However, a number of large prospective randomized clinical trials, comparing ACD-CPR to conventional CPR both in patients with OHCA and those with in-hospital cardiac arrest, found no difference in survival.
39,40 In the French Active Compression-Decompression Cardiopulmonary Resuscitation Study, 41 a randomized trial on patients with OHCA, CardioPump CPR was associated with higher rate of hospital discharge without neurologic impairment and better one-year survival rate as com- pared to manual CPR. Some clinical studies showed a higher short-term survival compared with conventional CPR. 38 Again, their clinical appli- cation yielded conflicting results. These devices required both pushing and pulling and were found to be more physically demanding for the rescuer than per- forming standard CPR. 36,37 The ACD principle firstly resulted in two different devices called the ResQpump and the CardioPump ( Figure 2(c)). 35 This hypothesis is consistent with the thoracic pump model, as the effi- cacy of the compression would be increased by the augmented venous return during the decompression phase. rationale of the ACD approach is that an active decompression -obtained by a suction cup that lifts the anterior chest during the decompression phase and creates a negative intrathoracic pressure -might favor venous return to the heart when added to the standard compression mechanic. 33 In the randomized Circulation Improving Resuscitation Care trial, which enrolled 4573 OHCA patients, the Auto-Pulse yielded an equivalent survival to hospital discharge, with no dif- ference in neurologic status at discharge when com- pared with manual CPR. 32 In the large multicenter ASPIRE trial on patients with out-of-hospital cardiac arrest (OHCA), the use of the Auto-Pulse CPR was associated with worse neurological outcomes and a trend toward worse four-hour survival. Despite initial encouraging results, 30,31 successive stu- dies did not confirm the clinical utility of these devices.
A similar principle was succes- sively followed to develop a more flexible version, the Auto-Pulse CPR load-distributing band ( Figure 2(b)). The vest was designed to be positioned around the patient's thorax, and rapidly inflated and deflated. 29 This device was based on pathophysiological principles that hinged on the thoracic pump theory, according to the idea that a compression device composed of a chest-constricting band, creating a load-distributing system, could pro- duce higher blood flow compared to CPR consisting of sternal compressions only. 1980, a new mechanical device design, known as the CPR vest, was introduced.