Medical knowledge | Infectology » Thomas P. Rauth - Pressure Volume Curves Define the Optimal Filling Pressure for Weight Loss in Patients with the Laparoscopic Adjustable Gastric Band

Source: http://www.doksinet Pressure Volume Curves Define the Optimal Filling Pressure for Weight Loss in Patients with the Laparoscopic Adjustable Gastric Band MPH Protocol Thomas P. Rauth, MD June 30, 2006 Background: Obesity, defined as BMI ≥ 30 kg/m2, has become a national epidemic with significant healthcare implications.1-3 In 2001, nearly 21% of the US population met BMI criteria for obesity and 23% carried a BMI ≥ 40 kg/m2. By 2005, the estimated prevalence of obesity climbed to 25% and the trend in increasing weight appears to be continuing4. The health consequences of obesity are well known and include diabetes mellitus, weight related osteoarthritis, coronary heart disease, hypertension and dyslipidemia. In 2000, annual direct health care costs for obesity-related medical conditions in the United States were estimated to be nearly $40 billion, with another $30 billion related to efforts at weight reduction.5 Studies demonstrate that traditional methods of weight loss,

including diet and exercise, fail to promote long-term weight reduction.6 It has been shown that the surgical management of morbid obesity is the most effective means of producing long-term weight loss.7, 8 Several options for the surgical management of morbid obesity are available through the multidisciplinary Vanderbilt Center for Surgical Weight Loss: open gastric bypass, laparoscopic gastric bypass and laparoscopic adjustable gastric banding (Lap-Band System, Inamed, Santa Barbara, CA). Laparoscopic adjustable gastric banding has produced sustained weight loss with a low rate of severe complications.9-11 The minimally invasive approach, individual adjustability and complete reversibility of the device are quickly making it the preferred means of managing morbid obesity for a large group of patients. Following placement of the Lap-Band, excess weight is lost at a rate of approximately 1-2 pounds per week for the first year. Published literature reports 35-72% excess weight loss at

36 month follow up11-13. Most importantly, the reduction or cure of weight related comorbid conditions (hypertension, type II diabetes, gastroesophageal reflux, sleep apnea, arthritis and incontinence) parallels the success of the roux-en-Y gastric bypass procedure.11 Gastric banding promotes weight loss by reinforcing a program of physician supervised caloric restriction. Encircling the band around the proximal stomach functionally decreases the stomach’s capacity to 30-50 mL while simultaneously producing a mild obstruction to the passage of food. Patients thus are restricted in their intake and experience satiety earlier. One feature unique to the Lap-Band is its adjustability The device consists of an inflatable diaphragm lining the inner circumference of a 10 cm silicone band. This diaphragm, which holds a total of 4 mL of fluid, is connected to an implantable infusion port which sits within the soft tissue of the abdominal wall. Once placed in the operating room and secured

about the proximal stomach, it is left in the deflated position until a postoperative visit at 6 weeks. Based upon an institutional Lap-Band protocol (Figure 1) which assesses initial weight loss and feelings of satiety, the implanted infusion port is accessed and the Lap-Band is filled with saline at the 6 week visit. At each follow up visit, subsequent Lap-Band adjustments are made using the institutional Lap-Band protocol based upon the following clinical parameters: weight loss, satiety, frequency of dysphagia and intolerance of various foods. 1 Source: http://www.doksinet Figure 1: Current Lap-Band Adjustment Protocol from the Vanderbilt Center for Surgical Weight Loss The adjustability of the Lap-Band, however, has several limitations. Complications related to the infusionport site have been reported in 7-14% of patients13-16 Soft tissue infection, infusion-port leakage and damage to the connection tubing are all well documented and are related to the blind, percutaneous

approach used to access the infusion port with the non-coring needle. While relatively infrequent, port site complications carry significant morbidity. The management of each of the three most common complications requires an additional operative procedure at the expense of patient cost and convenience. The single most effective way to limit the incidence of port-site complications is to decrease the number of times that the port is manipulated. A second shortcoming of the Lap-Band system is that there is no consensus in the literature regarding the best method of postoperative band management nor is there a universally accepted algorithm outlining how much volume to instill into the inflatable diaphragm to create optimal weight loss. Some centers choose incremental, short interval adjustments in Lap-Band volume while others prefer one-time bolus 13, 17, 18 Placing too little volume in the Lap-Band will slow the rate of weight loss and require more filling. frequent clinic visits for

