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Gastroduodenal mucosal hemodynamics by endoscopic reflectance spectrophotometry
0016-5107/87/3304-0284$02.00 GASTROINTESTINAL ENDOSCOPY Copyright © 1987 by the American Society for Gastrointestinal Endoscopy
Gastroduodenal mucosal hemodynamics by endoscopic reflectance spectrophotometry Felix W. Leung, MD, Enrique Siodownik, MD Dennis M. Jensen, MD, Gary M. Van Deventer, MD Paul H. Guth, MD Los Angeles, California
The reflectance spectrophotometric technique measures an index of mucosal hemoglobin concentration and an index of oxygen saturation by spectral analysis of light reflected from the mucosal surface. Using a commercially available unit, a technique for obtaining reproducible endoscopic measurements with acceptable intraobserver and interobserver variability was developed in the anesthetized dogs. The reflectance spectrophotometric finding that experimentally induced prehepatic portal hypertension did not affect gastric mucosal blood flow was confirmed by hydrogen gas clearance measurements. Endoscopic studies in patients with active duodenal ulcer disease revealed a higher index of mucosal hemoglobin concentration and a normal index of oxygen saturation (i.e., an increase in blood flow) at the margin of the ulcer compared with the adjacent normal appearing mucosa. (Gastrointest Endosc 1987;33:284-288)
Animal studies have demonstrated that blood flow plays an important role in mucosal injury and defense. l Hydrogen gas clearance is a well validated blood flow measurement technique 2- 4 that has been employed endoscopically.5-7 The major drawback is the time (20 to 30 min) required for one flow measurement. Although there are some reports (largely preliminary) of the endoscopic use of laser Doppler velocimetry,8 unpublished personal observations indicate that motion artifact is a major limiting factor. The reflectance spectrophotometric technique 9 - 12 permits rapid and repeated measurements of an index of mucosal hemoglobin concentration (lHB) and an index of oxygen saturation (180 2 ) based on spectral analysis of light reflected from the mucosal surface. Although the technique does not measure blood flow in quantitative terms, 1HB and 1802 together allow for accurate determination of the change in mucosal perfusion status. 12 The present study demonstrates that reproducible endoscopic results, with acceptable intraobserver and interobserver variability, can be achieved with a commercially available reflectance Received August 25, 1986. Accepted September 29, 1986. From the Research and Medical Services, Wadsworth Veteran's Administration Hospital Center, University of California, Los Angeles, and the Center for Ulcer Research and Education, Los Angeles, California. Reprint requests: Felix W. Leung, MD, Sepulveda Veterans Administration Medical Center, 111 G, 16111 Plummer Street, Sepulveda, California 91343. 284
spectrophotometer. The feasibility of endoscopic measurement of gastroduodenal mucosal hemodynamics is illustrated in an experimental model of prehepatic portal hypertension and in clinical duodenal ulcer disease. MATERIALS AND METHODS
Endoscopic studies in dogs
For endoscopic studies, mongrel dogs (N = 7) weighing 20 to 25 kg were fasted overnight. They were anesthetized with intravenous pentothal (45 mg kg-I) and intubated. Anesthesia was maintained with inhaled ethrane. Preparation of a canine model of portal hypertension
The procedure has been described previously.I3 Briefly, after anesthesia and laparotomy, a side to side portacaval shunt was performed. The inferior vena cava was ligated proximal to the shunt, and an ameroid constrictor was placed around the portal vein cephalad to the shunt. Four to 6 weeks after surgery the dogs (N = 7) developed prehepatic portal hypertension and esophageal varices. Endoscopic studies in duodenal ulcer patients
Twenty outpatients with acute duodenal ulcers were endoscoped by one of the authors (F.W.L.) at the Peptic Ulcer Clinic of the Center for Ulcer Research and Education. These patients were not on any antiulcer medication prior to the study measurements. After informed consent, the patients were sedated with intravenous meperidine (25 to 50 GASTROINTESTINAL ENDOSCOPY
