The ventilator was investigated by our field service engineer.The ventilator failed internal leakage test during pre-use check.Crystallized debris was noted on the expiratory cassette membrane.The membrane was cleaned and the ventilator then passed pre-use check.Further functional and safety tests were performed with good results and the ventilator was then cleared for clinical use.Provided ventilator logs were reviewed.The reported event date was april 1, 2021 but there was no ventilation on that date.Evaluation of ongoing ventilation just prior the reported event date show that continuous nebulization of medication was used during the patient treatment and that the ventilator alarmed for airway pressure high, expiratory minute volume low and peep high.Peep high alarms are most likely generated due to the clogged membrane in the expiratory cassette, or a clogged expiratory filter (if used).Airway pressure high and expiratory minute volume low alarms indicate that ventilation was ongoing but with higher airway pressure than intended.The airway pressure high alarm is generated when the, by the user, set upper pressure limit is reached whereby the inspiration phase is terminated and goes over to expiration.The expiratory minute volume low is generated when the measured expiratory minute volume is lower than the, by the user, set lower expiratory minute volume alarm limit.The airway pressure high alarm and the termination of the inspiration phase, leads to that the patient not receiving the set volume and this may be related to an increased expiratory resistance.Information concerning what type of patient breathing circuit or if any bacterial filter was used on the expiratory side was not provided.Successful pre-use check was performed prior and after the event.The technical log does not contain any technical error codes to indicate that there was a ventilator malfunction at the time of the event.Based on the investigation findings and the log evaluation, our conclusion is that the root cause of the reported expiratory flow restriction was the found crystallized debris on the expiratory cassette membrane, which most likely occurred due to the continuous nebulization of medication.Appropriate alarms for the situation were generated.There are no indications of a ventilator malfunction.
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