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Table 1 Common parameters derived from transcranial Doppler

From: How I use Transcranial Doppler

 

Abbreviation or formula

Normal values

Elevated ICP

Brain death

Cerebral autoregulation

Cerebral vasospasm

Pulsatility index

PI = (sFV − dFV)/mFV

< 1.4

> 1.4

Mean FV

mFV

60–80 cm/s [2]

Mild ≥ 120 cm/s

Moderate = 120–200 cm/s

Severe ≥ 200 cm/s (with LR < 3)

Diastolic FV

dFV

> 20 cm/s

< 20 cm/s

Negative or absent

Increased

Mean flow index

Mx

< 0.3

> 0.3

> 0.3 (impaired)

> 0.3

Lindegaard ratio

LR = mFV MCA/mFV extracranial ICA

< 3

Mild ≥ 3

Moderate = 3–6

Severe ≥ 6

THR test

    

Less than 10% increase from baseline sFV (impaired)

 
  1. FV flow velocity, MCA middle cerebral artery, ICA internal carotid artery, Mx mean flow index, dFV diastolic flow velocity, mFV mean flow velocity, sFV systolic flow velocity, CA cerebral autoregulation, THR transient hyperemic test