Methods for determination of blood flow Stefan P. Mortensen, DMSc - - PDF document

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Methods for determination

• f blood flow

Stefan P. Mortensen, DMSc Department of Cardiovascular and Renal Research University of Southern Denmark

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Venous occlusion plethysmography

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Cuff

Venous occlusion plethysmography Venous occlusion plethysmography

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Advantages:

• Easy to use
• Inexpensive
• Non-invasive
• Reliable

Disadvantages:

• Exercise not possible

(early recovery)

• Increase in venous pressure

can impede BF

• Cuff pressure can impede

arterial blood flow

Venous occlusion plethysmography

50mmHg ~ 28% Pa Pv R

Q = (Pa – Pv) R

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Pletysmography & xenon wash-out: Peak muscle blood flow = 50-60 ml/min/100g In pigs and other species: 200-400 ml/min/100g (Radiolabled microspheres)

Low peak blood flow compared to animals

Secher et al. 1977

Peak muscle blood flow = 50-60 ml/min/100 g 30 kg of muscle x 0.5 l/min = 15 l/min

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• +

Cuff

Strain-gauge

ring

• M. quadriceps femoris
• Art. femoralis
• Ven. femoralis

biopsy

One legged knee-extensor model

Andersen and Saltin: J Physiol,1985

Constant infusion thermodilution

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Chart Window

Blood temp. (degrees C) 34.5 35.0 35.5 36.0 36.5

• Inf. temp (degrees C)

5 10 15 20 25 30 32:40 32:45 32:50 32:55 33:00 59 30-03-2006 15:06:29.251

1 ) ( ) ( ) ( ) (

1

−         − −             =

M B I B B B I I

T T T T C S C S V flow blood

Endurance trained athletes: 385 ml/min/100 g at 99 watts (Richardson et al. 1993) 15 kg x 4 l/min = 60 l/min (endurance trained subjects) Young subjects: 250 ml/min/100 g at 55 watts (Andersen & Saltin 1985) 15 kg x 2.5 l/min = 38 l/min (untrained subjects)

Peak perfusion rates

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50 100 150 200 250 300 350 400 Low Moderate High Rat Peak BF Fitness ml/100g x min Advantages:

• Can be used during whole-body exercise and maximal exercise
• No recirculation
• Easy to learn
• Fairly inexpensive

Constant infusion thermodilution

Disadvantages:

• Invasive
• No resting measurements
• Cooling

Temperature of surrounding tissue will be reduced after 15-18 s of infusion Tissue re-warming is slow (>45 s) Femoral arterial temperature is reduced after 20-25 s The ”problem” is exaggerated with high infusion rates and a low blood flow

• Poor resolution
• Haemodilution with many measurements
• Some data interpretation
• Availability

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Dye dilution

Same principle as thermodilution, but with dye as the indicator instead of saline Arterial injection (bolus or continous) Venous detection photo-densitometer

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Disadvantages:

• Invasive
• Expensive
• Poor resolution
• Allergic reactions to the dye can occur

Advantages:

• Can be used during whole-body exercise and maximal exercise
• Reliable measurements
• Can be used to determine the mean transit time (MTT)
• Can be combined with NIRS to determine regional blood flow

Dye dilution

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Ultrasound Doppler

<60 (lower is better) Mean velocity Volume flow = Cross-sectional Area × Time-averaged velocity Area = π × radius2

Ultrasound Doppler

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Advantages:

• Can be used during exercise (forearm, leg kicking)
• High resolution
• Continuous measurement
• Non-invasive

Disadvantages:

• Sensitive to movement
• Expensive equipment
• Infusion noise
• Difficult/time-consuming to learn

exercise measurements

Ultrasound Doppler Thermodilution versus Doppler

Rådegran 1997 Knee-extensor exercise ATP infusion

Thermodilution blood flow (l min-1) 1 2 3 4 5 Doppler blood flow (l min-1) 1 2 3 4 5 r=0.989

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Microbubbles (SonoVue): 2.5 µm in diameter (range 0.7-10). SF6 gas encapsulated by a phospholipid shell Contrast-enhanced ultrasound (CEUS)

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Contrast-enhanced ultrasound (CEUS) Contrast-enhanced ultrasound (CEUS)

Advantages:

• Measures microcirculatory flow
• Minimally invasive

Disadvantages:

• Expensive
• Difficult (impossible) to quantify
• Difficult (impossible) to perform during execise – movement + contraction acts like a flash
• Measures bubble flow – is it the same as plasma/erythrocyte flow?

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Thank you for your attention!