Autonomic function tests

1. Postural test: patient remains 10 min in resting supine position (45˚ angle). Blood pressure, heart rate are measured after 2, 5 and 10 minutes. Then the patient is asked to stand unaided for 5 minutes. The same parameters are measured. A decrease of SBP > 20 mmHg or DBP > 10 mmHg within 3 min of standing and delayed orthostatic hypotension as a sustained  BP fall occurring beyond 3 minutes of standing are considered as sympathetic adrenergic failure.
2. Valsalva maneuver: The patient is asked to blow through a mouthpiece attached to a manometer monitoring a pressure of 40 mmHg for 15 minutes, during ECG monitoring. The Valsalva ratio (longest R-R after/shortest R-R during) is then determined.
3. Pressor tests:

isometric exercise: grip sphyngomanometer cuff inflated to 20 mmHg with dominant hand at one third of maximal volimetric contraction force for 2 minutes. Blood pressure is measured at rest and at end of 2 minutes.

cutaneous cold pressor test: hand is immersed up to wrist in ice cold (4˚ C) for 2 minutes. Blood pressure and heart rate is measured before and after test.

4. Mental arithmetic test: serial subtractions for 2 minutes. Blood pressure and heart rate is measured before and after test.
5. Deep breathing test: six deep breaths in one minute while in supine position. The difference in heart rate is measured between maximal and minimum heart rate is calculated in an individual respiratory cycle and expressed as the mean of the difference in six successive cycles.
6. Measures of plasma catecholamines. Antecubital venous blood is drawn through an indwelling catheter, after at least 15 min of supine rest and after 5 min of standing. Plasma noradrenaline, adrenaline and dopamine is assayed.
7. Response of growth hormone after administration of clonidine. Increased in healthy individuals, PD and PAF.