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Intro To Anesthesia > Ventilators and Airway monitors > Flashcards

Ventilators and Airway monitors Flashcards

1
Q

Respirometer

A
  • In expiratory limb
  • exhaled TV sensor
    • activated automatically once breaths are sensed and always active during mechanical ventilation
  • gas flow converted to electrical pulses
  • apnea- if sufficient breath (based on TV setting) not achieved within 30 seconds
  • low minute volume
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2
Q

Expiration phase- bellows ventilator

A
  • drive gas exits the bellows chamber via ventilator pop off valve and pressure in chamber drops to zero
  • exhaled pt gas fills the bellows before any scavenging occurs
    • b/c valve ball produces a 2-3 cm H2O back pressure.
    • relief (pop off) valve is ONLY open during expiration when all scavenging takes place
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3
Q

PSV

A
  • Pressure support ventilation
    • aid in normal breathing with predetermined level of positive pressure
    • pt spontaneously breathing
    • senses pt insp effort and gives pressure support
    • results in larger TV than pt would produce independently
    • useful to support MV and control arterial CO2 for spontaneously breathing patients during maintenance or emergence
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4
Q

Pressure controlled

A
  • cuts off inspiration when pressure meets the predetermined level. TV and inspiratory time vary
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5
Q

possible issues with bellows

A
  1. leaks, improper seating
  2. hole in bellows
    1. hyperinflation of the lungs
    2. O2 concentration can change
  3. ventilator relief valve problems
    1. hypoventilation- gas goes to scavenger rather than drive
    2. caused by- disconnection, ruptured valve, or other damage
    3. valve stuck in closed position- additional peep and excess pressure
    4. excess suction from scavenge can also cause the valve to remain closed.
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6
Q

Ventilator settings

A
  • TV: 5-6 ml/kg (ideal weight)
  • RR: 8-12
  • Flow rate: about 4-6 x minute ventilation
  • I:E ratio: physiologic is 1:2
    • Time Inspired= TV/ Flow rate
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7
Q

drive gas

A
  • either air or oxygen
    • using oxygen depletes supply quickly because so much goes to scavenge.
  • some machines can entrain air, reducing the need for oxygen
    • used in austere conditions (military)
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8
Q

Ventilation VOLUME

A
  • measure of the tidal volume delivered by ventilator to patient
  • volume of gas pt breaths
  • expressed in mls
    • Liters for minute volume
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9
Q

ICU vents Vs anesthesia vents

A
  • ICU
    • more powerful- greather insp pressures and tidal volumes
    • more modes of ventilation
    • gas supplied by the ICU ventilator directly ventilates the patient
  • Anesthesia
    • CO2 absorber
    • driving gas never reaches the patient
      • 100% O2 in older machines
      • air/100% O2 in newer models
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10
Q

To Select Ventilation mode:

A
  1. Push the Ventilator key
  2. Review the settings for the new mode.
  3. Select Mode
  4. Select desired mode (mode is changed immediately upon selection)

*Ventilator is electonically controlled and pneumatically driven.

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11
Q

possible issues with pistons

A
  1. refill even if a circuit disconnection occurs
  2. if a circuit leak is present, piston ventilators may entrain RA through the leak, diluting O2 and anesthetic
  3. risk of hypoxemia and awareness
    1. an alarm will sound
  4. a positive-pressure relief valve on the ventilator prevents excessively high breathing circuit pressure (60-80 cm H2O)
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12
Q

TI equation

A

TI = TV/ Flow rate

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13
Q

feedback mechanisms for Pneumatic bellows ventilators

A
  • help administer more stable tidal volume
  • circuit compliance compensation and measure tidal volume as a feedback signal.
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14
Q

MV

A

MV = TV x RR

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15
Q

monitors

A
  1. ETCO2- capnography- best for revealing disconnect.
  2. Oxygen analyzer- most important monitor on the machine. Calibrate at 21%
  3. Respirometer- measures exhaled volumes
  4. PAP monitors- peak airway pressure
  5. vigilence is the best monitor
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16
Q

