Mechincal ventilation Basics Flashcards
3 methods to deliver O2
Face mask - non invasive
Face mask via CPAP/BiPAP - non invasive
EDT mech. ventilation - invasive
Benefits of CPAP and PEEP?
keeps intra alveolar pressure positive airways open at a PEEP at least of 5
CPAP is the same thing what mode, and what is their main difference?
CPAP has the same mode as PEEP.
The difference:
->CPAP = non-invasive
->PEEP = invasive
When would you consider endotracheal intubation and mechanical ventilation?
Think ABCs or when patients cannot breath:
-A: can the airway be maintinaed
-B: can breathing be maintained
-C: Circulation
-causes of hypoventilation
What is the purpose of mech. ventilation during surgery?
deliver anesthetic drugs
prevents aspiration syndrome (gastric-content aspiration)
controls PaO2 and PaCO2
-i.e oxygenation and pH
Generally describe CMV
Vent mode that does not allow for spontaneous breathing; the machine does all the work or gives assisted breaths.
Cons to CMV
Asynchronous breathing; the machine and pt do not match
-aka they fight
Generally describe IMV
Allows for spontaneous breathing; pt can’t trigger it whenever
Give an example of IMV
Patient can breath between set breaths; used wen pt is conscious and is able to breath regularly.
mode would hopefully be switched to pressure support.
i.e we set 12 breaths as a minimum but allow for a RR of 13. They can take an extra breath but will not fall bellow 12.
Describe the modes you may see on a old system
Assist control (AC) = CMV
Pressure control
Pressure support
CPAP/BiPAP
Synchronized interment mandatory ventilation (SIMV)
Flow rate describes what?
how FAST would you like to push volume in
Flow = volume/time
What is volume?
volume = tidal volume
aka
How much air would you like to give into the patient and out
Describe the relationship in lung compliance
i.e Compliance
Compliance = delta V/ delta P
- If the volume is constant, the relation between C and P is inverse
-(one increases, other decreases) - If pressure is constant, relationship between C and V is direct.
-(both increase or decrease)
Lung compliance what happens when compliance decreases?
pressure increases to fill the airways
What does it mean when a lung is compliant
A lung is compliant when it expands a big deal (volume increases) with only a slight pressure (low pressure)
C = delta v/ delta P
What is volume control
you control (set) the volume, and keep an eye on the pressure.
If pressure increases, compliance is decreasing
when pressure increases too much -> alarms
What is pressure control
you control (set) the pressure, and keep an eye on the volume.
If volume decreases -> Compliance is decreasing
when volume decreases too much —> alarm
What vent. settings affect PCO2
RR and Vt
They both change alveolar ventilation
Which vent. settings determine PO2?
FiO2 and PEEP
manipulation of oxygenation
If a patient is hypoventilation; what is happening to his vitals; what is the appropriate response?
PCO2 increasing -> pH deceasing = resp. acidosis
Response:
Increase RR and tidal volume
What should you do if a patient with high hypoxemia? what is happening to his vitals?
PaO2 = 50 = low
response:
increase FiO2 and PEEP
When is a lung is considered compliant?
when giving a small amount of pressure, it increases its volume drastically
OR
if P is constant; lungs compliance decreases and volume decreases as a result
What factor determines peak pressure?
Airway resistance
The greater the resistance the lower the pressure
change in peak pressure = what change?
change in airway resistance
What is plateau pressure?
edit
needs a check for accuracy
when the air stops moving in (end of inspiration), the factor that determines the pressure in compliance
what increases inspiratory pause or plateau pressures?
Compliance
What does it mean when peak pressure (PIP) increases?
edit
needs a check for accuracy
Airway resistance, such as secretions
What does it mean when Pplat increases?
Lung compliance is decorticating
Review: low vs high lung compliance?
low = stiff lungs
high = floppy
wanna be somewhere in the middle.
If there is a problem with the peak pressure; where can you usually assume the problem lies?
airway issue
if there is a problem with the Pplat; what can you assume (usually) is the problem?
Lung compliance issue
edit add factors from a screen on shot on phone
Pulmonary MV and Alveolar MV
Pulmonary MV = RR x Vt
Alveolar MV = RR x (Vt - dead space)
If RR is increased and FiO2 is maxed out, what could be the reason as to a patient who is not improving in condition?
Alveolar ventilation is not necessarily increased because of Deadspace (or Shunting?) where there is no gas
-i.e hyperventilating; you’re only ventilating dead space
How do you increase alveolar ventilation
Deep, slow breathing
or adding pressure (forces air into airways)
continune watching medicos is perfctinalis vid on mech. vent
edit
left off at RR
What is a normal Vt range?
5-8 ml/Kg of patients IBW
so somwhere between 350-700mL
What should you set PEEP at?
4-6, but rule of thumb stick w/5 on the initial vent setting
What happens when you increase inspiratory time?
Increase oxygenation, but may have diminishing returns because it affects the I:E ratio
Why are is too much Ti bad?
edit
Stresses the body too much; normally you want a higher expiration ratio to inspiratory ratio
Normal Ti range?
0.9 - 1.10
How do you calculate MV?
Vt x RR
Normally you count RR according to the patient; how do you determine the RR for a vent?
insert image from SMS
IBW x 6 (OR choose something between 5-8) = X
[x] take that value * 100 = Y
y/x = RR
Normal MV range?
5-6 L/min
Normal Vd/Vt ratio? aka deadspace?
2.2
Why would deadspace be increased?
◦Increased due to ventilation of areas of lung with poor perfusion
◦Altered V/Q (increased ventilation)
Result = increased MV with PPV required to control PaCO2.
What is the Trigger, Limit, cycle, and Baseline for: VC-CMV
Trigger: Time OR Patient
Limit: Flow
Cycle: Volume
Baseline: PEEP
What is PEEP also known as?
Base airway pressure
What is the Trigger, Limit, cycle, and Baseline for:
PC-CMV
Trigger: Time or Patient
Limit: Pressure
Cycle: Time
Baseline: PEEP or BAP
What is the Trigger, Limit, cycle, and Baseline for:
PC-CMV Adaptative
Trigger: Time or Patient
Limit: Pressure
Cycle: Time
Baseline: PEEP or BAP
On the PB980; what mode is PRVC?
AC-VC+
What is driving pressure?
Pplat - PEEP
How do you calculate resistance from a vent?
- What is a bad range?
Ppeak - Pplat > 10
Implies too much resistance (or artifact)
What does a Ppeak - Pplat < 10 imply?
Compliance problem
