Jeffrey J. Shultz

Improving Active Compression-Decompression Cardiopulmonary Resuscitation With an Inspiratory Impedance Valve

BACKGROUND Active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) has recently been demonstrated to provide significantly more blood flow to vital organs during cardiac arrest. To further enhance the effectiveness of this technique, we tested the hypothesis that intermittent impedance to inspiratory gas exchange during the decompression phase of ACD CPR enhances vital organ blood flow. METHODS AND RESULTS ACD CPR was performed with a pneumatically driven automated compression-decompression device in a porcine model of ventricular fibrillation (VF). Nine pigs were randomized to receive ACD CPR alone, while 8 pigs received ACD CPR plus intermittent impedance to inspiratory gas exchange with a threshold valve set to 40 cm H2O. Results comparing 2 minutes of ACD CPR alone versus ACD CPR with the inspiratory impedance threshold valve (ITV) revealed significantly higher mean (+/- SEM) coronary perfusion pressures (diastolic aortic minus diastolic right atrial pressures) in the ITV (31.0 +/- 2.3 mm Hg) group versus with ACD CPR alone (21 +/- 3.6 mm Hg) (P < .05). Total left ventricular and cerebral blood flows, determined by radiolabeled microspheres, were 0.77 +/- 0.095 and 0.47 +/- 0.06 mL/min per gram, respectively, with ACD CPR plus the ITV versus 0.45 +/- 0.1 and 0.32 +/- 0.016 mL/min per gram, respectively, with ACD CPR alone (P < .05). Similar improvements in the ITV group were observed after 7 minutes of ACD CPR. After 16 minutes of VF and 13 minutes of ACD CPR, 6 of 8 pigs in the ITV group were successfully resuscitated with less than three successive 150-J shocks, whereas only 2 of 9 pigs with ACD CPR alone were resuscitated with equivalent energy levels (P < .02). With up to three additional and successive 200-J shocks, all pigs in the ITV group and 7 of 9 pigs with ACD CPR alone were resuscitated (P = .18). CONCLUSIONS Intermittent impedance to inspiratory flow of respiratory gases during ACD CPR significantly improves coronary perfusion pressures and vital organ blood flow and lowers defibrillation energy requirements in a porcine model of VF.

Evaluation of standard and active compression-decompression CPR in an acute human model of ventricular fibrillation.

BackgroundThe mechanisms that underlie cardiopulmonary resuscitation (CPR) in humans remain controversial and difficult to study. This report describes a new human model to evaluate CPR during the first 1 to 2 minutes after the onset of ventricular fibrillation (VF). With this model, standard CPR was compared with active compression-decompression (ACD) CPR, a method that uses a handheld suction device to actively compress and actively decompress the chest. Methods and ResultsDuring routine inductions of VF as part of a transvenous lead cardioverter/defibrillator implantation procedure, CPR was performed in 21 patients if the first defibrillation shock failed and until a successful rescue shock was delivered. Compressions during CPR were performed according to American Heart Association guidelines. For ACD CPR, decompression was performed with up to −30 lbs. Radial arterial and right atrial pressures were measured in all patients. Esophageal pressures, intratracheal pressures, or minute ventilation was measured in the last 13 patients. Application of both CPR techniques increased arterial and right atrial pressures. The mean coronary perfusion pressure was increased throughout the entire CPR cycle with ACD CPR (compression, 21.5±9.0 mm Hg; decompression, 21.9±8.7 mm Hg) compared with standard CPR (compression, 17.9±8.2 mm Hg; decompression, 18.5 ±6.9 mm Hg; P < .02 and P < .02, respectively). Ventilation per compression-decompression cycle was 97.3±65.6 mL with standard CPR and 168.4±68.6 mL with ACD CPR (n=7, P < .001). Negative inspiratory pressure was −0.8±4.8 mm Hg with standard CPR and −11.4±6.3 mm Hg with ACD CPR (n=6, P < .04). ConclusionsPatients undergoing multiple inductions of VF during cardioverter/defibrillator implantation with transvenous leads provide a well-controlled and reproducible model to study the mechanisms of CPR. Using this model, ACD CPR significantly increased arterial blood pressure, coronary perfusion pressure, minute ventilation, and negative inspiratory pressure compared with standard CPR.

Comparison of exertion required to perform standard and active compression-decompression cardiopulmonary resuscitation

