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In Situ ph of Duodenal Bulb Contents in Normal and Duodenal Ulcer Subjects
Vol. 52, No.6 Printed in U.S.A.
GASTROENTEROLOGY
Copyright
© 1967 by The Williams & Wilkins Co.
IN SITU pH OF DUODENAL BULB CONTENTS IN NORMAL AND DUODENAL ULCER SUBJECTS ANDRE P. ARCHAMBAULT, M.D., RANDOLPH A. ROVELS'l'AD, M.D., AND HARLEY C. CARLSON, M.D. Gastrointestinal Research Unit, Mayo Clinic and Mayo Foundation, Rochester, Minnesota
In earlier studies 1 , 2 of the pH of duo- the duodenal bulb. It further documents denal and gastric contents recorded from the resting pH pattern in the duodenal an in situ glass electrode, we found that bulb in normal subjects and in subjects at times the pH recorded from the duo- with duodenal ulcer. denal bulb appeared to be indistinguishMethods and Subjects able from that recorded from the gastric antrum. Determination of the exact locaIntestinal (4 by 8 mm) glass electrodes, two tion of the electrode required prohibitively expanded scale pH meters (Beckman Infrequent fluoroscopy and the use of barium struments, Inc., Fullerton, California, model to define the pylorus. These requirements 76), and calomel half-cells were used. Polymade it difficult to use the technique to vinyl tubing (0.036 inch in internal diamestudy the effect of food and antacid on the ter) filled with a saturated solution of KCl an electrolytic bridge from a calomel acidity of duodenal contents. We were in- formed cell to a pinhole in the closed end of the tube terested in measurements of pH within within the intestinal tract. (PD recordings the duodenal bulb for at least three rea- were less stable when the pinhole was in the sons. First, significant differences in pH side of the tube.) A two-channel pen-writing have been found between the bulb and the recorder was used (Texas Instruments, Inc., more distal duodenal contents. 1 Second, Houston, model PSD-1004). One of the pH bulb contents bathe the usual duodenal meters served as a millivolt meter for reulcer. Third, the close proximity of the cording PD. With expanded-scale operation, bulb to the pylorus makes it the first recip- full scale represented 200 mv or 4];2 inches ient of acidic gastric contents and thus of chart width on one channel of the recorder. The other channel recorded pH values from 1 the duodenal neutralizing mechanism to 10 on the other 4];2 inches of chart width. would receive greatest stress at this site. The simplified circuit and arrangement of This report describes the use of trans- equipment are illustrated in figure 1. mucosal potential differences (PD) of The PD measurements used to monitor the stomach and duodenum to assist in posi- position of the glass electrode were intertioning the recording glass electrode within preted on the basis of studies2 , 3 confirming Received December 15, 1966. Accepted February 11, 1967. Address requests for reprints to: Mayo Clinic, Rochester, Minnesota 55901. This investigation was supported in part by Research Grant AM-6908 from the National Institutes of Health, Public Health Service. Appreciation is expressed to Dr. Lila R. Elveback, Section of Medical Statistics, Epidemiology and Population Genetics, and Mr. Anders N eSB, Section of Engineering, for assistance with this study.
that the luminal surface of the gastric mucosa is negative with respect to the luminal surface of the duodenal mucosa. A skin reference site was used for gastric and duodenal PD measurements. The unabraded index finger was immersed in a plastic (Lucite) cylinder (taped to the finger) containing saturated KCl in 1.5% agar. A polyvinyl tube filled with KCl-agar connected this finger contact to a calomel half-cell which became one input to the millivolt meter. By means of a switching device, the recorder displayed the PD between finger and orad intraluminal
940
June 1967
941
pH OF DUODENAL BULB CONTENTS Multivibrator
Skin ground - - - - - - ,
,------+-------',o--- - - --
KCI-agar bridge to finger Intra-
Flowing [ KCI
luminal tube assembl y
bridges [
---f------.
Orad
Power sup ply
L.Jl;::===f=::::::(s
Caudad Glass electrode
L::=': ==::::.-_-_-:
ltO v
--:~
,","
l!
To roller pump and KCI supplies
• •I
, " " "
Tw o channel strip chart
"
recorder
FIG. 1. Schematic circuit for simultaneous measurement of duodenal bulb pH and skinantral and skin-duodenal potential difference (PD). Duodenal salt-bridge is shared between pH measuring circuit and PD measuring system. Switching device permits use of twochannel recorder and, by varying the dwell of each switch closure, identifies the PD intraluminal recording site and its varying polarity with respect to the skin. S, source of alternating current.
bridge contact site for 5 sec and then the PD between finger and caudad bridge contact site during the next 3 sec. To provide a continuously renewed interface between the KCI bridges and the luminal contents, saturated KCI solution was forced bya roller pump through Silastic tubing to the calomel cell and then through the polyvinyl bridge tubing to the contact site at a rate of 1 to 2 ml per hr. Calomel cells with side openings were used. A T-tube of plastic was inserted into this side opening so that KCI solution pumped past the cell to the intraluminal contact site had, through one link of the T, a junctionfree electrical contact with the KCI solution in the calomel cell. The normally used fiber contact of the cell was occluded by capping this end of the cell. This is shown schematically in figure 1. Electrical isolation between the two KCI bridges required separate KCI reservoirs and separate supply tubes through the roller pump. Because of the observations by Helm and co-workers' that, during short-term studies, repeated pull-through records at the gastroesophageal junction were not entirely reproducible with KCI-agar bridges, we performed limited studies of the reliability of KCI-agar compared to flowing KCI bridges. Figure 2 is representative of these studies (for convenience, III the gastroesophageal
'T'------'--~ o
"~i~
~
'"
KCI agar
~j
'------~--------------------- -\l. .\-.; .-~-;:;- ;: -:;-: O-; .:- : -: ; -~- . ,;, ---
30° [
~,
':[I--------~----~-----.-~~- =; .; -:.; :;.- ~=- Esophagus
Gastroesophageal junction
Stomach
Fro. 2. Results of repeated withdrawals of KCIagar and flowing KCI bridges through gastroesophageal junction from stomach at rate of approximately 1 cm per 10 sec. Intraluminal electrical contact through both leads was made at identical levels (that is, at the same distance from the teeth). Flow rate of KCI solution was 1 ml per hr. The three withdrawals were done over a 30-min period.
