Care, Maintenance, and Tests
260
Changes in the overall breath rate are tracked and the Adaptive I-Time™
algorithm will seek to adjust the inspiratory time over approximately 10 breaths
in order to maintain the I:E ratio at 1:2. The Adaptive Flow™ algorithm will
accommodate changes in the i-time and automatically adjust the peak flow so
that the delivery of the set tidal volume for the i-time determined by the
Adaptive I-Time™ algorithm is assured.
• The Adaptive I-time™ changes inspiratory time as required to achieve a
1:2 I:E ratio.
• If respiratory rate increases, the inspiratory time will decrease and the
mandatory peak inspiratory flow will increase to deliver the set tidal
volume.
• If respiratory rate decreases, the inspiratory time will increase and the
mandatory peak inspiratory flow will decrease to deliver the set tidal
volume.
Should the Adaptive Flow™ algorithm determine that the peak flows achieved
by the patient’s spontaneous breathing exceed the peak flows that are
determined to be necessary to achieve the set tidal volume, the algorithm will
match the patient’s peak flow so as to avoid the feeling of “air hunger” in the
patient. In this situation, the ventilator will not realize an I:E ratio of 1:2.
If flow is insufficient to deliver the tidal volume, inspiratory time will be
gradually increased in an attempt to deliver the set tidal volume. In this situation
the ventilator will also not achieve I:E ratios of 1:2. For this reason, the user is
advised to leave the inverse I:E ratio alarm on when using Adaptive Flow™ and
adaptive I-Time™. If inverse I:E ratios are achieved it is recommended that the
ventilator controls be set manually.
The speed of change for peak flows and inspiratory times is based upon the
difference between the target flow / time and the desired flow / time. The
greater the difference, the greater the step changes in peak flow or inspiratory
time during the next breath. Most changes are gradual and may take 8 to 10
breaths to make a full change to the new patient condition. The iVent
201
turbine
will deliver peak inspiratory flow rates to a maximum of 120 liters per minute.
Factors limiting the delivery of gas flow are patient lung compliance, airway
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