requirements. Other than increasing the FiO2, increasing the PEEP is the most
effective way to increase oxygenation (see oxygenation below)
On VC and PRVC: The clinician/operator will set a desired Vt. Depending on the
clinical situation, the initial desired Vt could range from 6 to 10 ml/kg (ideal body
weight for height). The PIP becomes a dependent variable and will depend on the
chosen Vt, iT (shorter iT result in higher PIP), PEEP, and respiratory system
compliance.
On PC: The clinician/operator will set a pressure control (PC) above PEEP in order
to achieve the desired/intended Vt. The PIP is then the sum of the set PC+ set
PEEP. A range of 20-24 is a good starting point and should be titrated in order to
achieve adequate chest rise and the desired Vt (6-10 ml/kg). On this mode, the Vt
is the dependent variable and will depends on the set PC, iT (manipulating the iT
will also affect the Vt, with longer iT generally resulting in larger Vt) and the
respiratory system compliance.
D. Adjustments:
Oxygenation:
Oxygenation is related primarily to the mean airway pressure (MAP) and %
of inspired oxygen (FiO2). When you are having problems with oxygenation, you
might need to increase the MAP; changes in arterial PaO2 are directly related to
changes in MAP. The MAP is the average pressure of the airway throughout the
respiratory cycle. On PC mode it depends on the PEEP, iT, PIP, and RR; on VC
and PRVC, it depends on the PEEP, iT, Vt and RR. As stated above, the most
effective way to increase the MAP (in any mode) is to increase the PEEP.