junction, rather than in the pylorus). This comparison demonstrates greater stability and reproducibility of the PD pattern recorded by the flowing KCI bridge. Troublesome er-
942
ARCHAMBAULT ET AL.
rors with KCI-agar bridges were anticipated in studies of a number of hours' duration because we found that after immersion in gastric juice at 37 C for 30 min the KCI-agar was digested out of the end of the plastic tubing; this would permit establishment of significant junction potentials with immersion of such a bridge in solutions of changing electrolyte composition. In fact, junction potentials as great as 20 mv could be established at the end of the KCI-agar bridges, even when there was no visible digestion of the agar, when the tube was alternately immersed in 0.1 N HCI and 0.9% NaCI solutions. The flowing KCI bridge also permitted flushing of the bridge if a questionable PD pattern were apparent. This flushing, at a rate of 0.5 ml per sec, was done through a switching option on the pump, permitting rapid momentary flushing of the bridge when body capacitance effects on the recording system suggested, infrequently, a high resistance circuit from air bubbles. Total peripheral resistance of the KCI bridge circuit was approximately 85,000 ohms as measured between calomel cell wire leads, through both KCI tubes and leak holes immersed in a container of KCI solution. Scrupulous care was essential to avoid electrical leak paths between parts of the circuit because impedance in the measuring circuits was several thousand megohms, and even minimal current flow in such parallel leak circuits would seriously reduce the PD being measured. Standardization of glass electrodes was done at 37 C. It was often necessary to test at least several new glass electrodes, "seasoned" overnight by immersion in water, before one could be found that would standardize suitably in buffers at pH 2, 4, and 7 (pH 4 and 7, standard buffer solutions from Beckman Instruments, Inc.; pH 2, solution made from
Vol. 52, No.6
standard tablets, Coleman Instruments Corporation, Maywood, Ill.). Dry storage and avoidance of temperatures above 40 C between studies prolonged electrode life. A vinyl guard over the electrode prevented contact with mucosa yet provided free flow of liquids and semisolids (fig. 3). This moderately flexible device, constructed from vinyl tubing, was devised by trial and error until it was found that food particles were not impacted in it. A rubber finger-cot containing 3 ml of mercury and tied by an 8-cm Silastic-covered thread to the guard facilitated duodenal entry and anchorage. This arrangement, placing the anchoring balloon with mercury in the dsscending duodenum with 8 cm of attaching thread between it and the guarded electrode in the duodenal bulb, was thought to produce very little interference with flow of intraluminal contents distal to the electrode. In contrast to some previous studies," 2 the reference electrode for the glass electrode made electrical contact not with the skin but with the duodenal bulb contents through the caudad, flowing KCI bridge. This avoided the introduction, in series, of the skin-duodenal PD (with its variation from subject to subject) into the pH measuring circuit. The sharing of the reference cell for the caudad KCl bridge between pH and PD circuits provided a special additional control: the constant record of skin-duodenal PD indicated the stability of the junction potential between the distal bridge and the duodenal contents. One could thus exclude diffusion potential at the reference bridge contact site as the explanation of wide swings in pH. Seventy-five subjects were studied. Sixteen of these had duodenal ulcer deformities roentgenologically and a compatible history, 13 with a history of active ulcer disease in the week preceding the study. No ulcer patient
Glass electrode 0.5cm
I'
3cm
I
./
Openings for bridge contact
~~3!!rt~~=====F==========,><:saturated KCI Shielded glass electrode lead Caudad
Orad
Leadmarkers
FIG. 3. Construction of flexible vinyl guard with large lateral and distal fenestrations to permit circulation of fluids yet prevent contact of glass electrode with mucosa. The caudad salt bridge opening recorded transduodenal potential difference (PD) and the cephalad opening, PD on the antral side of the pylorus.
943
pH OF DUODENAL BULB CONTENTS
June 1967 10
9 8
4min
""¥~PD
6 pH
p H
5 4
JIIIIII
3sec PD 5sec
~PH
3
2
+30
o mv
PD
-30 pH
o Descending duodenum
Duodenal bulb
Gastric antrum
FIG. 4. Characteristic skin-mucosal potential difference (PD) and in situ pH patterns in fasting, normal subject. Note low, stable, antral pH with both KCI bridges recording antral PD about -10 mv with respect to skin. In duodenal bulb, pH is quite unstable and is higher; PD is characteristic of a straddling location: cephalad bridge (5-sec recording) in antrum is at -5 mv, and duodenal bridge (3-sec recording) is at +25 mv with reference to skin. In descending duodenum there is minimal PD between the intraluminal KCI bridges, but in this region both are about +25 mv compared with skin; pH is characteristically more stable and higher than in the duodenal bulb.
had clinical or roentgenological evidence of gastric outlet obstruction. No patient had received anticholinergic drugs for at least 2 weeks before being studied. The remaining 59 subjects were considered for practical purposes to be controls; they had normal barium studies of stomach and duodenum and no history of ulcer. They were being seen for relatively routine general examinations. Technically unsatisfactory records precluded using each of the 75 records for all of the comparisons shown in subsequent figures. Results
A preliminary study of normal subjects was done with KCI bridge contact sites 1 and 4 cm, respectively, orad to the glass electrode. Slow withdrawal of the electrode from duodenum to stomach, with barium opacification and cinefluoroscopy and with the subject in a prone oblique position, permitted an optimal profile projection of the pylorus during PD recording. During prolonged pH recording, the patient was studied in the sitting position because this was thought to facilitate more normal gastric emptying. Trials with this tube arrangement revealed, on cinefluorography, that the glass electrode was distal
to the apex rather than at the base of the duodenal cap unless the two bridge contact sites were separated by only 3 cm and unless the glass electrode was less than 1 cm distal to the caudad site. Less than 3-cm separation between KCI contact sites required almost constant advancement or withdrawal of the tube for maintenance of an appropriate and stable PD pattern indicating placement of the glass electrode in the bulb. The final arrangement is shown in figure 3. Illustrative PD and pH patterns are shown in figure 4, and a typical frame from a cinefluorogram is shown in figure 5. Fifteen cinefluorograms were correlated with synchronous PD patterns directly. The remaining 60 records from pullthrough studies were then reviewed and analyzed, on the basis of the previously demonstrated invariable pattern of abrupt change in potential at the pylorus, for calculations of representative PD patterns at the various sites. These data are summarized in figure 6, which shows PD between salt bridges having contact sites separated by 3 cm. Because no significant difference was demonstrable between
9J4
ARCHAMBA ULT ET AL.
