Leakage current from transvenous and subcutaneous implantable cardioverter defibrillators (ICDs): A risk to the rescuer?

Background: Implantable cardioverter-defibrillators (ICDs) are a well-established therapy for patients at risk of life-threatening ventricular arrhythmias. With rising implant rates, the risk of a rescuer performing chest compressions during discharge is increasing, leading to concerns over rescuer safety from the resultant leakage current. More recently, subcutaneous ICDs (S-ICD) have been developed, which utilise a higher energy and more superficial electrodes compared with transvenous ICDs (T-ICD), raising safety concerns further.

Achieving safe hands-on defibrillation using electrical safety gloves--a clinical evaluation.

Introduction: Safe hands-on defibrillation (HOD) will allow uninterrupted chest compression during defibrillation and may improve resuscitation success. We tested the ability of electrical insulating gloves to protect the rescuer during HOD using a 'worst case' electrical scenario.

Materials And Method: Leakage current flowing from the patient to the 'rescuer' during antero-lateral defibrillation of patients undergoing elective cardioversion was measured.

Do clinical examination gloves provide adequate electrical insulation for safe hands-on defibrillation? II: Material integrity following exposure to defibrillation waveforms.

Introduction: Maintaining contact with the patient during defibrillator discharge has been proposed as a method for reducing no flow time but carries an associated risk of electrocution of the rescuer. This study describes an investigation to determine if typical clinical examination gloves possess the dielectric strength needed to prevent breakdown at defibrillation voltages; a factor essential to protect the rescuer.

Methods: Four types of examination glove typically used in a clinical environment were tested with two types of defibrillation waveform commonly used.

Do clinical examination gloves provide adequate electrical insulation for safe hands-on defibrillation? I: Resistive properties of nitrile gloves.

Introduction: Uninterrupted chest compressions are a key factor in determining resuscitation success. Interruptions to chest compression are often associated with defibrillation, particularly the need to stand clear from the patient during defibrillation. It has been suggested that clinical examination gloves may provide adequate electrical resistance to enable safe hands-on defibrillation in order to minimise interruptions.

Hands-on defibrillation: theoretical and practical aspects of patient and rescuer safety.

Defibrillators are used to treat many thousands of people each year using very high voltages, but, despite this, reported injuries to rescuers are rare. Although even a small number of reported injuries is not ideal, the safety record of the defibrillator using the current protocol is widely regarded as being acceptable. There is increasing evidence that clinical outcome is significantly improved with continuous chest compressions, but defibrillation is a common cause of interruptions; even short interruptions, such as those associated with defibrillation, may detrimentally affect the outcome.

A novel fifteen minute test for assessment of individual time-dependent clotting responses to aspirin and clopidogrel using modified thrombelastography.

Background: A rapid, reliable, point of care test reflecting patient specific responses to antiplatelet therapy would be of great clinical value in percutaneous coronary intervention (PCI). The aim of this study was to establish whether modified thrombelastography (TEG) can be employed as a 15 minute test of individual patient responses to aspirin and clopidogrel using a novel parameter, percentage clotting inhibition (%CIn).

Methods And Results: Thirty healthy volunteers and 10 patients undergoing elective PCI were recruited into four groups: 10 volunteers received a single 300 mg dose of aspirin [A1]: 10 volunteers received aspirin 75 mg daily for 7 days [A2]: 10 volunteers received a 600 mg dose of clopidogrel [C1]: 10 patients received a 600 mg loading dose of clopidogrel prior to elective PCI [C2].

Ambient oxygen concentrations resulting from use of the Lund University Cardiopulmonary Assist System (LUCAS) device during simulated cardiopulmonary resuscitation.

Introduction: Supplementary oxygen is used routinely during cardiopulmonary resuscitation (CPR). High ambient oxygen levels from ventilation circuits have caused fatal fires and explosions. The Lund University Cardiopulmonary Assist System (LUCAS) device is driven by > 70 l min(-1) oxygen which is also likely to increase ambient oxygen concentrations and cause similar risk of fire and explosion.

Investigation of an anisotropic tortuosity in a biot model of ultrasonic propagation in cancellous bone.

The modeling of ultrasonic propagation in cancellous bone is relevant to the study of clinical bone assessment. Historical experiments revealed the importance of both the viscous effects of bone marrow and the anisotropy of the porous microstructure. Of those propagation models previously applied to cancellous bone, Biot's theory incorporates viscosity, but has only been applied in isotropic form, while Schoenberg's anisotropic model does not include viscosity.

