Physiological Effects of Electrical Current on the Heart

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What is the primary function of a ground-fault circuit interrupter?

To provide a conductive path to ground in medical devices
To increase the voltage of power lines
To monitor differences in currents between hot and neutral wires (correct)
To prevent overheating of electrical devices

In the event of an electrical accident, what path does the current typically take?

Through the body of the victim and back through ground (correct)
Through the neutral wire and back through the hot wire
Through the body of the victim and back through the hot wire
Through the hot wire and back through the neutral wire

What is the typical threshold value for a ground-fault circuit interrupter to interrupt the power supply?

1 mA
20 mA
10 mA
5 mA (correct)

What is the role of the differential transformer in a ground-fault circuit interrupter?

To monitor the difference between the currents in the hot and neutral wires (C) Signup and view all the answers

What is a common application of transformers integrated into the line plug?

Small electronic equipment and medical devices (A) Signup and view all the answers

What is the term for the resistance between the body of the victim and the ground in an electrical accident?

Rb - body resistance (B) Signup and view all the answers

What is the primary function of a line isolation monitor in an isolated power system?

To detect isolation faults and provide warning (A) Signup and view all the answers

What is indicated on an electric meter in an isolated power system?

The degree of isolation from ground (D) Signup and view all the answers

What is the function of the green lamp in an isolated power system?

To indicate that the system is adequately isolated (D) Signup and view all the answers

What type of receptacles are used in isolated power systems?

Either three-prong or special locking type (B) Signup and view all the answers

What is required in addition to an isolated distribution system in anesthetizing locations?

A high-quality grounding system (B) Signup and view all the answers

What is the purpose of the acoustical alarm in an isolated power system?

To indicate that the system has lost its protective properties (C) Signup and view all the answers

What happens to the heart if it receives enough current to tetanize the entire myocardium and the current is removed in time?

It will revert to normal rhythm after cessation of the current (C) Signup and view all the answers

What is the relationship between the duration of the shock and the current required to produce ventricular fibrillation?

The longer the duration, the smaller the current required to produce ventricular fibrillation (B) Signup and view all the answers

How does body weight affect the fibrillation threshold?

Fibrillation threshold increases with body weight (B) Signup and view all the answers

What is the relationship between the frequency of the current and the effects of the current on the body?

The effects of the current are almost independent of frequency up to about 1000 Hz (C) Signup and view all the answers

What is the most vulnerable period during which ventricular fibrillation is most likely to occur?

During the T wave (A) Signup and view all the answers

What is the let-go current?

The current at which a person can let go of an electrified object (C) Signup and view all the answers

What is the minimum patient resistance that can cause an above safe current of 10µA?

50kΩ (D) Signup and view all the answers

What is the potential difference that can occur due to a ground fault of 5A and a ground wire resistance of 0.1Ω?

500mV (D) Signup and view all the answers

What is the primary function of grounding systems in hospitals?

To keep all conductive surfaces and receptacle grounds at the same potential (B) Signup and view all the answers

What is the term used to describe the electrical shock that can occur due to differences in ground potential?

Microshock (B) Signup and view all the answers

Which of the following methods is used to prevent electrical accidents in hospitals?

Double insulation (D) Signup and view all the answers

What is the maximum resistance of a ground wire that can carry currents up to the circuit-breaker ratings?

0.15 Ω (B) Signup and view all the answers

What is the primary reason why no harmful effects are encountered in ECG machines despite large current flow through the body of the victim?

The interruption occurs so rapidly (C) Signup and view all the answers

Why did older ECG machines and patient monitors connect the RL lead to a power-line ground?

To ground the patient and establish a connection for an electrical accident (B) Signup and view all the answers

What is the purpose of isolation in patient-connected parts of medical equipment?

To prevent electrical shock to the patient (B) Signup and view all the answers

What is the common practice in modern ECG machines and patient monitors regarding the connection of patient leads?

Isolating patient-connected parts to prevent electrical accidents (B) Signup and view all the answers

What is the function of a current limiter in an ECG machine?

To limit the flow of electrical current to prevent electrical accidents (B) Signup and view all the answers

What is a potential risk of electrical connections in medical equipment?

Dangerous electrical currents may flow through the patient's body (C) Signup and view all the answers