Fro. 5. Frame from cinefiuorogram of pylorus region (subj ect in oblique prone position, right side down), showing lead markers at site of KCI bridge contact sites and position of pylorus outlined by barium. This position corresponds to the potential difference (PD) pattern shown in figure 4 as that designating a location of the glass electrode in the duodenal bulb.
Vol. 52, No.6
corded during advancement of the tube from stomach to duodenum. In fasting control subjects, 97% of the pH recordings were acceptable; 84% of the recordings were acceptable in subjects with duodenal ulcer. This difference, the result of instability of the straddling PD pattern, suggests greater peristaltic activity in duodenal ulcer subjects or possible variable recording of injury potentials from the ulcer itself. Figure 7 shows the distribution of pH in fasting normal subjects and subjects with duodenal ulcer. There are deficiencies in use of mean pH to characterize such records! because it requires linear treatment of log-based data. pH-percentage of time curves and difference curves! were constructed, but such a presentation is cumbersome for present purposes, so, in spite of the limitations of mean pH, this Gastroesophageal
50
Number 49 Mean 25.2 SO 5.6
0 Antroontral
normal subjects and those with duodenal ulcer, the mean PD represents the combined groups. The mean PD across the gastroesophageal junction (25.2 mv) was similar to that across the antroduodenal junction (24.9 mv). At the gastroesophageal straddling position, the orad bridge is more positive; at the pylorus straddling position, the orad bridge is the more negative of the two systems. Most important, as seen in figure 6, when both bridges were in the antrum or in the duodenum, the PD between bridges did not exceed 15 mv. Thus, a PD of greater than 15 mv between the two bridges, orad-negative, reflected a py lorus straddling position (orad bridge in the antrum and the other in the duodenal bulb) and, because the glass electrode was only 0.5 cm caudad to the caudad bridge contact site, insured location of the glass electrode in the duodenal bulb. The glass electrode could theoretically record pH briefly from the pyloric canal while an antroantral PD pattern was being re-
Number 58 Mean 4.5 SO 2.5
~
" .::-" t::" ~
1l ....
Antroduodenal 50
O L - - --
Number 53 Mean 24.9 SO 5.1
-=
Ouodenoduodenol Number 45 Mean 5.2 SO 2.3 35 40 45 Potential difference (mv)
Fro. 6. Histograms of potential difference (PD) between intraluminal KCI bridges (3 cm apart) at different sites. When PD > 15 mv, bridges are straddling gastroesophageal or antroduodenal junction. Orad bridge is negative when the pylorus is being straddled and positive when gastroesophageal zone lies between the bridges. Number of cases and mean PD ± SD are given for the four sets-gastroesophageal, antroantral, antroduodenal, and duodenoduodenal.
945
pH OF DUODENAL BULB CONTENTS
June 1967
has been used for simplicity and because the comparisons are mainly between sites having similar pH values. For similar reasons, Andersson and Grossman 3 have used this method of analysis. In fact, if duodenal functions are related to a logarithmic function of hydrogen ion concentration, as are many other biological phenomena, mean pH may be preferable. There was no significant difference in mean antral pH or in mean postbulbar duodenal pH between normal and duodenal ulcer subjects. However, the pH in the duodenal bulb was significantly lower in duodenal ulcer patients than in normal subjects (P < 0.01). There was also a significant difference in pH between the antrum and the duodenal bulb in normal subjects (P < 0.01); this difference was less in duodenal ulcer subjects but still was st atistically significant (P < 0.01). The pH pattern in the duodenal bulb more closely resembled that in the' antrum in ulcer subjects than in control subjects. The designation "postbulbar" duodenum is arbitrary and as used here it means that part of the descending duodenum just distal to the superior duodenal flexure. This site was selected because the electrode lead with its bend at the superior flexure made this location the closest roentgenologically distinctive site immediately caudad to the bulb. ' Data depicting the stability of the record at various recording sites are shown in table 1. An abrupt change in pH of at least 0.5 pH unit was considered to be a fluctu ation. Antral pH was most stable. Although the duodenal bulb pH may at times mimic the antral pH, the pattern in the bulb was usually more variable. The T ABLE
Number 42 Mean 1.7
SO
0
0.50
~~~--------------
50 Number 16
Mean SO
0 50
Duodenal bulbi normal Number 21 Mean 4.5 SO 1.4
~
" ....""~
0
<>
1.7 0.48
50
~
Number 14
"
~
~d!11lJlrz:;z~ D2
0 50
______jMe~a~n SO
Post-bulbar duodenum,normal
Number 36
Mean
SO
0 50
0
Post-bulbar duodenum, DU
3
4
6.7 0.56
Num be r 11
Mean SO 2
2.9 1.01
7
6
6.7 0.56
8
pH
FIG. 7. Histograms of mean pH at different sites in normal and duodenal ulcer subjects. Antral pH is significantly lower than bulb pH in both groups of subjects (P < 0.01). The only significant difference is that duodenal bulb pH is lower in ulcer patients than in normal subj ects (P < 0.01) . Number of cases and mean pH ± SD are given for normal and ulcer patient antrum, normal and ulcer patient duodenal bulb, and normal and ulcer patient postbulbar duodenum. "Postbulbar duodenum" is defined as that portion of the descending duodenum just caudad to t he superior duodenal flexure.
pattern became more stable again in records from sites in the duodenum distal to the bulb. Discussion
Our present study reveals similarities and differences when compared with the
1. Summary of abrupt pH fluctuations of more than 0.5 pH unit Patients F luctuations per minute
Site
Total Normal
Ulcer
-
Antrum . ... . ....... Bulb ............ .. . P ostbulbar .. . . .. . ..
