Cardiac loops have been used extensively to study myocardial function. With changes in cardiac pump function, loops are shifted to the right or left. Functional luminal imaging probe (FLIP) recordings allow for loop analysis of the anal sphincter and puborectalis muscle (PRM) function. The goal was to characterize anal sphincter area-pressure/tension loop changes in fecal incontinence (FI) patients. Fourteen healthy subjects and 14 patients with FI were studied. A custom-designed FLIP was placed in the vagina and then in the anal canal, and deflated in 20-ml steps, from 90 to 30 ml. At each volume, subjects performed maximal voluntary squeezes. Area-pressure (AP) and area-tension (AT) loops were generated for each squeeze cycle. Three-dimensional ultrasound imaging of the anal sphincter and PRM were obtained to determine the relationship between anal sphincter muscle damage and loop movements. With the increase in bag volume, AP loops and AT loops shifted to the right and upward in normal subjects (both anal and vaginal). The shift to the right was greater, and the upward movement was less in FI patients. The difference in the location of AP loops and AT loops was statistically significant at volumes of 50 ml to 90 ml ( P < 0.05). A similar pattern was found in the vaginal loops. There is a significant relationship between the damage to the anal sphincter and PRM, and loop location of FI patients. We propose AP and AT loops as novel ways to assess the anal sphincter and PRM function. Such loops can be generated by real-time measurement of pressure and area within the anal canal. NEW & NOTEWORTHY We describe the use of area-pressure (AP) and area-tension (AT)-loop analysis of the anal sphincters and puborectalis muscles in normal subjects and fecal incontinent patients using the functional luminal imaging probe (FLIP). There are differences in the magnitude of the displacement of the loops with increase in the FLIP bag volume between normal subjects and patients with fecal incontinence. The latter group shifts more to the right in AP and AT space.

Functional luminal imaging probe (FLIP) has been used to measure the distensibility of the anal canal. We hypothesized that with increasing distension of the anal canal with FLIP there will be an increase in length of the anal sphincter muscle allowing measurement of the length-tension function of anal sphincter and puborectalis muscles (PRM). We studied 14 healthy nulliparous women. A custom designed FLIP bag (30mm diameter) was placed in the vagina and then in the anal canal, distended in 10ml steps with volumes ranging from 30-90ml. At each volume, subject performed maximal voluntary squeezes. Length tension measurements were also made with a manometric probe system. Tension was calculated (pressure x radius) in Newtons/meter using a custom software program. Peak tensions at different FLIP volumes was compared with the manometric data. No change in the luminal CSA was noted at low fluid volumes; the sphincter muscles were able to fully collapse the FLIP bag within the anal canal/vagina even at rest. At larger volumes, with each squeeze there was an increase in the bag pressure and reduction in the cross-sectional area, which represents concentric contraction of the muscle. Both rest and squeeze tension increased with the increase in volume in the anal as well as vaginal canal indicating that the EAS and PRM produce more tension when lengthened. FLIP device, which has been used to describe the distensibility of the anal canal can also provide information on the length-tension function of the anal sphincters and PRM.

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Aim:To determine if a biofeedback therapy that includes concentric resistance exercise for the anal sphincter muscles can improve muscle strength/function and improve AI symptoms compared to the traditional/non-resistance biofeedback therapy.Background: Biofeedback therapy is the current gold standard treatment for patients with anal incontinence (AI). Lack of resistance exercise biofeedback programs is a limitation in current practice. Methods: Thirty-three women with AI (mean age 60 years) were randomly assigned to concentric (resistance) or isometric (non-resistance) biofeedback training. Concentric training utilized the Functional Luminal Imaging Probe to provide progressive resistance exercises based on the patient's ability to collapse the anal canal lumen. Isometric training utilized a non-collapsible 10 mm diameter probe. Both groups performed a biofeedback protocol once per week in the clinic for 12 weeks and at home daily.High definition anal manometry was used to assess anal sphincter strength; symptoms were measured using FISI and UDI-6. 3D transperineal ultrasound imaging was used to assess the anal sphincter muscle integrity.Results: Concentric and isometric groups improved FISI and UDI-6 scores to a similar degree. Both the concentric and isometric groups showed small improvement in the anal high-pressure zone; however, there was no difference between the two groups.Ultrasound image analysis revealed significant damage to the anal sphincter muscles in both patient groups. Conclusions: Concentric resistance biofeedback training did not improve the anal sphincter muscle function or AI symptoms beyond traditional biofeedback training. Anal sphincter muscle damage may be an important factor that limits the success of biofeedback training.

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