mg) and intravenous diazepam (5 to 10 mg). The research protocol was approved by the Human Investigation Committee of the Wadsworth Veterans Administration Hospital. Reflectance spectrophotometric measurements. In these studies, a Tissue Spectrum Analyzer TS-200 (Sumitomo Electric Industries, Ltd., Osaka, Japan) was used. The measuring probe consists of two coaxial light guides which couple the mucosal surface to the light source and spectrophotometer. The incident light from the light source travels toward the gastric mucosa in the outer coaxial ring, and the reflected light from the gastric mucosa travels in the central guide back to the spectrophotometer for analysis. The data are processed rapidly (40 msec) by a microcomputer data analysis unit. The spectral tracing and IHB and IS02 are displayed on the monitor screen. Details for the calculation of IHB and IS0 2 have been described. 9 ,12 Hydrogen gas clearance. Endoscopic measurement of gastric corpus mucosal blood flow was performed as previously described.? In this study, suction was not needed to position the electrode against the mucosa. Study design
Study 1: Reproducibility of reflectance spectrophotometric measurements. In the anesthetized dog (N = 7), the reflectance spectrophotometric probe was passed through the biopsy channel of the endoscope (GIF2D, Olympus) to make contact with the gastric mucosa. Measurements were obtained from the fundus, the body along the greater curvature, and the antrum. The endoscopist oriented the measuring probe perpendicularly toward the mucosal surface being studied. When the mucosal surface was gently touched, and without looking at the monitor screen, the endoscopist announced to the assistant that contact with the mucosa was made. The assistant would record the first set of IHB and IS02 readings displayed on the monitor screen immediately following the contact. Each set of readings took only a few seconds to perform and were repeated five times in the same location by the same observer. A total of six sets of IHB and 1802 readings were thus recorded. The mean of each set of six such readings was defined as the IHB or 180 2 measurement for the observer for that location. A second observer then repeated these readings in the same locations of the fundus, body, and antrum. The mean of six sets of these readings at each location was thus calculated and defined as the IHB or 1802 measurement at each location for the second observer. After these basal measurements were completed, a bolus (l dose/dog) of vasopressin (l to 5 IU) was injected intravenously over 2 min. Two to three min after completion of the injection, the readings by the same two observers in approximately the same locations in the stomach were repeated, and the measurements were calculated as described for the basal study. Study 2: IHB, IS02, and hydrogen gas clearance before and after the development of portal hypertension. 8even dogs were operated on to produce prehepatic portal hypertension by one ofthe authors (D.M.J.). IHB and 1802 by reflectance spectrophotometry and gastric corpus mucosal blood flow by hydrogen gas clearance were obtained in the gastric mucosa along the greater curvature 10 cm distal to the gastroesophageal junction. These measurements were obtained under anesthesia 1 week before and 4 to 6 weeks after the operation. VOLUME 33, NO. 4, 1987
Study 3: Endoscopic studies in patients with active duodenal ulcer disease. In the sedated patients (N = 20) the endoscope (GIFXQ, Olympus) was passed into the duodenum to examine the ulcer. The reflectance spectrophotometric probe was passed through the biopsy channel of the endoscope to make contact with the mucosa at the margin of the ulcer. Six pairs of IHB and 1802 readings were obtained. The probe was then placed in contact with the adjacent normal appearing duodenal mucosa 1 to 2 em from the margin of the ulcer. Again, six pairs of IHB and 180 2 readings were obtained. The technique used for obtaining each pair of readings was the same as that described for study 1. Data analysis
In study 1, the mean and standard error of each set of six IHB and 180 2 readings by each observer at each location were calculated. The means and standard errors of these readings were defined as each observer's measurements at that location. The mean absolute differences in the measurements between the two observers were calculated separately for IHB and 1802 , Regression analysis was carried out on the measurements of IHB and 1802 at each location obtained by the two observers, and the correlation coefficient (r) was determined. In study 2, the IHB, 1802, and hydrogen gas clearance measurements before and after the operation to produce portal hypertension were compared using the paired t test. In study 3, the mean of IHB and 1802 readings obtained at the margin of the ulcer and the adjacent normal appearing mucosa for each patient were calculated and defined as the measurements at these locations, respectively. The paired t test was used to determine whether a significant difference was present between IHB or 1802 measurements at the ulcer margin and the adjacent normal appearing mucosa.
