(b)(4).The 900pt531 junior heated breathing tube (hbt) is used with the airvo humidifier to deliver warmed and humidified respiratory gases to spontaneously breathing patients through a variety of patient interfaces.Method: the complaint 900pt531 hbt was returned to fisher & paykel healthcare and was visually inspected and resistance tested.Results: visual inspection of the heated breathing tube revealed that a small section was damaged in the central area of the tube.The damage was to the actual plastic of the hbt but still connected by the heater wire.The melted tube was very clean and no sign of burning or smoke damage was observed.The heated breathing tube was found to be functional.The heater wire insulation was observed to be intact and a resistance check on the heater wire was within specification.Conclusion: based on our observations of previous damaged heated breathing tubes, as well as the results of the investigative tests, the tube was very likely covered by material with a temperature greater than of typical room conditions and/or was under compressive load for a considerable length of time.The heater wires are coated with teflon, which remains intact even under compressive load and has a much higher melting point than the hbt.During production the heater wires are 100% visually inspected using a camera system.The heater wires are also tested for resistance, continuity, polarity and pitch during production.Before the product leaves the line a full functional test is conducted under load.The airvo system is designed to comply with the electrical safety standard ul60601-1.The case is composed of a flame retardant material.The surface temperature of the heated breathing tube is within the limits specified by iso 8185 with regard to hot tube surface temperature not exceeding 44° celsius.There are many safety features incorporated into the airvo to prevent overheating and fire.These include: the heater wires in the heated breathing tube are coated with teflon, completely insulating them from the gas path.The pcb at the [patient] end of hose is over moulded with the thermoplastic polymer polypropylene, ensuring it is excluded from the gas path.The airvo contains a transient current detector, tcd.This tcd is tested on the production line.It is also checked by the control system when the airvo is powering up before each use.An 'over-temperature' sensor will automatically cut power to the motor, heater plate and heater wire if it detects any overheating.The airvo is constantly checking power in the heated breathing tube and turns the heater wire off if the measured power is too high.The user instructions accompany the airvo 2 humidifier include the following warning: adding heat, above ambient levels, to any part of the breathing tube or interface, e.G.Covering with a blanket, or heating it in an incubator or overhead heater for a neonate, could result in serious injury.The user manual instructs the user to "use continuous oxygen monitoring on patients who would desaturate significantly in the event of disruption to their oxygen supply.".The user manual also states the "airvo 2 is for the treatment of spontaneously breathing patients who would benefit from receiving high-flow, warmed and humidified respiratory gases".And "the unit is not intended for life support.".
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