20-06-2013, 03:23 PM
Modern Ventilators
Modern Ventilators[.ppt (Size: 5.25 MB / Downloads: 54)
Ventilators
Power source is either compressed gas, electricity or both (contemporary require both).
Drive mechanism - modern vents classified as double-circuit, pneumatically driven.
Double-circuit means that a pneumatic force compresses a bellows, which empties its contents into the patient (aka bellows-in-a box).
Driving gas is oxygen, air, or a venturi mix of O2 and air (Dräger).
Cycling mechanism
time cycled, control mode.
Modern ventilators use solid state electronics for timing. Driving gas flow ceases when the set tidal volume is delivered to the breathing circuit or when a certain pressure is reached.
Set TV and delivered TV quantities may differ due to compliance, losses or leaks!
Anesthesia Ventilators
An electronic ventilator:
Re-circulates exhaled patient gas through the absorber (where CO2 is removed) and fresh gas is added with enough pressure to move the gas into the patient’s lungs
Helps protect the patient from high airway pressures
Supplies rate, volume, oxygen, and pressure monitoring
Vents excess gas out from the patient breathing circuit
Bellows-in-box Ventilator
A) Begin Inspiration
Driving gas being delivered into space b/w bellows & housing
Exhaust valve (driving gas to atmosphere) closed
Spill Valve (vents out excess gas to scavenger) closed
More on Alarms
High pressure
Pressure below threshold for 15 to 30 seconds (apnea or disconnect)
Continuing high pressure
Sub atmospheric pressure
Low tidal volume
High respiratory rate
Reverse flow (may indicate incompetence of expiratory unidirectional valve in the breathing circuit)
Apnea/disconnect alarms may be based on
Chemical monitoring (lack of end tidal carbon dioxide), or
Mechanical monitoring
Failure to reach normal inspiratory peak pressure, or
Failure to sense return of tidal volume on a spirometer
Advantages of Ventilators
Hands free
More regular ventilation (rate, rhythm, TV) than manual ventilation
Anesthesia Vent’s simpler in design & fewer controls than ICU vent’s
Disadvantages of Ventilators
Loss of contact b/w provider & pt.
Manual (bag) can detect disconnections changes in resistance and compliance, continuous positive press & spont. Vent.
False sense of “security”
Some vent’s cannot develop high enough inspiratory pressure, flow or PEEP to ventilate certain pts (ICU vent to OR)