RESULTS Study 1: Reproducibility of reflectance spectrophotometric measurements
Table 1 reveals that IHB and 1802 measurements (each measurement is the mean of six readings) for each observer before and after vasopressin injection. There were no significant differences in the measurements obtained by the two observers. The measurements by both observers demonstrated that the IHB in the corpus mucosa was higher than that in the antral mucosa. The 1802 measurements in the antral and corpus mucosa were not significantly different. With vasopressin infusion, there was a significant reduction in both IHB and 1802 in both locations. 8ince six sets of IHB and 1802 readings were obtained by each observer at each location, the standard error for these readings at each location can be calculated. The means of the standard error for IHB and 1802 for the two observers were 5.4 and 1.7, respectively. With a mean basal IHB of 52.5 and 105 and 1802 of 42.5 and 40 in the corpus and antrum, respectively, 285
Table 1. Summary of IS02 and IHB measurements (mean ± SEM) by the two observers in the antral and corpus mucosa before and after vasopressin injection-study 1a Observer A
N
Before IS0 2
Antrum Corpus
Observer B
IHB
42 ± 2 40± 2
7 7
After IS0 2
n ± b
53 ± 7 105 e ± 7
Before IHB
IS0 2
IHB
IS0 2
IHB
b
43 ± 3 40 ± 2
52 ± 7 105 e ± 8
7b ± 5 7b ± 3
26 b ± 5 53 b,e ± 12
3l ± 8 54 b,e ± 9
7
7b ± 2
After
Results from the body are not tabulated because these measurements were not obtained in every case. Significantly lower than before vasopressin, p < 0.05, paired t test. e Significantly higher than in antrum, p < 0.05, paired t test.
a
b
150
60
00
A
0
y=7.3+0.9x r=0.95
[]A
0
0
100 al II:
•
0
>al al
;l;
50
A
• • • •
0
50
y=1.3+0.9x r=0.97
40
A
II:
en
•
al
0
>al
0
0
A
~
20
•
BASAL VASOPRESSIN
A·
0
A
w > w
•
0
II:
en al
al II:
0 0
w > w
o
0
ANTRUM
A
BODY FUNDUS
0 0
100
• ••
•• • 150
IHB BY OBSERVER A
0
~
ANTRUM BODY FUNDUS
•
•• •
20
A
0 0
40
VASOPRESSIN
•
•• 60
ISO, BY OBSERVER A
Figure 1. Linear correlation between the independently obtained IHB measurements of observer A and observer B in study 1.
Figure 2. Linear correlation between the independently obtained 1802 measurements of observer A and observer B in study 1.
these were within acceptable limits for intraobserver variability. The mean absolute differences in IHB and 1802 for the two observers were 8 and 2, respectively. Regression analysis revealed a linear correlation between the two observers' IHB and 1802 measurements (Figs. 1 and 2), r being 0.95 and 0.97, respectively. Thus, acceptable interobserver variability was confirmed.
Study 3: Endoscopic studies in patients with acute duodenal ulcers
The mean IHB measurements at the margin of the duodenal ulcer were significantly (p < 0.05, paired t test) higher than that at the adjacent normal appearing mucosa (Table 3). The mean 1802 measurements were not significantly different. DISCUSSION
Study 2: IHB, IS02 , and hydrogen gas clearance in dogs before and after the development of portal hypertension
Table 2 shows that there was no significant difference in IHB, 1802 and hydrogen gas clearance measurements before and after the development of prehepatic portal hypertension and esophageal varices in the anesthetized dogs (N = 7). All of these dogs had developed small to medium size varices at the time when measurements were made after surgery. 286
Although hydrogen gas clearance is a well validated technique for the endoscopic measurement of gastric mucosal blood flow,2-7 its clinical application is limited by the time (20 to 30 min) required for one blood flow measurement. 7 Despite encouraging preliminary reports,8 unpublished personal experience with endoscopic application of laser Doppler velocimetry indicates motion artifact to be a potential limiting factor. On the other hand, reflectance spectrophotometry provides rapid measurements of IHB and 1802 • IHB GASTROINTESTINAL ENDOSCOPY
Table 2. Measurements by reflectance spectrophotometry and hydrogen gas clearance 1 week before and 4 to 6 weeks after operation to produce portal hypertension-study 2 IHB
IS0 2 Hydrogen gas clearance (ml min- 1 100 g-l)
Before
After
107 ± 8 42 ± 2 52 ± 6
111±8 40 ± 2 53 ± 5
Table 3. Reflectance spectrophotometric measurements in acute duodenal ulcer in humans-study 3 Mucosa at ulcer margin
IRB IS0 2 N o
±6 36 ± 1 20
135 0
Adjacent normal appearing mucosa 113±5 36 ± 1 20
Significantly higher than adjacent normal appearing mucosa, p
< 0.05, paired t test.
