Active compression-decompression cardiopulmonary resuscitation (CPR) involves minimising intrathoracic pressure in the decompression phase of CPR, a technique which is felt to improve cerebral and coronary flow.
In this study, two devices were used to achieve negative intrathoracic pressure in patients who suffered out-of-hospital cardiac arrest. Firstly, a hand held device attached to a suction cup and pressure gauge was used to ensure adequate chest compression, but also full decompression, of the chest wall. In addition, an impedance-threshold valve connected to a facemask or other airway was used to lower intrathoracic pressure during the decompression phase by impeding passive inspiratory gas exchange as the chest recoils, whilst simultaneously allowing periodic positive pressure ventilation.
46 emergency medical services in the USA took part and patients were assigned randomly to standard CPR or active compression-decompression CPR. The primary endpoint was survival to hospital discharge with favourable neurological function.
2470 patients were randomly allocated to treatment groups; 813 (68%) of 1201 patients were assigned to the standard CPR group (controls) and 840 (66%) of 1269 were assigned to intervention (compression-decompression) CPR. 47 (6%) of 813 controls survived to hospital discharge with favourable neurological function compared with 75 (9%) of 840 patients in the intervention group (odds ratio 1·58, 95% CI 1·07—2·36; p=0·019- figure]. At one year, 74 (9%) of 840 patients had survived in the intervention group compared with 48 (6%) of 813 controls (p=0·03), with equivalent morbidity levels. Of note more patients had pulmonary oedema in the intervention group (94 [11%] of 840) than the control group (62 [7%] of 813; p=0·015), however the overall major adverse event rate did not differ between groups.
The findings of this study indicate that active compression-decompression CPR with augmentation of negative intrathoracic pressure may increase long-term survival after cardiac arrest.
- Aufderheide TP, Frascone RJ, Wayne MA et al. Standard cardiopulmonary resuscitation versus active compression-decompression cardiopulmonary resuscitation with augmentation of negative intrathoracic pressure for out-of-hospital cardiac arrest: a randomised trial. Lancet 2011; 377: 301-11.