Mechanical Ventilation (MV) & ARF Flashcards
what is ventilation
movement of gases in and out of lungs
what is gas exchange
O2/CO2 across membrane
what is respiration
exchange of O2/CO2 out of cell (internal)
What is compliance
distensibility of the lung tissue
2 examples of when lung compliance may be decreased
PNA
pulmonary edema
what ventilation method is preferred in cases of decreased lung compliance
pressure support
what is meant by resistance in terms of ventilation and ARF
diameter of airways
i.e. increased airway resistance in asthma
what is respiratory failure
condition in which the respiratory system fails in one or both of its major fns - gas exchange or ventilation
how is respiratory failure diagnosed regarding blood gases
blood gases
PaO2 <60
PaCO2 >45
pH < 7.35
what are other diagnostic criteria for ARF aside from blood gases
clinical presentation, deviation from pts baseline if they have COPD, history, imaging, VQ scan
what is the difference between respiratory insufficiency and respiratory failure
insufficiency gradually needing some O2 support
failure - full O2 support with MV and O2
what are the 3 types of respiratory failure
Type 1: acute hypoxemic respiratory failure
type 2: acute hypercapnic respiratory failure
combined
what is the primary problem in type 1
gas exchange
what is the primary problem in type 2
ventilation
what are the two main causes of type 1 resp failure
diffusion
V/Q mismatch
what are the 4 components affecting diffusion in type 1 resp failure
SA of alveoli
thickness of AC membrane
diffusion coefficient CO2: O2
Driving pressure - difference between alveolar partial pressure and capilliary partial pressure
what are the two components of V/Q mismatch
intrapulmonary shunt
alveolar deadspace
what can cause alveolar deadspace
PE, decreased CO, shock
does respiratory acidosis or alkalosis occur in early stages of resp failure? why?
decreased PaO2 causes peripheral chemoreceptors to trigger resp center to increase rest rate/depth (ventilation) causes more CO2 exhaled resulting in resp alkalosis
what type of gas would you expect with prolonged type I resp failure
resp acidosis as pt fatigues and hypogentilation occurs, decreased O2 delivery to cells causes impaired tissue perfusion and lactic acidosis and MODS
what PaO2 triggers peripheral chemoreceptors to increase RR and depth
<60
what is the diffusion coefficeint and what does it mean
20:1 CO2 diffuses 20X faster than O2
What happens with CO2 in blood and alveoli in type 2 resp failure
equalize so CO2 can’t cross AC membrane
what is alveolar hypotension? what type of resp failure does it occur in?
amount of O2 to alveoli is insufficient to meet O2 demand
type 2
what can cause type II resp failure? (10)
neuromuscular disease (GBS, myasthinis gravis) spinal cord injury musculoskeletal abnormalities supression of CNS resp fxn - drug poisoning post cardiac arrest brain injury upper airway obstruction general anestehsia bedrest pneumo chest trauma obesity
what 3 things does resp failure type II result from
decreased muslc fn - malnutrition, underlying disease, fatigue
increased airway resistance - stridor, upper airway disease, asthma
decreased lung compliance
what are common management strategies for type 1 resp failure (4)
PEEP
minimize deadspace by optimizing CO
increase driving pressure (FiO2)
repositioning
What are common management for Type 2 Resp failure
improve ventilation - WOB, RR, tidal volumes
optimize O2 demand, CO and O2 transport
bicarb
intubation and MV
what are 4 ways in which pneumonia can be acquired
aspiration
inhalation
bloodborn
translocation - changing pH of gastric content encourages growth of microbes which can travel to the lungs
what are the two main types of pnuemonia
