There are few studies examining the ventilation strategies recommended by current CPR guidelines. We investigated the influence of different minute volume applying to untreated cardiac arrest with different duration, on resuscitation effects in a pig model. 32 Landrace pigs with 4 or 8 min (16 pigs each) ventricular fibrillation (VF) randomly received two ventilation strategies during CPR. "Guideline" groups received mechanical ventilation with a tidal volume of 7 ml/kg and a frequency of 10/min, while "Baseline" groups received a tidal volume (10 ml/kg) and a frequency used at baseline to maintain an end-tidal PCO2 (PETCO2) between 35 and 40 mmHg before VF. Mean airway pressures and intrathoracic pressures (PIT) in the Baseline-4 min group were significantly higher than those in the Guideline-4 min group (all P < 0.05). Similar results were observed in the 8 min pigs, except for no significant difference in minimal PIT and PETCO2 during 10 min of CPR. Venous pH and venous oxygen saturation were significantly higher in the Baseline-8 min group compared to the Guideline-8 min group (all P < 0.05). Aortic pressure in the Baseline-8 min group was higher than in the Guideline-8 min group. Seven pigs in each subgroup of 4 min VF models achieved the return of spontaneous circulation (ROSC). Higher ROSC was observed in the Baseline-8 min group than in the Guideline-8 min group (87.5% vs. 37.5%, P = 0.039). For 4 min VF but not 8 min VF, a guideline-recommended ventilation strategy had satisfactory results during CPR. A higher minute ventilation resulted in better outcomes for subjects with 8 min of untreated VF through thoracic pump.
Keywords: Cardiopulmonary resuscitation; Intrathoracic pressure; Thoracic pump; Ventilation.