Theoretical personalized optimum chest compression point can be determined using posteroanterior chest radiography.

AIM: Cardiopulmonary resuscitation guidelines suggest the lower sternal half be compressed. However, stroke volume has been assumed to be maximized by compressing the 'point' (P_max.LV) beneath which the left ventricle (LV) is at its maximum diameter. Identifying 'personalized' P_max.LV on computed tomography (CT), we derived and validated rules to estimate P_max.LV using posteroanterior chest radiography (chest_PA).

METHODS: A retrospective, cross-sectional study was performed with non-cardiac arrest (CA) adults who underwent chest_PA and CT within 1h (derivation:validation = 3:2). On chest_PA, we defined CD (cardiac diameter), RB (distance from right cardiac border to midline) and CH (cardiac height, from carina to uppermost point of left hemi-diaphragm). Setting P_zero (0, 0) at the midpoint of xiphisternal joint and designating leftward and upward directions as positive on x and y axes, we located P_max.LV (x_max.LV, y_max.LV). Mathematically, followings were inferable: x_max.LV = α0 *CD-RB; y_max.LV = ß0 *CH + γ0 . (α0 : mean of (x_max.LV + RB)/CD; ß0 , γ0 : representative coefficient and constant of linear regression model, respectively). We investigated their feasibility by applying them to in-hospital (IHCA) and out-of-hospital CA (OHCA) adults.

RESULTS: Among 266 (57.6 ± 16.4 years, 120 females), followings were derived: x_max.LV = 0.664*CD-RB; y_max.LV = 40 - 0.356*CH. Estimated P_max.LV was closer to the reference than other candidates and thus validated: 15 ± 9 vs 17 ± 10 (averaged P_max.LV, p = 0.025); 76 ± 13, 54 ± 11 and 63 ± 13 mm (3 equidistant points as per guidelines, all p < 0.001). Among IHCA and OHCA patients, 70.7% (106/150) and 38.0% (57/150) had previous chest_PA with measurable parameters to estimate P_max.LV.

CONCLUSION: Personalized P_max.LV, which is potentially superior to the lower sternal half and feasible in CA, is estimable with chest_PA.