2. Function and Method of AFT-800 Test?
1) Heart Rate Variation during deep breathing
Breathe 6 times for one minute while lying at supine position or at maintaining about 30 degrees in the bed. During breathing, the RR interval by ECG shortens while lengthens during expiration.

In other words, the heart rate increases during inspiration and decreases during exhalation.

 A. Evaluate the result by finding the difference between the maximum and minimum heart beats that occur during one breath.
 B. It displays as the ratio of the maximum and minimum values for the RR Interval. Normal ratio reference for each age follows the guidelines presented by the diabetic neuropathy association as below.

2) Blood Pressure Test from the supine to upright position : Use the Tilt table
 A. By analyzing the orthostatic blood pressure, it plays an important role of measuring the blood pressure to see the autonomic nerve function from the supine position. If a person is healthy, the blood pressure should be maintained while standing up from the supine position.

 B. Tilt Table Test
It is recommended to take the test more than 10 times in every minute from the supine position to upright position and if the blood pressure were drastically decreased, the person should be tested 1 or 2 times at supine position.

Check the decrease status of systolic blood pressure Measure whether there are normal orthostatic blood pressure changes or severe blood pressure changes.

Generally, when the systolic blood pressure differs by over 20mmHg or the diastolic blood pressure changes by over 10mmHg, an abnormal bar will be appeared on the graph.

If symptoms of syncope with feeling dizzy or nausea during a tilt table test, immediately stop the test and put the table down to lower the head and take a rest.

 C. POTS (Postural Orthostatic Tachycardia Syndrome)
Measure the MHR and blood pressure at the same time. POTS may appear as a compensatory mechanism in patients with decreased blood pressure, and orthostatic tachycardia syndrome (POTS) is also frequently observed in chronic fatigue patients, children and adolescents. It is mainly observed in chronic fatigue patients and in children, and is a symptom frequently observed when the orthostatic hypotension is normal during upright position, but only the heart beats are increasing.

3) Changes and Rates of Heart Rate due to Valsalva
 A. Put the mouthpiece into the hose attached to the device, inhale first and then, blow up to 40mmHg. Then, keep to exhale it for up to 15 minutes and maintain it from 20 seconds to 1 minute.

At this time, compare the minimum RR interval while blowing at a pressure of 40mmHg for 15 seconds and the maximum RR Interval for at least 20 seconds to 1 minute without blowing out. (Longest RR interval after interruption) / (Shortest RR Interval during Valsalva maneuver)

 B. Measurement Method
– At supine position, the patient takes a deep breath and then exhales strongly through a tube connected to the hand grip gauge for 15 seconds until the value on the hand grip gauge reaches 40mmHg or higher. During the Valsalva test, blood pressure and heart rate change in 4 steps.

– Changes of heart rate in the Valsalva test mainly reflect the activity of the parasympathetic nervous system. During the test, the RR interval is measured while recording the electrocardiogram, and the ratio of the longest RR interval divided by the shortest RR interval is called as Valsalva ratio.

– In normal people, the ratio is over 1.2 and if it is under 1.2, it is evaluated as the abnormal autonomic nervous system.
– It is necessary to repeat the test 3~4 times to make it accurately.

4) Changes in heart rate at 30:15 after standing up
When a normal person suddenly stands up from the supine position, the heart rate initially increases and then tends to gradually decrease. This is a test to observe changes in heart rate when changing from supine position to upright position.

In the ECG, the ratio (30/15 ratio) of the RR interval near to 30 times (longest) / RR interval near to 15 times (shortest) is obtained and used as an indicator reflecting the activity of the parasympathetic nervous system.

5) Heart Rate Variability: Measure at supine posture

6) HRV test according to the changes of posture  
After measuring HRV in supine and upright positions, the level of change due to changes in sympathetic and parasympathetic nerve is quantified through HRV PSD (Power Spectral Density).

 A. Necessity of HRV Orthostatic Test
By the stable HRV state, it is possible to observe the overall state of the autonomic nervous system mainly accompanied by functional abnormalities, chronic fatigue, headache and dizziness.

However, in case of patients with diabetes or neuropathy in particular, there is a rapid decline in HRV at a stable state. Therefore, it is the test to check responsiveness through HRV orthostatic test according to changes in posture.

In order to evaluate the activity of the autonomic nervous system using HRV, there are an orthostatic test method that applies a load to the autonomic nervous system and compares before and after the loading, and a method that analyzes signals measured once in a specific state. In principle, it is good to conduct an orthostatic test to evaluate the activity and response of the autonomic nervous system.

 B. Usefulness of HRV Load Test
As the complications related to the diabetes have the important meaning, according to Ewing et al., the degree of reduction in heart rate variability in diabetic patients is proportional to the degree of disease progression and the patient’s age, and the mortality of those who have decreased heart rate variability is generally high. In addition, measurement of heart rate variability in diabetic patients is very important in the diagnosis and prognosis of autonomic nervous system lesions, and is especially useful in early detection of asymptomatic autonomic nervous system abnormalities.

In diabetes, autonomic dysfunction initially affects the vagal conduction to the heart, and the sympathetic transit pathway is impaired later in the disease process. In diabetic neuropathy, a decrease in time-scale analysis parameters of HRV suggests a poor prognosis. In addition, it is known to appear before clinical symptoms, and it is reported that the absolute power of LF and HF is decreased in diabetic patients without autonomic symptoms.

In normal people, HRV changes in different postures generally mean that a certain level of response is healthy, and the degree of disease progression and the patient’s age. It is revealed that people with this decrease have a high mortality.

 C. Meaningful change in parameters during the HRV Load test to the changes of posture from supine to upright When comparing HRV results in a supine position(resting or lying down) with HRV results in an upright position, heart rate, normalized LF and LF/HF ratio among HRV parameters increase while SDNN, TP, HF and normalized HF decrease.

 D. CANRISK Index (Risk index of Cardiac Autonomic Neuropathy)
As a result of research conducted at 5 university hospitals in Korea, it is a value indexed by a comprehensive analysis of cardiovascular autonomic nervous system abnormalities by parameters according to the response of the HRV Load test.

The specificity of this CAN RISK index has a significance of 86.2% in comparison between the type 2 diabetes group and the diabetic neuropathy group.