and IS0 2 together can distinguish between hypoperfusion due to an absolute reduction in blood flow and blood volume (decrease IHB and IS0 2 ) and hypoperfusion due to vascular congestion (increase IHB, decrease IS0 2 ). 12 Increase in blood flow during postischemic hyperemia can be documented by a rise in IHB and a normal IS0 2 •12 The finding in study 1 that IHB was consistently higher in the corpus than the antral mucosa confirms previous findings by Kamada et a1.1O, 11 in humans, by Sato et a1. 9 in rats and by Leung and Guth 12 in rats. Vasopressin is a known mesenteric vasoconstrictor, 2,14 and its infusion brings about a significant reduction in both IHB and IS0 2 in the gastric mucosa. The pattern of change, i.e., reduction in both IHB and IS0 2 suggests that there was an absolute reduction in blood flow and blood volume during vasopressin-induced hypoperfusion of the gastric mucosa. 12 The reproducibility of the endoscopic measurements generated by the commercially available reflectance spectrophotometer is demonstrated in this report. The choice of the first pair of IHB and IS0 2 readings for recording is based on the following reasoning: the first pair of observations as soon as contact is made is least likely to be biased by mechanical influence such as contact pressure or the choice by the investigator of the "best" recording memorized by the computer9 when the prototype unit was used. Unbiasing the measurement in this fashion is important because sometimes it is not possible to blind the observer to the nature of the lesion under study. The technique described in this report that provides data with acceptable intraobserver and interobserver variability affirms the potential for clinical application of VOLUME 33, NO.4, 1987
this technique in an objective fashion and ensures the comparability of results among different investigators. The validity of endoscopically obtained IHB and IS0 2 measurements is further confirmed because hydrogen gas clearance corroborated the finding of reflectance spectrophotometry in the canine model of prehepatic portal hypertension and esophageal varices. Gastric corpus mucosal blood flow measurements by both techniques after surgery were not significantly different from those before surgery. Thus, in this animal model of portal hypertension, gastric mucosal blood flow was unchanged at a time when esophageal varices had developed. In acute ulcer disease, an increase in flow at the edge of the ulcer compared with the adjacent normal appearing mucosa was suggested. This implies that the presence of an active ulcer stimulates increased flow to the ulcer margin. This increase in flow might be an important factor in ulcer healing and warrants further study. The feasibility of endoscopic application of the commercially available reflectance spectrophotometric unit makes such clinical studies possible. Furthermore, in addition to the study of ulcer disease, the ease with which the reflectance spectrophotometric measurements can be obtained will make this potentially useful in the early endoscopic diagnosis of ischemic bowel disease in the segments accessible to the endoscope. The pattern of IHB and IS0 2 in various types of acute and chronic colitis can also be determined. Hypotheses concerning a potential role of altered mucosal perfusion in these diseases in humans can now be tested by endoscopic studies. ACKNOWLEDGMENTS
This work was supported by the National Institute of Arthritis and Metabolism and Digestive Diseases grant AM 34840 and American Society for Gastrointestinal Endoscopy Career Development Award H850208, Veterans Administration Medical Research Funds, and University of California, Los Angeles Academic Senate grant 4063. The authors acknowledge the technical assistance of Ernst Tallos, Ken Hirabayashi, Duke Martin, Dave Hill, Rebecca Chan, and Dr. Gustavo A. Machicado and thank Drs. Terry Ready and Janet Elashoff for assistance in statistical analysis and David Claus for preparation of the. manuscript. REFERENCES 1. Leung F, Itoh M, Hirabayashi K, Guth P. Role of blood flow in gastric and duodenal mucosal injury in the rat. Gastroenterology 1985;88:281-9. 2. Leung F, Guth P, Scremin 0, Golanska E, Kauffman G Jr. Regional gastric mucosal blood flow measurements by hydrogen gas clearance in the anesthetized rat and rabbit. Gastroenterology 1984;87:28-36. 3. Murakami M, Moriga M, Miyake T, Uchino H. Contact electrode method in hydrogen gas clearance technique: a new
287
4. 5.
6. 7. 8.
method for determination of regional gastric mucosal blood flow in animals and humans. Gastroenterology 1982;82:457-7. Ashley S, Cheung L. Measurement of gastric mucosal blood flow by hydrogen gas clearance. Am J PhysioI1984;247:G33945. Fukutomi H, Miyomoto J, Sakita T. Endoscopical measurement of gastric blood flow of patients suffering from gastric ulcer. In: Tsuchya M, Asano M, Oda M, eds. Basic aspects of microcirculation, Proceedings of the Tokyo International Symposium on Microcirculation, July 26, 1981. Amsterdam: Excerpta Medica, 1982:251-8. Ashley SW, Van ZY, Soybel DI, Cheung LY. Endoscopic measurements of gastric mucosal blood flow in dogs. J Surg Res 1985;38:416-23. Leung FW, Washington J, Kauffman GL, Guth PH. Endoscopic measurement of gastric mucosal blood flow in conscious dogs. Dig Dis Sci 1986;31:625-30. Murakami M, Saida H, Seki M, Inada M, Miyake T. Measurements of mucosal blood flow of the esophagus and stomach in humans: regional differences and changes with aging. Gastroenterology 1984;86:1191.