Defibrillation during renal dialysis: a survey of UK practice and procedural recommendations.

Introduction: Defibrillation of patients connected to medical equipment that is not defibrillation proof risks ineffective defibrillation and harm to the operator as a result of aberrant electrical pathways taken by the defibrillation current. Many renal dialysis systems are not currently defibrillation proof. Although national and international safety standards caution against defibrillating under this circumstance, it appears to be an area of confusion that we have investigated in more detail.

Assessment of the quality of cardiopulmonary resuscitation following modification of a standard telephone-directed protocol.

Introduction: Current Advanced Medical Priority Dispatch System (AMPDS) V.11.1 telephone instructions are limited in their ability to produce correctly performed basic life support.

A prospective manikin-based observational study of telephone-directed cardiopulmonary resuscitation.

Introduction: Bystander cardiopulmonary resuscitation (CPR) significantly improves the outcome from sudden cardiac arrest (SCA) and is therefore encouraged by offering telephone instructions to the bystander. The effectiveness of this technique was examined in a manikin-based study.

Methods: Subjects performed CPR on an instrumented adult manikin by following Advanced Medical Priority Dispatch System v11.

Gender differences in the relationship between leptin, insulin resistance and the autonomic nervous system.

Objectives: Leptin, an important hormonal regulator of body weight, has been shown to stimulate the sympathetic nervous system (SNS) in vitro although the physiological relevance remains unclear. Increased SNS activity has been implicated in the pathogenesis of insulin resistance and an increased cardiovascular risk. We have therefore investigated the relationship between leptin, insulin resistance and cardiac autonomic activity in healthy young adults.

External defibrillation in the left lateral position--a comparison of manual paddles with self-adhesive pads.

Introduction: Firm paddle force during defibrillation lowers transthoracic impedance (TTI) and increases transmyocardial current, increasing the chances of successful cardioversion. Current protocols recommend that if defibrillation using the anterior-apical (AA) paddle position fails, the anterior-posterior (AP) position should be used. This generally requires the patient to be placed in the left lateral position with the operator leaning over the patient.

Differential contribution of skin impedance and thoracic volume to transthoracic impedance during external defibrillation.

Background: Two mechanisms by which firm external paddle force decreases transthoracic impedance (TTI) have been proposed. Decreased impedance at the paddle-skin interface has been assumed to be the primary mechanism, but expulsion of air from the lungs, reducing lung volume is also likely to contribute. The relative contribution of each mechanism is unknown.

Is optimal paddle force applied during paediatric external defibrillation?

Introduction: Optimal paddle force minimises transthoracic impedance; a factor associated with increased defibrillation success. Optimal force for the defibrillation of children < or =10 kg using paediatric paddles has previously been shown to be 2.9 kgf, and for children >10 kg using adult paddles is 5.

Comparison of the effects of removal of chest hair with not doing so before external defibrillation on transthoracic impedance.

Chest hair contributes significantly to transthoracic impedance (TTI) during defibrillation. The magnitude of this effect has not been established using external paddles. We compared TTI in 40 men before elective cardiac surgery, and before and after shaving their chests.

What is the optimal paddle force during paediatric external defibrillation?

Introduction: Transthoracic impedance (TTI) is a major determinant of transmyocardial current flow, and therefore, the success of defibrillation. European Resuscitation Council (ERC) paediatric guidelines recommend that 'firm' paddle force should be applied to the paddles during defibrillation. No study has yet established the optimal paddle force required to minimise TTI in children of different ages.

Estimation of critical and viscous frequencies for Biot theory in cancellous bone.

The use of Biot theory for modelling ultrasonic wave propagation in porous media involves the definition of a "critical frequency" above which both fast and slow compressional waves will, in principle, propagate. Critical frequencies have been evaluated for healthy and osteoporotic cancellous bone filled with water or marrow, using data from the literature. The range of pore sizes in bone gives rise to a critical frequency band rather than a single critical frequency, the mean of which is lower for osteoporotic bone than normal bone.

Is the orientation of the apical defibrillation paddle of importance during manual external defibrillation?

Objective: Transthoracic impedance (TTI) is a factor determining the magnitude of the transmyocardial current during external defibrillation. Minimising TTI increases the chances of successful defibrillation. Most external defibrillation paddles are rectangular in shape and can, therefore, be placed in a transverse or longitudinal orientation.