The purpose of this study is to increase the utility of quantitative physiological sensing during urodynamic studies. Specifically, we hope to capture and quantify bladder pressure parameters during bladder filling to target signals that may be associated with autonomous or low amplitude rhythmic contractions. 
Numerous studies have demonstrated the presence of low amplitude rhythmic contractions in in-vitro detrusor tissue strips [1], whole bladders in preclinical studies and early clinical testing [2]. These contractions, and their organization into organ-level signals, have also been implicated in dysfunctions of lower urinary tract control (see review in [3]). The efficient ability to capture and quantify these signals in clinical settings remains in its infancy. For temporal dynamics and spectral composition of pressure signals, appropriate tests and scalable clinical methods are not readily available to analyze data, link outcomes with population or diagnosis norms or to make comparisons over time within a single patient.  
In this retrospective clinical study, our primary aim was to establish an initial, scalable workflow to manage and analyze temporal pressure dynamics using existing urodynamics data. A secondary aim was to test early functional implications of these measurements by testing for fill-dependent changes during cystometric filling. As a proof of concept for this approach, we specifically tested two hypotheses: 1) Does the spectral power for bladder pressure across this frequency band (1-10 cycles per minute (CPM)) change with bladder filling? 2) Does the mean weighted frequency of bladder pressure dynamics change with bladder filling?

Deidentified data from 12 recent urodynamics tests performed at the clinic over a 60-day period were extracted from a Laborie Aquarius XTTM multichannel UDS system (Laborie Medical Technologies, Toronto, Canada) and converted to a suitable format for analyses in MATLAB. Each urodynamics series was divided into 300-second segments and smoothed using a 10-point moving average. Pressure changes over time were calculated for each segment to test for frequency components of both vesical and abdominal pressures (P¬ves; P¬abd). A reduction in True Volume was used as a marker of voiding or leakage and restricted the analysis to filling-only segments. Temporal dynamics of the P¬ves and P¬abd vs time were calculated for the frequency range of 1-10 CPM using Fast Fourier Transform (FFT) with a resolution of 0.2 CPM for 300s segments. Segments abbreviated by a void were analyzed with a resolution of 0.35 to 1.55 CPM depending upon their duration. For frequencies with FFT(P¬ves) > FFT(P¬abd), the total FFT power attributable to the vesical-only signal and the weighted mean frequency for the spectral distribution were calculated for each filling segment.

The spectral power and weighted mean frequency were measured for a total of 48 segments in 12 data sets. Voiding was not detected in 3 data sets. For each data set we were able to measure power and mean frequency for each segment during filling, creating fill-dependent spectral analysis plots for all 12 patients.
For 10 of 12 data sets the spectral power in the final segment (just prior to void) was larger than the power measured during the initial filling duration (Fig 1). As a group, the mean spectral power significantly increased during filling (12.6 ± 3.5 vs 54.1 ± 19.0; mean ± SEM, P <0.05, Student’s paired t-test, n=12). 
The signal spectral composition (1-10 CPM) also changed with bladder filling. For 9 of 12 data sets the final mean weighted frequency (measured just prior to void) was less than that measured during the initial filling segment (Fig 2). Across the 12 data sets, there was a small but significant decrease in the mean weighted frequency during bladder filling (initial duration, 5.2 ± 0.3 CPM, vs final duration, 4.4 ± 0.4 CPM; mean ± SEM, P <0.05, Student’s paired t-test, n=12). 
For all segments across all patients, there was a weak but statistically significant relationship between the mean weighted frequency and spectral power (Pearson, P < 0.05, R = -0.312, N = 48). Higher total power was generally associated with lower mean weighted frequency.

Our workflow was useful for initial processing of clinical urodynamics data and allowed filling-dependent signal processing of relevant pressures and temporal dynamics. Initial results revealed filling-related changes in both summed spectral power as well as the mean weighted frequency with bladder filling.   
While very early, the preliminary results suggest that we can capture and quantify the spectral composition of urodynamics signals captured during routine clinical testing. The filling dependent increase in spectral power in frequencies of 1-10 CPM is consistent with increasing autonomous contraction amplitudes observed during bladder filling. The small filling dependent decrease in mean frequency of the spectral distribution is more surprising; perhaps related to increased synchronization across detrusor areas during bladder filling. We will repeat and extend this study in additional retrospective and future clinical and preclinical prospective studies.

We have developed an early workflow process and have generated initial functional data using quantitative analytics of clinical urodynamics based upon temporal spectral composition and FFT power over the range from 1-10 CPM. Initial results suggest that these measurements may differentiate filling related activities in patients. Future work will expand these results to additional data sets and explore relationships between these measures and clinical diagnoses related to bladder dysfunctions.

Colhoun AF, Speich JE, Cooley LF, et al: Low amplitude rhythmic contraction frequency in human detrusor strips correlates with phasic intravesical pressure waves. World J Urol 2017; 35: 1255–1260.
Cullingsworth ZE, Kelly BB, Deebel NA, et al: Automated quantification of low amplitude rhythmic contractions (LARC) during real-world urodynamics identifies a potential detrusor overactivity subgroup. PLOS ONE 2018; 13: e0201594.
Drake MJ, Kanai A, Bijos DA, et al: The potential role of unregulated autonomous bladder micromotions in urinary storage and voiding dysfunction; overactive bladder and detrusor underactivity. BJU Int. 2017; 119: 22–29.