Breathing Systems Flashcards
7 basic components of breathing systems
- CO2 absorbent
- two unidirectional valves
- fresh gas inlet
- Y connector
- resevoir bag
- adjustable pressure limiting valve
- low resistance tubing
Soda lime
Calcium hydroxide, some sodium hydroxide and potassium hydroxide. silica added to decrease dust
water and heat are produced which adds humidity and heat to breathing circuit
Why does color change occur soda lime
pH sensitive rxn
L/100g absorbent can soda lime absorb
23-26L of CO2 per 100g
size of granules in absorbents
smaller granules have great surface area for absorption but increased resistance to air flow
incompetence of either valve causes ____
rebreathing
where does fresh gas enter in circle system
between absorber and inspiratory valve
what does reservoir bag store
O2 and anesthetic gases
where is APL valve positioned
near exhalation unidrectional valve, gas scavenging systems collect any gas exiting system via relief valve
safety features in anesthesia breathing system that ensure patient receives adequate oxygen sypply
- fail safe valve
- rotameter
- proportioning device
when does fail-safe prevent hypoxic mixture
if decreased oxygen supply at flowmetes level
device present in gas lines except for O2 and is controlled by O2 sypply pressure
how does fail safe device work
interupts supply of other gases if O2 supply is reduced to a certain level, usually below 30 psi
that level is the opening threshold pressure for the other gases
flowmeters/rotameters control what
control gas proprotions and gas flow to common gas outlet
how does rotameter work
adjusts gas flow by means of flow control needle valves and flow tubes
gas flow enters at base of glass flow tube and glass tube is tapered in that its diameter increases with height
small metal bobbin rides the gas jet
variables that affect flowmeters
temp and altitude (higher altitude, increased flow)
oxygen ratio and proportioning devices
links 2 flows to prevent a final inspired O2 conc of less than 25%. 14teeth in gear for nitrous and 29 for O2
gases that ratio and proportioning devices work on
ONLY O2 and N2O
rebreathing effect on patient depends on
FGF and mechanical dead space
relationship between flow and rebreathing
inverse
system with no valves, tubing or reservoir bag, patient has access to atm gases
open
system with resevoir but no rebreathing, mapleson circuit or circle at high gas flow
semi-open
system with resevoir bag and allows for partial rebreathing
semi-closed
system with resevoir bag and allows for complete rebreathing, CO2 absorbed
closed
noncircle systems
insufflation, open-drop, draw-over, unidirectional, mapleson
insufflation noncircle system
open, fire risk, depth of anesthesia unpredictablek insufflated over face
open-drop non circle
ether, chloroform on gauze
draw-over noncircle
non rebreathing valve, self inflating bag, vaporization chamber
unidirectional valve noncirce
Ambubag
Mapleson circuit
semi-open or semi-closed,
Advantages of circle system
Maintenance of relatively stable inspired gas conc, conservation of resp moisture and heat, prevention of operating room pollution, closed-system or semi-closed
sevo reacts with what to form Compound A
soda lime
from greatest production of carboxyhemoglobin to least, anesthetic gases
des > en > iso > halothane = sevo
factors that increase production of carboxyhemoglin
inhaled anesthetics, type of absorbent, low FGF, increased absorbent temp, dry absorbent, higher conc of inhaled, size of patient
max concentration ppm of halogenated agent alone
2
max concentration ppm of nitrous alone
50
max concentration of combined, halogenated agent
0.5
max concentration of combination, nitrous
25
scavenging system components
gas collecting assembly, transfer tubing (19 or 30mm), scavenging interface, gas disposal tubing, disposal assembly
Closing capacity
volume in the lungs at which small airways that do not have cartilaginous support begin to close
what happens when CC > FRC
atelectasis
possible trigger variables
time, pressure, flow, volume
how to avoid breathstacking for COPD on ventilators
MV uses higher Vt with decreased RR, avoid high airway pressures, longer expiratory time
during negative pressure ventilation (spont breathing) inspiration _____ venous return
increases
PPV ______ blood return and _____ preload during inspiration
reduces, decreases
PPV _____ RV afterload
increases, because of high intrathracic pressure
afterload is ______ in PPV
decreased, improves left ventricular emptying
what is auto PEEP
incomplete exhalation prior to the next inhalation causing progressive air trapping leading to higher alveolar pressure at end expiration
assist control ventialtion (CMV)
delivers preset volume or pressure at specified rate but allows patient to trigger breath anytime, can be pressure or volume controlled
AC rate
is the minimum number of full ventilator breaths patient will receive
IMV is volume control that delivers ______ volume at _____ rate
preset, preset
difference between AC and IMV
with IMV, if patient takes breath on own they get no addtl support
both need to set FiO2 and PEEP
pressure support
provides assistance to each spont breath
airway pressure release ventilation applies ?
continuous postive airway pressure for a prolonged time to maintain adequate lung volume and alveolar recruitment
