VE=
f x Vt..
Minute Ventilation VE
Meet demand of pt metabolism..Based on Gender, BSA
Increased metabolism..
Fever, exercise, acidosis
Body Surface Area BSA
Measure in squared meters..DUBOIS CHART
Normal VE Male
4 x BSA
Normal VE Female
3.5 x BSA
Normal spontaneous VT, in humans
5-7 ml/kg of IBW
Tidal Volume..
Uses Ideal body weight....obese people don't have bigger lungs..normal is 6-12 ml/kg of IBW
1 lb =
2.2 kg
IBW Female
105 x 5(Height in inches -60)
IBW Male
106 x 6(Height in inches -60)
Barotrauma
Lung injury caused by high pressures, pneumo
Volutrama
Lung injury caused by high volumes
Spontaneous breathing frequency
12-18 bpm
Ideal starting breathing rate for VENT
10-12 bpm
OBSTRUCTIVE VT
8-10 ml /kg
OBSTRUCTIVE Rate (f)
8-12 bpm
RESTRICTIVE VT
4-8 ml/kg
RESTRICTIVE Rate (f)
15-25 bpm
Tubing Compliance CT
amt of air compressed or lost in ventilator circuit, in ml. for every 1 ml/cmH20 PIP
AKA for Tubing compliance
Compressible Volume....the amt of air that stays in circuit...the higher the pressure on vent, the more air lost in tubing.
Average CT
1.5-2.5 ml/cmH20
Formula for volume lost to circuit
CT x PIP
Example of volume lost..
2.9(CT) x 30(PIP) = 87(volume lost)...so if your VT is set at 400, your only actually getting 400-87 or 313 ml.
VDanat
anatomical dead space..conducting airways
Normal VDanat
1 ml/lb of IBW
Mechanical Deadspace
Vol of air rebreathed during ventilation..anything placed AFTER the Y...HME, MDI, flextubing
Formula Alveolar minute ventilation
VA=(VT-VD) x f
Alveolar ventilation
VT - VDmech-VDanat
Total Cycle Time TCT
TCT = TI + TE
V...with a dot means
Flow.. needs to be liters/min
Initial Peak Flow
40-80 L/min, a guidline
Initial Inspiratory Time
0.8sec(faster)-1.2sec Need to look at pt..do they look comfortable with the flow rate?
Increase Flow rate
turbulent flow..Increase in PIP..POOR gas distribution, not a nice slow deep breath....Reduces airtrapping(Longer E Time)
Decrease Flow Rate
Longer Inspiratory time, Can be an inverse I:E ratio....
Inverse I:E ratio used for...
Oxygenation...ARDS, APRV Mode
Three Flow patterns
1 Constant 2 Sine 3 Descending(decelerating)
Constant
shortest I time of all patterns
Sine
Flow tappers at beginning, and end of I phase
Descending
Flow is highest at beginning of breath when pt has more demand
PEEP
Increase FRC, keeps alveoli open
physiologic PEEP
minimum PEEP to preserve FRC..3-5 cmH20, everyone should have PEEP on vent to overcome resistance from tubing
Therapeutic PEEP
Used to improve oxygenation >5cmH20...NBRC>10cmH20.
How to determine PCV 1
1 Volume ventilate first..determine plateau pressure( I Hold), set I pressure same as plateau
How to determine PCV 2
2 Start at a low I pressure (10-15 cmH20) and adjust
How to determine PCV 3
3 Volume ventilation...PIP-5cmH20
Pressure support goals
Help increase VT of spontaneous breath..decrease WOB..
Raw=
PIP-Plataeu/flow...
PRVC
Pressure ventilation..smart pressure automatically adjust to reach a TARGET volume..High pressure alarm sounds 5 below limit.
Normal Spontaneous VE
about 100 ml/kg of IBW
CT Formula
Change in Volume / Change in pressure..in ml/cmH20
Formula for mechanical deadspace
aprox. 10 ml / inch of tubing
PSV setting
PIP-Plateau...
Formula for FLOW(V)
V=VT/Ti...can re-arrange formula.