42 21 36
With fluctuations Normal
Ulcer
6 (14%) 20 (95%) 21 (58% )
2 (13%) 13 (93%) 6 (55% )
Normal
Ulcer
-
16 14 11
15/799 386/449 82/281
= = =
0.02 0.9 0.3
3/158 = 0.02 135/176 = 0.8 14/74 = 0.2
946
ARCHAMBA ULT ET AL.
findings of Andersson and Grossman,3 but our conclusions are essentially the same as theirs. They defined the pylorus on the basis of serial roentgeno;;rams of subj ects in the supine position. We are more confident of the location of the electrode in our study on the basis of cinefluorography, dilute barium contrast, and oblique prone positioning to facilitate opacification of the profile of the pylorus. Review of the cinefluorographic record at slow speed proved very helpful because the electrode often passed through the pylorus abruptly despite slow withdrawal of the lead. In the work of Andersson and Grossman,3 because of the positioning of the PD recording leads, the pH recording from the duodenal bulb required roentgenographic control of the position of the glass electrode. Consequently, they justifiably suspected that fluctuations in duodenal bulb pH might reflect intermittent retraction of the glass electrode toward or away from the pylorus. With our system of simultaneous skin-gastric and skin-duodenal PD recording, we found that maintenance of the glass electrode in the duodenal bulb required frequent adjustments of tube length. However, the frequency of records of fluctuating pH in the duodenal bulb despite a stable straddling PD convinces us that the unstable pH pattern is physiological and not an artifact. Results were remarkably similar despite minor variations in technique. They reported a mean antroduodenal PD of 26.9 mv ± 9.5 (present study, 24.9 ± 5.1) and a mean gastroesophageal PD of 24.9 mv ± 11.6 (present study, 25.2 ± 5.6). Of interest are their larger standard deviations which are in keeping with their noting a ±15% difference between paired studies on repeated withdrawal of electrodes. This may reflect the difference between their use of agar-KCI bridges and our use of flowing KCI bridges. A very helpful contribution is their observation that the skinblood PD was 36 mv, with skin negative with respect to blood. In their studies with an intravascular KCI-agar bridge, gastroduodenal and esophagogastric PD were nearly identical with those obtained with
Vol. 52, No.6
a skin reference, a reassuring justification for our continued use of a skin reference. The PD which we found between two sites in the antrum or duodenum may reflect minor diffusion potentials not entirely eliminated by the flowing KCI bridge system. They may also indicate changing proximity of the bridge to the mucosa or to the antrofundic junction in essentially a volume conductor. Rapid fluctuations in skin potential seem unlikely. We have not related duodenal pH to antral pH for each subject, as Andersson and Grossman3 did. However, in both ulcer and control subjects antral pH was predominantly below 2.5 (fig. 7). They found antral pH values of 3 or less associated with lower pH levels in the first portion of the duodenum when compared with the more distal part. The decreased duodenal bulb pH, despite an apparently normal antral pH, in our subjects with duodenal ulcer can be explained in several ways. First, in the low pH range seen in the antrum, minor changes in pH reflect relatively great changes in hydrogen ion activity. Such minor changes are not easily recognized by conventional methods of analysis, nor are they very reliably recorded by readily applicable, continuously recording pH meters and electrodes. Second, the volume of gastric secretions in ulcer patients may increase more than the acid concentration so that the increased total acid output may exceed duodenal neutralizing reserves. Furthermore, if gastric acid secretions of equal volume and acidity emptied into the duodenum of ulcer patients more intermittently, these transient influxes of accumulated acid might decrease the pH, whereas a slower but steadier introduction of the same amount of acid into the duodenum might not overwhelm duodenal neutralizing mechanisms. Finally, there remains the possibility that, in ulcer patients, duodenal neutralizing mechanisms are less effective than in normal persons. The pH values in the ulcer patients were different from those in the control subjects only in the region of the duodenal bulb. This emphasizes the importance of
June 1967
pH OF DUODENAL B ULB CONTENTS
947
tral pH values were similar (1.7). There was no significant difference between ulcer and control groups with respect to the pH of antral or postbulbar duodenal conSummary tents. Antral pH was much more stable The pH of duodenal bulb contents has than duodenal bulbar pH. Postbulbar been recorded with a guarded, in situ, duodenal pH was higher and more stable glass electrode in 75 subjects, 16 with than the pH of the duodenal bulb. duodenal ulcer. The antrocutaneous and REFERENCES duodenocutaneous potential differences (PD) were simultaneously recorded from J., C. V. Mann, H. C. Carlson, C. F. flowing KCI bridges attached to the glass 1. Bircher, Code, and R. A. Rovelstad. 1965. Intraluelectrode lead (these bridges were found minal and juxtamucosal duodenal pH. Gasto be superior to KCI-agar bridges for troenterology 48 : 472-477. this purpose), and PD patterns were used 2. Rovelstad, R. A., C. A. Owen, Jr., and T. B. to position the glass electrode and moniMagath. 1952. Factors influencing the continuous recording of in situ pH of gastric and tor its location. That a PD between duoduodenal contents. Gastroenterology 20: denum and gastric antrum of greater than 609-624 . 15 mv (duodenum more positive) was a reliable sign that the glass electrode was 3. Andersson, S., and M. 1. Grossman. 1965. Profile of pH, pressure, and potential difin the duodenal bulb was confirmed by ference at gastroduodenal junction in man . simultaneous cinefluorography. Mean duoGastroenterology 49 : 364-371. denal bulb pH was significantly higher 4. H elm, W. J., C. F. Code, and W. H. J. Sumthan antral pH in both normal and ulcer merskiIl. 1961. Simultaneous identification of subjects. In ulcer subjects, mean duodenal the gastroesophageal junction by pH, pot en tial difference and pressure (abstr.). bulb pH (2.9) was significantly lower Gastorenterology 40: 805. than normal (4.5). Normal and ulcer anstudying this region in investigation of acid secretion and gastrointestinal physiology .