volume adjustments, increasing cost and the risk of potential complications. Conversely, placing too much volume in the Lap-Band can lead to excessive dysphagia, band slippage and proximal gastric pouch dilation. Furthermore, several studies have demonstrated that there is considerable inter-patient variability in the Lap-Band volume that maximizes weight loss and limits adverse symptoms.13 In a series of 379 patients who underwent adjustable gastric banding, Busetto et al report that mean band volume for the population producing optimal weight loss was 2.8 mL (SD 12 mL) Using their data, approximately 68% of the population had band volumes between 1.6 and 40 mL This range in band volumes, using the current volume based protocol, is equivalent to five separate 0.5 mL band adjustments with each manipulation increasing the risk of port-site complication and patient cost. The current volume guided protocol for Lap-Band adjustments fails to utilize objective data to guide band filling and

is fraught with considerable inter-patient variability. The clinical decision making involved in band adjustment is based upon the patient’s subjective feelings of satiety and dysphagia and the clinician’s anecdotal experience (see above protocol). Few attempts have been made to standardize Lap-Band adjustment using an evidence based approach. In its original design described by Kuzmak19, an elaborate method of calibration was used to set the gastric stomal diameter during placement of the adjustable gastric band. Using and automated esophageal manometer (Gastrostenometer®) and knowledge from previous experience with vertical banded gastroplasty, the gastric band was inflated to 2 Source: http://www.doksinet create a small gastric pouch with a 12.5 mm diameter outlet This process of intra-operative filling was poorly tolerated with most patients experiencing significant dysphagia and regurgitation during the immediate postoperative period. It was thought that the 125 mm

gastric stoma became obliterated by normal post-operative edema leading to gastric outlet obstruction. At the recommendation of the manufacturing company, this method was abandoned and currently, no saline is placed within the band at the time of operation. Ex-Vivo Pressure-Volume Curve Analysis – Available Data: Following the lead of Kuzmak, several investigators have tried to standardize gastric band filling by looking at the physical properties of the device. Two groups have separately attempted to describe the relationship between band volume and intra-band pressure in the Lap-Band. Ceelen et al compare the pressure-volume curves of two Lap-Bands to two Swedish Adjustable Gastric Band (SAGB, pending FDA 11 approval) in Figure 2 below. Concentrating on the data points from the Lap-Band device, their analysis fails to provide a clear description of the pressure-volume relationship for several reasons. First, the pressure recordings for the Lap-Band were taken at band volumes of 0

through 2 mL (in 0.5 mL increments) when clinically; the band may be inflated to 4 mL. Also, there is an unexplained 96 kPa of pressure within the bands at a volume of 0 mL which, from an engineering standpoint, is only possible if the manometer was measuring ambient atmospheric pressure at an altitude of roughly 1500 ft. Lastly, they present ex-vivo data only, there are no pressure-volume recordings taken with the band in place about the proximal stomach. The data does not consider how the pressure-volume relationship of the band changes when it compresses the stomach wall. Figure 2: Ex-vivo PV Curves from 2 Lap-Bands and 2 SABG’s. The included data set lists pressure recordings for 2 Lap-Bands in kPa for volumes 0-2mL in 0.5mL intervals 101325 kPa = 760mmHg = 1 ATM In another attempt to describe the physical properties of adjustable gastric bands, Lechner graphically displays the pressure-volume curves of four commercially available gastric bands in Figure 3 below.20 The graph

suggests that the Lap-Band (LAP) starts with a baseline volume of 3 mL and is filled with an additional 5 mL to a total of 8 mL, a volume profile for which the device has not been approved. In fact, one questions why the investigators placed twice the recommended volume within the band. Furthermore, when units are standardized between the Ceelen’s and Lechner’s data (101.325 kPa equals 760 mmHg), a comparison of intra-band pressures shows them to be quite different (Fig. 4) Using available published data, it becomes quite evident that the pressure-volume relationship of the Lap-Band remains unclear. 3 Source: http://www.doksinet Figure 3: Ex-Vivo pressure volume curves for 4 clinically available gastric bands (SAGB – Swedish adjustable gastric band; LAP – Lap-Band; LAP-VG – Vanguard band; AMI – AMI band 0 Pressure (mmHg) 100 200 300 400 PV-Curves: Available Published Data 0 2 4 Volume (mL) Ceelen 1 Lechner 6 8 Ceelen 2 Figure 4: Standardized graphical

