1 / 50

Impedance Measurement Technique

Impedance Measurement Technique. Jia-Feng Wu, M.D. Division of Gastroenterology, Department of Pediatrics, National Taiwan University Children Hospital. Impedance. Impedance measurement is used to show the bolus transit in the esophagus.

virgil
Download Presentation

Impedance Measurement Technique

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Impedance Measurement Technique Jia-Feng Wu, M.D. Division of Gastroenterology, Department of Pediatrics, National Taiwan University Children Hospital

  2. Impedance • Impedance measurement is used to show the bolus transit in the esophagus. • Traditional method uses X-ray to visualize the bolus movement (video pharyngeography) • Because of the low price per channel many measuring points can be used (2 cm spacing) to cover the total esophagus

  3. What is impedance? Georg Simon Ohm 1789-1854 • Impedance is the electrical resistance measured with an alternating current • Impedance is the inverse of conductance (Imp = 1/Cond) • Impedance is measured in Ohm ( Ω ) • Low impedance ► many ions are moving • High impedance ► a few ions are moving

  4. Impedance: • In order to reduce the oxidation of the metal electrodes, an alternating current is used at 3.2 kHz • That means the Plus and Minus are changing 3200 times per second.

  5. Ohm*cm (at 1 kHz) Gastric contents 30 – 100 Bile 90 Physiologic saline solution 100 Saliva 110 Skeletal muscle 250 - 700 Milk / Yoghurt 300 Custard-based dessert / curds 400 Drinking water 1100 Cola 1100 Esophageal wall 2000 Epidermis 2000 – 100.000 Air 10.000.000 Impedance values A.J.P.M. Smout, UMC-Utrecht, The Netherlands

  6. Impedance measurementin the esophagus

  7. Measuring technique • Use a impedance catheter • A small electrical current is used to measure the impedance between the 2 rings Ring R1 R2 Patient safe low electrical current

  8. Measuring technique • Catheters with multiple metal rings • A ring can be used for 2 channels if the distance is not too big (2 cm) Ring R1 R2 R3 R4 Channel 1 2 3

  9. Impedance signals Oesophagus wall Pressure contraction Water bolus Air in front of bolus Impedance ring Pressure sensor

  10. Impedance signals • Baseline signal IMP PRES

  11. Impedance signals • Air in front of the bolus IMP PRES

  12. Impedance signals • Bolus IMP PRES

  13. Impedance signals • Pressure contraction (increased impedance) IMP PRES

  14. Impedance signals • Baseline signal IMP PRES

  15. Impedance signals Baseline Air Bolus Contraction Baseline Bolus entry …. exit

  16. Impedance signals Belching Baseline Air Baseline

  17. Impedance signals A B • A Wet swallow: The liquid ‘falls’ down into the esophagus • B The front of the pressure wave clears the esophagus WS Clearing Peak Imp Pres 4 sec

  18. Impedance catheters • Impedance + pH • Single use • pH antimony • Internal reference • 1 or 2 pH channels • 7 or 8 rings

  19. Calculations impedance signals

  20. Calculations • BPT (Bolus Presence Time) • Time elapsed between: • Bolus entry and • Bolus exit using a 50% threshold. BPT 50 %

  21. Calculations BHAT • BHAT (Bolus Head Advance Time) • Time elapsed between: • Bolus entry at top channel and • Bolus entry at each channel • Speed of bolus moving down BHAT BHAT BHAT BHAT BHAT BHAT BHAT

  22. Calculations TBTT • TBTT (Total Bolus Transit Time) • Time elapsed between: • Bolus entry at top channel and • Bolus exit at lowest channel

  23. Calculations STT STT • STT (Segment Transit Time) • Time elapsed between: • Bolus entry at a channel and • Bolus exit at next (lower) channel

  24. Clinical applications of impedance recording

  25. Clinical applications • Esophagus • bolus transit • gas transport (air swallowing and belching) • gastro-esophageal reflux

  26. Bolus transport

  27. Normal bolus transit

  28. Esophageal function testing with combined multichannel intraluminal impedance and manometry: multicenter study in healthy volunteers 43 healthy subjects solid-state manometry 10 liquid, 10 viscous swallows Normal esophageal transit when : Tutuian R et al. Clin Gastroenterol Hepatol 2003;1:174-182

