1. Anesthesia Machine Flashcards
ASA mandated monitored levels
oxygenation
ventilation
circulation
temperature
blood pressure
pressure exterted by blood aginst the interior walls of blood vessels
sytolic pressure
systole
diastolic pressuyre
diastole
why is BP monitoring important
how we measure whether or not the patient is being adquately perfused
normal BP
120/80 mmhg
hypertenstion
> = 140/90 mmhg
high bp
hypotension
<= 90/60 mmhg
low bp
mean arterial pressure
the avg pressure in a patients arteries during one cardiac cycle
mean arterial pressure calculation
MAP = [(2*diastolic BP)+Systolic BP]/3
normal MAP
70-100 mmHG
pulse pressure
systolic pressure minus diastolic pressure
S-D
normal pulse pressure
30-40mmHG
ECG measures
heart rhythm
normal HR
60-100
tachycardia
> 100
high HR
bradycardia
<60
low HR
pulse oximetry
SpO2
percentage of heme saturated w/O2
“oxygen saturation”
normal SpO2
93-98% (on room air)
end tidal CO2
EtCO2
amount of CO in expired air
normal EtCO2
35-45mmHg
capnograph (EtCO2) monitor functions
reveals pts EtCO2
reveals pts RR
respiratory rate
RR
spontaneously breathing RR
12-20 breaths per min
increase pain
increase RR
narcotics
decrease RR
normal RR on ventilator
8-12 breaths per min
ventilator RR is slower than spntaneous because
ventilator tidal volumes are largert than spontaneous tidal volumes
room temp
23 C
core body temp
36-38C
purposes of anesthesia machine
- Positive pressure ventilation (PPV)
- anesthetize pt w/inhaled anesthetic gas
2 types of anesthetic gases
volatile agents
fresh flow gasses
volatile agents
keep pts anesthetized during surgery
stay asleep
types of volatile agents
sevo
des
iso
fresh gas flow types
O2
air
NO2
fresh gas flow
picks up and delivers volatile agent to the pt
O2 (fresh flow gas)
higher FiO2 compensates for atelectasis
some pts (lung pathology) need higher FiO2 to have adquate O2 saturation
higher FiO2 allows patient to mx adequate O2 saturation for longer periods during unexpected apnea
NO2 (Fresh flow gas)
only anesthetic gas that has analgesic properties
allows anesthetist to use lower concentrations of volatile agent
Air (fresh flow gas)
too much oxygen for too long can be toxi
higher FiO2 can cause absorption atelectasis
FiO2 above 30% and/or NO2 increase risk of airway fire
wall supply pressure
50psi
pt gas pressure
16psi
Diameter index safety system
DISS
prevents NO2 from connecting to O2 line for wall connections
Pin Index safety system
PISS
prevents connecting machine to worng gas tank
Flowmeter mechanical proportioning system
built in system that limits the % of NO2 that can be given to a pt
max NO2:O2 ratio
3:1
75% NO2
25% O2
Low pressure pathway order
Flowmeters
Common Manifold
Vaporizers
Fresh gas outlet
Inspiratory tubing
Patient
Expiratory tubing
Rebreathing bag/vent
CO2 absorber/APL valve
Exhaled gas joins fresh
rebreathing
pt rebreathes their own exhaled gas
circle system
new fresh flow is contantly added
pt continually rebreathes gas they exhale
rebreathing causes pressure to
increase
why do we need positive pressure
to ventilate!
