Femoral artery collapse ratio as an indicator of chest compression quality during cardiopulmonary resuscitation in a porcine cardiac arrest model

Cardiopulmonary resuscitation (CPR) quality is crucial for improving patient survival rates after cardiac arrest. This study aimed to investigate the usefulness of femoral artery collapse ratio (systolic diameter/diastolic diameter ratio) measurement using M-mode ultrasound versus end-tidal carbon dioxide (ETCO2) for the assessment of high-quality CPR in a porcine cardiac arrest model. A total of 10 male mongrel pigs (age range, 16–20 weeks; weight, 45–50 kg) were used. After anesthesia, the carotid artery was dissected and exposed. The animals were instrumented with an arterial catheter in the exposed carotid artery to monitor arterial blood pressure. Cardiac arrest was induced by injecting potassium chloride (KCl, 40 equivalents of weight). The animals underwent chest compression using a mechanical device, and the chest compression depth and ETCO2 were measured using a defibrillator. To obtain hemodynamic information, two investigators performed an ultrasound examination on both femoral arteries. One examiner measured the femoral peak systolic velocity (PSV), while the other measured the diameters of the femoral artery (systolic diameter and diastolic diameter) in a transverse or longitudinal position using the M-mode of the linear ultrasound probe. As the compression depth increased, ETCO2, femoral artery diameter, collapse ratio (systolic diameter/diastolic diameter), and blood flow increased; however, PSV decreased. The ETCO2 and collapse ratio were positively correlated. The femoral artery collapse ratio, measured using the M-mode ultrasound, could be an alternative and simple method to evaluate high-quality CPR.