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Frequently Asked Questions > Sleeve Catheters & Sidehole Catheters

1: What is the sleeve?
  This is a validated long pressure sensor (usually 6cm for adults). It consists of a very thin top membrane that is glued onto a base moulded along the side of a multi-channel silicone rubber manometric extrusion (Dent). One end of the sleeve channel is closed and the other open, to vent the water that perfuses it.

2: What is special about the pressure sensing properties of the sleeve?
  It signals the highest pressure anywhere along its length. Thus, if the lower oesophageal sphincter is within the 6cm span of the sleeve, the highest pressure exerted by the sphincter at that moment will be recorded.

3: What is needed to make a sleeve work?
  Exactly the same arrangement used to make sidehole pressure recordings - that is, a standard hydraulic resistor to water perfuse it, and an external pressure transducer.

4: How many recording channels does the sleeve use?
  Only one. The sleeve is perfused through one of the channels of a multi lumen extrusion.

5: What sort of a tracing does the sleeve gives?
  A continuous tracing of true maximal sphincter pressure which has minimal movement artefact and which can be compared directly with pressures recorded from sideholes in the stomach and oesophageal body (Dent).

6: Why can a sidehole or intraluminal transducer fail to record absent or incomplete lower oesophageal sphincter relaxation on swallowing when the sleeve does not?
  Because swallowing displaces a sidehole from the sphincter, when the sleeve keeps in contact with the sphincter. Several studies show that a parked sidehole in the centre of the sphincter drops into the stomach during swallowing because of a 1.5-2.0cm upwards movement of the sphincter caused by swallowing(4).

7: But surely the point made in the answer to Q6 is invalid, as a parked sidehole or transducer detects incomplete relaxation in patients with achalasia?
  No. It is true that stationed sideholes usually record impaired relaxation in achalasia patients who have oesophageal dilatation, but in the difficult to diagnose achalasia case with minimal or no dilatation and vigorous oesophageal body contraction, sideholes will record spurious relaxation because the sphincter still moves upwards in such patients. These are the people most in need of a reliable diagnostic study.

Problems with sphincter relaxation after anti-reflux surgery may also be assessed misleadingly by stationed sidehole or transducer recordings because of sphincter movement.

8: Apart from swallowing, surely a 'parked' sidehole or transducer can record basal sphincter pressure reliably over time?
  No - Because the sphincter moves up and down the catheter with breathing and other body movement, giving big oscillations of recorded pressure, with no assurance that maximal sphincter pressure is being sampled. The sleeve tracing signals this pressure despite these movements(1).

9: How does use of the sleeve transform patient tolerance?
  By removing the need for pull-through measurement of sphincter pressure. An 8 channel sleeve/sidehole catheter records all that is needed at one catheter position without requiring constant adjustment.

10: How are the recording points on a sleeve/sidehole catheter used to give a 'complete' picture?
  Eight channels are needed to achieve this. Sideholes record basal gastric pressure (one), oesophageal peristalsis (five) and pharyngeal swallowing (one); the sleeve records from the lower oesophageal sphincter (one). These recording points give a complete readout of oesophageal function which is easy to evaluate (Holloway & Dent).

11: How does the sleeve give continuous information on its position relative to the sphincter?
  It is not the sleeve that does this, but sideholes that are always positioned at either end of the sleeve. If the sidehole at the top of the sleeve shows an oesophageal body pattern and the sidehole at the bottom of the sleeve a gastric pattern, then the sleeve must be correctly positioned. Thus the pressure recording gives continuous feedback (and audit) on correct position.

12: Why is the sphincter tracing easy to interpret?
  The pressure tracing is not subject to the oscillations of pressure recorded with a side hole and transducer as they move relative to the sphincter. The real sphincter pressure is therefore easy to evaluate (Dent, Holloway & Dent).

Also, when the arrangement described in the answer to Q10 is used, changes of sphincter pressure can be evaluated in the light of swallowing and oesophageal body motor events.

13: Why does an 8 channel sleeve/sidehole catheter boost laboratory productivity?
  Reliable, easily interpreted data are gathered very quickly, with a much reduced need for the manometrist to intervene in the measurements.

14: Does the sleeve overcome measurement problems caused by lower oesophageal sphincter pressure radial asymmetry?
  Yes and No! Sleeve measurements are sensitive to radial orientation, but the clinical importance of radial asymmetry has been over-estimated. What matters most with lower oesophageal sphincter manometry is to get a continuous valid measurement of sphincter pressure. The sleeve achieves this.

15: Why not make a circumferential sleeve?
  This has been tried. It introduces more limitations and uncertainties than it solves.