representation of pressure-volume data from Ceelen and Lechner In Vivo Analysis – Available Data: The only published attempt to quantify band adjustment using objective data is reported in the same series of articles by Lechner et al.20, 21 In these, they report a technique where intra-band pressure measurements are recorded at the time of band adjustment. Using this technique of band manometry, a pressure tracing is recorded during wet swallows. This is analogous to trans-nasal esophageal manometry performed using intra-esophageal pressure transducers. The author reports that primary and secondary esophageal peristaltic waves were measured during gastric compression at various band volumes. For the series of 25 patients, the mean band pressure at which there was no evidence of secondary peristalsis following a wet swallow was 25.5 mmHg Using a conservative approach, an arbitrary filling pressure of 20 mmHg was selected and all patients were filled to that pressure. No patient in

this series developed dysphagia following the pressure guided band adjustment. While illustrative, the study has several shortcomings. First, no attempt was made to follow weight loss in the individuals who underwent pressure directed filling. Thus, while the series demonstrates that this 4 Source: http://www.doksinet method is feasible, there was no weight loss data to validate it as an effective means to adjust gastric bands. Several assumptions were also made with respect to the experimental methods The authors claim to measure esophageal peristalsis with band manometry during sequential wet swallows. With correct placement of the gastric band around the proximal stomach, it would be more accurate for the authors to describe their measurements as gastric peristaltic waves, not esophageal. Without the concurrent use of esophageal manometry catheters, one cannot assume that pressure tracings recorded from the stomach approximate those more proximally in the esophagus. The group

did not make the effort to correlate intra-band pressures to intra-luminal esophageal pressures before publishing their data as a surrogate for esophageal manometry. Furthermore, because the adjustable gastric band used in the study has not received FDA approval for use in the U.S, the applicability of their study to our population is limited. Lastly, the intra-band pressure data from the Lap-Band system in this study (Fig 3) is not consistent with preliminary results from this institution nor with other published data (Fig. 2) raising the concern that the current instrumentation or techniques used to measure band pressures have not been perfected. Purpose: The current algorithm guiding Lap-Band adjustments is not based upon objective evidence. This is in part due to the fact that there is significant inter-patient variability in the band volume that generates efficient weight loss. Previous attempts to devise a protocol based upon empiric evidence have been ineffective, insufficient

or inapplicable. Specific aims of this project: 1. Describe a pressure-volume relationship for the Lap-Band System that: i. explains the large amount of inter-patient variability seen in Lap-Band volumes ii. supports the use of intra-band pressure for band adjustment 2. Describe how the pressure-volume curve of the Lap-Band changes over time 3. Describe the relationship between weight loss and intra-band volume 4. Describe the relationship between weight loss and intra-band pressure i. Define the optimal filling pressure that generates efficient weight loss with minimal adverse symptoms 5. Construct a pressure-directed adjustment protocol that: i. overcomes the problem of inter-patient volume variability ii. decreases the number of post-operative band adjustments Study Design: Study Design: Prospective Observational Study (E+) Our ability to construct a pressure-guided algorithm for Lap-Band adjustment is based on the following assumption: while there is considerable variability in

the Lap-Band volume that produces weight loss, the pressure within the Lap-Band that restricts intake and produces satiety will be similar among all patients. With IRB approval and informed consent, a cohort of patients will be identified and followed for one year following insertion of the laparoscopic adjustable gastric band. Following current, institutional guidelines, each patient will receive the standard postoperative band adjustment schedule. At each adjustment, the intra-band pressure will be measured at the volume designated by the current algorithm. Correlating intra-band pressure to weight loss over one year will identify a pressure at which weight loss is maximized and adverse symptoms of dysphagia are minimized. Variability in the cohort’s intra-band pressure will be compared to the variability in band volume over the same time period. We hypothesize that during 5 Source: http://www.doksinet periods of sustained weight loss (1-2 lb./week between clinic visits),

intra-band pressure for the cohort will demonstrate less variation than band volume. Enrollment / Randomization: Consideration for bariatric surgery at the Vanderbilt Center for Surgical Weight Loss is based upon the 1991 NIH Consensus Statement regarding surgical management of morbid obesity: the patient must have a BMI > 40 or ≥ 35 with associated weight related comorbidities, must have failed a supervised weight loss program and must successfully complete preoperative psychologic counseling and receive support for surgery. Those who meet the criteria for bariatric surgery will then be considered for adjustable laparoscopic gastric banding. Contraindications to Lap-Band placement are established as: The presence of an inflammatory disease or condition of the gastrointestinal tract, such as ulcers, severe esophagitis, or Crohn’s disease. The presence of severe heart or lung disease or any autoimmune connective tissue disorder. The presence of a problem that could cause