288
9. Sato N, Kamada T, Schichiri M, Kawano S, Abe H, Hagihara B. Measurement of hemoperfusion and oxygen sufficiency in gastric mucosa in vivo. Gastroenterology 1979;76:814-9. 10. Kamada T, Sato N, Kawano S, Fusamoto H, Abe H. Gastric mucosal hemodynamics after thermal or head injury. Gastroenterology 1982;83:535-40. 11. Kamada T, Kawano S, Sato N, Fukuda M, Fusamoto H, Abe H. Gastric mucosal blood distribution and its changes in the healing process of gastric ulcer. Gastroenterology 1983;84:15416.
12. Leung FW, Guth PH. Interpretation of reflectance spectrophotometric measurements of gastroduodenal mucosal hemodynamic changes. Gastroenterology 1986;90:1517. 13. Jensen DM, Machicado GA, Tapia JI, Kauffman G, Franco P, Beilin D. A reproducible canine model of esophageal varices. Gastroenterology 1983;84:573-9. 14. Zinner M, Kerr J, Reynolds D. Distribution and arteriovenous shunting of gastric blood flow in the baboon: effect of epinephrine and vasopressin infusions. Gastroenterology 1976;71:299302.
GASTROINTESTINAL ENDOSCOPY
Gastroduodenal mucosal hemodynamics by endoscopic reflectance spectrophotometry Felix W. Leung, MD, Enrique Siodownik, MD Dennis M. Jensen, MD, Gary M. Van Deventer, MD Paul H. Guth, MD Los Angeles, California
The reflectance spectrophotometric technique measures an index of mucosal hemoglobin concentration and an index of oxygen saturation by spectral analysis of light reflected from the mucosal surface. Using a commercially available unit, a technique for obtaining reproducible endoscopic measurements with acceptable intraobserver and interobserver variability was developed in the anesthetized dogs. The reflectance spectrophotometric finding that experimentally induced prehepatic portal hypertension did not affect gastric mucosal blood flow was confirmed by hydrogen gas clearance measurements. Endoscopic studies in patients with active duodenal ulcer disease revealed a higher index of mucosal hemoglobin concentration and a normal index of oxygen saturation (i.e., an increase in blood flow) at the margin of the ulcer compared with the adjacent normal appearing mucosa. (Gastrointest Endosc 1987;33:284-288)
Animal studies have demonstrated that blood flow plays an important role in mucosal injury and defense. l Hydrogen gas clearance is a well validated blood flow measurement technique 2- 4 that has been employed endoscopically.5-7 The major drawback is the time (20 to 30 min) required for one flow measurement. Although there are some reports (largely preliminary) of the endoscopic use of laser Doppler velocimetry,8 unpublished personal observations indicate that motion artifact is a major limiting factor. The reflectance spectrophotometric technique 9 - 12 permits rapid and repeated measurements of an index of mucosal hemoglobin concentration (lHB) and an index of oxygen saturation (180 2 ) based on spectral analysis of light reflected from the mucosal surface. Although the technique does not measure blood flow in quantitative terms, 1HB and 1802 together allow for accurate determination of the change in mucosal perfusion status. 12 The present study demonstrates that reproducible endoscopic results, with acceptable intraobserver and interobserver variability, can be achieved with a commercially available reflectance Received August 25, 1986. Accepted September 29, 1986. From the Research and Medical Services, Wadsworth Veteran's Administration Hospital Center, University of California, Los Angeles, and the Center for Ulcer Research and Education, Los Angeles, California. Reprint requests: Felix W. Leung, MD, Sepulveda Veterans Administration Medical Center, 111 G, 16111 Plummer Street, Sepulveda, California 91343. 284
spectrophotometer. The feasibility of endoscopic measurement of gastroduodenal mucosal hemodynamics is illustrated in an experimental model of prehepatic portal hypertension and in clinical duodenal ulcer disease. MATERIALS AND METHODS
Endoscopic studies in dogs
For endoscopic studies, mongrel dogs (N = 7) weighing 20 to 25 kg were fasted overnight. They were anesthetized with intravenous pentothal (45 mg kg-I) and intubated. Anesthesia was maintained with inhaled ethrane. Preparation of a canine model of portal hypertension
The procedure has been described previously.I3 Briefly, after anesthesia and laparotomy, a side to side portacaval shunt was performed. The inferior vena cava was ligated proximal to the shunt, and an ameroid constrictor was placed around the portal vein cephalad to the shunt. Four to 6 weeks after surgery the dogs (N = 7) developed prehepatic portal hypertension and esophageal varices. Endoscopic studies in duodenal ulcer patients
Twenty outpatients with acute duodenal ulcers were endoscoped by one of the authors (F.W.L.) at the Peptic Ulcer Clinic of the Center for Ulcer Research and Education. These patients were not on any antiulcer medication prior to the study measurements. After informed consent, the patients were sedated with intravenous meperidine (25 to 50 GASTROINTESTINAL ENDOSCOPY
