(b)(4).Method: the complaint mr290v vented autofeed humidification chamber was returned to fisher & paykel healthcare in (b)(4) for investigation.The chamber was visually inspected for the reported damage.A scanning electron microscopy (sem) analysis was conducted for a previous complaint mr290 chamber with the same fault, which was returned from the same customer.Results: visual inspection of the complaint mr290 chamber revealed cracks around the base of the chamber dome.The first crack was observed on the left side of the bracket and the second crack was observed between one of the ports and the baffle.The surface of the dome was whitened between the base and the maximum fill line of the chamber.Sem analysis of a previous complaint mr290 chamber from the same customer provided evidence of environmental stress cracking (esc).Esc was shown by surface deformations on the crack surface, radiating out from the point of exposure to a harsh chemical.Multiple points of a chemical attack on the chamber's surface were present.Conclusion: the nature of the cracking and previous investigation into this failure mode suggest that the damage was caused by the chamber coming into contact with a solution containing ethanol/alcohol, which has resulted in environmental stress cracking of the chamber dome.Every mr290 chamber is pressure tested following the manufacturing process to check for any leaks present in the chamber dome due to cracks and other causes.Any chamber which fails this test is rejected.In addition, the pressure test is followed by a visual inspection of each chamber.No cracks in the chamber dome are acceptable.Any chamber that fails this inspection is rejected.The subject mr290v chamber would have met the required specification at the time of production.Our user instructions that accompany the mr290v vented autofeed humidification chamber state the following: "do not soak, wash, sterilize, or reuse this product.Avoid contact with chemicals, cleaning agents, or hand sanitizers." "set appropriate ventilator alarms." "perform a pressure and leak test on the breathing system and check for occlusions before connecting to a patient.".
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