Mark Gelfand

A Preliminary Study of Cardiopulmonary Resuscitation by Circumferential Compression of the Chest with Use of a Pneumatic Vest

BACKGROUND More than 300,000 people die each year of cardiac arrest. Studies have shown that raising vascular pressures during cardiopulmonary resuscitation (CPR) can improve survival and that vascular pressures can be raised by increasing intrathoracic pressure. METHODS To produce periodic increases in intrathoracic pressure, we developed a pneumatically cycled circumferential thoracic vest system and compared the results of the use of this system in CPR (vest CPR) with those of manual CPR. In phase 1 of the study, aortic and right-atrial pressures were measured during both vest CPR (60 inflations per minute) and manual CPR in 15 patients in whom a mean (+/- SD) of 42 +/- 16 minutes of initial manual CPR had been unsuccessful. Vest CPR was also carried out on 14 other patients in whom pressure measurements were not made. In phase 2 of the study, short-term survival was assessed in 34 additional patients randomly assigned to undergo vest CPR (17 patients) or continued manual CPR (17 patients) after initial manual CPR (duration, 11 +/- 4 minutes) had been unsuccessful. RESULTS In phase 1 of the study, vest CPR increased the peak aortic pressure from 78 +/- 26 mm Hg to 138 +/- 28 mm Hg (P < 0.001) and the coronary perfusion pressure from 15 +/- 8 mm Hg to 23 +/- 11 mm Hg (P < 0.003). Despite prolonged unsuccessful manual CPR, spontaneous circulation returned with vest CPR in 4 of the 29 patients. In phase 2 of the study, spontaneous circulation returned in 8 of the 17 patients who underwent vest CPR as compared with only 3 of the 17 patients who received continued manual CPR (P = 0.14). More patients in the vest-CPR group than in the manual-CPR group were alive 6 hours after attempted resuscitation (6 of 17 vs. 1 of 17) and 24 hours after attempted resuscitation (3 of 17 vs. 1 of 17), but none survived to leave the hospital. CONCLUSIONS In this preliminary study, vest CPR, despite its late application, successfully increased aortic pressure and coronary perfusion pressure, and there was an insignificant trend toward a greater likelihood of the return of spontaneous circulation with vest CPR than with continued manual CPR. The effect of vest CPR on survival, however, is currently unknown and will require further study.

Goal directed fluid therapy.

A method includes setting a hydration goal and administering a diuretic to the patient to induce increased urine flow and collecting urine expelled by the patient. The amount of urine expelled by the patient is determined based on the collected urine. The patient is infused with fluid from a fluid source. The amount of fluid infused into the patient is determined. Diuresis is induced by automatically and continuously adjusting the amount of fluid infused into the patient from the fluid source to meet the hydration goal based on the set hydration goal, the determined amount of urine expelled by the patient and the fluid infused.

Servo-controlled indenter for determining the transverse stiffness of ventricular muscle

A dynamic indentation system has been developed that can determine transverse stiffness of ventricular muscle in as little as 10 ms, allowing estimation of wall stress over a single contraction cycle. The apparatus consists of an indentation probe coupled to a linear motor. This indentation system was tested on two beating canine ventricular septa that were mounted in a biaxial system that could apply strains in the plane of the septa and measure the resulting in-plane stresses. The probe indented the septa with peak displacements of 0.1-0.5 mm at frequencies of 20 and 50 Hz. The transverse stiffness was calculated as the slope of the relation between the indentation stress and the indentation strain during each high-frequency indentation. Consistent with earlier studies, the transverse stiffness was related to the in-plane stress. In contrast to earlier studies, however, these dynamic transverse stiffness determinations could be made during a single contraction. Thus, dynamic transverse stiffness determinations allow estimation of wall stress in the isolated septa by minimal surface contact, and may lead to methods for estimating wall stress in the intact heart.<<ETX>>

Vest CPR - A Promising New Modality Of Resuscitation

Studies of cardiopulmonary resuscitation (CPR) have lead to development of a theory that the movement of blood during CPR is largely due to rises in intrathoracic pressure rather than direct squeezing of the heart during chest compression. A logical consequence of this theory was the development of vest CPR, whereby an inflatable vest encircles the patients chest and cyclically generates relatively uniform chest compression. Animal studies have demonstrated improved survival over standard CPR, and preliminary human studies have shown improved hemodynamics. Survival studies in patients are underway.