GASTROENTEROLOGY
Copyright
© 1967 by The Williams & Wilkins Co.
IN SITU pH OF DUODENAL BULB CONTENTS IN NORMAL AND DUODENAL ULCER SUBJECTS ANDRE P. ARCHAMBAULT, M.D., RANDOLPH A. ROVELS'l'AD, M.D., AND HARLEY C. CARLSON, M.D. Gastrointestinal Research Unit, Mayo Clinic and Mayo Foundation, Rochester, Minnesota
In earlier studies 1 , 2 of the pH of duo- the duodenal bulb. It further documents denal and gastric contents recorded from the resting pH pattern in the duodenal an in situ glass electrode, we found that bulb in normal subjects and in subjects at times the pH recorded from the duo- with duodenal ulcer. denal bulb appeared to be indistinguishMethods and Subjects able from that recorded from the gastric antrum. Determination of the exact locaIntestinal (4 by 8 mm) glass electrodes, two tion of the electrode required prohibitively expanded scale pH meters (Beckman Infrequent fluoroscopy and the use of barium struments, Inc., Fullerton, California, model to define the pylorus. These requirements 76), and calomel half-cells were used. Polymade it difficult to use the technique to vinyl tubing (0.036 inch in internal diamestudy the effect of food and antacid on the ter) filled with a saturated solution of KCl an electrolytic bridge from a calomel acidity of duodenal contents. We were in- formed cell to a pinhole in the closed end of the tube terested in measurements of pH within within the intestinal tract. (PD recordings the duodenal bulb for at least three rea- were less stable when the pinhole was in the sons. First, significant differences in pH side of the tube.) A two-channel pen-writing have been found between the bulb and the recorder was used (Texas Instruments, Inc., more distal duodenal contents. 1 Second, Houston, model PSD-1004). One of the pH bulb contents bathe the usual duodenal meters served as a millivolt meter for reulcer. Third, the close proximity of the cording PD. With expanded-scale operation, bulb to the pylorus makes it the first recip- full scale represented 200 mv or 4];2 inches ient of acidic gastric contents and thus of chart width on one channel of the recorder. The other channel recorded pH values from 1 the duodenal neutralizing mechanism to 10 on the other 4];2 inches of chart width. would receive greatest stress at this site. The simplified circuit and arrangement of This report describes the use of trans- equipment are illustrated in figure 1. mucosal potential differences (PD) of The PD measurements used to monitor the stomach and duodenum to assist in posi- position of the glass electrode were intertioning the recording glass electrode within preted on the basis of studies2 , 3 confirming Received December 15, 1966. Accepted February 11, 1967. Address requests for reprints to: Mayo Clinic, Rochester, Minnesota 55901. This investigation was supported in part by Research Grant AM-6908 from the National Institutes of Health, Public Health Service. Appreciation is expressed to Dr. Lila R. Elveback, Section of Medical Statistics, Epidemiology and Population Genetics, and Mr. Anders N eSB, Section of Engineering, for assistance with this study.
that the luminal surface of the gastric mucosa is negative with respect to the luminal surface of the duodenal mucosa. A skin reference site was used for gastric and duodenal PD measurements. The unabraded index finger was immersed in a plastic (Lucite) cylinder (taped to the finger) containing saturated KCl in 1.5% agar. A polyvinyl tube filled with KCl-agar connected this finger contact to a calomel half-cell which became one input to the millivolt meter. By means of a switching device, the recorder displayed the PD between finger and orad intraluminal
940
June 1967
941
pH OF DUODENAL BULB CONTENTS Multivibrator
Skin ground - - - - - - ,
,------+-------',o--- - - --
KCI-agar bridge to finger Intra-
Flowing [ KCI
luminal tube assembl y
bridges [
---f------.
Orad
Power sup ply
L.Jl;::===f=::::::(s
Caudad Glass electrode
L::=': ==::::.-_-_-:
ltO v
--:~
,","
l!
To roller pump and KCI supplies
• •I
, " " "
Tw o channel strip chart
"
recorder
FIG. 1. Schematic circuit for simultaneous measurement of duodenal bulb pH and skinantral and skin-duodenal potential difference (PD). Duodenal salt-bridge is shared between pH measuring circuit and PD measuring system. Switching device permits use of twochannel recorder and, by varying the dwell of each switch closure, identifies the PD intraluminal recording site and its varying polarity with respect to the skin. S, source of alternating current.
bridge contact site for 5 sec and then the PD between finger and caudad bridge contact site during the next 3 sec. To provide a continuously renewed interface between the KCI bridges and the luminal contents, saturated KCI solution was forced bya roller pump through Silastic tubing to the calomel cell and then through the polyvinyl bridge tubing to the contact site at a rate of 1 to 2 ml per hr. Calomel cells with side openings were used. A T-tube of plastic was inserted into this side opening so that KCI solution pumped past the cell to the intraluminal contact site had, through one link of the T, a junctionfree electrical contact with the KCI solution in the calomel cell. The normally used fiber contact of the cell was occluded by capping this end of the cell. This is shown schematically in figure 1. Electrical isolation between the two KCI bridges required separate KCI reservoirs and separate supply tubes through the roller pump. Because of the observations by Helm and co-workers' that, during short-term studies, repeated pull-through records at the gastroesophageal junction were not entirely reproducible with KCI-agar bridges, we performed limited studies of the reliability of KCI-agar compared to flowing KCI bridges. Figure 2 is representative of these studies (for convenience, III the gastroesophageal
'T'------'--~ o
"~i~
~
'"
KCI agar
~j
'------~--------------------- -\l. .\-.; .-~-;:;- ;: -:;-: O-; .:- : -: ; -~- . ,;, ---
30° [
~,
':[I--------~----~-----.-~~- =; .; -:.; :;.- ~=- Esophagus
Gastroesophageal junction
Stomach
Fro. 2. Results of repeated withdrawals of KCIagar and flowing KCI bridges through gastroesophageal junction from stomach at rate of approximately 1 cm per 10 sec. Intraluminal electrical contact through both leads was made at identical levels (that is, at the same distance from the teeth). Flow rate of KCI solution was 1 ml per hr. The three withdrawals were done over a 30-min period.
