2/26/2018
DOCA3667B Pro Series Operating Manual.doc
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GETTING STARTED (Continued)
Our ventilator, for those of you familiar with the term, is considered a MV divider. For those
unfamiliar with the term, the ventilator delivers a consistent MV to the patient and that MV is
divided into different size TVs by the RATE control. You can change the RATE control all you
want without changing the total ventilation delivered to the patient. Let me repeat that. You can
change the RATE control all you want and it will not effect the total ventilation delivered to the
patient.** In order to change the MV delivered you need only, in fact you must, change the
VOLUME controls. This point will be quite important when you go to wean the patient from the
ventilator.
Remember, when you change the VOLUME controls it is the inspiratory flow that you are
changing directly. The rate and, therefore, the time that flow is delivered has not changed, thus
the delivered TV will be either larger or smaller than before. Stop and think about it, you are now
delivering a different volume of gas to the same compliance of the patient; it follows that the PIP
will be different. This different PIP may be fine or it may be unnecessarily high or low. In the
high extreme the MWPL alarm will sound, a short steady tone, and the PIP will be limited to the
set value or in the low extreme, the LO BSP alarm will sound, a warbling tone.
Back to the change being implemented, you have changed the MV as desired now, If needed, trim
the delivered TV size with the RATE control to obtain a new TV that results in a more
appropriate PIP, and no alarms.
Now do it and get comfortable with it.
Don't just put this document away - setup the ventilator
and a test lung. Read this again trying what is discussed as you read.
Note that no discussion has been made of I-time and E-time and the need to keep them in a proper
relation to each other. This relation is automatically held constant by the ventilator. The I:E ratio
is a consistent 1:2, no need to think about it - there will be enough time for exhalation. For those
of you that want to think about it, we offer the model 2KIE with an adjustable ratio from 1:1.5 to
1:4. Even when the I:E ratio is adjustable that ratio is still held constant over the full range of rate
settings.
**This statement is somewhat of a simplification as you deviate greatly from the current RATE
setting. There is a difference in MV delivered by the ventilator and the alveolar ventilation
received by the patient. This difference is related to the dead space and BS compliance. With
each TV delivered, a portion ventilates the dead space and BS, the more TVs per minute the
greater the portion of the delivered MV that is not seen by the alveoli and, thus, is of no use to the
patient. The significance of this difference is small unless the BS being used is severely
mismatched with the patient or the deviation from the current setting is great. Similarly the
amount of variation is minimal with the small changes needed to trim the TV after adjusting the
MV.
