Hazards and safety

Question 1

What is the most important electrical safety feature of electromedical devices?

Answer 1

Avoidance of earth leakage currents

Question 2

Electrical safety

Answer 2

• Wet skin reduces the electrical impedence and increases the risk of shock
• Modern diathermy return plates are not directly connected to earth, to avoid earth leakage currents
• Microshock (from electrical contact placed inside the body) can cause VF at currents above 100 microamps
• Leakage currents may be caused by voltages induced in other circuits by alternating mains current

Question 3

Laser

Answer 3

= Light amplification by the stimulated emission of radiation
* Monochromatic
* Almost non-divergent
* High intensity beam
* In phase
* May be of a very small cross-sectional area

Question 4

Types of laser

Answer 4

• Argon - produces a blue-green light which is used for retinal surgery
• Carbon dioxide - most common laser in surgery. Produces infrared light that vaporizes water in tissues, cutting with haemostasis and low penetrance. It is not suitable for endoscopic use
• Neodynium-doped yttrium aluminium garnet (Nd:YAG) - Produces near infrared light. Not absorbed by water, used for coagulation and cutting with deep penetration. Can be used endosopically

Question 5

Laser safety and hazards

Answer 5

• High intensity laser light may burn the retina and optic nerve, resulting in partial or total blindness
• Low FiO2 should be used
• If an airway fire occurs - switch off the laser and flood the site with saline