For each mmHg of PO2 …

A

…there is .0031 ml O2/100ml of blood

*normal arterial blood with a PO2 of 100 mmhg contains 0.3 ml of O2/100 ml

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17
Q

Maquet FLOW-i Anesthesia System With Volume Reflector

A
  • uses “volume reflector”
    • volume reflector is functional and “in circuit” during all modes
  • expired gas gets “balanced” by Reflector gas
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18
Q

TE equation

A

TE = total time for each breath - TI

Total time for each breath:

60 sec/ RR (12 bpm) = 5 sec/breath

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19
Q

Ventilation TIME

A
  • divided into inspiratory and expiratory
  • expressed in seconds
  • OR by relation of insp to exp. I:E ratio
  • used to define the number of respiratory cycles within a given time period.
20
Q

modes of ventilation

A
  1. CV
  2. IMV
  3. SIMV
  4. AC
  5. PSV
  6. HFV
  7. PCV
  8. CPAP
21
Q

Ventilator relief valve

A

aka pop-off valve

  • closes during inspiration so that pressure can be maintained and can push down the bellows.
  • opens during expiration so driving gases can leave casing and go to scavenge and make room for bellows to expand.
22
Q

SIMV

A
  • SIMV- like IMV but synched with pt’s effort
    • Pt breaths spontaneously and at interval the breath is supported by the machine
23
Q

one gram of pure hemoglobin…

A

…can combine with 1.39 ml of O2

24
Q

Parameters used to describe ventilation

A
  1. time
  2. volume
  3. pressure
  4. flow rate
25
Q

Ventilation PRESSURE

A
  • impedence to gas flow rate
  • impedance encountered in:
    • breathing circuit
    • pts airway and lungs
  • amount of backpressure generated as a result of:
    • airway resistance
    • lung-thorax compliance
  • expressed in cmH2O, mmHg, or kPa
26
Q

How much O2 do we give?

A

PaO2 = (PIO2 - PaCO2)/R

R = extraction ratio (0.8)

** Hypoventilation reduces PaO2 except when the subject breathes enriched O2 mixture

27
Q

ventilation FLOW RATE

A
  • rate at which the gas volume is delivered to the pt
    • from the pt connection of the breathing system to the patient
  • refers to the volume change/time
  • expressed in L/sec or L/min
28
Q

Modes of ventilation newer machines

A
  • Patient can trigger
    • thus, “Non-controlled ventilators”
  • Synchronized intermittent mandatory ventilation (SIMV)
  • Assist control (AC)
  • Pressure support (PSV)
29
Q

Increased FiO2

A
  • each time you increase FiO2 by 10%, you increase PaO2 by about 50 mmHg
30
Q

Oxygen content equation

A

oxygen content = (hemoglobin x saturation x 1.4 ml O2) + (PaO2 x .0031 ml O2)

31
Q

HFV

A
  • High frequency ventilation
    • Jet ventilator- used for lithotripsy so that the kidney stones dont move every time pt takes breath
    • low volumes, high rate, less dead space
    • typical settings
      • BPM 100-200
      • IT 33%
      • Drive pressure 15-30 PSI
    • goal to maintain pulm gas exchange at lower mean airway pressures
32
Q

CV or CMV

A

Controlled ventilation

33
Q

Bellows

A
  • Almost always pneumatic
  • Ascending- bellows ascends during expiratory phase
  • Descending- bellows descends during expiratory phase
34
Q

Pneumatically driven bellows ventilator

A
  • bellows separates driving gas from pt. circuit gas
    • double circuit
  • bellows serves as reservoir for pt breathing gas
    • bellows is kind of equivalent to provider squeezing bag.
  • force driving the bellows during inspiratory phase is pressurized gas. Increasing pressure causes 2 things to occur.
    • ventilator relief valve closes off so no gas can escape into scavenge
    • the bellows are then compressed and the gasses in bellows are delivered into patient.
35
Q

