Effects of Positive Pressure Ventilation Flashcards
What must you have when using positive pressure ventilation?
A closed system
PPV increases __ and decreases __
MAP; CMO
What does ventilation impede?
Venous return
What enhances venous return?
Spontaneous breathing
When you create negative interthoracic pressure, you ___ the diaphragm
Pull down
MAP is always equal to what?
Greatest surface area
High volumes or PEEP overdistend the alveoli and squeeze pulmonary vessels, ____ PVR and cardiac work
Increasing
PVR is most increased by what?
MAP
Increased PVR ___ RV afterload
Increases
Normal can overcome PVR by doing what to RV contraction?
Increasing
Abnormal can’t overcome and RVSV ___
Drops
What does RVSV stand for?
Right ventricle stroke volume (amount objected per beat)
___ of RV can also force the intraventricular septum shift to the left
Dilation
What does PVR stand for?
Pulmonary vascular resistance
Dilation of RV is often with PEEP __ than 15 cmH20
greater
Dilation of RV causes LVSV to ___
Decrease
___ endocardial (coronary) blood flow is a cardiovascular consideration
Decreased
PPV reduces venous return and CMO, which can decreased ____
Coronary perfusion
What can contribute to myocardial dysfunction?
Ischemia
M aortic DP - LVEDP equals what?
CorArtPP
Patients who have ___tension have a ___ venous return
Hypotension; decreased
Patients who have ___ tension have an ___ venous return to the left ventricle
Hypertension; increased
An increase in intrapulmonary shunt can cause ___ blood flow and ventilation to most gravity dependent areas of the lung is ___
Increased; decreased
An increase blood flow can increase to ___%
10%
How do you calculate oxygen delivery?
CaO2 x CMO
PPV results in __ V/Q mismatch and hypoxemia, which in turn ___ O2 content and ___ O2 delivery
High; decreases; decreased
Normal people rarely have a ___ in compensation
Decrease
A decreased in stroke volume is compensated by ____ and increase is ____, as well as shunts away from the kidneys and lower extremeties
Tachycardia; SVR
Effectiveness of ____ depends upon integrity of neuroreflexes
Compensation
What can vascular effects be blocked by?
- Spingal/general anesthesia
- Spinal chord transection
- Polyneuritis
___ levels of PEEP make situation worse when trying to compensate
Increased
What happens when you impede venous return?
Lower stroke volume
When you apply PEEP to ____, you greatly increase surface area, which makes the situation worse
MAP
Patients with stiff lungs, like ___, are ___ likely to experience hemodynamic changes because ___ pressure is transmitted to the pleural space
ARDS; less; less
Who are at most risk for cardiovascular considerations of PPV?
People with compliant lungs and stiff chest walls
In patients with high ____, much of pressure is lost to the poorly conductive airways and less actually reaches the ____ level
Airway resistance; alveolar
What should you lower to reduce cardiovascular changes?
MAP
What 6 things play a role in cardiovascular changes?
- PIP
- Inspiratory flow
- MAP
- PEEP
- I:E ratio
- Inflation hold
What should you alter on the vent to reduce PPV complications?
- Reduce MAP
- High inspiratory flow to increase PIP
PIP stands for what?
Peak inspiratory pressure
What are three points about high flow?
- More pressure lost to patient circuit
- More pressure will be needed overcome Raw
- Uneven ventilation occurs with high flows
What needs to increase when flow goes down?
PRAMP
What creates the flow?
Pressure gradient
What is the goal of PPV when it comes to cardiovascular considerations?
Flow not too high to cause problems but not too low to cause an increase WOB
An I:E ratio of 1:1 may lead to ____ and ___ mean airway pressure
Air trapping; increase
When is an inflation hold used?
Diagnostically ONLY
What does PEEP always increase?
MAP
What may not always decrease CMO?
Stiff lungs
Holding breath greatly increases what?
Airway pressure
High peak PIP does not always reflect what?
Mean airway pressure
If a patient has auto-PEEP, will vent calculations of MAP be accurate?
Not always
What should you do to see if you have auto-PEEP?
Expiratory hold
What mode can reduce mean airway pressure by allowing a spontaneous breath?
SIMV
What is auto-PEEP?
When you allow alveoli to equal out with pressure at the airway
What are the main cardiovascular considerations when it comes to PPV?
- Dilation of RV
- Increased PVR, RAW, pulmonary shunt
- Decreased oxygen delivery, endocardial (coronary) blood flow
- Blood pressure changes
- Effectiveness of compensation
- Duration and magnitude of PPV
