N. T. Tgavalekos1,2

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Correlation in Degradation of Lung Mechanics with
Ventilation Distribution in Asthmatics
N. T. Tgavalekos1,2 R. S. Harris2, M.F. Vidal
Melo2, G. Musch2, T. Winkler2, K.R. Lutchen1 and
J. G. Venegas2 1 Dept. of Biomedical
Engineering, Boston University,
Boston, MA 2 Dept. of Anesthesia and Medicine,
Massachusetts General Hospital,
Boston, MA October 2, 2003 BMES conference
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Evidence of Mechanical Heterogeneity in Asthma
Healthy Mild-Moderate Asthmatic Severe Asthmatic
Airway closure/Heterogeneity
Heterogeneity
Heterogeneity
Lutchen, K.R., D.W. Kaczka, E. Israel, B. Suki,
E.P. Ingenito. Airway constriction pattern is a
central component of asthma severity the role of
deep inspirations. Amer. J. of Resp. and Crit.
Care Medicine 164 207-215, 2001.
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Evidence of Heterogeneity in Ventilation
Baseline
Post Challenge
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Main Goal
Are ventilation heterogeneity related to
mechanical heterogeneity?
l
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Lung Mechanics
RL, EL estimated from lung impedance (ZL) via
forced oscillations
RL Re ZL
EL -2pf Im ZL
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Quantifying Dynamic Lung Mechanics
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Features of Lung Mechanics
n13
plt.001
plt.001


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Relating Ventilation Heterogeneity to Mechanical
Heterogeneity
Baseline
Apnea
Washout
Time (secs)
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Multi - Compartmental Washout
Baseline
Post Challenge
R2.99
R2.99
Two Compartment Model
C(t) C1(0)e-t/t1 C2(0)e-t/t2
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Quantifying Ventilation Heterogeneity
.
.
Heterogeneity Index (HI)
.
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Mechanics vs. Ventilation Heterogeneity
Baseline Post Challenge
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Conclusions

• Elevation and frequency dependence in lung
  mechanics is
• also indicative of ventilation heterogeneity

• Airway constriction in asthma is inherently
  heterogeneous
• causing a distribution of poorly ventilated
  regions throughout the
• lung simultaneously with degradation lung
  mechanics

• These data sets can be combined with airway tree
• models to identify what level of airways are
  actually
• closing or constricting during asthma

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Acknowledgements
Anesthesia Critical Care José G. Venegas,
Ph.D. R. Scott Harris, M.D. Marcos Vidal Melo,
M.D. Ph.D. Guido Musch, M.D. Tilo Winkler,
Ph.D. Dominick Layfield, Ph.D.
BU Respiratory Lab K. R. Lutchen, Ph.D Cortney
Henderson, Ph.D Carissa Bellardine, M.S. Derek
Affonce, M.S
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Quantifying Airway Closure
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Rlow vs. HI
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PET Imaging in Asthmatics
End Washout Gas Trapping
PET functional imaging may provide useful
insights into the role of gas trapping in asthma