we dont want circuit pressure to be too high
lungs overinflate
scavenging system
takes excess gas away from the circuit
controls the amount of pressure inside the circuit
too much gas going to scavenging
circuit pressure might be too low
too little gas going to scavenging
circuit pressure might be too high
how do we control amount that goes to scavenging
APL valveA
Adjustable Pressure Limiting Valve
control the amount of pressure inside the circuit by controlling the amount of gas that goes to scavenging
close APL
increase P
clockwise
open APL
decrease P
counter clockwise
airway pressure units
cmH20
as volume goes into lungs
pressure increases inside lungs and circui
APL valve open, pressure gauge reads
0
APL valve closed, pressure guage reads
increase in pressure
max pressure when ventilating via mask or LMA
20cmH2O
max pressure when ventilating via ETT
40cmH2O
high pressure pathway of O2
carries fresh flow gas to flowmeters before pressure reduces
can bypass flowmeters w/oxygen flush valve
oxygen flush valve
allows 50psi to enter circuit quickly
allows rapid pressure increase
used in circuit leaks
if there is a circuit leak
wont be able to build up pressure in circuit or ventilate pt
finding leak
- trace circuit away from pt
- if you cant find cause of leak, its likely the ETT cuff
ways to increase circuit pressure
- turn up fresh gas flow (increase FR, increase P)
- close APL
- oxygen flush
- avoid leak in circuit
bag mode
manual/spontaneous mode
ventilator is not turned on
all exhlaed gas flows through breathing bag
when pt inhales
breathing bag deflates
when pt exhales
breathing bag inflates
when do we use manual/spontaneous mode
if pt is breathing on own
when do we use ventilator mode
if pt has no drive to breath
respiratory depression
ventilator mode
ventilator on
delivering positive pressure breaths
both breathing bag and ventilator are part of circuit
what controls APL valve/amt pressure in circuit when mask breathing
anethetist
what controls APL valve/amt pressure in circuit when ventilator breathing
anesthesia machine
when to use breathing bag
short duration
pt not intubated
when to use ventilator
long duration
pt intubated
common situations for mask ventilation
- after induction before intubation
- mask induction
- failed intubation
- unexpected apnea
spontaneous ventilation
pt breathing on won
spontaneous ventilation machine modes
manual/spontaneous
pressyure support mode
assist ventilation
provide larger breath (Vt) than if pt was breathing entirely on their own
deliver breath right as pt starts to inhale
pressure support mode
auto assist ventilates every spontaneous breath
decreases likelihood of atelectasis
switch to manual prior to extubation to verify Vt
mechanical ventilation
anesthetist breathing for pt w/ PPV
delivered by squeezing bag or using ventilator mode
What does the Anesthetist program on the ventilator:
- set respiratory rate
- 8-12 breaths/min
- set tidal volume
- 6-8 mL/kg
how to help pts tolerate ventilator
- Muscle rlaxants
(long term) - high dose narcotics
(long term) - propofol (short term)
tidal volume
how big of a breath we decide to give pt
6-8mL/kg
higher tidal volume generates
higher inspiratory pressure
Vt / P relationship
directly proportional
respiratory rate
how many breaths per minute we tell ventilator to give
8-12 breaths/minrespir
respiratory rate determins
how long each breath is
RR 20
each breath is 3 seconds
RR12
each breath is 5 seconds
slower respiratory rate
longer each breath
longer inspiratory time
lower pressure
faster respiratory rate
shorter each breath
shorter inspiratory time
higher pressure
peak inspiratory pressure (PIP)
max pressure allowed to be generated in chest with ventilator breath
stay under 35-40cmH2O
causes of high PIP (8)
- Right mainstem intubation
- bronchoconstriction/
bronchospasm - coughing/bucking on ventilator
- trendelenburg posn
- insufflation of abdomen
- increased resistance through ETT
- too high tidal volume
- too fast respiratory rate
ETT diameter
smaller: high resistance
larger: lower resistance
Positive End Expiratory Pressure (PEEP)
leave a small amount of PP in the lungs at the end of expiration
prevents atelectasis
normal: 5cmH2O
only on ventilator
Continuous Positive Airway Pressure
(CPAP)
leaves small amount of positive pressure in circuit at all times
constant PEEP
only in manual mode
Common uses for CPAP
- recovery room for sleep apnea
- nighttime CPAP mask
- preoxygenation for obsese pts
- lung surgery intubation
- laryngospasm: jaw thrust w/cpap mask
I:E Ratio
amount of time that is allotted for each inspiration and expiration in one breath
normal I:E ratio
1:2
expiratory time is 2x as long as inspiratory time
inspiratory time and expiratory time are
inversely proportional
prolong inspiration
shorten expiration
prolong expiration
shorten inspiration
slow RR
longer inspiratory/expiratory times
fast RR
shorter inspiratory/expiratory times
increasing inspiratory time
lowers peak airway pressure
shortens expiratory times (air trapping)
AUTO PEEP
air trapping
lungs cant exhale fully
due to short exhalation time
over time the lungs can overinflate
PIP increase
difficult ventilation
decreasing inspiratory time
PIP increase
vent has to push harder/faster to force breath over shorter time
inspiratory time
Ti
normal Ti
2 seconds (adults)
0.3-0.5s (neonates)
Ti vs PIP
inversely proportional
volume control ventilation
anesthetist sets tidal volume
vent will deliver Vt regardless of the pressure needed to do so
you can set pressure guard to limit amount of PP the vent will deliver
Volume control ventilation problems
- can gen high PIP
- accidentaly overinflation of lungs if you forget to change Vt
Pressure control ventilation
anesthetist sets the amt of PP they want to be generated with each vent breath
lungs expand until that pressure is reached
Pressure control ventilation (advantages)
lungs should never become overinflated
pressure control ventilation problems
you have to tinker with the pressure to adjust tidal volume to be appropriate for weight
tidal volumes can change in surgery
If pressure is constant, volume and resistance are
inversely proportional
increase resistance, less volume can go to lungs
decrease resistance, more volume go to lungs