In most patients blood flow during cardiopulmonary resuscitation (CPR) results from a rise in intrathoracic pressure rather than from direct heart compression. Intrathoracic pressure was increased by the use of positive-pressure ventilation synchronous with sternal compression in eleven arrested patients who were intubated. A computer system allowed 15-30 s periods of alternation between conventional CPR and "new CPR" (rate of 40/min, 60% compression duration, and simultaneous ventilation at airway pressures from 60 to 110 cm H2O). Compression force was identical with the two methods. New CPR increased mean systolic radial artery pressure significantly from 40·6±4·4 to 53·1±3·9 mm Hg for 14 runs in nine patients. In 15 runs in ten patients an index of carotid flow increased with new CPR to 252% (range 113-643%) of control values. Lowering airway pressure during new CPR lowered flow index and arterial pressure, confirming that these increases with new CPR were due to higher intrathoracic pressure. Thus, increased airway pressure synchronous with sternal compression increases arterial pressure and likely blood flow during CPR in man. However, further studies of potential complications and long-term effects of new CPR, particularly on adequacy of ventilation, are needed before clinical implementation is undertaken.
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