mg) and intravenous diazepam (5 to 10 mg). The research protocol was approved by the Human Investigation Committee of the Wadsworth Veterans Administration Hospital. Reflectance spectrophotometric measurements. In these studies, a Tissue Spectrum Analyzer TS-200 (Sumitomo Electric Industries, Ltd., Osaka, Japan) was used. The measuring probe consists of two coaxial light guides which couple the mucosal surface to the light source and spectrophotometer. The incident light from the light source travels toward the gastric mucosa in the outer coaxial ring, and the reflected light from the gastric mucosa travels in the central guide back to the spectrophotometer for analysis. The data are processed rapidly (40 msec) by a microcomputer data analysis unit. The spectral tracing and IHB and IS02 are displayed on the monitor screen. Details for the calculation of IHB and IS0 2 have been described. 9 ,12 Hydrogen gas clearance. Endoscopic measurement of gastric corpus mucosal blood flow was performed as previously described.? In this study, suction was not needed to position the electrode against the mucosa. Study design
Study 1: Reproducibility of reflectance spectrophotometric measurements. In the anesthetized dog (N = 7), the reflectance spectrophotometric probe was passed through the biopsy channel of the endoscope (GIF2D, Olympus) to make contact with the gastric mucosa. Measurements were obtained from the fundus, the body along the greater curvature, and the antrum. The endoscopist oriented the measuring probe perpendicularly toward the mucosal surface being studied. When the mucosal surface was gently touched, and without looking at the monitor screen, the endoscopist announced to the assistant that contact with the mucosa was made. The assistant would record the first set of IHB and IS02 readings displayed on the monitor screen immediately following the contact. Each set of readings took only a few seconds to perform and were repeated five times in the same location by the same observer. A total of six sets of IHB and 1802 readings were thus recorded. The mean of each set of six such readings was defined as the IHB or 180 2 measurement for the observer for that location. A second observer then repeated these readings in the same locations of the fundus, body, and antrum. The mean of six sets of these readings at each location was thus calculated and defined as the IHB or 1802 measurement at each location for the second observer. After these basal measurements were completed, a bolus (l dose/dog) of vasopressin (l to 5 IU) was injected intravenously over 2 min. Two to three min after completion of the injection, the readings by the same two observers in approximately the same locations in the stomach were repeated, and the measurements were calculated as described for the basal study. Study 2: IHB, IS02, and hydrogen gas clearance before and after the development of portal hypertension. 8even dogs were operated on to produce prehepatic portal hypertension by one ofthe authors (D.M.J.). IHB and 1802 by reflectance spectrophotometry and gastric corpus mucosal blood flow by hydrogen gas clearance were obtained in the gastric mucosa along the greater curvature 10 cm distal to the gastroesophageal junction. These measurements were obtained under anesthesia 1 week before and 4 to 6 weeks after the operation. VOLUME 33, NO. 4, 1987
Study 3: Endoscopic studies in patients with active duodenal ulcer disease. In the sedated patients (N = 20) the endoscope (GIFXQ, Olympus) was passed into the duodenum to examine the ulcer. The reflectance spectrophotometric probe was passed through the biopsy channel of the endoscope to make contact with the mucosa at the margin of the ulcer. Six pairs of IHB and 1802 readings were obtained. The probe was then placed in contact with the adjacent normal appearing duodenal mucosa 1 to 2 em from the margin of the ulcer. Again, six pairs of IHB and 180 2 readings were obtained. The technique used for obtaining each pair of readings was the same as that described for study 1. Data analysis
In study 1, the mean and standard error of each set of six IHB and 180 2 readings by each observer at each location were calculated. The means and standard errors of these readings were defined as each observer's measurements at that location. The mean absolute differences in the measurements between the two observers were calculated separately for IHB and 1802 , Regression analysis was carried out on the measurements of IHB and 1802 at each location obtained by the two observers, and the correlation coefficient (r) was determined. In study 2, the IHB, 1802, and hydrogen gas clearance measurements before and after the operation to produce portal hypertension were compared using the paired t test. In study 3, the mean of IHB and 1802 readings obtained at the margin of the ulcer and the adjacent normal appearing mucosa for each patient were calculated and defined as the measurements at these locations, respectively. The paired t test was used to determine whether a significant difference was present between IHB or 1802 measurements at the ulcer margin and the adjacent normal appearing mucosa.
