The mean noise level in the operating rooms in various studies is around

• 65–60 dB but it may even exceed 100 dB

• 25 – 45 dB

• 250 – 450 dB

• 160 – 220 dB

6- Boyle’s law

• At a constant volume, the absolute pressure of a fixed mass of gas is directly proportional to the absolute temperature

• At a constant pressure, the volume of a fixed mass of gas is directly proportional to the absolute temperature

• The pressure exerted by a fixed mass of gas in a mixture of gases is the same as the pressure it would exert alone

• At a constant temperature, the volume of a fixed mass of gas is inversely proportional to the absolute pressure

Regarding Diathermy safety

• Ohm’s law states that current = voltage x resistance

• Diathermy works because there is a high current density at the active electrode

• The heat energy produced by cautery is proportional to the current at the tip of the active electrode

• Bipolar diathermy requires a passive electrode (‘diathermy plate’)

When the relative humidity is 100% then

• relative humidity and absolute humidity are equal

• relative humidity and specific humidity are equal

• the relative humidity will decrease if the temperature decreases

• a patient’s perspiration will not evaporate

With regard to electrical safety and prevention of explosions

• A.  Anaesthetic machines should be isolated from ‘earth’ to prevent completion of an electrical circuit.

• Currents of 10 microamps may initiate ventricular fibrillation

• The neutral connection of a circuit is not at earth potential at the patient end of the circuit

• In surgical diathermy the heat released depends on the square of the potential difference between electrodes

Heat and moisture exchangers are contra-indicated when patients have:

• Copious secretions.

• Hypothermia.

• Hyperthermia.

• Tenacious sputum.

Which is true about heat loss

• Conduction is the largest factor in patient heat loss

• Radiation accounts for about 10% of the total heat loss

• Convection is due to heating of the adjacent air layer which is replaced by cooler air from the surroundings

• Heat lost in breathing dry gases is approximately 30% of total heat loss in the anesthetized subject

The current delivered to the patient by an electrocautery device differs from the current supplied by an electrical utility in its

• capacitance

• frequency

• amperage

• voltage

The  National  Fire  Protection  Association  mandates which one of these standards for operating rooms?

• Isolated power is required in all operating rooms

• Isolated power is required in areas designated as wet locations

• In the event of a power failure, emergency power must become operative within 1 second

• When isolated power is p resent, a line isolation monitor must also be present

Concerning humidity and humidification of gases

• Relative humidity is the ratio of absolute humidity to saturated humidity at a specified temperature

• Operating theatre humididty should be maintained at no more than 30%

• Heat and moisture exchangers can't achieve 50% humidity

• A nebuliser works on the poiseuille effect to entrain water across a pressure drop