Cardiopulmonary Physiology

Arrhythmias and atherosclerosis can produce heartbeats that do not translate into effective peripheral perfusion, making pulse rate a more clinically accurate measure than heart rate. The U-shaped PBR risk pattern is biologically consistent with homeostatic equilibrium, where excessive deviation in either direction disrupts balance and causes organ damage. Outliers in PBR, whether driven by a disproportionately fast pulse or disproportionately fast breathing, signal system-level dysregulation. Both very high and very low individual values of pulse rate and breathing rate are associated with increased mortality, following U-shaped distributions.