bleeding in the esophagus or stomach including esophageal or gastric varices, congenital or acquired intestinal telangiectasia. The presence of portal hypertension Abnormality of the esophagus, stomach, or intestine (congenital or acquired). The presence of an intra-operative gastric injury, such as a gastric perforation at or near the location of the intended band placement. The presence of cirrhosis. The presence of chronic pancreatitis Pregnancy Addiction to alcohol or drugs. Age <18 years The presence of a systemic infection The use of chronic, long-term steroid treatment. Inability to adhere to dietary requirements of the Lap-Band system Intolerance of the materials in the device. Those patients who refuse to sign the informed consent document fail to meet institutional criteria for weight loss surgery (as detailed above) or have any one of the contraindications to Lap-Band placement will be excluded from enrollment. Consecutive patients at the Vanderbilt Center for the

Surgical Weight Loss who receive multidisciplinary approval for laparoscopic gastric banding will be offered enrollment in the study in a non-randomized, non-blinded fashion. In this manner, there will be no preference for patient selection based upon gender, ethnicity, preoperative BMI, comorbidity etc. The composition of anticipated participants will be similar to the population who seeks bariatric surgery at Vanderbilt University Medical Center and nationally: morbidly obese (BMI ≥ 35) persons with weight related comorbidities, ages 18-65. Study participants will be followed for one year after Lap-Band placement Patients enrolled in the study may elect to withdraw at anytime without penalty. Subsequent postoperative care and Lap-Band adjustments through the Vanderbilt Center for Surgical Weight Loss will continue regardless of enrollment status. Patients who choose to enroll in this study and continue their post-operative care through the Vanderbilt Center for Surgical Weight Loss

will be followed as a study patient for the first year following the operation. Consent: In addition to the standard, Vanderbilt University informed consent sheet that is signed prior to undergoing laparoscopic adjustable gastric banding, each patient will be required to read and sign the Vanderbilt University Institutional Review Board Informed Consent Document for Research (see attached form). Those patients who refuse to sign the informed consent document will be excluded from enrollment. Methods: This protocol does not significantly deviate from the clinical pathway currently employed in the insertion and subsequent adjustment of the laparoscopic adjustable gastric band (Lap-Band). Patients who agree to participate will not require additional invasive procedures, blood draws, hospital or outpatient clinic visits. The “Institutional Protocol”, referred to below, is a pre-existing algorithm currently in use at the Vanderbilt Center for Surgical Weight Loss that guides

postoperative Lap-Band adjustment and will not be modified for the purposes of this protocol. Similarly, the intake demographic assessment that study 6 Source: http://www.doksinet patients will complete is a pre-existing document that is currently employed in the clinic and will not be modified as part of this protocol. Pressure Measurement: All Lap-Band pressure measurements will be performed using the same Validyne Multiple Range Pressure Transducer (Northridge, CA) connected to a digital recording device. The device is calibrated each day before its use. Eighty-four inch pressure tubing (Edwards Lifesciences ref:50P184) is flushed with 0.9% NaCl and connected to a three-way stopcock and 10 mL sterile syringe Ex-vivo pressure measurements will be made over the full 4 mL volume of the band in 0.5 mL increments Due to technical considerations, ex-vivo pressure measurements are made without the use of the Lap-Band port by directly connecting the 10 mL syringe to the band’s

silastic connection tubing. In-vivo pressure measurements are performed after the Lap-Band port is accessed in the usual fashion with a non-coring 4 inch Huber needle. A three-way stopcock connects the syringe to the pressure tubing and intra-band pressure measurements are recorded. Group 1: New Lap-Band Patients Upon enrollment, the following data will be collected for each patient: demographic data, baseline weight and weight associated comorbidities. Baseline assessments of satiety and dysphagia symptoms will be recorded on the clinic intake form at the Vanderbilt Center for Surgical Weight Loss. Intraoperative Procedure: An ex-vivo pressure-volume curve will be determined for each Lap-Band prior to placement within each patient. This will be performed in the operating room, prior to insertion, by one of the three study physicians in accordance with the sterile-field practices of the Vanderbilt University operating room suite. Pressure recordings will be measured in 05 mL

