B. Advanced Modes
- Pressure Regulated Volume Control (PRVC)
PRVC is a hybrid mode of mandatory ventilation that combine pressure and volume
control/limited ventilation. A preset Vt and frequency (minute ventilation) is
delivered with a pressure limit and at the lowest possible pressure by a changing
(adapting) decelerating flow. The preset Vt is achieved with a different pressure by
breath to breath regulation. This mode can be used in a controlled or SIMV mode - Airway Pressure Release Ventilation (APRV)
This mode of ventilation can be thought of as giving a patient two different levels of
CPAP. The clinician/operator sets “high” and “low” pressures with release time. The
length of time at “high” pressure is generally greater than the length of time at “low”
pressure. “Releasing” to the lower pressure, allows lung volume to decrease to
FRC (and promotes ventilation). Spontaneous breathing is allowed on all phases of
the cycle.
Biphasic Ventilation (aka Bi-Vent, BiLevel, BiPhasic, and DuoPAP) ventilation is
similar to APRV, except that T low is longer during biphasic ventilation, allowing
more spontaneous breaths to occur at P low. - Adaptive Support Ventilation
Based on respiratory mechanics, ventilator automatically adjusts respiratory rate
and inspiratory pressure to achieve a desired minute ventilation. The Clinician sets
desired minute ventilation and a patient weight (for estimating anatomic dead
space). The ventilator calculates expiratory time constant from the flow volume loop
and determines the respiratory rate that minimizes work of inspiration at a given