The delivery of high-quality cardiopulmonary resuscitation is a pivotal determinant of survival and neurological recovery in patients experiencing cardiac arrest. The effectiveness of resuscitation is contingent upon the adequacy of chest compressions in generating sufficient cardiac output and maintaining perfusion to vital organs. Conventional parameter used to evaluate the quality of cardiopulmonary resuscitation, such as invasive arterial pressure measurement, are constrained by practical and physiological limitations. Invasive arterial pressure monitoring requires invasive catheterization, which is not always feasible in emergency circumstances. These limitations underscore the need for a non-invasive, objective, and reproducible surrogate measure for real-time assessment of resuscitation quality.

The Femoral Artery Collapse Ratio, determined using point-of-care ultrasonography, has recently emerged as a promising alternative. This ratio, derived from systolic and diastolic diameters of the femoral artery obtained in motion-mode imaging, reflects dynamic arterial changes during compressions and may correlate with perfusion indices. Preliminary evidence from porcine model demonstrates a positive association between the femoral artery collapse ratio and end-tidal carbon dioxide, suggesting potential clinical applicability.

This prospective observational study will be undertaken in the Department of Emergency Medicine, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry. A total of one hundred and twenty-eight adult cardiac arrest patients undergoing advanced cardiac life support will be enrolled. Femoral artery ultrasonography and side stream capnography will be simultaneously performed during resuscitation to record arterial diameters and carbon dioxide values. Statistical analysis will evaluate correlations between the femoral artery collapse ratio, end-tidal carbon dioxide, and return of spontaneous circulation.

Validation of this parameter could establish the femoral artery collapse ratio as a novel, non-invasive, and physiologically meaningful indicator for real-time monitoring of cardiopulmonary resuscitation quality.