MNB.22 Electrical Safety & Hazards

Musculoskeletal System, Nervous System & Bioelectricity - MNB.22 Electrical Safety

• Learning Outcomes:
  • Identify hazards associated with static electricity, AC current, and microshock-sensitive patients.
  • Discuss precautions to manage static electricity.
  • Discuss precautions to prevent accidental electric shock (e.g., using fuses and ground fault interrupters).
  • Discuss management of microshock-sensitive patients.

Static Electricity

• Build-up:
  • Electrostatic effects are more prominent in dry conditions (low humidity).
  • Moisture drains excess charge through water molecules.
  • Shows examples of static electricity using Youtube.
• Hazards (Sparking):
  • Static electricity buildup can cause sparking during discharge.
  • This poses risks in flammable gas environments (e.g., oxygen or anesthetic gases).
  • Safety precautions are required.
  • Shows examples of static discharge using Youtube.

Precautions for Static Electricity

• General Precautions:
  • Maintain humidifiers in operating theatres.
  • Use materials that do not generate static (e.g., natural fibers like cotton instead of synthetic fabrics).
  • Employ anti-static flooring.
  • Incorporate anti-static rubber for masks, tubing, and equipment (e.g., wheel chairs, operating chairs).
• Discharge Precautions:
  • Individuals posing a static discharge threat should discharge themselves prior to entering environments with oxygen (e.g., oxygen tents).
  • All electrotherapy or ICU equipment should be correctly grounded.

Electrical Appliances

• Terminals:
  • Domestic appliances typically have three terminals (Live, Neutral, and Earth).
  • The potential difference (voltage) is applied between the live and neutral wires.
  • The earth wire is connected to the appliance casing for safety.
• Mains Supply:
  • UK/Ireland (Bahrain, Malaysia), mains is 50 Hz, 220/240 V.
  • U.S. mains is 60 Hz, 110 V.

Hazards Related to AC Current

• Accidental Contact:
  • If a person touches a live wire, a closed circuit to earth is created, and the current flows through them.
  • Ground (or earth) is common to both the person and the electrical socket.

Short Circuit Dangers

• 2-Pin Plugs:
  • A 2-pin plug indicates a breakdown in insulation between the live wire and the appliance casing.
  • The appliance might appear normal but current can flow through the person to earth rather than through the appliance (higher resistance).
• 3-Pin Plugs:
  • Connect the casing directly to earth.
  • Any leakage currents immediately flow back to earth.
  • Reduces electrocution risk.

Simple Precautions for Electric Current

• Earthing:
  • All appliances with metal casings must be properly grounded.
  • Patients should not be grounded whenever possible. (e.g., bed choice)

Precautions When Using a Defibrillator

• Electrode Isolation:
  • Electrodes (paddles) should be isolated from ground before charging and discharging.
• Large Area Paddles:
  • Large area paddles should be used to prevent unwanted burns.
• Patient Grounding:
  • Patients must not be in contact with ground.
• Physical Contact:
  • Physical contact with the patient should be avoided during defibrillation.
• Monitoring Equipment:
  • All monitoring equipment (e.g., ECG) should be isolated and current-protected.

Simple Safety Devices

• Fuses:
  • A fuse is a simple wire with a low melting point.
  • If current exceeds a threshold, the fuse melts and breaks the circuit.
  • The fuse rating should be slightly higher than the appliance's current draw (calculated using P = IV).
  • Shows examples using Youtube.

Ground Fault Interrupter (GFI)

• Leakage Currents:
  • Leakage currents flow to the appliance casing due to insulation breakdown.
• GFI Function:
  • GFI compares current flowing into and returning through an appliance.
  • If different, it indicates a hazard.
  • If the difference exceeds ~5 mA, the GFI breaks the circuit.

Microshock Hazard

• Low Current:
  • Microshocks are currents as low as 20 μA that can induce fibrillation.
  • Can be induced by a direct path to the heart.
• Reduced Danger Potential:
  • Internal electrical pathways to the heart can reduce the danger involved with current shocks by a factor of ~1000.

Microshock Sensitive Patients

• Patient Isolation:
  • Microshock sensitive patients should be completely isolated from ground.
• Grounding of Equipment:
  • All the electrical equipment connected to or near the patients must be individually earthed.

Test your knowledge on the electrical safety measures related to the musculoskeletal and nervous systems. This quiz covers static electricity, AC current hazards, and precautions for microshock-sensitive patients. Understand the risks and safety practices essential for healthcare environments.