ASV Flashcards
What is ASV?
a form of pressure ventilation where instead of guessing a pressure (and VT) - a minimum minute ventilation is set for the patient
What are the uses of ASV?
- as start-up procedure only
- to critique actual settings
- weaning with and w/o protocol
- for post-cardiac surgery patients
- for all patients, including ARDS
How to use ASV clinically (part 1)
- set body weight of patient and high pressure limit to 45
- set %minvol to 100% (except HME and COPD- set 110%)
- set PEEP and FIO2 according to clinical requirements
- connect patient
How to use ASV clinically (part 2)
- ventilate for some minutes and assess blood gases and/or WOB
- adjust %minvol to meet pH/PaCO2 targets or WOB targets
- adjust PEEP and FIO2
- Review high pressure limit setting, consider changes only in exceptions
- observe Ppeak and fSpont trends
How does ASV achieve a preset minvol while respecting boundary conditions?
maintains at least 100% of normal ventilation, takes spontaneous breathing into account, prevents tachypnea, prevents autopeep, prevents excessive deadspace ventilation, fully ventilates in apnea or low drive, gives control to patient in case breathing activity is okay, and does this without exceeding a 35 plateau pressure
What does the therapist control in ASV?
- IBW based on patient’s height (add 10% if HME or COPD)
- %minvol: goal is for complete rest and increase VE to meet needs
What should you do if you want to wean a patient off ASV?
decrease VE
How is VE determined in ASV?
-IBW and % minvol settings
-delivers 100 mL/kg (so if patient is 100% VE and 70kg, he receives 7 L; if patient is 50% VE and 70kg, he receives 3.5L)
[ 70kgs x 100 mL/kgs = 7000 mL or 7 L
7 L x 1 (for 100%) = 7 L
70kgs x 100 mL/kgs = 7000 mL or 7 L
7 L x .5 (for 50%) = 3.5 L ]
What does ASV control?
itime, minimum VT and rate based on compliance. RAW and etime are constant measurements
What is the difference between patient triggered and non-triggered breaths in ASV?
patient triggered breaths are PSV and non-triggered breaths are PC
What is the difference between PSV and PC?
how they are cycled. PSV is flow cycled and PC is time cycled
How does ASV adapt?
- if reduce the %MV, the target rate and VT will also decrease
- will not allow spontaneous VT to fall below target CT or rate to fall below target rate (it will increase PS if VT drops or decrease PS if VT increases)
- limits RR so that if rate increases, the PS will increase
What is the functional description of ASV?
- calculation of minute ventilation
- application of lung-protective rules
- optimal breath pattern
- approach the target
What should you do if a patient is ready to wean from ASV?
decrease %minvol to 50% and perform trial for 30-120 minutes. extubate if patient tolerates according to current practice/guidelines
