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Intro Nurse Anesthesia > Ventilators > Flashcards

Ventilators Flashcards

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1
Q

How are bellows classified?

A

Direction of bellows movement during expiration

Ascending- ascends during expiratory phase
Descending- descends during expiration

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2
Q

Classification of reservoirs?

A

Bellows
Piston
Volume

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3
Q

Drive mechanisms of reservoir?

A

Pneumatic

Mechanical

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4
Q

Bellows uses what drive mechanism?

A

Pneumatic

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5
Q

Piston uses what drive mechanism?

A

Mechanical

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6
Q

Equation for MV

A

MV= TV x RR.

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7
Q

Volume control ventilation (VCV)

A
  • Terminates when preselected TV delivered

- Percentage of TV is lost to compliance of system (4-5 cc/cmh2o)

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8
Q

Pressure control ventilation? When is it used, what is held constant, what changes?

A

Used with COPD, ARDS

-cycle into expiratory phase when airway pressure reaches predetermined level

  • Pressure constant
  • Volume and inspiratory time vary
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9
Q

Talk about relationship of drive gas and patient gas circuit with the bellows?

A

It’s a double circuit
DRIVE gas is separated and send to bellows to drive the bellows (usually 100%o2)

Pt gas circuit is inside bellows

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10
Q

What 2 things happen when drive gas enters the bellows?

A
  • Pop off valve closes so no gas can escape into scavenger

- Bellows compressed and gases in bellows are delivered to patient

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11
Q

Is the reservoir bag included in a bellows system?

A

No, it is completely separated

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12
Q

When is pop off valve open?

A

Only during expiration AFTER bellows have been filled with patient gases.

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13
Q

Issues with bellows? (3)

A

1) Leaks
2) Hole in bellows
- causes hyperinflation of lungs
- o2 concentration changes

3) Ventilator relieve valve problems
- Valve open- Hypoventiatlion (going to scavenger rather than drive)
- Caused by-disconnection, ruptured valve’
- Stuck valve in closed position which causes increased PEEP and excess pressure
- Excess suction from scavenging can close the valve and cause increased pressure

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14
Q

What is piston ventilation similar to?

A

Syringe

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15
Q

Describe the piston ventilator circuit?

A

Single circuit

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16
Q

Which uses more gases, bellows or piston?

A

Bellows

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17
Q

Which has more accurate TV delivery, bellows or piston?

A

Piston

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18
Q

What is the reservoir bag roll during a piston ventilator?

A

Involved in circuit during expiration.

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19
Q

What happens with the peep valve during inspiratory phase of piston ventilator?

A

Held close

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20
Q

How does the fresh gas decoupling valve work?

A

Allows gases from piston ventilator to flow into patient and not back into CO2 scrubber/res our bag

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21
Q

What happens during the first step exhalation of piston ventilators?

A

Gas flows through CO2 scrubber into reservoir bag. Fresh gas continue to flow into reservoir bag as well. Decoupling valve is closed

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22
Q

What happens during second step exhalation of piston ventilator?

A

Breathing gases stored in reservoir bag go into the piston ventilator through open decoupling valve. Once piston fills, it reverses, CLOSING decoupling valve and sending excess gas to the scavenger.

Fresh gas inflow sends excess gas to the scavenger.

23
Q

Issues with pistons

A

Refill even if circuit disconnection occurs
— piston ventilators May entail RA during leak, thereby diluting O2 and anesthetic agent
— may cause hypoxemia and awareness, but an alarm will alert operator
-positive pressure relief valve prevents excessively high breathing circuit pressure (60-80)

24
Q

Briefly describe reflector ventilators

A

Drive gas and patient gas mix and acts like piston.

25
Q

What is pressure?

A

Impedance to gas flow rate

26
Q

Where is impendance encountered?

A

Breathing circuit

Pt airway and lungs

27
Q

The backpressure generated during ventilation is a result of?

A

Airway resistance

Lung-thorax compliance

28
Q

What is flow rate, how is it described?