increments using a Validyne Multiple Range Pressure Transducer (Northridge, CA) and standardized pressure tubing. In this manner, each study patient will have their own ex-vivo pressure-volume curve to serve as a control. The LapBand will then be inserted using the pars flaccida technique As per routine practice, the infusion port will be accessed, flushed and tested for leaks. With the Lap-Band in place, in-vivo pressure and volume measurements will be obtained. Pressure measurements for volumes 0 through 4 mL (in 05 mL increments) will be recorded. Total additional operative time incurred with both the ex-vivo and in-vivo pressure-volume measurements will not exceed 10 minutes. First Postoperative Lap-Band Adjustment: The first post-operative Lap-Band adjustment occurs at approximately 6 weeks following the operation. At this visit, study patients will be asked to asses levels of satiety and dysphagia based upon a postoperative clinic note used by the clinic at the Vanderbilt Center

for Surgical Weight Loss. Body weight will be measured and percent excess weight loss calculated The infusion port will then be accessed as it would for any patient with a Lap-Band at the first post-operative visit. The same Validyne manometer will measure the pressure immediately following port access; this pressure will be denoted “opening pressure”. Then, similar to the intraoperative technique, pressure measurements for volumes 0 through 4 mL (in 0.5 mL increments) will be recorded With pressure measurements complete, the 4 mL of saline will be withdrawn. The Lap-Band will then be filled with the volume of saline designated by institutional protocol for the first postoperative visit (1mL). A final pressure measurement denoted “closing pressure” will be recorded and the port will be decannulated. Subsequent Lap-Band Adjustments: Study patients will be seen, questioned and examined every 6 weeks until the rate of weight loss approximates 1-2 pounds per week without severe

symptoms of dysphagia. At each subsequent clinic visit, the patients will again assess levels of satiety and dysphagia based upon the clinic questionnaire. The patients’ weight will be recorded If an adjustment is necessary based upon current institutional Lap-Band protocol, a complete set of pressure-volume measurements will be recorded (0-4 mL in 0.5 mL increments) Once weight loss has stabilized, follow-up will be every 3-6 months as necessary until the patient completes the study at 12 months. 7 Source: http://www.doksinet Group 2: Current Lap-Band Patients To further understand the relationship between weight loss and intra-band pressure measurements, we will retrospectively enroll patients who have previously undergone Lap-Band placement through the Vanderbilt Center for Surgical Weight Loss. Again, no significant deviation from the standard postoperative Lap-Band protocol will be made. Patients who agree to participate will not require additional invasive procedures, blood

draws, hospital or outpatient clinic visits. At the time of enrollment, the following information will be collected: demographic data, date of Lap-Band placement, pre-operative and current weight, weight loss to date, current band volume and the number of band adjustments. At each clinic visit, the patient will assess levels of satiety and dysphagia The decision to make a Lap-Band adjustment will be based upon institutional protocol. If an adjustment is made, pressure measurements for volumes 0 through 4 mL (in 0.5 mL increments) will be recorded The Lap-Band will then be filled with the volume of saline designated by institutional protocol, a final pressure will be recorded and the port will be decannulated. Once weight loss has stabilized, follow-up will be every 3-6 months as necessary until the patient completes the study at 12 months from the date of initial Lap-Band placement. Data Collection and Sample Size: Data Collection: A research file will be created for each study

patient and study data will be collected by one of the study physicians or nurse practitioners. The data will be entered into a database and stored in the locked office on the password protected computer of the principle investigator. Patient identifiers are concealed, all patient information will be de-identified at the time of database entry and each patient will randomly be assigned a unique study identification number. Only the study physicians will be able to correlate the patients’ study identification number with identifying information. Data for each study patient will be collected and recorded for one year following placement of the Lap-Band (patients retrospectively enrolled with likewise be followed until one year from the initial placement of their Lap-Band). The study results will be kept in the research file for at least six years following completion of the study. At that time, research data that has not been put in the medical record will be destroyed. Any research

data that has been put into the patient’s permanent medical record will be kept indefinitely. Sample Size Justification: Currently, there are no published studies reporting in-vivo pressure-volume curves for the Lap-Band, nor are there any studies correlating intra-band filling pressures to weight loss in patients with the Lap-Band. Without available data, sample size and power calculations cannot be performed. We set out to recruit 25 patients and have written for IRB approval to enroll up to 100 patients in this preliminary study. Statistical Analysis: Description of Pressure Volume Curve: The pressure-volume relationship of the Lap-Band system will be analyzed using regression modeling. A mixed effects regression model will describe how significantly different band volumes generate the same intra-band pressure for the study cohort. This will validate the concept of pressure directed Lap-Band adjustment. Description of Pressure Volume Curve over Time: We expect that with weight

