PPT on heat exchanger used during cardiopulmonary bypass

1. • HEAT EXCHANGER
– Karthi Murugan

2. HEAT EXCHANGER
• Integral component of the oxygenator helps in
thermal regulation of the blood usually
accomplished by passing warm or cold water.
• Transfer of energy occurs by circulation
warm/cold water from heater cooler unit.
• Precise temperature control achieved by the
HCU
• Mandatory to measure inlet &outlet
temperature

3. PRINCIPLE
• CONDUCTION - SOLID TO SOLID
• CONVECTION – SOLID TO LIQUID

4. BLOOD FLOW PATH

5. COMMON MATERIAL
MATERIAL QUALITY
PLASTIC In expensive, relatively poor conductor
ALUMINIUM Best, degrades on performance when coated
with biocompatible surface
STAINLESS STEEL Popular because of its combination exchange
coefficient, ease of fabrication in either pleated
or tubular form, and biocompatibility.
POLYPROPYLENE,
POLYETHYLENE
Most popular in recent oxygenators, ease of
fabrication, biocompatibility.

6. PERFORMANCE FACTOR
• Heat exchangers are rated with regard to a performance
factor, which may be calculated by use of the following
formula
• Performance factor
=
(𝐴𝑟𝑡𝑒𝑟𝑖𝑎𝑙 𝑏𝑙𝑜𝑜𝑑 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 − 𝑉𝑒𝑛𝑜𝑢𝑠 𝑏𝑙𝑜𝑜𝑑 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒)
(𝑊𝑎𝑡𝑒𝑟 𝑖𝑛𝑙𝑒𝑡 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 − 𝑉𝑒𝑛𝑜𝑢𝑠 𝑏𝑙𝑜𝑜𝑑 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒)
• The performance factor is frequently in range of 0.4-0.7
Example=
(34.0−32.0)
(37.0−32.0)
=
(2)
(5)
=0.4

7. PERFORMANCE FACTOR
MANUFACTURER OXYGENATOR
BUNDLE
(M2)
PRIMING
VOLUME
(ML)
HEAT EXCHANGER
(CM2)
PERFORMANCE
FACTOR
SORIN D 100 0.22 31 300 0.65
TERUMO BABY RX-05 0.50 43 350 0.65
MAQUET QUADROX I
NEONATAL
0.38 38 700 0.62
MAQUET QUADROX I
PAEDIATRIC
0.80 81 1500 0.62
TERUMO RX 15,40 1.50 135 1400 0.60
SORIN INSPIRE 6 1.40 184 4300 0.60
HILITE 7000 1.90 320 4500 NA
SORIN INSPIRE 8 1.75 219 4300 0.53

8. COOLING
• The temperature between circulating water and
blood temperature determines the heat transfer.
• Changing temperature alters the solubility of the
gas.
• Rate of cooling can be 1°C/minute
• Minimum safe cooling times to allow for
homogenous brain cooling for DHCA are usually
in the 20–25 min range.
• Inadequate cooling time before DHCA has been
associated with worse neurologic outcomes
including choreoathetosis.

9. REWARMING
• Rewarming should be done at rate of 1°C for 3-
5 minutes.
• Temperature gradients between the arterial
outlet and venous inflow on the oxygenator
during rewarming should not exceed 10°C to
avoid generation of gaseous emboli.

10. Cons of Rapid Rewarming
• Temperature gradient between the heater and
venous blood should not exceed 10°C. The
high gradient between core & peripheral
temperature can lead to after drop in
temperature.
• Higher gradient increases the risk of gaseous
micro emboli forming either in the pump
circuit or in the patient

11. • Rapid warming has been associated with a
transient cerebral oxygen demand greater
than supply.
• Aggressive rewarming and hyperthermia have
been linked to greater neuropsychologic
dysfunction after bypass.
• Oxygenator outlet temperature of greater
than 37 °C for prolonged time has been
correlated with acute kidney injury.

12. • Thank you