Vents Flashcards
2 Classification of Ventilators
1) Type of Reservoir
Bellows, Piston, Volume
2) Drive mechanism
Pneumatic vs Mech
all under eletrical control
Bellows Classified by
Direction bellow move during expiration
- Ascending
- Descending
Older Machine Modes
Time triggered, time cycled
Cycle to exp phase after set interval elapses from start of inspiraiton
TV product of set insp time and insp flow rate
“Controller Ventilators”
Modern Machines
Pt can trigger breath =
“Non-controlled ventilators”
SIMV, AC, PSV
Bellow driving gas
separate from pt gas circuit =
Double circuit
Air or O2
Bellows
Serve as reservoir for breathing gas
Bellows during Insp Phase
driving gas enters chamber and
1. Vent Relief valve closes (pop off) =
no escape to sacavenging
2. compresses bellow & gas delivered to pt
Bellows during Exp phase
drive gas leave chamber = P drop to 0 = Vent Relief valve to open Once exhaled pt gas fills bellows -scavenging (only happen when bellow filled completely)
Relief / Pop off valve
only open during exhalation
Bellow Problems
Leaks: improper seating hole in bellow (hyperinflate, change O2) Vent Relief valve issue: -hypoventilatle (gas to scavenging not drive) -disconnection, ruptured valve, damage - Stuck closed = >P/PEEP - >scavenging sxn => closed valve
Piston Ventialtor
Use computer controlled stepper motor
Single circuit
Less gas used
Accurate TV
Piston during Ins Phase
PEEP valved closed,
P in circuit from piston closes decoupling valve
FGF directed –> Res Bag
extra goes through APL bypass to scavenging
Ti =
Ti = TV / Flow Rate
Flow rate in ml/min so need to x 60 sec
TE
exp time
TE =
[ 60 sec / (RR/60sec) ] - Ti
MV
MV = TV x RR
I:E ratio
RR
1:2 or greater
8-12
Flow Rate
MV
~ 4-6 x MV
MV = TV x RR
Controlled Mech Ventilation
VC: vol controlled
SIMV
PC: Pressure controlled
Volume Controlled
Set TV delivered, ends inspiration
-most have 2nd limit on insp P
% of TV lost to system compliance (5cc/cmH2O)
Pressure Controlled
Cycle into Exp phase when airway P reaches set level
TV & Ti vary
Piston During Exp Phase
exhaled gas –> CO2 Scrub –> reservoir bag
FGF flows retrograde (-> bag)
Piston “opens” drawing gas in from bag & FGF
Once full, FGF retrograde flows
Piston Problems
Refill even if disconnections
W/ circuit leak, entrain RA =
dilute O2 & agent =
hypoxia / awareness
Positive P Relief valve
Prevent excessive high circuit P
(60-80 cm H2O)