RESULTS Study 1: Reproducibility of reflectance spectrophotometric measurements
Table 1 reveals that IHB and 1802 measurements (each measurement is the mean of six readings) for each observer before and after vasopressin injection. There were no significant differences in the measurements obtained by the two observers. The measurements by both observers demonstrated that the IHB in the corpus mucosa was higher than that in the antral mucosa. The 1802 measurements in the antral and corpus mucosa were not significantly different. With vasopressin infusion, there was a significant reduction in both IHB and 1802 in both locations. 8ince six sets of IHB and 1802 readings were obtained by each observer at each location, the standard error for these readings at each location can be calculated. The means of the standard error for IHB and 1802 for the two observers were 5.4 and 1.7, respectively. With a mean basal IHB of 52.5 and 105 and 1802 of 42.5 and 40 in the corpus and antrum, respectively, 285
Table 1. Summary of IS02 and IHB measurements (mean ± SEM) by the two observers in the antral and corpus mucosa before and after vasopressin injection-study 1a Observer A
N
Before IS0 2
Antrum Corpus
Observer B
IHB
42 ± 2 40± 2
7 7
After IS0 2
n ± b
53 ± 7 105 e ± 7
Before IHB
IS0 2
IHB
IS0 2
IHB
b
43 ± 3 40 ± 2
52 ± 7 105 e ± 8
7b ± 5 7b ± 3
26 b ± 5 53 b,e ± 12
3l ± 8 54 b,e ± 9
7
7b ± 2
After
Results from the body are not tabulated because these measurements were not obtained in every case. Significantly lower than before vasopressin, p < 0.05, paired t test. e Significantly higher than in antrum, p < 0.05, paired t test.
a
b
150
60
00
A
0
y=7.3+0.9x r=0.95
[]A
0
0
100 al II:
•
0
>al al
;l;
50
A
• • • •
0
50
y=1.3+0.9x r=0.97
40
A
II:
en
•
al
0
>al
0
0
A
~
20
•
BASAL VASOPRESSIN
A·
0
A
w > w
•
0
II:
en al
al II:
0 0
w > w
o
0
ANTRUM
A
BODY FUNDUS
0 0
100
• ••
•• • 150
IHB BY OBSERVER A
0
~
ANTRUM BODY FUNDUS
•
•• •
20
A
0 0
40
VASOPRESSIN
•
•• 60
ISO, BY OBSERVER A
Figure 1. Linear correlation between the independently obtained IHB measurements of observer A and observer B in study 1.
Figure 2. Linear correlation between the independently obtained 1802 measurements of observer A and observer B in study 1.
these were within acceptable limits for intraobserver variability. The mean absolute differences in IHB and 1802 for the two observers were 8 and 2, respectively. Regression analysis revealed a linear correlation between the two observers' IHB and 1802 measurements (Figs. 1 and 2), r being 0.95 and 0.97, respectively. Thus, acceptable interobserver variability was confirmed.
Study 3: Endoscopic studies in patients with acute duodenal ulcers
The mean IHB measurements at the margin of the duodenal ulcer were significantly (p < 0.05, paired t test) higher than that at the adjacent normal appearing mucosa (Table 3). The mean 1802 measurements were not significantly different. DISCUSSION
Study 2: IHB, IS02 , and hydrogen gas clearance in dogs before and after the development of portal hypertension
Table 2 shows that there was no significant difference in IHB, 1802 and hydrogen gas clearance measurements before and after the development of prehepatic portal hypertension and esophageal varices in the anesthetized dogs (N = 7). All of these dogs had developed small to medium size varices at the time when measurements were made after surgery. 286
Although hydrogen gas clearance is a well validated technique for the endoscopic measurement of gastric mucosal blood flow,2-7 its clinical application is limited by the time (20 to 30 min) required for one blood flow measurement. 7 Despite encouraging preliminary reports,8 unpublished personal experience with endoscopic application of laser Doppler velocimetry indicates motion artifact to be a potential limiting factor. On the other hand, reflectance spectrophotometry provides rapid measurements of IHB and 1802 • IHB GASTROINTESTINAL ENDOSCOPY
Table 2. Measurements by reflectance spectrophotometry and hydrogen gas clearance 1 week before and 4 to 6 weeks after operation to produce portal hypertension-study 2 IHB
IS0 2 Hydrogen gas clearance (ml min- 1 100 g-l)
Before
After
107 ± 8 42 ± 2 52 ± 6
111±8 40 ± 2 53 ± 5
Table 3. Reflectance spectrophotometric measurements in acute duodenal ulcer in humans-study 3 Mucosa at ulcer margin
IRB IS0 2 N o
±6 36 ± 1 20
135 0
Adjacent normal appearing mucosa 113±5 36 ± 1 20
Significantly higher than adjacent normal appearing mucosa, p
< 0.05, paired t test.
