[Functional studies of the autonomic nervous system].

There are many methods to choose from in the investigation of the autonomic nervous system. The value of the individual tests to the clinician varies according to the method of investigation used. No one test can elucidate all the information needed for all functional disturbances. As a routine, measurement of blood pressure and heart rate reaction to active orthostasis and heart rate variation with deep breathing and the Valsalva manoeuvre can be useful. Spectral analysis of the heart rate is an easily performed test, only minimally disturbing for the patient, and is a valid means of investigation which may find a way into routine clinical use in the future.