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(b)(4).Customer reported that machine sn (b)(4) had uf balance air in dialyzer alarm during therapy.According to the report, the facility (b)(4) inspected the machine and found small crack in one of the sensors (item number not reported).Sensor was replaced and a mock therapy was performed to check temperatures, conductivity and uf removal.Machine passed all checks and it was released for operation.All information associated with this event was forwarded to b.Braun avitum ag (manufacturer) for further evaluation.Also submitted for evaluation was the replaced component.Based on their investigation, the manufacturer confirmed that the component had some cracks at the connection point to the df-block.The investigation indicates that during therapy there is negative pressure at the conductivity cells.So a leakage at this point leads to air being sucked into the fluid system of the device.Air sucked into the fluid system at this point is pumped through the dialysis fluid system until it reaches the air separator, where it is accumulated.If the air separator gets filled with air, the air is separated by opening the air separator valve vla.The openings of vla are counted, and after the 10th opening of this valve the alarm 1026 is triggered as mentioned: alarm text: "uf balance? air leakage in dialyz.Coupl." as a result of other reports associated with uf deviations, the manufacturer discovered that a limited number of flanges assembled into bicarbonate and end conductivity cells showed hairline cracks.As described above, the conductivity sensors are utilized in an area of the dialysis fluid system which is under negative pressure.The negative pressure allows air to be sucked into the dialysis fluid.The air collects in an air separator which forms part of the dialysis fluid system.When the air separator is filled, the air separator valve (vla) opens and the air is purged and replaced by dialysis fluid from outside the balance circuit.The leakage has different consequences dependant upon whether or not the dialog+ hemodialysis machine is equipped with a df-filter or not.In dialog machines with df-filter (option df-filter, hdf online machines) the air passes this filter on its way to the air separator.Since air blocks the filter it is flushed out during cyclic filter rinsing, collected in the air separator and flushed out as described.Continuous air entry due to the leakage of the conductivity cells can lead to cyclical pressure fluctuations due to excess air inside the df-filter, thus blocking it.This might lead to an excess uf for the patient ("excessive removal").The maximum possible amount of the excess uf (theoretical worst case) caused by this failure type was determined in a laboratory setting artificially producing the maximum leakage at which the dialysis machine can be put in therapy.At a dialysis flow of 800 ml/min, the uf deviation was 636 ml/h with the alarm triggered after 55 min of therapy.In addition, 77 conductivity cells returned from the market and showing this failure type were investigated.64 of these cells showed an uf deviation below 200 ml/h and 13 above 200 ml/h at a dialysis fluid flow of 800 ml/min.The maximum uf deviation measured in this case was 488 ml/h.In dialog machines without df-filter the air is also transported to the air separator, where it accumulates and is released as described above.Since there is no df-filter, in these devices no accumulating air might cause an excess uf.The air accumulated in the air separator expands when it is separated and substituted with dialysis fluid from outside the balance circuit.So the fluid volume is bigger than the volume of the compressed air and the uf volume is decreased.Therefore, in devices without df-filter air entry might lead to a too low ultrafiltration ("insufficient removal").This mechanism occurs also in devices with df-filter but is superimposed by the described cyclical pressure fluctuations inside the df-filter.The amount of insufficient uf caused by this failure type in dialysis machines without df-filter was determined in the above mentioned theoretical worst case setting.The maximum uf deviation in this case was 250 ml/h at a dialysis fluid flow of 800 ml/min.The respective alarm was triggered for the first time after 13 min.To further investigate the uf deviation 24 conductivity cells returned from the market were tested.Three of these conductivity cells showed a deviation between 100 to 200 ml/h with a maximum at 148 ml/h, the other conductivity cells showed lower or no uf deviation.The tests showed that the uf deviations decreased with decreasing dialysis fluid flow.They also imply that the cracks at the conductivity cells develop and increase with time during continuous use of the device.With an increasing leakage, the amount of air sucked into the dialysis fluid system increases and the frequency of the opening of the vla valve.This means that the above described alarm starts to occur first towards the end of a therapy and occurs earlier and earlier with the growth of the crack.If the leakage might approach the maximum, the alarm is triggered early in therapy and more frequently.If the maximum is reached, follow-up alarms will stop the preparation or therapy phase.Root cause: the principle cause of failure of the product is due to variation in molding parameters of the flanges utilized in the construction of the conductivity sensors.Due to the variation in molding parameters, there is potential for thermal and mechanical stresses during normal operation to induce cracks in the conductivity sensors which causes the ingress of air into the dialysis fluid.Correction: b.Braun avitum ag (manufacturer) and (b)(4) (importer) have initiated an urgent medical device correction (recall) on april 1, 2016.Action taken to prevent recurrence of problem: b.Braun avitum ag (manufacturer) has initiated capa(b)(4).(b)(4) (importer) has initiated capa(b)(4).If additional pertinent becomes available, a follow up report will be submitted.
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As reported by the user facility: event 1: dialog evolution #201917 v9.12 wtc 7172 customer reports machine getting uf balance air in dialyzer couplings during therapy.Found small crack in biclf sensor.Replaced biclf sensor part #3456102.Ran mock therapy checking temperatures, conductivity and uf removal.Machine tested fine after sensor replaced.Event 2: dialog evolution #201913 v9.12 wtc 7175 customer reports machine getting uf balance air in dialyzer couplings during therapy.Found small crack in biclf sensor.Replaced biclf sensor part #3456102a.Ran mock therapy checking temperatures, conductivity and uf removal.Machine tested fine after sensor replaced.Event 3: dialog evolution #201911 v9.12 wtc 6449 customer reports machine getting uf balance air in dialyzer couplings during therapy.Found small crack in biclf sensor.Replaced sensor part #33456102a.Ran mock therapy checking temperature, conductivity and uf removal.Machine tested fine after sensor replaced.Event 4: dialog evolution # 203890 v9.12 wtc 7559 customer reports getting uf balance air in dialyzer couplings.Found small crack in biclf sensor.Replaced biclf sensor part #3456102a.Ran mock therapy checking temperatures, conductivity and uf removal.Machine tested fine after sensor replaced.Event 5: dialog evolution #201916 v9.12 wtc 8328 customer reports getting uf balance air in dialyzer couplings.Found small crack in biclf sensor.Replaced biclf sensor part #3456102a.Ran mock therapy checking temperatures conductivity and uf removal.Machine tested fine after sensor replaced.Event 6: dialog evolution #201862 v9.12 wtc 8390 customer reports getting uf aballance air in dialyzer couplings during therapy.Customer has pulled machine and will inspect.Event 7: dialog evolution #203892 v9.12 wtc 7228 customer reports getting uf balance air in dialyzer couplings.Customer will pull machine and inspect.Additional information: alarm uf balance air in dialyzer couplings triggered no patient harm:.
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