OBJECTIVE Active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) utilizes a hand-held suction device with a pressure gauge that enables the operator to compress as well as actively decompress the chest. This new CPR method improves hemodynamic and ventilatory parameters when compared with standard CPR. ACD-CPR is easy to perform but may be more labor intensive. The purpose of this study was to quantify and compare the work required to perform ACD and standard CPR. METHODS Cardiopulmonary testing was performed on six basic cardiac life support- and ACD-trained St. Paul, MN fire-fighter personnel during performance of 10 min each of ACD and standard CPR on a mannequin equipped with a compression gauge. The order of CPR techniques was determined randomly with > 1 h between each study. Each CPR method was performed at 80 compressions/min (timed with a metronome), to a depth of 1.5-2 inches, and with a 50% duty cycle. RESULTS Baseline cardiopulmonary measurements were similar at rest prior to performance of both CPR methods. During standard and ACD-CPR, respectively, rate-pressure product was 18.2 +/- 3.0 vs. 23.8 +/- 1.7 (x 1000, P < 0.01); mean oxygen consumption 15.98 +/- 2.29 vs. 20.07 +/- 2.10 ml/kg/min or 4.6 +/- 0.7 vs. 5.7 +/- 0.6 METS (P < 0.01); carbon dioxide production 1115.7 +/- 110 vs. 1459.1 +/- 176 ml/min; respiratory exchange ratio 0.88 +/- 0.04 vs. 0.92 +/- 0.04 (P = NS); and minute ventilation 35.5 +/- 5.1 vs. 45.6 +/- 9.2 l/min (P < 0.01). CONCLUSIONS Approximately 25% more work is required to perform ACD-CPR compared with standard CPR. Both methods require subanaerobic energy expenditure and can therefore be sustained for a sufficient length of time by most individuals to optimize resuscitation efforts. Due to the slightly higher work requirement, ACD-CPR may be more difficult to perform compared with standard CPR for long periods of time, particularly by individuals unaccustomed to the workload requirement of CPR, in general.

Syncope Associated With Exercise, a Manifestation of Neurally Mediated Syncope

A retrospective review of patients evaluated at a university-based referral hospital was performed to assess the basis for syncope associated with exercise in young patients. Over an 8-year period, 54 consecutive young patients (aged 12 to 30 years) were referred for evaluation of frank syncope. Twelve patients had syncope associated with exercise (group I) and 42 patients had syncope not associated with exercise (group II). Patients underwent physical examination, chest x-ray, 2-dimensional echocardiography, and in selected cases, cardiac catheterization. Head-up tilt-table testing was performed in 11 of 12 group I patients. Ten group I patients had no evidence of structural heart disease: 9 of these 10 (90%) developed syncope with tilt-table testing. Head-up tilt-table testing was performed in 41 of 42 group II patients: 34 (83%) developed syncope with tilt-table testing. Standard cardiac electrophysiologic study was performed in 9 of 12 group I and in 30 of 42 group II patients, and identified a basis for syncope in only 2 group I and 1 group II patients. Among 9 group I patients with a positive result on head-up tilt-table testing and no evidence of structural heart disease (mean follow-up 4.3 years), 7 are without further episodes of syncope; 3 have discontinued medication and 5 have resumed at least limited exercise. In conclusion, susceptibility to tilt-induced syncope was the most frequent finding in young patients without structural heart disease referred for evaluation of exercise-associated syncope. Tilt-table testing may be an important diagnostic tool for the evaluation of these patients.

Effect of parenteral d-sotalol on transvenous atrial defibrillation threshold in a canine model of atrial fibrillation

In an effort to reduce energy requirements for atrial defibrillation to a level low enough to perform painless electrical cardioversion with an implantable atrial defibrillator, we tested the hypothesis that drug therapy with the class III agent d-sotalol, when used concurrently with a low-energy shock, reduces atrial defibrillation threshold. In a nonthoracotomy canine model of atrial fibrillation, intracardiac shocks were delivered between the distal coronary sinus and the mid-right atrium. Based on a step-up energy delivery protocol the atrial defibrillation threshold was defined as the least amount of energy that resulted in a >10% and <90% rate of successful defibrillation. At a dose associated with class III antiarrhythmic effects (5 mg/kg), d-sotalol significantly reduced atrial defibrillation threshold from 1.72 +/- 1.12 J to 0.59 +/- 0.60 J (p < 0.01). These results support the feasibility of using antiarrhythmic drug therapy with d-sotalol to minimize energy requirements for intracardiac electrical cardioversion of atrial fibrillation.

'Sagging heart syndrome': A cause of acute lead dislodgment in two patients

Acute passive fixation atrial lead dislodgment occurred due to an unexpected and marked postural descent of the heart after permanent pacemaker implantation in two patients. Sagging of the heart in these two individuals may have been related to a history of morbid obesity followed by weight loss of over 100 pounds. Lead replacement with active fixation leads was required in both cases. The term “sagging heart syndrome” is proposed to describe this clinical entity. In certain adult populations, such as in patients with a history of significant weight loss, the “sagging heart syndrome” may represent a previously unrecognized cause of acute lead dislodgment.

Recurrent supine syncope: An unusual manifestation of the neurally mediated faint

Supine Syncope. Introduction: Syncope occasionally may occur in the supine patient due to severe brady‐ or tachyarrhythmia. However, recurrent syncope upon assumption of the supine position as a result of a neurally mediated reflex mechanism has not been reported previously.

Alternative Mechanical Methods of Cardiopulmonary Resuscitation.

Cardiopulmonary resuscitation (CPR) has become the standard of care for providing circulatory support to victims of cardiac arrest. However, despite its widespread acceptance, few victims ever survive to hospital admission and even fewer to hospital discharge. In hopes of improving survival rates of those suffering cardiac arrest, investigators have suggested and tested several modifications to standard CPR to optimize its hemodynamic effects. In this review, we discuss the important chest compression techniques that have been used over the past 3.5 decades which have mirrored our evolving understanding of the mechanisms underlying CPR.