A

Rate at which the gas volume is delivered to pt

Refers to volume change/time

Expressed in L/sec of L/min

Gotta get air in quick to get it out

29
Q

Standard TV?

A

5-7 mL/kg

30
Q

Standard RR?

A

8-12/min

31
Q

Flow rate standard?

A

4-6 X MV

32
Q

MV =?

A

TV*RR

33
Q

What is physiologic I:E ratio?

A

1:2

34
Q

How do we calculate I:E ratio?

A

TI = TV/flow rate (TV in L)

Ex 0.5mL/30,000mL/min=0.0167 minx60 sec= 1 second
Answer in min, change to second x60

TE

Total time for ventilation 60seconds/12 bpm= 5 second/breath
5 seconds total-1 for inhale= 4 for exhale
1:4

35
Q

Oxygen content equation

A

Oxygen content= (hgb x %sat x 1.39mLo2)+ (PaO2 X0.0031mL o2)

36
Q

Calculate paO2?

A

PIO2- PaCO2/ (R+F)

R= EXTRACTION RATIO 0.8
F= correction factor
F is very small number

Thus
PaO2=PIO2-Paco2/R

37
Q

Relationship between Fio2 and pao2?

A

10% increase FIO2= increase PaO2 ~50mmHg

38
Q

Low pressure alarm (disconnect alarm)

A

Detected by a drop in peak circuit pressure

39
Q

Sub atmospheric pressure alarm

A

PRESSURE OF < OF = -10 CMh20.

Inhaling against machine

40
Q

High peak airway pressure alarm

A

Detects excess pressure in system, activated at 60 cmH2o or set by practitioner

41
Q

What is the best monitor to reveal a disconnect?

A

ETCO2 monitor

42
Q

What is the most important monitor on the machine?

A

Oxygen analyzer. How much o2 delivering to machine

43
Q

Where is the TV sensor?

A

Expiratory limb

44
Q

Formula for exhaled TV on respirometer?

A

VT= VT set on vent +VT fresh gas flow- VT lost in system

45
Q

Describe SIMV

A

Ventilator delivers preset TV at predetermined interval, patient allowed to breath spontaneously in addition to ventilator. Patient’s breaths will be supported by ventilator.

Good for waking up pt in OR.

Good for when patient may lack ability to take full breath.

If patient not reaching certain MV, the vent will assist; otherwise, breaths on own

46
Q

Describe A/C ventilation.

A

Intermittent mode positive pressure ventilation.

Patient’s inspiratory effort creates “sub baseline” pressure in inspiratory limb and triggers vent to deliver predetermined TV

If patient’s rate doesn’t meet min rate, ventilator takes over with controlled vent mode

  • all breaths are full assisted ventilator breaths
  • can be pressure/volume controlled
47
Q

Describe PSV?

A

Pressure support ventilation aids in normal breathing with predetermined level of positive a/w pressure.

Pt must be spontaneously breathing

Vent senses inspiratory effort and delivers pressure support, resulting in larger TV than pt would get on own

PSV useful to support minute ventilation and control CO2 for spontaneously-breathing pt

Good for emergence with residual NMB

48
Q

Describe high frequency ventilation.. What are typical settings? When is it used?

A

Low tidal

49
Q

What is disadvantage to O2 used for drive gas in bellows?

A

O2 can be depleted quickly

50
Q

What happens during inspiration on piston ventilators?

A

1) PEEP/PMax valve closed.
2) Pressure in breathing circuit generated by the ventilator closes fresh gas decoupling valve.
3) This directs fresh gas flow toward breathing bag during inspiration so it doesnt’ interfere with TV accuracy
4) Excess gas flows past open APL bypass valve, through exhaust check valve, to the scavenger.

Breathing bag integral to circuit function

51
Q

TI=?

A

TV/flow rate

52
Q

Total time for cycle?

A

TI+TE

53
Q

Total time (seconds) for cycle?

A

60/RR

54
Q

Flow rate=?

A

4-6 xMV

Intro Nurse Anesthesia (5 decks)

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