M aterials and M ethods. 3.1 Oesophageal m anom etry
Oesophageal manometry remains the investigation o f choice for the identification o f the LOS, other methods such as by either endoscopic means or the pH withdrawal technique are inaccurate. Manometry enables the accurate and standardised placement o f any further monitoring catheter eg 24 hour pH catheter or the bilitec, 5 cm above the identified LOS. Manometry has an important role to play in the identification o f LOS abnormalities and in particular any associated motility disorders, prior to contemplating anti reflux surgery.
The parameters evaluated include: (i) Total LOS length.
(ii) Intra abdominal LOS length. (iii) Resting LOS pressure. (iv) LOS relaxation profile.
(v) Oesophageal clearance (motility / peristalsis).
Indications:
(i) Clinical history suggestive o f GORD, in the absence of endoscopic confirmation. (ii) Preoperative evaluation, to exclude a primary motility disorder.
(iii) Postoperative surveillance, especially in the presence o f recurrent symptoms. (iv) Patients with atypical symptoms o f GORD eg dysphagia.
M ethods,
Patients were requested to abstain from solids and liquids for approximately 6 hours prior to the procedure, in order to reduce the risk o f aspiration. In addition, H2 receptor antagonists and proton pump inhibitors were discontinued for 5 and 7 days prior to the investigation.
Conventional stationary oesophageal manometry was performed on all patients to identify the lower oesophageal sphincter (LOS) parameters and to exclude a primary motility disorder, using a Synectics PC Polygraf (Synectics Medical, Stockholm, Sweden). A 4 port manometry catheter, utilising water, perfused at a rate o f 0.5 ml / min, was calibrated in the standard manner, using a manometric pump.
Each port was connected via a series of pressure transducers, to the manometric pump which in turn was connected to a multi channel recording polygraf. The polygraf
transmitted the obtained data to an attached computer, which was analysed with the Synectics PW oesophageal manometry module software.
The manometry catheter was positioned via a trans nasal route, so that all 4 ports sat below the LOS. This was readily confirmed by asking the patient to inspire deeply, which resulted in a concomitant rise in pressure if all the ports were in the stomach. If this was not the case the catheter was placed a further 10.0cm forward and the procedure repeated. Prior to starting the study, a reference (gastric) baseline was established. This enabled any variations in pressure to this baseline to be easily detected.
Identification o f LOS parameters: LOS Total length:
With the patient supine, no initial measurements were undertaken in order to let the equipment equilibriate. Identification o f the distal border o f the LOS took place by manually withdrawing the catheter in 1.0cm steps. Entry o f the most proximal port into the high pressure zone (characterised by amplification of the pressure wave) was consistent with the distal border o f the LOS (Fig.3.1). Withdrawal took place in 0.5cm steps from this stage. Departure from the high pressure zone was consistent with the proximal border o f the LOS (Fig.3.1). Total LOS length was calculated by noting the length at which a particular port entered and subsequently left the high pressure zone. In this way 4 estimates o f total LOS length were obtained for each port.
LOS Intra abdominal length:
Intra abdominal length was determined by estimating the respiratory inversion point (RIP) (Fig. 3.1 lower). This was the transition point at which the LOS passed through the diaphragm and was characterised by a pressure change from positive to negative On inspiration, on entering the thorax. 4 estimates o f intra abdominal length were obtained by subtracting this distance from the distal measurement o f the LOS for each port.
LOS pressure:
The LOS pressure was determined by estimating the peak of the highest trough for each port, within the LOS region. This was equivalent to the maximal end expiratory pressure (EEP) o f the LOS. The difference between this value and the gastric baseline (also an EEP value) gave rise to the LOS pressure (Fig. 3.2). Separate values were obtained for each port and a mean value was thus obtained.
LOS relaxation profile with swallowing;
The ability o f the LOS to relax with swallowing was determined by asking the patient to perform a series o f 5 wet swallows, when the most distal port was within the LOS A 10 ml bolus o f water was given to the patient and each swallow was noted. Following each swallow the LOS pressure should relax completely to the reference gastric baseline or to within 90 % o f the distance (Fig.3 .2 lower).
Oesophageal clearance :
Using the above technique, with the most distal port out of the LOS and sited in the distal oesophagus, the following parameters were determined, by asking the patient to perform 5 wet swallows.
Peristalsis / oesophageal motility:
Oesophageal motility was measured by calculating the time taken for a wave form to travel a given distance. This was done by the direct comparison o f wave forms in respective ports (Fig.3.3).
The number o f contractions / swallow:
This was defined as the number of contractions per peristaltic wave. Abnormalities are used in the identification o f disorders eg achalasia, diffuse oesophageal spasm (Fig. 3.3 lower).
Amplitude :
The difference in value between the oesophageal baseline and the highest peak was measured (Fig.3. 4).
