What is autonomic testing?

Autonomic testing helps find out if your autonomic nervous system (ANS) is working as well as it should. Your ANS controls body functions that happen automatically (without you thinking about them). These functions include your breathing, heartbeat, body temperature, and digestion. If there are problems with the function of your ANS, it's known as autonomic neuropathy.

Autonomic neuropathy damages the nerves that control your internal organs. This can lead to problems with your:

• Heart rate and blood pressure
• Digestive system
• Bladder
• Sex organs
• Sweat glands
• Eyes
• Blood glucose

The most common causes of autonomic neuropathy include diabetes, autoimmune diseases, some types of medicines, and certain infections, such as HIV.

Autonomic testing can show which part of your ANS is affected and how seriously it's affected. This can help your health care provider develop the most effective treatment strategy for you.

Other names: tilt table test, quantitative sudomotor axon reflex test (QSART), thermoregulatory sweat test (TST), passive head-up tilt test, head-upright tilt test

What is it used for?

Autonomic testing is used to check for problems with your autonomic nervous system (ANS).

Why do I need autonomic testing?

You may need this test if you have symptoms of autonomic neuropathy, sometimes referred to as dysautonomia. Symptoms will vary depending on which part of your nervous system is affected.

Stomach and gastrointestinal symptoms can include:

• Constipation
• Diarrhea
• Nausea and vomiting

Bladder and urinary symptoms can include:

• Difficulty urinating
• Leaking urine
• Urinating more often than usual

Heart and lung symptoms can include:

• Rapid heart rate
• Shortness of breath with activity or exercise
• Dizziness
• Fainting
• Weakness

Other symptoms can include:

• Too much or not enough sweating
• Sexual problems; such as erectile dysfunction in men and vaginal dryness in women
• The pupils of your eyes being slow to adjust to changes in light and darkness
• Getting low blood glucose and not knowing it (since you may not have the symptoms)

What happens during autonomic testing?

There are different types of autonomic tests. Depending on your symptoms, your provider may perform one or more of the following tests:

Deep Breathing Test and Valsalva Maneuver. These tests measure your heart rate and blood pressure while doing certain types of breathing.

• For both tests, your provider will place electrodes on your chest and a small blood pressure cuff on your finger.
• For a deep breathing test, you will take slow, deep breaths for one minute.
• For the Valsalva maneuver, you will breathe out forcefully through a mouthpiece while your nose is pinched shut.
• The electrodes and cuff will record your heart rate and blood pressure.

Tilt Table Test. This test measures your blood pressure and heart rate as you change your posture and position to find why you have had lightheadedness or fainted. During the first part of the test:

• You will lie flat on a motorized table that has a footrest.
• Soft safety straps will be placed across your body.
• Your provider will put electrodes on your chest and blood pressure cuffs on one of your arms and a finger. An intravenous (IV) line may also be placed in your arm or hand to inject medicine or fluids if needed.
• You will remain flat on the table for about 15 minutes.
• Your provider will tilt the table to 30 degrees for two to three minutes, then 45 degrees for two to three minutes, and then to an an almost standing position for up to 45 minutes.
• Your provider will check your blood pressure and heart rate.
• If the test causes you to faint, the table will be quickly returned to the flat position.

You may have to do the second part of the test if your blood pressure doesn't lower during the first part of the tilt table test. During the second part of the test:

• Your provider will give you medicine that makes your heart beat faster to see how your body reacts.
• Your provider will tilt the table to 60 degrees for up to 15 minutes and monitor your blood pressure.
• If your blood pressure lowers, the test will end sooner than 15 minutes.
  

The test takes from 30 to 90 minutes.

Quantitative Sudomotor Axon Reflex Test (QSART). This test measures the function of the nerves that control sweating. During the test:

• You will remove your shoes and socks.
• You will sit or lie flat on an exam table.
• Your provider will clean and dry your skin and then place electrodes on the part of the body where are doing the test. This is usually on your foot, wrist, and leg. The electrodes will contain a substance that stimulates sweating.
• A mild electrical current will be sent through the electrodes. You might feel a warm, tingling sensation as this is done.
• A computer will analyze how your nerves and sweat glands react to the electrical current.
• Your provider may move the electrodes and repeat these steps on different body parts.

The test takes about 45 minutes to an hour to complete.

Thermoregulatory Sweat Test (TST). This test measures how well your body sweats in a warm environment. During the test:

• A special powder will be applied to your skin.
• You will lie in a special room that is slowly heated up to stimulate sweating. The heat and humidity may be a little uncomfortable.
• The powder will change color as you sweat.
• The pattern of your sweat can show if you are sweating normally.

The test takes usually takes 40-65 minutes to complete.

Bladder Ultrasound. This test is used to check for problems with your bladder, which is controlled by autonomic nerves. The ultrasound is done after you urinate to see how much urine is left in the bladder. During the test:

• You will lie on a table with your lower abdomen exposed.
• Your provider will spread a special gel on the skin over that area.
• Your provider will move a wand-like device, called a transducer, over the area.
• The device sends sound waves into your body.
• The waves are recorded and turned into images on a monitor.

Will I need to do anything to prepare for the test?

Your provider will give you specific instructions on how to prepare, but many autonomic tests require the following preparations:

• Don't eat or drink anything with caffeine for eight hours before your test.
• Keep well hydrated with noncaffeinated beverages the day before your test.
• Don't drink alcohol for 12 hours before your test.
• Don't smoke or use tobacco products for four hours before your test.

Check with your provider about how to prepare for your test. They will also let you know if you need to stop taking any medicines before your test.

Are there any risks to the test?

Some people faint during a tilt table test. If that happens, you will immediately be tilted back to a normal position. During and after a tilt table test, you may experience nausea, vomiting, or weakness. Weakness may last a few hours, but other symptoms usually go away quickly.

There are no known risks to having an ultrasound.

You may have some skin irritation from the electrodes used in a sweat test.

What do the results mean?

If any of your autonomic test results were not normal, it likely means that there is a problem with your ANS. To make a diagnosis, your provider will also consider your medical history, symptoms, and results from your physical exam. Sometimes they will order more tests, especially if the cause of your ANS problem is unknown.

If another disease is causing your ANS problems, treating that disease may help. Otherwise, treatment focuses on helping with your symptoms. This could include medicines and/or lifestyle changes.

If you have questions about your results, talk to your provider.