Exploratory Ultrasound Analysis of the Diaphragm and Respiratory Capacity in Women with Primary Dysmenorrhea: A Cross-Sectional Observational Study

Abstract

Primary dysmenorrhea (PD) is a common gynecological condition characterized by menstrual pain without underlying pelvic pathology. It has been linked to functional and structural changes in the core musculature, but limited evidence exists regarding its association with diaphragmatic and respiratory mechanics. This study aimed to elaborate on these potential associations by assessing the diaphragmatic structure and respiratory function in women with PD compared to healthy controls, utilizing ultrasound imaging, spirometry and respiratory pressure measurements. Methods: An observational, cross-sectional study was conducted with 44 female participants (22 with PD and 22 healthy controls). Diaphragmatic structure was evaluated through ultrasound, measuring the intercostal distance, diaphragmatic thickness, and diaphragmatic excursion at rest and during maximum voluntary contraction. Spirometric assessments included forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and the FVC/FEV1 ratio, along with measurements of maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP). Group differences were analyzed using Student’s t-test and effect sizes were reported with Cohen’s d. Results: No significant differences were observed between the groups in diaphragmatic thickness, diaphragmatic excursion, or global respiratory capacity (p > 0.05). However, women with PD presented a significant reduction in the left intercostal distance both at rest (p = 0.035, d = 0.56) and during contraction (p = 0.039, d = 0.54). No other significant group differences were detected. Conclusions: While primary dysmenorrhea does not appear to affect overall diaphragmatic function or respiratory capacity, it is associated with subtle localized changes in the left intercostal dynamics. These findings suggest a potential compensatory mechanical adaptation rather than global respiratory dysfunction. Further longitudinal studies with larger sample sizes are needed to explore the clinical significance of these findings.