Pressure Support Ventilation (PSV) Fundamentals

This set covers definitions, adjustments for CO2 management, clinical applications, and a comparison between Pressure Support Ventilation (PSV) and Pressure Control (PC) based on lecture notes.

Pressure Support (PSV)

A spontaneous breathing mode where the patient must initiate all breaths; it is defined as patient-triggered, pressure-limited, and flow-cycled.

PSV Inspiratory Flow Pattern

A decelerating flow pattern, also visually described as a "shark fin."

Primary PSV Settings

The adjustable parameters in PSV mode, which are $PS$ (Pressure Support), $PEEP$, and $FiO_2$.

Under Ventilating in PSV

A state characterized by high $PaCO_2$, which is corrected by increasing $PS$ to increase $V_T$ and $V_E$, thereby lowering $PaCO_2$.

Over Ventilating in PSV

A state characterized by low $PaCO_2$, which is corrected by decreasing $PS$ to decrease $V_T$ and $V_E$, thereby raising $PaCO_2$.

Effect of Increasing $PS$

Usually leads to an increase in Tidal Volume ($V_T$).

Effect of Decreasing $PS$

Forces the patient to perform more work of breathing.

Clinical Uses for PSV

Supporting spontaneous breathing, overcoming artificial-airway or circuit resistance, and weaning or liberation assessment.

Mandatory Breaths

Breaths that are set by the machine; these are present in Pressure Control (PC) but NOT present in Pressure Support (PSV).

Cycling Mechanism: PC vs. PSV

In Pressure Control (PC), inspiration is ended by time; in Pressure Support (PSV), inspiration is ended by flow.

Respiratory Rate ($RR$) Setting

A parameter that can be set in Pressure Control (PC) but cannot be set in Pressure Support (PSV).

$I\text{-time}$ (Inspiratory Time)

A parameter that is set in Pressure Control (PC) but is not set in Pressure Support (PSV) because the mode is flow-cycled.

Time Triggered Breaths

Breaths initiated by the ventilator based on a set time interval; these occur in Pressure Control (PC) but do not occur in Pressure Support (PSV).

$V_T$ Guarantee

The assurance of a specific tidal volume; neither Pressure Control (PC) nor Pressure Support (PSV) guarantees $V_T$ as they are both pressure-targeted modes.