loss, the pressure-volume relationship for a given patient will change over time. Specifically, we anticipate that over time, significantly more volume will be required to generate the same intra-band pressure. This relationship is a function of weight loss for the group. Capturing consecutive clinical encounters for each patient will provide a longitudinal description of this phenomenon. Using the regression model constructed for the initial analysis, multivariate analysis of variance with time dependent covariables will be used to describe the change in pressure-volume relationship over time. Description of Weight Loss: A separate mixed effects regression model will be constructed to model the effect that band volume and intra-band pressure have on weight loss. Time dependent covariables will be included in the model to account for the changes in the rate of weight loss that are known to occur following placement of the gastric band. Analysis of the models should demonstrate that

intra-band 8 Source: http://www.doksinet pressure correlates more closely with weight loss than does intra-band volume. From this, an optimal pressure range for band filling will be determined. Adverse Event Reporting: As stated previously, the study protocol does not require significant deviation from standard institutional protocol following placement of the Lap-Band. This study simply calls for the measurement of Lap-Band pressures during insertion and subsequent adjustments. It does not change the standard Lap-Band protocol utilized by the Vanderbilt Center for Surgical Weight Loss. The risk that this protocol contributes to the established risk inherent in laparoscopic gastric band surgery is negligible. It is widely accepted that the risks of Lap-Band surgery are outweighed by the potential benefits seen in weight loss. Lap-Band placement will be performed in the Vanderbilt University operating room by surgeons trained in advanced laparoscopic technique. All Lap-Band

adjustments will be made in the Vanderbilt University Surgery Clinic by physicians/nurse practitioners trained in access port cannulation. Safety concerns and adverse outcomes may be reported by any one of the study physicians or nurse practitioners and will be monitored by the Principle Investigator. These events will be promptly reported to the study participant, co-investigators and IRB committee on a case by case basis. Study Limitations: There are several limitations to the study. We envision that the most useful information regarding band pressure and weight loss will be gained from the longitudinal data gathered from consecutive clinical encounters for each patient. Conservatively, we estimate 20% of patients in Group 1 (new Lap-Band patients) will have missing data due to the logistics of capturing every clinical encounter. The missing data will be accounted for in the statistical analysis. Missing data will reduce the power of the analysis but should not introduce bias. A

minority of patients who undergo placement of the Lap-Band experience significant weight loss with the band empty or only minimally filled; this is termed the “motivated patient effect”. It is believed that undergoing an operation serves as motivation for these patients to adhere to the strict dietary restriction required for weight loss. We expect that these patients will experience weight loss at band pressures significantly lower from the rest of the cohort. Because such patients are encountered in all bariatric surgical practices, these individuals will be included in all statistical analysis so that the results of the study are applicable to the general population. The number of these outliers is expected to be less than 10% and should not materially affect the outcome of the study. In order to minimize the possibility of accidental port or tubing damage during band adjustment, patients who do not require band adjustment using the current protocol will not have their bands

accessed for the sole purpose of gathering data. Thus, patients who experience adequate weight loss generate less data than patients who fail to loose weight and require more frequent adjustments. We anticipate that this will occur in a minority of patients. Previous studies suggest that most patients will require between 6 and 8 adjustments during the first 12 months following Lap-Band placement and thus will generate 6 to 8 sets of pressure data. 1. 2. 3. Mokdad AH, Ford ES, Bowman BA, et al. Prevalence of obesity, diabetes, and obesity-related health risk factors, 2001. Jama 2003; 289(1):76-9 Visscher TL, Seidell JC. The public health impact of obesity Annu Rev Public Health 2001; 22:355-75. Mokdad AH, Bowman BA, Ford ES, et al. The continuing epidemics of obesity and diabetes in the United States. Jama 2001; 286(10):1195-200 9 Source: http://www.doksinet 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. Survey NHI. Prevalence of Obesity in US, 2006 Sugerman

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14(4):520-3 Kuzmak LI. A Review of Seven Years Experience with Silicone Gastric Banding Obes Surg 1991; 1(4):403-408. Lechner W, Gadenstatter M, Ciovica R, et al. In vivo band manometry: a new access to band adjustment. Obes Surg 2005; 15(10):1432-6 Fried M, Lechner W, Kormanova K. Physical principles of available adjustable gastric bands: how they work. Obes Surg 2004; 14(8):1118-22 10