Some degree of dysfunction with the autonomic nervous system is probably very widespread, especially as we get older.
Almost any medical problemor even treatmentcan impact the autonomic nervous system either directly or indirectly.
A problem with the autonomic nervous system is calleddysautonomia.
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The usual reason for this is dehydration, which is why we also check the pulse.
This can also be done during deep breathing.
Up to age 40, an exhalation to inspiration ratio of less than 1:2 is abnormal.
This ratio is expected to decrease as we age and also decreases with even a very milddiabetic neuropathy.
The Valsalva ratio is another simple, noninvasive bedside test that can be used to assess for dysautonomia.
The patient bears down by exhaling with her mouth closed so that no air actually escapes.
If the heart rate does not increase during the Valsalva, there is likely sympathetic dysfunction.
If it fails to slow afterward, it suggests parasympathetic dysfunction.
Sweat Tests
The sympathetic nervous system is responsible for causing secretion from sweat glands.
Sometimes the sympathetic innervation to part of the body is lost, and this part no longer sweats.
The downside is that this test is very messy.
A variety of eye drops might be used to assess the autonomic innervation of the eyes.
We’ve only described some of the many tests used to assess the autonomic nervous system.
2009 Jan;23(1):33-9. doi:10.1038/jhh.2008.81.
Epub 2008 Jul 24.