CAP
HCAP
what is a subset pneumonia of HCAP
VAP
CAP dx vs HCAP
CAP dx <48hrs from admission
HCAP dx >48 hrs within hospital or w/in last 90 days
what are typical gram positive bacteria responsible for CAP
streptoccus pneumonia, MRSA
what are typical gram negative bacteria responsible for CAP
mycoplasma, legionella, chlamydia, psudomonmas
Aside from bacteria what else can cause pneumonia
viruses - coronavirues, adenovirus, influenza, RSV
fungi - aspergillosis, spiralis
is HAP typically gram positive or gram negative
negative
what is VAP typically caused by (3)
MRSA, pseudomonas, Enterobacter
4 things about ETT that increase chance of VAP
prevents cough - bodies natural defense
prevents upper airway filtering and humidification
inhibits ciliary transport by epithelium
direct conduit into lungs for airborne pathogens
how is VAP dx
positive cultures
new consolidation on CXR
worsening infiltrates
S&S
8 ways VAP can be prevented
semi recumbent position HOB 30-45 degrees
hand hygiene
sedation vacation
ETT with polyurethane cuff, subglottic or EVAC suction
non-invasive postive pressure ventilation/extubate ASAP
conduct SBT trial daily
early mobilization and exercise
oral care
how do you treat atypical pneumonias
antivirals - tamiflu
antifuncal - clotrimazaole, fluconazole, micafungin
how do atypical pneumonias present
inflammation in alveolar septums and interstitial of lung
appear as patchy infiltrates on CXR more diffuse
fungal pneumonias are most often found in what type of pts
immunocompromised
2 types of ventilation and main difference between the two
spontaneous - negative pressure for inspiration
mechanical - positive pressure for inspiration
what causes the start of inspiration in spontaneous breathing
increased PaCO2 stimulates resp center in medulla
is inspiration in spontaneous breathing passive or active? exhalation?
inhalation - active
exhalation - passive
Is which mode of ventilation is intrathoracic pressure increased, what can this cause
MV
inhibits venous return and lowers preload
T or F exhalation is passive in both MV and spontaneous breathing
T
Benefits of mech vent
alveoli recruitment reversal of atelectasis increased FRC decreases WOB improves gas exchange
what is the best indicator for needing MV
PaCO2 >55 or pH < 7.20
above what RR might we consider MV
35
at what PO2 might we consider MV
<55
What are the 3 types of ventilator breaths
controlled
assisted - delivered if they attempt to trigger breath
spontaneous - triggered by pt effort and provides some support
in spontaneous ventilator breaths who determines the TV
pt
when is pressure cycle ventilation indicated
for decreased compliance and pts at inc risk for barotrauma
what is Vt
tidal volume
how is Vt calculated
4-7mL/kg to protect lungs
calculated based on pts ideal body weight to reduce baotraumas
what is Mv and how is it caluclated
minute volume
amount of air delivered to pt in one min
TV x RR
what is goal MV
5-10 L/min
how do you calculate PiP or Ppeak
PEEP + pressure
what is measured to determing lung compliance; how is this done
plateau pressure
measured @ end of inspiration by inspiratory hold goal <30 increased values indicate poor lung compliance
what is FRC and how do we improve it
functional residual capacity
opening more alveoli and preveenting collapse
PEEP and CPAP
what is the most common mode of ventilation
volume control/assist control
what is set in Assisted Volume Control
RR and TV, trigger
PEEP, FiO2
what can the pt do in VC
breathe above set RR receive set TV
what values should you monitor in VC (3)
RR
PIP
plateau pressures
what happens if compliance deteriorates in VC how would you know and what should you do
will see inc PiP
change to PC
can VC cause resp alkalosis?
