2. Overview
• Eagle’s Medium - pH 7.2 - 7.5; essential amino acids, glucose (5.6
mM), sodium bicarb (26.2 mM) equilabrated with 75% O2 / 5% CO2
gas mixture (balance N2) warmed to ~37ºC and placed in incubator;
media pCO2 20-35 pO2 300-440 mmHg
• Sensor wire ~3 cm long sensing elements in the middle ~1-2 cm from
tip; sensor values validated with media values before placing in plaque
tissue; typically takes 30 min to equilibrate with tissue
• Distance between pH, pCO2, and pO2 sensors (in that order from tip)
may allow the pH reading to be in thinner tissue and pO2 in thicker
tissue
• Tissue pH and pCO2 stable for ~ 4 hours in the media
• Conclusion: perform readings in thicker (>0.7 mm) tissue areas first
3. 9/7 plaque
• Plaque thickness 0.35 - 0.8 mm; ~3
cm x 2 cm area
• plaque in media for one hour
before sensor put in
• 4.5 hrs in media; tissue values
– pH : 7.03 - 7.06
– pCO2 : 60 - 95 mmHg
– pO2 : 170 - 290 mmHg
– Correlations: pCO2 & T
strongest,R2
=0.74; pH-pCO2
R2
=0.38
• 2 hrs in humidified 37ºC air
– pH sl. increase as pCO2, pO2
temperature dropped
tip
Sensor wire
oxygenated liquid media
15. Purpose
• To demonstrate hypothesized pH heterogeneity in a plaque
is not equilibrating with oxygenated media
• To assess living state of plaque in physiologic conditions
over expected time course
16. Methods
• Sensor A:
– placed about half way into plaque thickness
– in semi-calcified/necrotic spot thickness along sensor ~1-2.6 mm
(pO2 near thinner end)
• Sensor B:
– placed closer to exterior portion of vessel wall ~0.75 mm in wall
– in/under thrombus 1.2-1.6 mm thickness (pO2 near thinner piece,
closest to media)
• After 1.5 hrs, tank w/ 75% O2, 5% CO2 was empty; switched
to 21% O2, 5% CO2 to keep same pH-pCO2buffering
capacity
• Monitored for additional 2.5 hrs at 21% Oxygen
21. Results
Sensor A
R
2
= 0.9027
0
10
20
30
40
50
60
70
80
6.90 7.00 7.10 7.20 7.30 7.40
pH
pCO2
• Strong pH-pCO2 correlation suggest sensors are firmly placed in tissue
• Sensor A in thicker tissue exhibited lower pH than Sensor B over the 4
hr. time course
• Physiologic pH, CO2 readings and trend with different levels of
oxygenation suggest plaque is in living state closest to in vivo situation
Sensor B R
2
= 0.9464
0
10
20
30
40
50
60
7.20 7.30 7.40 7.50 7.60 7.70
pH
pCO2
