CRM IBHRE|QUESTION AND ANSWERS| GUARANTEED TO PASS CONCEPTS

Rheobase Correct Answer the lowest point on a strength duration curve at an infinitely long pulse duration Chronaxie time Correct Answer the pulse width at twice the rheobase value. It approximates the most efficient stimulation pulse duration Charge (formula) Correct Answer Charge= I(current) x T(time) Energy (formula) Correct Answer Energy(microjoules)= I(current)xVxT Functional Refractory Period Correct Answer the coupling interval which first results in a measurable degree of delay in impulse conduction Effective Refractory Period Correct Answer the longest coupling interval to be associated with block Devices with NO interaction with pacers Correct Answer 1. microwave oven, 2. CT scan/Ultrasound 3. X-rays (diagnostic) Devices that cause transient or 1 beat inhibition Correct Answer 1. EAS 2. Cellphones 3. Arc Welding 4. airport metal detector 5. TENS 6. Electric appliances such as electric blanket & power tools Devices that may damage the pacemaker Correct Answer 1. MRI 2. Defibrillator 3. Cardio version 4. Cautery/RF Ablation 5. Radiation Therapy Resistance in Series Correct Answer Series means the beginning of one resistance is connected to another Sum the resistances: R1+R2= total resistance. EX: A LEAD FRACTURE (fractures INCREASE impedance) Resistance in Parallel Correct Answer Parallel means all the resistances are connected to the same point. (R1xR2)/(R1+R2)= total resistance EX: LEAD INSULATION DEFECTS (insulation defects DECREASE impedance) Permanent pacemakers are constant voltage or constant current? Correct Answer ALL permanent pacemakers are constant voltage devices.