory gas flow is impeded, the end-expiratory pressure is too high, or the end-expiratory flow is too low. Consequently, the ventilator triggers the high priority alarm "Exhalation Obstructed". 
The obstructed air is released through the device, e.g.the obstruction valve opens so that the patient can exhale through the inspiratory limb.