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
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
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
4
Q
Pressure controlled
A
- cuts off inspiration when pressure meets the predetermined level. TV and inspiratory time vary
5
Q
possible issues with bellows
A
- leaks, improper seating
- hole in bellows
- hyperinflation of the lungs
- O2 concentration can change
- ventilator relief valve problems
- hypoventilation- gas goes to scavenger rather than drive
- caused by- disconnection, ruptured valve, or other damage
- valve stuck in closed position- additional peep and excess pressure
- excess suction from scavenge can also cause the valve to remain closed.
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
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)
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
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
10
Q
To Select Ventilation mode:
A
- Push the Ventilator key
- Review the settings for the new mode.
- Select Mode
- Select desired mode (mode is changed immediately upon selection)
*Ventilator is electonically controlled and pneumatically driven.
11
Q
possible issues with pistons
A
- refill even if a circuit disconnection occurs
- if a circuit leak is present, piston ventilators may entrain RA through the leak, diluting O2 and anesthetic
- risk of hypoxemia and awareness
- an alarm will sound
- a positive-pressure relief valve on the ventilator prevents excessively high breathing circuit pressure (60-80 cm H2O)
12
Q
TI equation
A
TI = TV/ Flow rate
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.
14
Q
MV
A
MV = TV x RR
15
Q
monitors
A
- ETCO2- capnography- best for revealing disconnect.
- Oxygen analyzer- most important monitor on the machine. Calibrate at 21%
- Respirometer- measures exhaled volumes
- PAP monitors- peak airway pressure
- vigilence is the best monitor
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
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
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
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
- CV
- IMV
- SIMV
- AC
- PSV
- HFV
- PCV
- 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
- time
- volume
- pressure
- 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
- Low pressure alarm (disconnect)- detected by a drop in peak circuit pressure
- sub atmospheric pressure alarm- pressure of < or = -10 cm H2O
- Sustained/continuing pressure alarm- 15 cm H2O for more than 10 secs
- Pt in bag mode and you havent opened relief valve
- High peak airway pressure alarm- detects excess pressure in system about 60 cm H2O
- Low O2 supply alarm
- 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
