Abstract Body:
Introduction: Active thoracic deconstriction (ATD) is an impactful addition to standard closed-chest CPR, thought to increase perfusion pressure (CPP) by augmenting venous return. Most studies of ATD, however, have been conducted using piston-based sternal compression CPR (PBSC-CPR), which can cause significant thoracic skeletal trauma. In contrast, circumferential constriction CPR (CC-CPR) does not cause significant structural damage, possibly preserving the thoracic-recoil-based venous return mechanism. If that is the case, CC-CPR would not benefit from ATD.

Hypothesis: ATD has no effect on CC-CPR hemodynamic parameters.

Methods: Ventricular fibrillation was induced in Yorkshire swine (n = 3, ~30 kg). CPR was provided by a custom pneumatic CC-CPR system. ATD during CC-CPR was achieved by active deflation against a hard outer shell, called a cuirass, using Velcro interfaces between the animal, the belt, and the cuirass. CC-CPR was alternated in 45-second epochs between active pneumatic deflation with and without a rigid cuirass. Aortic (Ao) and right atrial (RA) pressures were measured, and coronary perfusion pressure (CPP) derived. ETCO2 and carotid flow were also measured. Results from all experiments were grouped by treatment type and subjected to Analysis of Variance.

Results: 39 epochs in three studies were included. There were no statistically significant differences (P < 0.1) in CPP, ETCO2, or carotid flows between treatment types (Table).

Conclusion: Because of its much larger contact surface area, the total possible decompression force during CC-CPR is greater than during PBSC-CPR. Despite this, the presence or absence of the rigid cuirass—and thus active deconstriction—appeared to have no impact on hemodynamic parameters. This finding suggests that the benefit of ATD during PBSC may derive from compensating for the damaged thoracic recoil mechanism, not enhancement of an extant mechanism. If the skeletal trauma of PBSC-CPR devices is avoided, the apparent benefit of ATD might be lessened. Further study to test this potentially important hypothesis is indicated.