Additional Adaptive and Servo Modes of Ventilation

what type of mode is volume support

pressure control continuous spontaneous ventilation with an adaptive targeting scheme

what is the control variable in volume support

pressure

what type of breaths occur in volume support

all breaths are spontaneous

what phase variables are used in volume support

patient triggered and flow cycled

what targeting scheme is used in volume support?

adaptive

how does volume support compare to PC-CMV adaptive modes

it is similar but uses only spontaneous breaths

how does the ventilator deliver tidal volume in volume support

it adjusts pressure support to achieve a preset tidal volume

how does the ventilator adjust pressure support

by monitoring changes in compliance and resistance

what happens if the set tidal volume cannot be delivered

the ventilator will alarm

what is a disadvantage of adaptive modes like volume support

the ventilator cannot distinguish between patient improvement and increased demand

what happens if a patient attempts shallow, rapid breathing in volume support

the ventilator will instead deliver preset volumes, potentially causing hyperventilation

how is hyperventilation detected in volume support

through appropriate volume alarms

when is volume support commonly used

in infants with infant respiratory distress syndrome

why are infants with IRDS good candidates for volume support

they have low compliance due to lack of surfactant and their lung function can change rapidly with treatment

what is the benefit of volume support in neonates

it maintains a constant tidal volume despite changes in lung characteristics and patient effort

why is maintaining a constant tidal volume important in neonates

because they are sensitive to rapid changes in carbon dioxide levels

what is volume guarantee (VG)

an adjunct used with pressure control modes that ensures a set tidal volume is delivered

how does volume guarantee work

the ventilator adjusts pressure to achieve the set tidal volume

what happens to the targeting scheme when VG is activated

it becomes adaptive

what type of mode is mandatory minute ventilation (MMV)

pressure control continuous spontaneous ventilation with an adaptive targeting scheme

what is the control variable in MMV

pressure

what type of breaths occur in MMV

primarily spontaneous breaths with backup mandatory breaths if needed

what targeting scheme is used in MMV

adaptive

how is MMV different from IMV

it is a spontaneous mode with a backup CMV option rather than a mix of mandatory and spontaneous breaths

what does the operator set in MMV

a minimum minute ventilation

what happens if the patient’s spontaneous ventilation is insufficient

the ventilator delivers time-triggered mandatory breaths

how are mandatory breaths delivered in MMV

they are synchronized with spontaneous breathing

how is tidal volume delivered during mandatory breaths in MMV

pressure is adjusted to achieve the set tidal volume

what type of mode is proportional assist ventilation (PAV)

pressure control continuous spontaneous ventilation with a servo targeting scheme

what is the control variable in PAV

pressure

what type of breaths occur in PAV

spontaneous breaths

what phase variables are used in PAV

patient triggered and flow cycled

what targeting scheme is used in PAV

servo

what is a servo targeting scheme

a system where the ventilator adjusts output based on changing patient inputs

what types of inputs does the ventilator track in servo targeting

patient effort, compliance, and resistance

how does the ventilator respond to these inputs

it adjusts pressure output in response

is the output constant in servo targeting

it varies between breaths but remains constant within a single breath

what is the output delivered by the ventilator in servo targeting

pressure at the airway opening

how does the ventilator generate pressure in PAV

it creates pressure at the mouth in response to the patient’s inspiratory effort

what determines the amount of pressure delivered in PAV

patient effort, lung compliance, airway resistance, and the percent support setting

what role does PAV play in breathing

it acts as an inspiratory amplifier

what determines the level of amplification in PAV

the percent support setting

what parameters does the ventilator continuously measure in PAV

inspiratory flow and inspiratory volume

how often does the ventilator estimate compliance and resistance in PAV

every 5 to 10 breaths

what are considered the “moving inputs” in PAV

compliance and resistance

how does the ventilator use these inputs

it adjusts pressure support based on the moving inputs and percent support

what happens when percent support is set at 35% in PAV

the ventilator provides 35% of the work of breathing and the patient provides 65%

what happens if work of breathing increases in PAV

the ventilator increases pressure support

what happens if the patient’s inspiratory effort increases

pressure support increases to meet demand

what happens if the patient’s inspiratory effort decreases

pressure support decreases

how is work of breathing monitored in PAV

using a displayed work of breathing scale

what is the goal when setting percent support in PAV

to keep the patient’s work of breathing within the green zone

what type of targeting scheme is used in PS + CPAP

set point

how does PS + CPAP respond to changes in compliance and resistance

it provides a single constant pressure output

does PS + CPAP consider patient effort

no, patient effort does not change the level of pressure support

what happens if patient effort increases in PS + CPAP

the pressure support remains the same

what does PS + CPAP allow regarding patient work of breathing

the patient does some work but can still remain relatively passive

what happens to tidal volume when pressure support is decreased in PS + CPAP

tidal volume decreases without a compensatory increase in patient effort

what type of targeting scheme is used in PAV

servo

how does PAV respond to patient effort

it adjusts pressure support proportionally to the patient’s effort

what happens when percent support is decreased in PAV

the patient must increase their work of breathing to maintain tidal volume

how does PAV affect tidal volume when support is reduced

tidal volume can be maintained if the patient increases effort

how does PAV differ from PS + CPAP in output delivery

PAV provides a variable output while PS + CPAP provides a constant output

how does PAV affect patient control of breathing

the patient controls when inspiration starts, how deep the breath is, and when it ends

what are the benefits of PAV

reduced patient-ventilator asynchrony and reduced respiratory muscle weakness

what is patient-ventilator asynchrony

a mismatch between ventilator support and patient demand

what are the consequences of patient-ventilator asynchrony

increased mortality and longer duration of mechanical ventilation

what is respiratory muscle weakness

a reduction in respiratory muscle capacity due to passive ventilation or overload

what is a consequence of respiratory muscle weakness

delayed weaning from mechanical ventilation