AC

A
  • Assist control
    • Intermittent positive pressure ventilation
    • pts insp effort creates a sub-baseline pressure in the inspiratory limb of circuit that triggers the vent to deliver a predetermined TV
    • if pts rate drops below a preset min, machine takes over with controlled vent mode
    • Can be pressure controlled or volume controlled
36
Q

Piston Ventilators

A
  • use computer controlled stepper motor instead of drive gas
  • single circuit
  • less gas used-great for remote locations
  • more accurate TV delivery
37
Q

Modes of Ventilation on older machines

A
  • Time triggered and time cycled
  • cycle to the exp phase once a predetermined interval elapses from the start of inspiration
  • TV is a product of the set insp time and insp flow rate
  • “Controller Ventilators”- has only one mode
38
Q

Alarms

A
  1. Low pressure alarm (disconnect)- detected by a drop in peak circuit pressure
  2. sub atmospheric pressure alarm- pressure of < or = -10 cm H2O
  3. Sustained/continuing pressure alarm- 15 cm H2O for more than 10 secs
    1. Pt in bag mode and you havent opened relief valve
  4. High peak airway pressure alarm- detects excess pressure in system about 60 cm H2O
  5. Low O2 supply alarm
  6. ventilator setting alarm- vent’s inability to deliver the
39
Q

Expiratory phase- piston ventilator

A
  • Step 1: pt exhales into the breathing bag. FGF flows backward toward bag and CO2 scrubber.
  • Step 2: Piston returns to starting position, pulling gas from breathing bag and FGF.
    • once piston reaches bottom of stroke, FGF flows backward toward breathing bag and absorber again.
  • **gas flows through CO2 scrubber during exhalation for this machine
40
Q

Inspiratory phase- bellows

A
  • driving gas enters the bellows chamber, increasing pressure and thereby compressing the bellows which delivers the gas to the patients lungs.
41
Q

Classification of Ventilators

A
  • Classified according to the type of reservoir the ventilator has
    • Bellows
    • Piston
    • Volume
  • And how it delivers the gas (drive mechanism)
    • pneumatic
    • mechanical
42
Q

Inspiratory phase- Piston ventilator

A
  • during inspiration the PEEP valve is held closed.
  • The pressure in the breathing circuit that is generated by the ventilator closes the fresh gas decoupling valve
    • this directs the FGF toward the breathing bag during inspiration so it does not interfere with TV accuracy
  • excess gas flows past the APL valve, through the exhaust check valve, and to the scavenger
  • ***reservoir bag is integral to funtion during mechanical ventilation.
43
Q

IMV

A
  • IMV- intermittent mandatory volume
    • pt breaths spontaneously while the vent delivers a preset TV at a predetermined interval through a parallel vent circuit. Used for weaning.
    • fixed rate, not synched with patient
44
Q

Volume controlled

A
  • cuts off inspiration when preselected TV is delivered.
    • most have a second limit for inspiration and pressure limit to prevent barotrauma.
    • a percentage of TV is always lost to the compliance of the system (4-5cc/cmH2O)
45
Q

PCV

A
  • Pressure control ventilation
  • pt or time triggered pressure limited, support
  • gas flow decreases as airway pressure rises and ceases when airway pressure equals the set peak inflation pressure
    • TV not fixed
    • used in situations where pressures can be high
    • used in neonates/premies
46
Q

CPAP

A
  • Continuous positive airway pressure
    • positive pressure is maintained during both inspiration and expiration
    • can be provided with a mask
      • if pressure > 15 cm H2O, can cause regurgitation and aspiration
47
Q

Oxygen delivery equation

A

Oxygen delivery = CO x O2

Intro To Anesthesia (8 decks)

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