Design and Testing Novel Wearable Instrumentation for Assessing Pelvic Floor Function and Exploring Continence Mechanisms

Abstract

Urinary incontinence (UI) and fecal incontinence (FI) affect 20% of North Americans, with a higher prevalence in women and the elderly. The prevention and treatment of these conditions unfortunately leaves much to be desired, despite the $88B and $49B annual U.S. costs associated with managing UI and FI, respectively. Recent research suggests that the major problem lies with the sphincters themselves, rather than other structures. More needs to be learned about how age, injury and disease affect these sphincters. The literature is reviewed in Chapter 1, knowledge gaps are identified and testable hypotheses formulated. In Chapter 2, we describe the first subject-specific, 3-D, biomechanics model of the urethra capable of contracting the three individual muscle layers along their lines of action. This was developed to better understand how the different layers contribute to urethral closure during activities of daily living. Exploratory studies of the vascular plexus suggest a role in affecting functional urethral length. While this model helps one to understand which muscles contribute to continence, it could not provide insights into the amount of urine leaked which, after all, is what bothers women the most. In Chapter 3, we describe a novel approach for quantifying urine leakage both in and out of the clinic. While one can presently obtain micturition flowmetry in the seated posture in the clinic, this precludes the possibility of any information being gathered on leakage during activities of daily living (ADL). Instead, a patient must keep a leakage diary for several days, which unfortunately is prone to recall bias and other errors. Therefore, a novel wearable personal uroflowmeter (PUF) was invented and developed to attach over the urethral meatus in women to collect urine flow rate and leakage data during ADL leakage episodes. This was connected with a waist-mounted inertial measurement unit (IMU) to provide data on the pose and ADL associated with the volume of each leakage episode. Chapter 4 describes the first-in-human testing of the PUF in women in and outside the clinic, demonstrating the feasibility of wearable uroflowmetry. Moreover, theoretical studies of labia majora coaptation suggest that the labia can inadvertently form a potential reservoir for urine leakage during a sneeze or cough. This insight will help eliminate the confusion over the relationship between the ADL causing the passage of urine through the urethra (i.e., a cough) and that which later causes urine to leak from the labial reservoir (i.e., rising from a chair). A few incidents of this phenomenon were measured for the first time while testing the PUF in women. In terms of anorectal function, Chapter 5 reports the design and development of a disposable point-of-service instrumented anorectal manometry glove (“digital manometry”, DM) for testing anal sphincter and anorectal function at an order of magnitude lower cost than the standard high resolution anorectal manometry (HR-ARM). Chapter 6 reports first-in-human testing of the DM device in patients with and without FI and chronic constipation. Comparisons of the DM and HR-ARM results show reasonable agreement. In addition, the DM also provided myoelectric information useful for identifying paradoxical contraction of the anorectal muscle in patients with dyssynergic defecation. In summary, the dissertation provides novel and inexpensive approaches for a clinician or researcher to better document and understand incontinence.