CPR Electrical Therapy Principles 2 — Questions and Answers
Question 1: Which waveform type is used by most modern defibrillators and requires less energy than older monophasic devices?
- Sinusoidal waveform
- Biphasic waveform (Correct answer)
- Monophasic waveform
- Triphasic waveform
Correct answer: Biphasic waveform
Biphasic waveforms deliver current in two directions and are more effective at lower energy levels than monophasic waveforms.
Question 2: When performing transcutaneous pacing, the rate for a symptomatic bradycardia patient is typically set to:
- 40-50 bpm
- 60-80 bpm (Correct answer)
- 100-120 bpm
- 150-180 bpm
Correct answer: 60-80 bpm
Transcutaneous pacing for symptomatic bradycardia is typically initiated at 60-80 bpm to restore adequate perfusion.
Question 3: A patient in ventricular fibrillation receives a shock but immediately returns to VF. What is the recommended next step?
- Increase the defibrillation energy by 50 joules
- Resume CPR for 2 minutes then reassess rhythm (Correct answer)
- Administer lidocaine before the next shock
- Repeat the shock immediately at the same energy
Correct answer: Resume CPR for 2 minutes then reassess rhythm
After a failed shock, 2 minutes of high-quality CPR should resume to re-perfuse the myocardium before the next rhythm check.
Question 4: What term describes the minimum current needed to reliably capture the myocardium during transcutaneous pacing?
- Threshold current
- Capture threshold (Correct answer)
- Pacing impedance
- Defibrillation threshold
Correct answer: Capture threshold
Capture threshold is the minimum milliamp output needed to consistently depolarize the myocardium and produce a mechanical response.
Question 5: In synchronized cardioversion, the shock is timed to which part of the cardiac cycle?
- P wave
- QRS complex (Correct answer)
- T wave
- U wave
Correct answer: QRS complex
Synchronized cardioversion delivers energy with the QRS complex to avoid the vulnerable T-wave period and prevent VF induction.
Question 6: A patient with stable supraventricular tachycardia at 180 bpm does not respond to vagal maneuvers or adenosine. What electrical therapy is appropriate?
- Unsynchronized defibrillation at 200J
- Synchronized cardioversion at 50-100J (Correct answer)
- Transcutaneous pacing at 80 bpm
- Synchronized cardioversion at 360J
Correct answer: Synchronized cardioversion at 50-100J
Stable SVT refractory to medications is treated with synchronized cardioversion starting at 50-100J.
Question 7: What is the PRIMARY danger of delivering a defibrillation shock in asynchronized mode to a patient in atrial flutter?
- Skin burns at electrode sites
- Inducing ventricular fibrillation by shocking on the T wave (Correct answer)
- Failure to convert the rhythm
- Excessive pain to the patient
Correct answer: Inducing ventricular fibrillation by shocking on the T wave
Unsynchronized shocks during atrial flutter can coincide with the T wave's vulnerable period, triggering ventricular fibrillation.
CPR Electrical Therapy Principles 2
Which waveform type is used by most modern defibrillators and requires less energy than older monophasic devices?