and IS0 2 together can distinguish between hypoperfusion due to an absolute reduction in blood flow and blood volume (decrease IHB and IS0 2 ) and hypoperfusion due to vascular congestion (increase IHB, decrease IS0 2 ). 12 Increase in blood flow during postischemic hyperemia can be documented by a rise in IHB and a normal IS0 2 •12 The finding in study 1 that IHB was consistently higher in the corpus than the antral mucosa confirms previous findings by Kamada et a1.1O, 11 in humans, by Sato et a1. 9 in rats and by Leung and Guth 12 in rats. Vasopressin is a known mesenteric vasoconstrictor, 2,14 and its infusion brings about a significant reduction in both IHB and IS0 2 in the gastric mucosa. The pattern of change, i.e., reduction in both IHB and IS0 2 suggests that there was an absolute reduction in blood flow and blood volume during vasopressin-induced hypoperfusion of the gastric mucosa. 12 The reproducibility of the endoscopic measurements generated by the commercially available reflectance spectrophotometer is demonstrated in this report. The choice of the first pair of IHB and IS0 2 readings for recording is based on the following reasoning: the first pair of observations as soon as contact is made is least likely to be biased by mechanical influence such as contact pressure or the choice by the investigator of the "best" recording memorized by the computer9 when the prototype unit was used. Unbiasing the measurement in this fashion is important because sometimes it is not possible to blind the observer to the nature of the lesion under study. The technique described in this report that provides data with acceptable intraobserver and interobserver variability affirms the potential for clinical application of VOLUME 33, NO.4, 1987
this technique in an objective fashion and ensures the comparability of results among different investigators. The validity of endoscopically obtained IHB and IS0 2 measurements is further confirmed because hydrogen gas clearance corroborated the finding of reflectance spectrophotometry in the canine model of prehepatic portal hypertension and esophageal varices. Gastric corpus mucosal blood flow measurements by both techniques after surgery were not significantly different from those before surgery. Thus, in this animal model of portal hypertension, gastric mucosal blood flow was unchanged at a time when esophageal varices had developed. In acute ulcer disease, an increase in flow at the edge of the ulcer compared with the adjacent normal appearing mucosa was suggested. This implies that the presence of an active ulcer stimulates increased flow to the ulcer margin. This increase in flow might be an important factor in ulcer healing and warrants further study. The feasibility of endoscopic application of the commercially available reflectance spectrophotometric unit makes such clinical studies possible. Furthermore, in addition to the study of ulcer disease, the ease with which the reflectance spectrophotometric measurements can be obtained will make this potentially useful in the early endoscopic diagnosis of ischemic bowel disease in the segments accessible to the endoscope. The pattern of IHB and IS0 2 in various types of acute and chronic colitis can also be determined. Hypotheses concerning a potential role of altered mucosal perfusion in these diseases in humans can now be tested by endoscopic studies. ACKNOWLEDGMENTS
This work was supported by the National Institute of Arthritis and Metabolism and Digestive Diseases grant AM 34840 and American Society for Gastrointestinal Endoscopy Career Development Award H850208, Veterans Administration Medical Research Funds, and University of California, Los Angeles Academic Senate grant 4063. The authors acknowledge the technical assistance of Ernst Tallos, Ken Hirabayashi, Duke Martin, Dave Hill, Rebecca Chan, and Dr. Gustavo A. Machicado and thank Drs. Terry Ready and Janet Elashoff for assistance in statistical analysis and David Claus for preparation of the. manuscript. REFERENCES 1. Leung F, Itoh M, Hirabayashi K, Guth P. Role of blood flow in gastric and duodenal mucosal injury in the rat. Gastroenterology 1985;88:281-9. 2. Leung F, Guth P, Scremin 0, Golanska E, Kauffman G Jr. Regional gastric mucosal blood flow measurements by hydrogen gas clearance in the anesthetized rat and rabbit. Gastroenterology 1984;87:28-36. 3. Murakami M, Moriga M, Miyake T, Uchino H. Contact electrode method in hydrogen gas clearance technique: a new
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