呼吸器MODE介紹

MODE
INTRODUCTION
Mechanical ventilation is required when a patient cannot ventilate adequately, resulting in gas exchange.
As all functions of the ventilator are represented by electrical signals in the Patient Unit, a continuous and real-time recording of the inspiratory and expiratory pressure, flow and volume is displayed on the User Interface.
    
GENERAL
   The respiratory cycle comprises:
    - Inspiration
    -Inspiratory pause
    -Expiration
VOLUME CONTROL VENTILATION
VOLUME CONTROL VENTILATION
   Volume Control provides controlled ventilation, and by setting the correct parameters the patient is assured of adequate ventilation.
INSPIRATION
Gas flows into the lungs at a constant rate. The more the lungs are filled, the greater the airway pressure becomes, and is at its greatest at the end of inspiration.
Flow-adapted Volume Controller
     If the patient may demand a higher Tidal Volume/flow than is set on the ventilator. The flow-adapted Volume Controller will always work with the patient and deliver the extra volume requested. If the patient decreases airway pressure by 3 cmH20 during the inspiratory phase, the ventilator switches to Pressure Support and delivers a flow profile adapted to the patient’s immediate needs.
EXPIRATION
To reduce the resistance at the beginning of expiration, the expiratory valve has a controlling algorithm which continually calculates the elastic and resistive forces on the respiratory system.
The initial opening of the expiratory valve is adapted to keep resistance as low as possible while strictly maintaining the set PEEP in the airway.
PRESSURE CONTROL VENTILATION
GENERAL
Pressure Control provides controlled ventilation, and by setting the correct parameters the patient is assured of adequate ventilation.
In Pressure Controlled ventilation the ventilator delivers a flow to maintain the preset pressure during the preset Inspiratory time and at the preset Respiratory rate.
INSPIRATION
The flow is greatest at the start of inspiration. Since the pressure is constant, then the more the lungs are filled the more the flow decreases (i.e. decelerating flow).
EXPIRATION
When the expiratory valve opens, the flow of expired gas is greatest at the start since the pressure is then greatest (1). To reduce the resistance at the beginning of expiration, the expiratory valve has a controlling algorithm which continually calculates the elastic and resistive forces on the respiratory system. The initial opening of the expiratory valve is adapted to keep resistance as low as possible while strictly maintaining the set PEEP in the airway.
USER CONSIDERATIONS
The SERVO-i keeps the pressure constant during the inspiratory time.
A decrease in pressure will give a precise increase in flow to keep the pressure constant during the inspiratory time
PRESSURE SUPPORT VENTILATION
GENERAL
Pressure Support (PS) is a spontaneous mode of ventilation where no mandatory breaths are given.
The patient regulates the Respiratory Rate and the Tidal Volume with support from the ventilator.
INSPIRATION
   When the patient triggers a breath which corresponds to the pre-set value on the User Interface, then pressure support is given and gas flows into the lungs at a constant pressure.
Inspiratory rise time
Inspiratory rise time is the time(s) taken to reach peak inspiratory flow or pressure at the start of each breath.
EXPIRATION
   Expiration starts when the instantaneous flow rate drops to a user set value of the peak inspiratory flow. Settings are within the range 1 - 70% of the inspiratory peak flow.
BACKUP
If the patient is not breathing and the set apnea alarm limit is reached, then the SERVO-i will automatically switch to Backup Pressure Support - Pressure Controlled ventilation.
Default settings are used for:
     I:E ratio = 1:2
     Respiratory rate adults = 15 breaths/min
     Respiratory rate infant = 30 breaths/min
     PC level above PEEP adult = 20 cmH2O
     PC level above PEEP infant = 10 cmH2O
The apnea alarm can be set for:
     Adult apnea alarm can be set from 15 - 45 s.
     Infant apnea alarm can be set from 5 - 45 s.
SAFETY FUNCTIONS
SAFETY FUNCTIONS
SAFETY FUNCTIONS
  - if the flow drops to a flow range between 25% of the peak flow and the lower limit for the Inspiratory cycle off fraction level, and the time spent within this range exceeds 50% of the time spent in between the start of the inspiration and entering this range.
SYNCHRONIZED INTERMITTENT MANDATORY VENTILATION (SIMV)
General
With the SERVO-i it is possible to implement three different SIMV modes:
     SIMV - Volume Control and Pressure Support  ventilation
     SIMV - Pressure Control and Pressure Support ventilation
     SIMV - PRVC and Pressure Support Ventilation
BREATH CYCLE TIME (BREATH CYCLE T)
    This is the length of the total respiratory cycle of the mandatory breath. The total time for inspiration and expiration.
    The SIMV cycle is calculated as follows: 60 seconds divided by the SIMV rate. The SIMV cycle is divided into an SIMV period and a spontaneous period.
EXAMPLE
In the first SIMV period/Breath cycle time, the patient triggers a mandatory breath. In the Spontaneous period the patient can take one or more breaths, depending on the length of the Spontaneous period.
In the next SIMV period the ventilator will wait for the patient to trigger, but if this does not happen within the first 90% of the SIMV period, then a mandatory breath will be delivered.
If the patient is not breathing (i.e. triggering) at all, then only the mandatory breaths will be delivered.
NIV PRESSURE SUPPORTED VENTILATION
GENERAL
NIV Pressure Support is a spontaneous mode of ventilation with back-up apnea ventilation.
INSPIRATION
The SERVO-i delivers a breath when the patient triggers by:
   -lowering the pressure 1 cmH2O below PEEP, or
   -causing an expiratory volume decrease of 6 ml during 100 ms.
EXPIRATION
Expiration starts when the flow rate drops to the user set value of the peak inspiratory flow.
Settings are within the range 10-70% of the inspiratory peak flow.
NIV BACKUP