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Autonomic Function Tests


Suspected diabetic autonomic neuropathy.
Shy-Drager Syndrome.
Suspected autonomic failure from other causes.


Patients with proliferative retinopathy should not perform the Valsalva manoeuvre because of the risk of retinal haemorrhage.
Atrial fibrillation (tests uninterpretable, except postural hypotension and handgrip tests).




Mouthpiece to attach to sphygmomanometer (5ml syringe minus plunger).
ECG machine (old fashioned type as long rhythm strips recorded).
Tests of cardiac parasympathetic damage

  1. Heart rate response to the Valsalva manoeuvre
    Start ECG machine (limb leads only, use lead II)
    Patient blows into sphygmomanometer and maintains pressure at 40mmHg for 15 seconds, continue recording for 30 seconds after release of pressure.
    Measure shortest R-R interval during manoeuvre and longest after.
    Valsalva ratio = longest after/shortest during.
    Take mean of three readings.
  2. Heart rate variation during deep breathing
    Start ECG machine
    Ask patient to breathe quietly at a rate of six breaths over one minute (5 seconds in and 5 seconds out).
    Mark ECG at start of each inspiration and expiration.
    Measure maximum and minimum R-R interval for each cycle and convert to beats/min.
    Result is mean difference (max - min) for heart rate during deep breathing.
  3. Heart rate response to standing
    Start ECG recording with patient lying.
    Ask the patient to stand, continue recording ECG for 1 minute.
    Measure shortest R-R interval around the 15th beat after standing and the longest around the 30th beat.
    Calculate longest/shortest = 30:15 ratio.
    Tests of sympathetic damage
    Blood pressure response to standing
    Measure blood pressure lying and then 2 minutes after standing
    Record postural difference


TESTS Normal Borderline Abnormal
Valsalva ratio =1.21 1.11-1.20 =1.10
(max-min) HR >15 11-14 <10
(30:15 ratio) >1.04 1.01-1.03 =1.00
fall in BP =10 11-29 =30
These tests can be used to determine the degree of abnormality present: if two or more of the parasympathetic tests plus the sympathetic tests are clearly abnormal then this indicates significant autonomic damage, earlier damage is signified by abnormalities in at least two parasympathetic tests.


Caution should be taken in interpreting these tests in patients who are poorly co-operative and in the elderly.


Clarke B.F. and Ewing D.J., BMJ 285, 918-920 (1982).