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Introduction: Lap band adjustments have traditionally relied upon volume adjustment. However, individual anatomy, location of band placement, and time of implantation between patients vary greatly, and the standard size of the lap band does not accommodate for these variations. Thus, band volume does not allow for a reliable explanation to weight loss following an adjustment. Another factor that may serve to explain the weight loss seen after adjustment is intra-band pressure. This study seeks to compare correlations between intra-band pressure and band volume with duration of band placement and average weight loss.Participants: A random sample of 40 morbidly obese patients with the AP LAP-BANDTM implanted between 2007 to 2010 was enrolled in the study. Participants must have had the band implanted for more than three months before the time of study as well completing a 2nd follow up visit after the adjustment visit within 90 days. Adjustments were conducted using a manometer to measure intra-band pressure.Results: Participants in this study loss an average of 7.6 lb ± 0.5 lb over a period of 30 days after their adjustment. Furthermore, greater weight loss is correlated with more recent band implantation. Interestingly, there is also a positive correlation between intra-band pressure and time of band implantation. It takes more intra-band pressure to obtain weight loss as time goes on. Data reveals that the correlation between band volume and time of band placement is very weak compared to intra-band pressure (R2 = 0.07 and R2 = 0.66 respectively). Conclusion: This study reveals that intra-band pressure is more highly correlated to weight loss after an adjustment than adjusted band volume. Furthermore, it seems that intra-band pressure increases as time goes on after the initial date of band implantation. As time passes, it takes more pressure to get the same response from the band. Perhaps the capsule formation around the band and foreign body reaction cause the band to need more pressure to inflate. Therefore, it is critical that patients take the band seriously right after they have the procedure done as it takes more pressure to achieve the same weight loss as time passes.
Intra-Band Pressure and Average Weight Loss

Year of Band Implantation	Average Intra-Band Pressure (psi)	Average Weight Loss (lbs)	Year of Band Implantation
9/2007	3.70	-3.5	2007
1/2008	2.35	-6.4	2008
4/2008	2.90	-6.5	2009
8/2008	2.66	-9.8	2010
1/2009	2.27
4/2009	2.05
8/2009	1.62
1/2010	1.63

Intra-band pressure data are divided into groups of three month interval. Average weight loss data are group by one year interval.