yes if pt is breathing at inc RR for non-resp reasons such as pain, anxiety
what type of patients is PC used for
pts with decreased lung compliance and severe oxygenation problems
what do you set in PC
pressure, RR, Ti, trigger
PEEP, FiO2, alarms
what can a pt do in PC
can breathe above set RR but receive set P
what values should you monitor in PC
RR
MV
TV
EtCO2 - will vary based on MV
what setting do you see I:E
PC
in what setting do we see laminar flow
PC
what are the benefits of laminar flow
less turbulent better at opening smaller airways
what can affect I:E
RR
why is PC better for sever oxygenation issues
because you can alter I:E, improves V/Q mismatch
what does inc PiP over time indicate
decreased lung compliance
what can an isolated event of inc PiP incidate
ETT obstruction secretions pneumo kink in system bronchospasms
what is the most common mode for weaning a pt from the vent
pressure support
what is set for PS mode
level of inspiratory pressure
flow and trigger parameters
FiO2/PEEP/CPAP alaras and apena mode
what must the pt be able to do for PS mode
spontaneously breath
own RR and TV
what values should be monitored for PS
RR
TV and MV
EtCOT2 - will change based on MV
What does SIMV stand for and when is it used
sychrnoized intermittent mandaotry ventilation SIMV
short term post anasethsia CSICU
what is set in SIMV
RR and TV triggers
Peep, Fio2 and alarms
what can the pt do in SIMV
breathe above rate and receive own TV
what should be monitored in SIMV
RR
TV and MV - minute volume is set to gaurantee a minimum
PIP - fluctuate based on compliance
why is SIMV synchronized
ventilator has the ability to sense pts inspiratory effrot and can reschedule mandatory breaths to avoid breath stacking
when do apnea alarms occur
occurs if no breath is taken for 10-20s
what would cause a high pressure alarm
biting on ETT water in tubing secretions kinked tube pneumo bronchospasm
what would cause a low pressrure
leak in system
leak in cuff
disconnection
what can cause a low exhaled volume
leak in system or cuff
pt tiring
pressure limit being reached - decreased lung compliance
what can cause high RR
anxiety, agitation, hypoxia, hypercapnia, pain, readiness to wean?
when can O2 toxicity occur
FiO2 > 50% for over 24 hours
what happens in O2 toxicity and what can it cause
O2 free radiacls toxic metabolites of O2 metabolism can damage AC membrane
can cause atelectasis, localized edema, reduced compliance
what is absorption atelectasis
too much O2 can wash out nitrogen in the alveoli
nitrogen helps keep alveoli open so can cause them to collaspse
what are the 7Ps of RSI
preparation preoxygenate for 3-5 mins pre-treatment paralysis positioning sniff position placement post intubation managment
what type of trauma can occur with insufficient PEEP
atelectrauma - shearing injury d/t alveoli repeatedly opening and closing
weaning criteria
able to initiate spontaneous breathing
cause has resolved
hemodynamically stable low or no pressers
able to protect airway
does a patient have to be awake and alert to wean from ventilator
no
what results in failure to wean
HR >140 bpm SBP <90 or >180 RR >35 for >5 mins, inc WOB diaphroesis changes in mental status spO2 <90 or PaO2 decrease by 10 or <50
what are 3 weaning methods
SBT - spontaneous breathing trials
Progressive decrease in PS in PSV
progressive decrease in ventilator initated breaths in SIMV mode
when would a MV pt be switched from from ETT to trach
1-3 weeks
why are trachs preferred to ETT (3)
less analgesia and sedation required
facilitates communication
facilites weaning
hwy are post pyloric feedings preferred in MV
lowers risk of aspiration
fewere GI complications
higher caloric/protein intake
what vitamin do we need to ensure is supplemented in MV and why
thimaine
glucose/dextrose load increases demand for thiame
thiamine deficiency can occur in <28 days
and can cause lactic acidosis, cardiac dysfxn, hypertrophy and arrhythmias
what is gluconeogenesis
creating glucose from non-carb sources mainly in liver
what is glycogenolysis
breakdown of glycogen to provide energy for muslce contraction
why does hyperglycemia occur in critically ill
hypermetabolic state results in increased glycogenolysis and glucoenoesis results in increased glucose levels
what can hyperglycemia do to the body
weakened immune system
decreased GI motility
increased cardiovascular tone
abnormal inflammatory response
what are benefits of feeding
decreased catabolic response reduces risk of infection improved healing improved GI fn improved glucose absorption prevents bacterial translocation decreases lenght of stay