  29. ‘Combined multichannel intraluminal impedance and manometry clarifies esophageal function abnormalities: study in 350 patients’Tutuian R, Castell DO. Am J Gastroenterol 2004;2:230-236 Manometric diagnosis N Normal transit Achalasia 24 0% Scleroderma 4 0% IEM 71 51% DES 33 55% Normal 125 95% Hypertensive LES 25 96% Nutcracker 30 97% LES dysrelaxation 33 100% Hypotensive LES 5 100% IEM = Ineffective Esophageal Motility DES = Diffuse Esophageal Spasms

  30. Non obstructive dysphagia • 40 patients with non-obstructive dysphagia • Combined manometry+impedance • Manometry findings Impedance (transit findings) • Normal 20 35% abnormal transit • Ineffective motility 13 85 % abnormal transit • Esophageal spasms 4 67 % abnormal transit • Achalasia 3 100 % abnormal transit • total 40

  31. Gas transportair swallowing and belching

  32. Air swallow • Normal air intake during: • Dry swallow • Wet swallow • Food intake 32

  33. Gastric belch (type I) • Type I belches • Gastric belch • Normal venting of gastric air • After intake of CO2 like Coca Cola 33

  34. Supra-gastric belch (type II) • Type II belches • Supragastric belch • Sucking air into the esophagus with immediate expulsion • Aerophagia • [A] Suck air in • [B] Belch out A B 34

  35. Summary of transit test • Manometry (=pressure waves) • Impedance (=transit) • Main indication: • (non-obstructive) Dysphagia • Belching • Clarify functional defects

  36. Gastro-esophageal reflux

  37. Gastro-esophageal reflux (GERD) • Reflux of gastric content into the esophagus • Symptoms: heartburn / regurgitation • Damage to the esophageal wall (esophagitis) • Up to 10% of world population • Golden standard diagnostic tool: • 24 hr pH monitoring

  38. Gastro-esophageal reflux (GERD) • Reflux is acid which flows from the stomach into the esophagus • Detected with pH probe

  39. 7 pH 4 0 60 seconds imp Reflux Non-acid reflux  Weakly acidic reflux Not detected by pH probe but by impedance PAIN pH>4 ‘Non-acid’ reflux 39

  40. New category (consensus meting) • Reflux subcategories: • Acid reflux (pH falls below 4) • Super-imposed acid reflux (reflux while pH is already below 4) • Weakly acidic reflux (pH nadir >4 but <7) • Non-acid reflux (pH >7)

  41. Effect of omeprazole on acid and non-acid reflux in 12 patients with reflux symptoms 55% 97% Off PPI On PPI Vela M et al. Gastroenterology 2001;120:1599-1906

  42. Weakly acid reflux • Weakly acid reflux (pH >4) can cause symptoms • Most of the patients who visit a GI doctor continue to use PPI • Weakly acid reflux cannot be analysed with a pH probe • Impedance-pH detects ALL reflux episodes

  43. Pediatrics and infants • Gastric content is very often not acid due to milk intake. Sometimes even higher than pH 7 due to buffering • Reflux cannot be detected with a pH probe • Impedance recording • Bolus transit and reflux measured • Reflux contents does not matter • 24 hour (just like ambulatory pH)

  44. Pediatrics and infants • 17 Infants with regurgitation, asthma, apnea • 6-8 meals (milk) per day • Gastric pH often > 4 • Patient group: 17 children • 675 refluxes185 acid 490 non-acid Skopnik et al, J. Pediatric Gastroenterol Nutr 1969

  45. Summary: impedance-pH investigation • Esophageal impedance monitoring can detect reflux with a pH above 4 • Weakly acid reflux • It can detects acid and non-acid reflux episodes • Clinical useful for evaluation of: • Symptoms under PPI • Symptoms off PPI • Unexplained cough • Pediatric practice 45

  46. Equipment for impedance recording 46

  47. Ambulatory impedance - pH 47

  48. OhmegaAmbulatory impedance - pH • Ω Ohmega specs • 8 to 13 Impedance rings • 1 to 4 pH Antimony • 2 glass pH – 2 ISFET pH (optional) • 4 pressure channels (optional) • Bluetooth wireless connection (up to 50 meter) • Memory 128 MB • USB interface with PC • Power supply 1 AA battery (recording time 28-35 hr) 48

  49. Technical data Ohmega • Data size ambulatory investigation 24 hr • 50 MB for 24 hours • Sample rate: • 50 samples/sec impedance channels (6 channels) • 1 sample/sec pH channel • MMS non destructive data compression 50 MB into 15 MB • Download time 5 – 10 minutes • Use CD-R or DVD-R as backup • Recording time 1 AA battery 28-35 hr • Internal memory 2-3 days

  50. Stationary equipment (Solar-GI)

More Related