junction, rather than in the pylorus). This comparison demonstrates greater stability and reproducibility of the PD pattern recorded by the flowing KCI bridge. Troublesome er-
942
ARCHAMBAULT ET AL.
rors with KCI-agar bridges were anticipated in studies of a number of hours' duration because we found that after immersion in gastric juice at 37 C for 30 min the KCI-agar was digested out of the end of the plastic tubing; this would permit establishment of significant junction potentials with immersion of such a bridge in solutions of changing electrolyte composition. In fact, junction potentials as great as 20 mv could be established at the end of the KCI-agar bridges, even when there was no visible digestion of the agar, when the tube was alternately immersed in 0.1 N HCI and 0.9% NaCI solutions. The flowing KCI bridge also permitted flushing of the bridge if a questionable PD pattern were apparent. This flushing, at a rate of 0.5 ml per sec, was done through a switching option on the pump, permitting rapid momentary flushing of the bridge when body capacitance effects on the recording system suggested, infrequently, a high resistance circuit from air bubbles. Total peripheral resistance of the KCI bridge circuit was approximately 85,000 ohms as measured between calomel cell wire leads, through both KCI tubes and leak holes immersed in a container of KCI solution. Scrupulous care was essential to avoid electrical leak paths between parts of the circuit because impedance in the measuring circuits was several thousand megohms, and even minimal current flow in such parallel leak circuits would seriously reduce the PD being measured. Standardization of glass electrodes was done at 37 C. It was often necessary to test at least several new glass electrodes, "seasoned" overnight by immersion in water, before one could be found that would standardize suitably in buffers at pH 2, 4, and 7 (pH 4 and 7, standard buffer solutions from Beckman Instruments, Inc.; pH 2, solution made from
Vol. 52, No.6
standard tablets, Coleman Instruments Corporation, Maywood, Ill.). Dry storage and avoidance of temperatures above 40 C between studies prolonged electrode life. A vinyl guard over the electrode prevented contact with mucosa yet provided free flow of liquids and semisolids (fig. 3). This moderately flexible device, constructed from vinyl tubing, was devised by trial and error until it was found that food particles were not impacted in it. A rubber finger-cot containing 3 ml of mercury and tied by an 8-cm Silastic-covered thread to the guard facilitated duodenal entry and anchorage. This arrangement, placing the anchoring balloon with mercury in the dsscending duodenum with 8 cm of attaching thread between it and the guarded electrode in the duodenal bulb, was thought to produce very little interference with flow of intraluminal contents distal to the electrode. In contrast to some previous studies," 2 the reference electrode for the glass electrode made electrical contact not with the skin but with the duodenal bulb contents through the caudad, flowing KCI bridge. This avoided the introduction, in series, of the skin-duodenal PD (with its variation from subject to subject) into the pH measuring circuit. The sharing of the reference cell for the caudad KCl bridge between pH and PD circuits provided a special additional control: the constant record of skin-duodenal PD indicated the stability of the junction potential between the distal bridge and the duodenal contents. One could thus exclude diffusion potential at the reference bridge contact site as the explanation of wide swings in pH. Seventy-five subjects were studied. Sixteen of these had duodenal ulcer deformities roentgenologically and a compatible history, 13 with a history of active ulcer disease in the week preceding the study. No ulcer patient
Glass electrode 0.5cm
I'
3cm
I
./
Openings for bridge contact
~~3!!rt~~=====F==========,><:saturated KCI Shielded glass electrode lead Caudad
Orad
Leadmarkers
FIG. 3. Construction of flexible vinyl guard with large lateral and distal fenestrations to permit circulation of fluids yet prevent contact of glass electrode with mucosa. The caudad salt bridge opening recorded transduodenal potential difference (PD) and the cephalad opening, PD on the antral side of the pylorus.
943
pH OF DUODENAL BULB CONTENTS
June 1967 10
9 8
4min
""¥~PD
6 pH
p H
5 4
JIIIIII
3sec PD 5sec
~PH
3
2
+30
o mv
PD
-30 pH
o Descending duodenum
Duodenal bulb
Gastric antrum
FIG. 4. Characteristic skin-mucosal potential difference (PD) and in situ pH patterns in fasting, normal subject. Note low, stable, antral pH with both KCI bridges recording antral PD about -10 mv with respect to skin. In duodenal bulb, pH is quite unstable and is higher; PD is characteristic of a straddling location: cephalad bridge (5-sec recording) in antrum is at -5 mv, and duodenal bridge (3-sec recording) is at +25 mv with reference to skin. In descending duodenum there is minimal PD between the intraluminal KCI bridges, but in this region both are about +25 mv compared with skin; pH is characteristically more stable and higher than in the duodenal bulb.
had clinical or roentgenological evidence of gastric outlet obstruction. No patient had received anticholinergic drugs for at least 2 weeks before being studied. The remaining 59 subjects were considered for practical purposes to be controls; they had normal barium studies of stomach and duodenum and no history of ulcer. They were being seen for relatively routine general examinations. Technically unsatisfactory records precluded using each of the 75 records for all of the comparisons shown in subsequent figures. Results
A preliminary study of normal subjects was done with KCI bridge contact sites 1 and 4 cm, respectively, orad to the glass electrode. Slow withdrawal of the electrode from duodenum to stomach, with barium opacification and cinefluoroscopy and with the subject in a prone oblique position, permitted an optimal profile projection of the pylorus during PD recording. During prolonged pH recording, the patient was studied in the sitting position because this was thought to facilitate more normal gastric emptying. Trials with this tube arrangement revealed, on cinefluorography, that the glass electrode was distal
to the apex rather than at the base of the duodenal cap unless the two bridge contact sites were separated by only 3 cm and unless the glass electrode was less than 1 cm distal to the caudad site. Less than 3-cm separation between KCI contact sites required almost constant advancement or withdrawal of the tube for maintenance of an appropriate and stable PD pattern indicating placement of the glass electrode in the bulb. The final arrangement is shown in figure 3. Illustrative PD and pH patterns are shown in figure 4, and a typical frame from a cinefluorogram is shown in figure 5. Fifteen cinefluorograms were correlated with synchronous PD patterns directly. The remaining 60 records from pullthrough studies were then reviewed and analyzed, on the basis of the previously demonstrated invariable pattern of abrupt change in potential at the pylorus, for calculations of representative PD patterns at the various sites. These data are summarized in figure 6, which shows PD between salt bridges having contact sites separated by 3 cm. Because no significant difference was demonstrable between
9J4
ARCHAMBA ULT ET AL.
