Page 120 - Clinical Application of Mechanical Ventilation

86 Chapter 4

11. Adaptive support ventilation (ASV)
12. Proportional assist ventilation (PAV)

13. Volume-assured pressure support (VAPS)
14. Pressure-regulated volume control (PRVC)
15. Adaptive pressure control (APC)

16. Volume ventilation plus (VV1)
17. Pressure-controlled ventilation (PCV)
18. Airway pressure release ventilation (APRV)
19. Biphasic positive airway pressure (Biphasic PAP)

20. Inverse ratio ventilation (IRV)
21. Automatic tube compensation (ATC)
22. Neurally adjusted ventilator assist (NAVA)

23. High-frequency oscillatory Ventilation (HFOV)

CLOSED-LOOP SYSTEM

In mechanical ventilation, a simple operating mode provides one output based on
one input. An example is the tidal volume in volume-controlled ventilation. The
clinician sets the tidal volume (input), and the ventilator delivers the tidal volume
using a constant flow (output). The set tidal volume (input) is constant, and inspi-
ratory flow (output) does not vary during the delivery of the tidal volume breath.
In other operating modes, the output changes during delivery of a mechanical
breath. Pressure support ventilation is an example. During pressure support ven-
tilation, the clinician sets the peak pressure plateau (input) and the ventilator uses
a variable flow (output) to maintain the pressure plateau. Since the variable flow
(output) is dependent on the changing characteristics of the airways and lungs, pres-
sure support ventilation is a closed-loop system in which the input (set pressure) is
constant and the output (flow) is variable (Branson et al., 2002).
In addition to pressure support ventilation, other examples of a closed-loop sys-
tem in mechanical ventilation include mandatory minute ventilation, adaptive sup-
port ventilation, proportional assist ventilation, volume-assured pressure support,
pressure-regulated volume control, and neurally adjusted ventilator assist.

SPONTANEOUS

Spontaneous setting on the ventilator is not an actual mode since the frequency and
tidal volume during spontaneous breathing are determined by the patient. The ven-
tilator simply provides the flow and supplemental oxygen. Even though the spon-
taneous mode is not a direct ventilator function, the role of the ventilator during

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