Bilateral measurement of pelvic floor muscle dysfunction in females with lower urinary tract symptoms using near infrared spectroscopy

Introduction and Objective: Near infrared spectroscopy (NIRS) is a noninvasive method of measuring oxygen recovery kinetics in skeletal muscle. NIRS detects changes in oxygenated (O₂Hb) and deoxygenated (HHb) hemoglobin in response to exercise, to provide interpretation of muscular capacity to restore incurred oxygen debt. Assessment of pelvic floor muscle (PFM) function is central to managing urinary incontinence (UI) and lower urinary tract symptoms (LUTS) but currently lacks oxygen kinetic parameters. This project aims to develop a NIRS probe that measures oxygen kinetics of bilateral PFM in females with UI/LUTS (cases) related to altered pelvic innervation compared to continent controls. Methods: A transvaginal NIRS prototype to detect bilateral PFM was developed. The vaginal NIRS probe monitored female volunteers during sustained PFM contraction (SMVC). O₂Hb, HHb and HbDiff (O₂Hb-HHb) allowed measurement of oxygen kinetics unique to bilateral PFM. Oxygen recovery kinetics determined by HbDiff half recovery time (½RT). PFM manometry assessed SMVC peak and average cmH₂O. Home-based 8-week PFM therapy (PFMT) intervention was performed by both participant groups and an exercise diary measured adherence, determined as total percentage of volume and frequency. Results: Observational NIRS findings demonstrated typical hemodynamic and ½RT responses in controls. Case group demonstrated atypical findings consistent with impaired muscle function. NIRS found quicker ½RT for controls (7.87 vs 38.03 seconds, p 0.01). Manometer detected greater PFM strength and endurance in controls (SMVC peak 35 vs 13 cmH2O, p