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

2. + 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. + 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 Georg Simon Ohm 1789-1854

4. + 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 A.J.P.M. Smout, UMC-Utrecht, The Netherlands

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

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

10. + Baseline signal IMP PRES

11. + Air in front of the bolus IMP PRES

12. + Bolus IMP PRES

13. + Pressure contraction (increased impedance) IMP PRES

14. + Baseline signal IMP PRES

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

16. Belching Baseline Air Baseline

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

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

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

21. + 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

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

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

25. + Esophagus – bolus transit – gas transport (air swallowing and belching) – gastro-esophageal reflux

28. Liquid swallows 80 % complete bolus transit Viscous swallows 70 % complete bolus transit Tutuian R et al. Clin Gastroenterol Hepatol 2003;1:174-182 43 healthy subjects solid-state manometry 10 liquid, 10 viscous swallows Normal esophageal transit when :

29. Manometric diagnosis N Normal transit Achalasia 24 0% Scleroderma 4 0% IEM 71 51% DES 33 55% Normal125 95% Hypertensive LES 25 96% Nutcracker 30 97% LES dysrelaxation 33100% Hypotensive LES 5100% IEM = Ineffective Esophageal Motility DES = Diffuse Esophageal Spasms

30. + 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

32. + Normal air intake during: – Dry swallow – Wet swallow – Food intake April 200732

33. + Type I belches + Gastric belch – Normal venting of gastric air – After intake of CO 2 like Coca Cola April 200733

34. + Type II belches + Supragastric belch – Sucking air into the esophagus with immediate expulsion – Aerophagia + [A] Suck air in + [B] Belch out April 200734 AB

35. + Manometry (=pressure waves) + Impedance (=transit) + Main indication: – (non-obstructive) Dysphagia – Belching – Clarify functional defects

37. + 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. + Reflux is acid which flows from the stomach into the esophagus + Detected with pH probe

39. April 200739 imp pH 7 4 0 60 seconds pH>4 Non-acid reflux PAIN Reflux Non-acid reflux Weakly acidic reflux Not detected by pH probe but by impedance

40. + 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. Off PPI On PPI 55% 97% Vela M et al. Gastroenterology 2001;120:1599-1906

42. + 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. + 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. + 17 Infants with regurgitation, asthma, apnea + 6-8 meals (milk) per day + Gastric pH often > 4 + Patient group: 17 children – 675 refluxes 185 acid 490 non-acid Skopnik et al, J. Pediatric Gastroenterol Nutr 1969

45. + 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 April 200745

46. April 2007 46

47. April 200747

48. + 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) April 200748

49. + 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