Pathophysiology
P-I-25. Diabetic neuropathy: autonomic testing & Ewing test
糖尿病性自律神経障害の検査；Ewingテスト
Context
- GI/urogenital autonomic problems are rarely tested instrumentally → diagnosed mainly by questionnaires
- Cardiovascular autonomic neuropathy has several dedicated tests
Cardiovascular Reflex Tests
- Non-invasive, easy to perform
- Parasympathetic (PARA) regulation → measure HR responses to: respiration, Valsalva maneuver, changing posture
- Sympathetic (SYM) regulation → measure BP decrease to: orthostatic changes, Valsalva, provocation (cold-pressure or hand-grip tests)
Ewing Test
- Standardized combination of 5 cardiovascular reflex tests
- Each scored: normal = 0, borderline = 1, abnormal = 2
Scoring Reference
| Reflex test | Measured variable | Normal | Borderline | Abnormal |
|---|---|---|---|---|
| PARA – Deep inhalation/exhalation | Difference between lowest & highest HR (bpm) | ≥ 15 | 11–14 | ≤ 10 |
| PARA – Valsalva maneuver | Valsalva quotient | ≥ 1.21 | 1.11–1.20 | ≤ 1.10 |
| PARA – Getting up | 30:15 quotient | ≥ 1.04 | 1.01–1.03 | ≤ 1.00 |
| SYM – Getting up | Decrease in systolic BP (mmHg) | < 10 | 11–29 | ≥ 30 |
| SYM – Handgrip test | Increase in diastolic BP (mmHg) | > 16 | 11–15 | ≤ 10 |
Test Performance
- HR fluctuation on controlled breathing (PARA): difference between lowest & highest HR
- Valsalva maneuver (PARA): hold 40 mmHg for 15 s → longest RR after ÷ shortest RR during → Valsalva quotient
- Getting up (PARA): stand up quickly, record 1 min → max tachycardia ~15th beat, max bradycardia ~30th beat
- Getting BP up (SYM): measure BP supine → stand → re-measure at 1 & 5 min → max systolic BP decrease vs supine
- Handgrip test (SYM): max grip of dominant arm, hold 5 min → measure BP on other arm → increase in diastolic BP
一問一答
▶How is sympathetic regulation assessed in cardiovascular reflex tests?
By measuring BP decreases to orthostatic changes, Valsalva, and provocation tests (cold-pressure or hand-grip).
▶How is parasympathetic regulation assessed in cardiovascular reflex tests?
By measuring heart rate responses to respiration, the Valsalva maneuver, and changing posture.
▶How are GI and urogenital autonomic problems usually diagnosed?
Mainly by questionnaires, since they are rarely tested instrumentally.
▶What is the Ewing test?
A standardized combination of 5 cardiovascular reflex tests for autonomic neuropathy.
▶Which type of autonomic neuropathy has several dedicated reflex tests?
Cardiovascular autonomic neuropathy.
▶How is each Ewing test scored?
Normal = 0, borderline = 1, abnormal = 2.
▶Which three Ewing tests assess parasympathetic function?
Deep inhalation/exhalation (HR variation), the Valsalva maneuver (Valsalva quotient), and getting up (30:15 quotient).
▶Which two Ewing tests assess sympathetic function?
Getting up (systolic BP decrease) and the handgrip test (diastolic BP increase).
▶What is the normal HR difference on deep breathing (Ewing parasympathetic test)?
≥15 bpm difference between lowest and highest HR (borderline 11–14, abnormal ≤10).
▶What is a normal Valsalva quotient?
≥1.21 (borderline 1.11–1.20, abnormal ≤1.10).
▶What is a normal 30:15 quotient on standing up?
≥1.04 (borderline 1.01–1.03, abnormal ≤1.00).
▶What systolic BP fall on standing is normal vs abnormal (Ewing sympathetic test)?
Normal <10 mmHg, borderline 11–29 mmHg, abnormal ≥30 mmHg.
▶What diastolic BP rise in the handgrip test is normal vs abnormal?
Normal >16 mmHg, borderline 11–15 mmHg, abnormal ≤10 mmHg.
▶How is the Valsalva quotient calculated?
Hold 40 mmHg for 15 s; divide the longest RR interval after by the shortest RR interval during the maneuver.
▶On standing up, around which beats do max tachycardia and bradycardia occur (30:15 test)?
Maximum tachycardia around the 15th beat and maximum bradycardia around the 30th beat.
▶How is the orthostatic (getting BP up) sympathetic test performed?
Measure BP supine, then stand, then re-measure at 1 and 5 minutes; the maximum systolic BP decrease vs supine is recorded.
▶How is the handgrip test performed?
Maximal grip of the dominant arm is held for 5 minutes while BP is measured on the other arm; the diastolic BP increase is recorded.
▶Why is HR variation with respiration a marker of parasympathetic function?
Normal respiratory sinus arrhythmia depends on vagal (parasympathetic) modulation; its loss indicates parasympathetic damage.
▶Why does an excessive systolic BP fall on standing indicate sympathetic dysfunction?
Intact sympathetic reflexes normally vasoconstrict on standing; failure causes orthostatic hypotension.
▶Why are the cardiovascular reflex tests considered advantageous for screening?
They are non-invasive and easy to perform, allowing standardized bedside autonomic assessment.