Fro. 5. Frame from cinefiuorogram of pylorus region (subj ect in oblique prone position, right side down), showing lead markers at site of KCI bridge contact sites and position of pylorus outlined by barium. This position corresponds to the potential difference (PD) pattern shown in figure 4 as that designating a location of the glass electrode in the duodenal bulb.
Vol. 52, No.6
corded during advancement of the tube from stomach to duodenum. In fasting control subjects, 97% of the pH recordings were acceptable; 84% of the recordings were acceptable in subjects with duodenal ulcer. This difference, the result of instability of the straddling PD pattern, suggests greater peristaltic activity in duodenal ulcer subjects or possible variable recording of injury potentials from the ulcer itself. Figure 7 shows the distribution of pH in fasting normal subjects and subjects with duodenal ulcer. There are deficiencies in use of mean pH to characterize such records! because it requires linear treatment of log-based data. pH-percentage of time curves and difference curves! were constructed, but such a presentation is cumbersome for present purposes, so, in spite of the limitations of mean pH, this Gastroesophageal
50
Number 49 Mean 25.2 SO 5.6
0 Antroontral
normal subjects and those with duodenal ulcer, the mean PD represents the combined groups. The mean PD across the gastroesophageal junction (25.2 mv) was similar to that across the antroduodenal junction (24.9 mv). At the gastroesophageal straddling position, the orad bridge is more positive; at the pylorus straddling position, the orad bridge is the more negative of the two systems. Most important, as seen in figure 6, when both bridges were in the antrum or in the duodenum, the PD between bridges did not exceed 15 mv. Thus, a PD of greater than 15 mv between the two bridges, orad-negative, reflected a py lorus straddling position (orad bridge in the antrum and the other in the duodenal bulb) and, because the glass electrode was only 0.5 cm caudad to the caudad bridge contact site, insured location of the glass electrode in the duodenal bulb. The glass electrode could theoretically record pH briefly from the pyloric canal while an antroantral PD pattern was being re-
Number 58 Mean 4.5 SO 2.5
~
" .::-" t::" ~
1l ....
Antroduodenal 50
O L - - --
Number 53 Mean 24.9 SO 5.1
-=
Ouodenoduodenol Number 45 Mean 5.2 SO 2.3 35 40 45 Potential difference (mv)
Fro. 6. Histograms of potential difference (PD) between intraluminal KCI bridges (3 cm apart) at different sites. When PD > 15 mv, bridges are straddling gastroesophageal or antroduodenal junction. Orad bridge is negative when the pylorus is being straddled and positive when gastroesophageal zone lies between the bridges. Number of cases and mean PD ± SD are given for the four sets-gastroesophageal, antroantral, antroduodenal, and duodenoduodenal.
945
pH OF DUODENAL BULB CONTENTS
June 1967
has been used for simplicity and because the comparisons are mainly between sites having similar pH values. For similar reasons, Andersson and Grossman 3 have used this method of analysis. In fact, if duodenal functions are related to a logarithmic function of hydrogen ion concentration, as are many other biological phenomena, mean pH may be preferable. There was no significant difference in mean antral pH or in mean postbulbar duodenal pH between normal and duodenal ulcer subjects. However, the pH in the duodenal bulb was significantly lower in duodenal ulcer patients than in normal subjects (P < 0.01). There was also a significant difference in pH between the antrum and the duodenal bulb in normal subjects (P < 0.01); this difference was less in duodenal ulcer subjects but still was st atistically significant (P < 0.01). The pH pattern in the duodenal bulb more closely resembled that in the' antrum in ulcer subjects than in control subjects. The designation "postbulbar" duodenum is arbitrary and as used here it means that part of the descending duodenum just distal to the superior duodenal flexure. This site was selected because the electrode lead with its bend at the superior flexure made this location the closest roentgenologically distinctive site immediately caudad to the bulb. ' Data depicting the stability of the record at various recording sites are shown in table 1. An abrupt change in pH of at least 0.5 pH unit was considered to be a fluctu ation. Antral pH was most stable. Although the duodenal bulb pH may at times mimic the antral pH, the pattern in the bulb was usually more variable. The T ABLE
Number 42 Mean 1.7
SO
0
0.50
~~~--------------
50 Number 16
Mean SO
0 50
Duodenal bulbi normal Number 21 Mean 4.5 SO 1.4
~
" ....""~
0
<>
1.7 0.48
50
~
Number 14
"
~
~d!11lJlrz:;z~ D2
0 50
______jMe~a~n SO
Post-bulbar duodenum,normal
Number 36
Mean
SO
0 50
0
Post-bulbar duodenum, DU
3
4
6.7 0.56
Num be r 11
Mean SO 2
2.9 1.01
7
6
6.7 0.56
8
pH
FIG. 7. Histograms of mean pH at different sites in normal and duodenal ulcer subjects. Antral pH is significantly lower than bulb pH in both groups of subjects (P < 0.01). The only significant difference is that duodenal bulb pH is lower in ulcer patients than in normal subj ects (P < 0.01) . Number of cases and mean pH ± SD are given for normal and ulcer patient antrum, normal and ulcer patient duodenal bulb, and normal and ulcer patient postbulbar duodenum. "Postbulbar duodenum" is defined as that portion of the descending duodenum just caudad to t he superior duodenal flexure.
pattern became more stable again in records from sites in the duodenum distal to the bulb. Discussion
Our present study reveals similarities and differences when compared with the
1. Summary of abrupt pH fluctuations of more than 0.5 pH unit Patients F luctuations per minute
Site
Total Normal
Ulcer
-
Antrum . ... . ....... Bulb ............ .. . P ostbulbar .. . . .. . ..
