Transthoracic Impedance 50-150 Ω — FRCA Primary MCQ

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ModeratePhysics & Clinical MeasurementTransthoracic Impedance 50-150 ΩFRCA Primary

The transthoracic impedance to defibrillation is normally approximately:

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Correct answer: E — 50-150 Ω

Normal transthoracic impedance is approximately 50-150 Ω (typically ~70-80 Ω). High impedance reduces the current delivered to the myocardium. Impedance is reduced by: firm paddle pressure / conducting gel/pads / correct paddle position / optimal pad size / expiration (smaller chest volume) / and repeated shocks.

Reference: Al-Shaikh Stacey 2019 Essentials of Anaesthetic Equipment