MACHINE SAFETY FEATURES
|FEATURES common to both Drager and Ohmeda due to industry standardization||PISS & DISS|
|O2 PRESSURE FAILURE ALARM||Warns when O2 supply is LOW/NO FLOW (25-30psi)|
OHMEDA Alarm Switch ASSEMBLY "Ritchie Whistle" - Assembly has OWN DEDICATED O2 TANK for alarm activation at psi BELOW 30!! Includes a reservoir, regulator, metal reed, and adjustable flow regulator. AUDIO warning.
DRAGER Oxygen Supply PRESSURE ALARM - Consists of Bellows, Spring, connecting rod, & Electric switch. Activated when psi drops below 30!!! Audio/Visual warning. Less than 30psi, pin pulls and O2 pressure alarm sounds.
|Clinical Implications of O2 failure alarm||Re-establish supply pressure - TURN ON E-CYLINDER|
DISCONNECT DISS hose b/c inlet pipeline check valve may become incompetent (prevents RETROGRADE flow)
Ambu w/separate O2 source
Use LOW FGF
Contemporary machines use BOTH Audio and Visual alarms.
|FAIL SAFE SYSTEM|
(not really fail safe r/t pressure as triggering event)
|OHMEDA pressure sensor shutoff - When O2 pipeline fails shuts off Air and N2O. Consists of inlet connected to N2O, outlet connected to flow control valve for N2O, Control port connected to O2 supply via SYSTEMS SWITCH. Makes sure O2 is LAST GAS IN TO PATIENT. If O2 less than 20psi closes outlet port to gases other than O2.|
DRAGER Oxygen Failure Protection Device - Proportional reduction. N2O/air not shutoff completely.
50psi N2O and 25psi O2 at inlet will allow only 25psi N2O to outlet port.
|HYPOXIC GUARD SYSTEMS|
(Function at level of flow control valves)
|OHMEDA Link 25 Proportioning System - Prevents unintentional hypoxic mixture. Maintains 25% O2 FG mixture and maximum N2O/O2 ratio of 3:1 r/t 26psi of N2O and 14psi of O2. "bicycle chain" mechanical linkage w/ 2:1 gear ratio 28 teeth on O2 flow and 14 teeth on N2O flow. If N2O turned two full revolutions (28teeth) O2 turns as well due to GEAR RATIO.|
PNEUMATIC (26psi N2O/14psi O2) AND MECHANICAL (gear link) CONTROLS
DRAGER Oxygen Ratio Monitor/Controller - Ratio monitor ALARMS but actually allows hypoxic mixture!!!
Controller = Shuts off N2O when O2 less than 10psi, will physically not allow a hypoxic mixture.
DRAGER Sensitive Oxygen Ratio Controller - Fabius GS, shuts off N2O if O2 flow less than 200ml/min or if O2 FG valve is closed. Audio/Visual alarms if pipeline pressure less than 20+/- 4psi
IN Case of complete O2 pipeline failure Machine will supply pipeline AIR so some oxygen and agent can be delivered.
|HYPOXIC GUARD Clinical Actions/Considerations||Hypoxic mixtures can occur if wrong supply gas in O2 pipeline or cylinder|
Pneumatic or mechanical components are defective
Leaks exist downstream of flow control valves
|GAS LINE CROSS CONNECTION||OHMEDA & DRAGER use O2 Analyzer|
the ONLY way to discern gas line cross connection is via O2 analyzer
|O2 ANALYZERS||ONLY SAFETY DEVICE THAT CAN DETECT LEAK DOWNSTREAM OF FLOW-METER|
GALVANIC CELL - More effective than polargraphic.
Cathode/Anode in electrolyte bath/gel. Chemical energy converted to electronic signal. Cells last around 9 mos. Detach and cover overnight to extend life.
O2 molecules reduced to hydroxyl ions and react w/lead anode to form LEAD OXIDE and releases electrons. Output is voltage and voltage is proportional to # of O2 molecules reduced at gold cathode.
POLARGRAPHIC - N2O can alter analyzer readings
|O2 supply contamination considerations||-Open E-cylinder|
-Disconnect DISS from wall/boom arm (E-cylinder will not flow if hose is connected and flowing at HIGHER psi!!)
-LOW FGFs and MANUALLY ventilate patient w/ambu
|VAPORIZER PROTECTION SYSTEM||Stops more than 1 vaporizer from being turned on|
OHMEDA Selectatec Vaporizer Manifold system - Interlock system uses pins in manifold LINKED to CONTROL DIAL. Pins extend when one vaporizer turned on to prevent others from engaging.
DRAGER Vaporizer Exclusion - Uses cams, pins, and levers to prevent activation of additional vaporizers.
|TIDAL VOLUME MONITORING||TV monitors detect reduced MV or disconnects, failure to ventilate, anoxic encephalopathy|
Tidal Volume Monitor Sensor - Counts spinning of vane to
approx. TV. Based on physical displacement phenomenon
D-Lite Flow Sensor - Two sided PILOT TUBE, measures
flow by pressure difference across a flow resistor. Based
on displacement phenomenon
Minute Volumeter - Requires positive volume displacement
which requires a certain volume of gas to turn the rotors
one complete cycle. Spiromed.
Ultrasonic Flow Sensor - Measures influence of gas flow on
transmission times of pulses btwn two crystals. Flow rate
calculated on transmission time difference-Similar to D-Lite
ADVANTAGES of UFS = no moving parts, accuracy
independent of gas composition, LOW RESISTANCE
|AIRWAY PRESSURE MONITORING||OHMEDA & DRAGER use Airway Pressure Monitors to monitor real time info on airway pressures in both auto and manual vent modes|
Freestanding or Incorporated into machine.
ALARMS MUST be set to 5cmH2O below cusp of waveform peak pressure!! if a PARTIAL disconnection occurs pressure peak may be above set alarm (if not high enough) and alarm will fail to alert provider of disconnect) (P.60 middle slide)