Autonomic Tests Flashcards
Test principals
Noninvasive test detect autonomic failure via measurement of how various systems are controlled by autonomic nerves and their response to stimulation
Monitor hr, abp, blood flow, skin temperature and sweating
Causes of autonomic dysfunction
Primary (idiopathic) degeneration of autonomic postganglionic fibers
Diabetes Mellitus
Nutritional causes as vitamin B12 deficiency
Toxic /metabolic causes as porphyria
Central causes Cerebral vascular accidents (hemorrhages), syringomyelia
Systems regulated
Abp
Hr
Git
Bladder
Thermal regulation
Respiration
Sexual functions
Cause of respiratory sinus arrhythmia
Central mechanism: inhibitory impulses from R.C. on vagal control of the heart
Peripheral mechanism: inhibitory impulses from pulmonary stretch receptors
Bainbridge reflex
Detection
Recording HR using (ECG) lead II
➢ Deep breathing 6 / min for 3 cycles (5 seconds each for inspiration and expiration)
➢ R-R interval is shortened during inspiration and prolonged during expiration
➢ Record maximum and minimum heart rate with each respiratory cycle
Average the 3 differences
Normal
> or equal 15 beats /min
Borderline
= 11-14 beats/min
Abnormal
< or equal 10 beats /min
Hr response during standing
Monitor HR for 30 seconds before & 60 secs after standing
When supine and When standing
Loss of gravity effect on the lower limb veins
→↑ VR & ↑CO
Blood pooling in lower limb veins
→↓VR and CO
→ stimulating reflex ↑in the HR (tachycardia),
• Is maximal approximately 15 seconds after standing
• Then HR returns to normal (near-supine rate)
HR response to valsalva
Valsalva: is forced expiration against resistance
(Simple, inexpensive, non-invasive test→diagnose variety of conditions as heart murmur)
Maintained forced expiration against resistance for 15 seconds,
with intra-thoracic pressure of about 40 mmHg
Phase I (Onset of strain):
ABP ↑slightly
Due to ↑intrathoracic
pressure transmitted
to rest of circulation
Hr is normal/ constant
