quick course in inhalant kinetics the alveolar tension curve written for bwh anesthesia sunrise...
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Quick Course in Inhalant Kinetics
The Alveolar Tension Curve
Written forBWH Anesthesia Sunrise Lecture Series 2008 - 2009
© Copyright 1995 - 2008, James H Philip, all rights reserved.
Dr. James Philip has performed funded research on Isoflurane, Sevoflurane, and Desfluraneand is often supported by the manufacturers of these drugs to teach about these drugs.
Ready
Quick Course in Inhalant Kinetics
The Alveolar Tension Curve
James H. Philip ME(E) MD
Anesthesiologist and Director of BioengineeringDepartment of Anesthesia Brigham and Women’s Hospital
Associate Professor of Anaesthesia, Harvard Medical SchoolPresident, Med Man Simulations, a nonprofit organization
that distributes Gas Man®, worldwide
AlveolarTensionCurve
Focus on the
Alveolar response to an Inspired Step
Alveolar Tension Curve
The time course of alveolar tension = PA
in response to a step change ininspired tension = PI
=
PI PA
Alveolar Tension is important
Tension = Partial Pressure
Tension equalizes when Concentration equilibrates
Concentration does not drive molecular motion
Tension drives molecular motion
Inspired Tension drives Alveolar Tension
Alveolar Tension drives Arterial Tension
Arterial Tension drives Tissue Tension
Brain it the important tissue for Anesthesia
Brain Tension drives depth of anesthesia
Alveolar Tension is important
Tension = Partial Pressure
Tension equalizes when Concentration equilibrates
Concentration does not drive molecular motion
Tension drives molecular motion
Inspired Tension drives Alveolar Tension w loss + delay
Alveolar Tension drives Arterial Tension = approx
Arterial Tension drives Tissue Tension w delay
Brain it the important tissue for Anesthesia
Brain Tension drives depth of anesthesia
If we know Alveolar Tension, we know the hard part
Gas Man® Picture shows path of anesthetic tension
I BrA a V
Axes and Labels
0 1 20.0
1.0
A / I
3 minutes (time)
0 1 20.0
1.0
A / I
3 minutes (time)
Alveolar response to a stepchange in inspired agent
Inspired Step
0 1 20.0
1.0
A / I
3 minutes (time)
Inspired Step
0 1 20.0
1.0
A / I
3 minutes (time)
Pure Lung wash-inWithout Uptake into Blood
is the same as
Cardiac Output = zero ( CO = 0) or
Drug solubility in blood = zero ( = 0)
Call this Zerothane
Inspired Tension
Alveolar Tension
Alveolar response to a stepchange in inspired Zerothane
is an
exponential curve
0 1 20.0
1.0
A / I
3 minutes (time)
0.63
0.5 min =
Alveolar Tension
Inspired Tension
Time constant, tau ( )is the time required to achieve
63% of the final value*
0 1 20.0
1.0
A / I
3 minutes (time)* Derive in long course
Now, add uptake into blood
Uptake into bloodproduces
an Alveolar TensionPlateau
Inspired Tension
0 1 20.0
1.0
A / I
3 minutes (time)
Pure Lung wash-inWithout Uptake into Blood
Alveolar Tension Plateau
Plateau
0 1 20.0
1.0
A / I
3 minutes (time)
Inspired
Alveolar
Plateau is produced by Removal by Blood
Tail
Alveolar Tension Plateau
Plateau
0 1 20.0
1.0
A / I
3 minutes (time)
Inspired
Alveolar
Delivery
Removal
Tail
Alveolar Tension Plateau
Plateau
0 1 20.0
1.0
A / I
3 minutes (time)
Inspired
Alveolar
Delivery = VA
Removal = CO •
Hal Enf
Iso
SevoN O 2
Des
Zerothane
Infinithane
0 1 20.0
1.0
A / I
3 minutes (time)
Alveolar Plateaus
Alveolar Plateau Heights
.38
.54
.66
Ht 1
.24
.00
Hal Enf
Iso
SevoN O 2
Des
Zerothane
Infinithane
0 1 20.0
1.0
A / I
3 minutes (time)
Alveolar Plateau Heights and solubilities
.38
.54
.66
Ht 1
.24
.00
Hal Enf
Iso
SevoN O 2
Des
Zerothane
Infinithane
0 1 20.0
1.0
A / I
3 minutes (time)
1.3
.67
.42
0
2.4
Inf.
Alveolar Plateau Height Equation
.38
.54
.66
Ht 1
.24
.00
Hal Enf
Iso
SevoN O 2
Des
Zerothane
0 1 20.0
1.0
A / I
3 minutes (time)
1.3
.67
.42
0
2.4
Inf.V I .O A 1
1 + C Plateau Ratio = A
=
Tail
Venous Return converts Plateau
Plateau
0 1 20.0
1.0
A / I
3 minutes (time)
Inspired
Alveolar
Plateau produced by Removal by Blood
0 1 20.0
1.0
A / I
3 minutes (time)
Venous Return converts Plateau into Tail
Plateau
TailAlveolar
Inspired
Alveolar
0 1 20.0
1.0
A / I
3 minutes (time)
Alveolar Tension Curve sections named
Inspired
Initial Rise
Knee
Tail
Plateau
Real drugs and real curvesNext,
Des
Sev
Iso
Hal
300 Minutes of administration 300
PI
PA
1.0
Yasuda & Eger, 1991
Real drugs and real curves
A / I
Des
Sev
Iso
Hal
300 Minutes of administration 300
PI
PA
1.0
What is the similarity among these curves?
A / I
Des
Sev
Iso
Hal
300 Minutes of administration 300
PI
PA
1.0
Initial rise follows the same Zerothane curve
ZeroA / I
Des
Sev
Iso
Hal
300 Minutes of administration 300
1.0
What is the difference between these curves?
ZeroA / I
Des
Sev
Iso
Hal
300 Minutes of administration 300
1.0ZeroA / I
Plateau Height is the only kinetic difference !
Des
Sev
Iso
Hal
Des
Sev
Iso
Hal
300 Minutes of administration 300
1.0ZeroA / I
And, plateau height is determined by
DesSev
Iso
Hal
1.3
.67
.42
0
2.4
inf.
.38
.54
.66
1
.24
.00
Ht
Inf
Blood / Gas Solubility
Dominates Inhalation Kinetics
Determines
how closely
Expired Tension
approaches
Inspired Tension
in the first few minutes of anesthesia
The endof
The Alveolar Tension Curvein its first few minutes