Cycles Of Cardiopulmonary Resuscitation Research Articles

Simultaneous aortic, jugular bulb, and right atrial pressures during cardiopulmonary resuscitation in humans. Insights into mechanisms.

Pressure gradients across and between the head and chest were studied during mechanical cardiopulmonary resuscitation (CPR) in 22 humans. Patients in medical cardiac arrest, managed by ACLS guidelines, underwent placement of aortic arch (Ao), jugular venous bulb (JVB), and right atrial (RA) catheters. Simultaneous pressures were measured, and intercatheter gradients were calculated. The JVB to RA pressure difference is the gradient between the cervical and central venous circulations. It was negative when averaged throughout the CPR cycle and was more negative during compression than relaxation, -19 +/- 12 and -2 +/- 6 mm Hg, respectively. This indicates that the intrathoracic pressure rise was not transmitted to the jugular venous system, supporting the concept of a competent jugular valve mechanism during CPR. It is consistent with the thoracic pump model of cerebral perfusion. JVB to RA was positive only during early relaxation, allowing blood return from the head. The Ao to JVB gradient, although not equal to cerebral perfusion pressure, is the maximum potential pressure gradient for blood flow across the cerebral vasculature. It was positive throughout CPR, 25 +/- 17 during compression, and 9 +/- 10 mm Hg during relaxation. The Ao to RA gradient during the relaxation phase is CPR coronary perfusion pressure. In most patients, it was minimally positive in both phases of the CPR cycle: 7 +/- 14 in compression and 7 +/- 9 mm Hg during relaxation. This appears to be inadequate in providing sufficient blood flow to meet the metabolic needs of the myocardium. Four patients had larger gradients during compression suggestive of cardiac compression.(ABSTRACT TRUNCATED AT 250 WORDS)

Visualization of cardiac valve motion in man during external chest compression using two-dimensional echocardiography. Implications regarding the mechanism of blood flow.

Five patients who underwent cardiopulmonary resuscitation (CPR) were studied by two-dimensional echocardiography to assess valve motion. The mitral valve remained open throughout the entire compression-release cycle of CPR. The aortic valve opened during the compression phase of CPR and closed during the release phase. The pulmonic valve moved toward the closed position during the compression phase and the valve leaflets opened during release. Tricuspid valve leaflets never completely apposed, even during maximum chest compression, and they were widely open during release. Left ventricular dimensions did not change appreciably during CPR. These findings support the theory that forward blood flow during CPR depends on a generalized increase in intrathoracic pressure and not on direct compression of the heart itself. The left heart appears to act as a conduit for passage of blood, and mitral valve closure is not necessary for forward blood flow during CPR.