Upper oesophageal sphincter (UOS) study:
Using a similar method to that used to establish LOS parameters, namely the withdrawal technique, the following UOS parameters were evaluated:
Resting UOS pressure:
The UOS pressure relative to the oesophageal baseline pressure (Fig.3. 4 lower). Relaxation on swallowing :
The UOS pressure relaxed to the oesophageal baseline pressure on swallowing (Fig. 3.4 lower).
Coordination between pharyngeal peristalsis and UOS relaxation ;
The manometry catheter was withdrawn until the second port was within the UOS, with the first port distal to the UOS. Pharyngeal contraction in port 1 should then correspond to relaxation of the UOS in port 2 on swallowing.
LOS parameters responsible for defective function have been reliably identified by oesophageal manometry.A resting LOS pressure < 6 mm Hg, a total length < 20 mm and an intra abdominal length < 10 mm have resulted in probability values o f 92 %, 65 - 88 % and 69 - 76 % calculated,dependent on the number o f abnormal variables present (Zaninotto et al, 1988).
3.2 24 hour ambulatory pH monitoring
Following the manometrically identified LOS, 24 hour pH monitoring remains the gold standard investigation for the investigation o f GORD. It has a sensitivity approaching 90 % and an associated specificity o f 95 %. It is not a mandatory preoperative investigation, but is used routinely by most clinicians as further confirmatory evidence o f symptomatic acid reflux.
Indications
(i) Clinical history suggestive of GORD, in the absence o f endoscopic confirmation. (ii) Pre operative confirmation o f increased oesophageal acid exposure time.
(iii) Post operative surveillance.
(iv) Patients with atypical symptoms o f GORD.
Methods.
Calibration was achieved by placing a pH catheter, containing an antimony pH electrode (Synectics Medical), in an alkaline pH (7) solution prior to placing it in an acidic pH (1) solution. The catheter was placed via a trans nasal route, initially into the stomach (as confirmed by an acidic pH) and then withdrawn to a distance o f 5.0 cm proximal to the manometrically determined LOS. The catheter was secured in this position. The external reference electrode was attached to the chest wall with adhesive gel.
The pH catheter was connected to a portable Synectics Digitrapper Mk III for a 24 hour period, data analysis was then undertaken using the Synectics PW oesophagram reflux analysis module software.
The patient was given a list o f instructions as to how to record a symptomatic reflux episode and similarly record any event such as eating,drinking or sleeping. In addition, he was given a list o f foods to be avoided and instructed to attempt to spend as normal a day as possible, within the confines o f the equipment. The following variables were evaluated :
The symptom index (value > 50 % is clinically significant)
no. o f svmptoms experienced when pH < 4 x 100 total no. o f symptoms
The DeMeester & Johnson scoring system has been calculated,using the following parameters and is a means o f comparing a patients total oesophageal exposure time (to a pH less than 4) to a standardised figure. It has a sensitivity o f approximately 85 % and a specificity approaching 90% (Johnson, De Meester; 1986)
1 Percentage total time < pH 4 (> 4.2 %) 2 Percentage upright time < pH 4 (> 6.3 %) 3 Percentage supine time < pH 4 (> 1.2 %) 4 No o f reflux episodes < pH 4 (> 50) 5 No o f reflux episodes > 5 mins (>4)
6 Duration o f the longest reflux episode recorded (> 9 .2 min)
Abnormal values are quoted in brackets.
A calculated DeMeester score o f 14 or greater is considered to be significant in terms o f symptomatic acid reflux.
F ig . 3 .1
Identification o f the high pressure LOS region Total length = 45. 0 cm - 43.0 cm
62aCll> 4 ) 3(58h<2> 58.
44cm :M.
Identification o f LOS abdominal length (REP) = 45.0 cm - 43.5 cm
4) 3(ÿ8h<2> 2 >
:M. 43
Fig. 3.2
Identification o f resting LOS pressure (from the peak o f the highest trough, within LOS region, to gastric baseline, as demonstrated
5^ i 4 > 3g8h<2)t58 Di f = 1 3 . 5 0 6 2 a ( 6 2 a ( l l ) 6 0 a ( 1 3 ) 47cn;
LOS sphincter relaxation profile (follow ing a high pressure swallow, the LOS relaxes down to the gastric baseline)
Fig. 3.3
Oesophageal peristalsis (direct comparison o f 2 waveforms)
(9)
37
33 30
Number o f contractions / swallow (one as demonstrated)
32
F ig . 3 .4
Amplitude (the difference between the peak o f the swallow and the oesophageal baseline)
w (10) ■ w (9)
28
37
Identification of the high pressure UOS region ( 22. 0 cm -18.0 cm)
UOS relaxation profile
8) ]34a<40) 3 2 a < 4 ^ b 3 .< 4 :o : ;1 [ . . . • 6 9 1 Q 9a( 38a<3 .•9 CM 2 4 c A 2 3 c n f h 2 2 è 4