Canine sternal force-displacement relationship during cardiopulmonary resuscitation

A viscoelastic model developed to model human sternal response to the cycli c loading of manual cardiopulmonary resuscitation (CPR) [8] was used to eva luate the properties of canine chests during CPR, Sternal compressions with ventilations after every fifth compression were applied to supine canines (n = 7) with a mechanical resuscitation device. The compressions were appli ed at a nominal rate of 90/min with a peak force near 400 N, From measureme nts of sternal force, sternal displacement, and tracheal airflow, model par ameters were estimated and their dependence on time and lung volume evaluat ed. The position to which the chest recoiled between compressions changed w ith time at a mean rate of 1.0 mm/min, Within each ventilation cycle (five compressions) the sternal recoil position decreased by 2.0 cm for each lite r of decrease in lung volume, The elastic force and damping decreased with time and decreasing lung volume, Canine and human [8] model parameters were found to be similar despite the notable differences in thoracic anatomy be tween the species, supporting the continued use of canines as models for hu man CPR, These parameters may be useful in the development of a model relat ing sternal compression forces to blood flow during CPR.