42 21 36
With fluctuations Normal
Ulcer
6 (14%) 20 (95%) 21 (58% )
2 (13%) 13 (93%) 6 (55% )
Normal
Ulcer
-
16 14 11
15/799 386/449 82/281
= = =
0.02 0.9 0.3
3/158 = 0.02 135/176 = 0.8 14/74 = 0.2
946
ARCHAMBA ULT ET AL.
findings of Andersson and Grossman,3 but our conclusions are essentially the same as theirs. They defined the pylorus on the basis of serial roentgeno;;rams of subj ects in the supine position. We are more confident of the location of the electrode in our study on the basis of cinefluorography, dilute barium contrast, and oblique prone positioning to facilitate opacification of the profile of the pylorus. Review of the cinefluorographic record at slow speed proved very helpful because the electrode often passed through the pylorus abruptly despite slow withdrawal of the lead. In the work of Andersson and Grossman,3 because of the positioning of the PD recording leads, the pH recording from the duodenal bulb required roentgenographic control of the position of the glass electrode. Consequently, they justifiably suspected that fluctuations in duodenal bulb pH might reflect intermittent retraction of the glass electrode toward or away from the pylorus. With our system of simultaneous skin-gastric and skin-duodenal PD recording, we found that maintenance of the glass electrode in the duodenal bulb required frequent adjustments of tube length. However, the frequency of records of fluctuating pH in the duodenal bulb despite a stable straddling PD convinces us that the unstable pH pattern is physiological and not an artifact. Results were remarkably similar despite minor variations in technique. They reported a mean antroduodenal PD of 26.9 mv ± 9.5 (present study, 24.9 ± 5.1) and a mean gastroesophageal PD of 24.9 mv ± 11.6 (present study, 25.2 ± 5.6). Of interest are their larger standard deviations which are in keeping with their noting a ±15% difference between paired studies on repeated withdrawal of electrodes. This may reflect the difference between their use of agar-KCI bridges and our use of flowing KCI bridges. A very helpful contribution is their observation that the skinblood PD was 36 mv, with skin negative with respect to blood. In their studies with an intravascular KCI-agar bridge, gastroduodenal and esophagogastric PD were nearly identical with those obtained with
Vol. 52, No.6
a skin reference, a reassuring justification for our continued use of a skin reference. The PD which we found between two sites in the antrum or duodenum may reflect minor diffusion potentials not entirely eliminated by the flowing KCI bridge system. They may also indicate changing proximity of the bridge to the mucosa or to the antrofundic junction in essentially a volume conductor. Rapid fluctuations in skin potential seem unlikely. We have not related duodenal pH to antral pH for each subject, as Andersson and Grossman3 did. However, in both ulcer and control subjects antral pH was predominantly below 2.5 (fig. 7). They found antral pH values of 3 or less associated with lower pH levels in the first portion of the duodenum when compared with the more distal part. The decreased duodenal bulb pH, despite an apparently normal antral pH, in our subjects with duodenal ulcer can be explained in several ways. First, in the low pH range seen in the antrum, minor changes in pH reflect relatively great changes in hydrogen ion activity. Such minor changes are not easily recognized by conventional methods of analysis, nor are they very reliably recorded by readily applicable, continuously recording pH meters and electrodes. Second, the volume of gastric secretions in ulcer patients may increase more than the acid concentration so that the increased total acid output may exceed duodenal neutralizing reserves. Furthermore, if gastric acid secretions of equal volume and acidity emptied into the duodenum of ulcer patients more intermittently, these transient influxes of accumulated acid might decrease the pH, whereas a slower but steadier introduction of the same amount of acid into the duodenum might not overwhelm duodenal neutralizing mechanisms. Finally, there remains the possibility that, in ulcer patients, duodenal neutralizing mechanisms are less effective than in normal persons. The pH values in the ulcer patients were different from those in the control subjects only in the region of the duodenal bulb. This emphasizes the importance of
June 1967
pH OF DUODENAL B ULB CONTENTS
947
tral pH values were similar (1.7). There was no significant difference between ulcer and control groups with respect to the pH of antral or postbulbar duodenal conSummary tents. Antral pH was much more stable The pH of duodenal bulb contents has than duodenal bulbar pH. Postbulbar been recorded with a guarded, in situ, duodenal pH was higher and more stable glass electrode in 75 subjects, 16 with than the pH of the duodenal bulb. duodenal ulcer. The antrocutaneous and REFERENCES duodenocutaneous potential differences (PD) were simultaneously recorded from J., C. V. Mann, H. C. Carlson, C. F. flowing KCI bridges attached to the glass 1. Bircher, Code, and R. A. Rovelstad. 1965. Intraluelectrode lead (these bridges were found minal and juxtamucosal duodenal pH. Gasto be superior to KCI-agar bridges for troenterology 48 : 472-477. this purpose), and PD patterns were used 2. Rovelstad, R. A., C. A. Owen, Jr., and T. B. to position the glass electrode and moniMagath. 1952. Factors influencing the continuous recording of in situ pH of gastric and tor its location. That a PD between duoduodenal contents. Gastroenterology 20: denum and gastric antrum of greater than 609-624 . 15 mv (duodenum more positive) was a reliable sign that the glass electrode was 3. Andersson, S., and M. 1. Grossman. 1965. Profile of pH, pressure, and potential difin the duodenal bulb was confirmed by ference at gastroduodenal junction in man . simultaneous cinefluorography. Mean duoGastroenterology 49 : 364-371. denal bulb pH was significantly higher 4. H elm, W. J., C. F. Code, and W. H. J. Sumthan antral pH in both normal and ulcer merskiIl. 1961. Simultaneous identification of subjects. In ulcer subjects, mean duodenal the gastroesophageal junction by pH, pot en tial difference and pressure (abstr.). bulb pH (2.9) was significantly lower Gastorenterology 40: 805. than normal (4.5). Normal and ulcer anstudying this region in investigation of acid secretion and gastrointestinal physiology .