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

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).

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.

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.

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