Archived - Important Advisory to Users of Siemens Servo 300 / 300A Ventilators

IMPORTANT ADVISORY TO USERS OF SIEMENS SERVO 300 / 300A VENTILATORS

2003-05-23

Dear Servo 300 / 300A User,

Over the past several years, Siemens has received problem reports concerning the Servo 300 / 300A (SV300 / 300A) ventilators. This letter describes corrective actions you can take to prevent problems, and should also serve as a reminder to follow the procedures for service and maintenance as outlined in the Operating Manual and Service Manual for the SV300 / 300A.

Gas Modules

Siemens has received reports from Canadian hospitals and worldwide in which smoke is produced from the gas module circuit board, after which the ventilator ceases to operate. The reported incidence among installed units worldwide is low, but a much higher incidence has been seen in Canada, and will be investigated by Siemens.

The Servo 300 / 300A ventilator contains separate modules for air and oxygen delivery. Each module contains electronic circuitry that regulates the flow of gas into the ventilator's mixing chamber. The modules are secured to the ventilator with screws located on the top of each module.

A poor connection between the module and the ventilator, or repeated power surges can damage the electronic components inside the module. Over time these actions may result in the meltdown of an inductor coil on the module's circuit board. Should this happen, the circuit board may produce smoke. The module may continue to function for a short time, but it will eventually cease to operate.

The gas module is designed to shut off in case of power loss or electronic circuit failure. This can result in the delivery of incorrect gas concentrations and/or decreased volumes to the patient. This situation will produce both visual alerts and auditory alarms. The ventilator will not function properly until the faulty gas module is replaced.

Although actual smoke or a smoky odour may be produced this will take place outside the gas-conveying channel, i.e. it is not introduced into the ventilation pathway leading to the patient. There have been no reports of fire associated with a defective gas module. Extensive fire hazard testing performed by Siemens has demonstrated that there is no risk of a sustained fire with the Servo 300 / 300A ventilator even in the presence of 100% oxygen. The smell associated with the smoke is noticeable and may be alarming to hospital staff.

The primary cause of a gas module failure has been identified with a sudden interruption of power to the module (hot swapping) or repeated power surges to the module. This can happen in any of the following circumstances:

• The modules are serviced or exchanged with the ventilator powered "ON" or in Standby - either in AC or DC modes.
• When the modules are serviced or exchanged while the ventilator is switched "OFF", but the AC power cord is still connected to the electrical wall outlet.
• The ventilator is moved by pulling on the Air or O2 gas hoses that are directly connected to the modules.
• The mounting screw on the module is not fully tightened or missing, which allows the module to vibrate during ventilation.

The power to the battery charger is always "ON" when the AC power cord is connected to the mains power. For this reason the ventilator will not be completely disconnected from mains power, even with the mode selector switched to the "OFF" position.

Power surge damage appears to be time-related. Health Canada recommends the replacement of the gas modules in the SV300. Siemens supports this recommendation by offering a special reduced price for replacement modules. Ordering information, part numbers, and pricing can be obtained by calling Customer Service at Dynamed at 1-800-227-7215.

To reduce the risk of these power surges occurring we recommend the following:

• Do not "hot swap" modules when changing, servicing, or manipulating the modules in any way. Always unplug the AC power cord and turn the ventilator to "OFF".
• Make sure that the module mounting screw is present and properly tightened at each service or maintenance involving the gas modules.
• Do not move the ventilator by pulling on the Air or Oxygen supply hoses.

Siemens has re-designed the gas module circuitry to improve surge protection and preclude damage to electronic components. The revised gas module was introduced to production and as a spare part in July 2002.

• SV300 / 300A ventilators from serial number 24578
• Gas module Air, part no. 64 63 504 from serial number 523 001.
• Gas module 02, part no. 64 63 751 from serial number 617 001.

Maintenance of the Servo Ventilator 300 / 300A

The requirement to disconnect the AC mains power before doing any service or maintenance on the Servo 300 / 300A is described in the SV300 / SV300A Operating Manual on page 2 in the "1000 hour overhaul" section, and page 3 on the "3000 hour overhaul section", as well as in the SV300 / SV300A Service Manual.

As part of the routine SV300 / 300A maintenance procedures, every three (3) years the power section must be accessed for replacement of the internal batteries. Section 3 of the SV300 / 300A Service Manual "Disassembling and Assembling" describes the proper procedure to be followed. The power section might also be opened for other service requirements.

Ground Springs

When the SV300 / 300A ventilator is assembled, eight (8) ground springs (contact clips) are held in position between the upper and lower part of the housing. These ground springs serve to make an electrical connection between the pneumatic and power sections of the ventilator.

Siemens has received a few reports worldwide where ground springs were found to have broken and fallen into the electronic section of the ventilator. The ground springs may break due to bending, fatigue, or corrosion. If the ground springs are missing or defective they should be replaced.

Page 101, Section 3 (Disassembling and Assembling) of the SV300 / 300A Service Manual states that the ground springs should be checked before final assembly. An illustration shows the correct alignment of the ground springs.

Technical Service Training - SV300 / 300A Ventilator

Siemens requires that service technicians are authorised and trained by Siemens to perform SV300 / 300A service and maintenance procedures. This requirement is stated in both the SV300 / 300A Service Manual and SV300 / 300A Operating Manual.

For more information on this issue or the SV300 / 300A Technical Service training course, please call Dynamed - Customer Service 1-800-227-7215.



Regards,

original signed by

Derek Piper

Director

Electromedical Group

Siemens Canada Limited

ph (604) 671-5060

fax (604) 574-9180

Voicemail 1-877-882-2969 ext: 374