EDAIC I MCQs from the ESAIC sample paper with simplified explanations. Weekly free uploads by targetedaic. (5)

A. the use of a condenser humidifier B. the use of low flow anaesthesia C. piping waste gases to floor level D. passing waste gases through activated charcoal B. passive ducting to the external atmosphere

A. FALSE B. TRUE C. TRUE D. TRUE E. TRUE

EXPLANATION: EFFECTIVE WAYS TO REDUCE OT POLLUTION INCLUDE:
Air-suction system: The air-suction device removes the air/gas mixture emitted through the overflow valves of the breathing circuit’s expiratory limb thereby preventing the mixture to get into the surgical air space.
Air circulation systems: A system has an optimal capacity if it’s capable of replacing the operating theatre’s air at least 15 times per hour when in use while atleast3/hour when not in use. The direction of airflow is also important. The air inflow should take place close to the ceiling, while the outflow should befall at a lower level.
Recirculation and Recycling of Halogenated Gases: Activated charcoal can absorb halogenated agents and can be used in expiratory limb to remove the exhaled agents. Silica zeolite (Deltazite®) effectively absorbs isoflurane from the suction system. The absorbed agent can be converted and reused with steam extraction and fractional distillation, in this way the emission of anaesthetic gases into the atmosphere can be significantly reduced.
Use of the circle breathing system: This system recycles the exhaled anaesthetic vapours, absorbing CO2. It requires a very low fresh gas flow, so reducing the number of inhalational agents used. This decreases the level of theatre environment contamination.

Low flow anaesthesia reduces occupational exposure to inhalation anaesthetics.

Passive ducting, although not a very efficient system, still helps in reducing the inside pollution of the theatre.

A humidifier helps in retaining exhaled moisture and has no active role in the management of OT pollution.

Although not universally agreed upon, the recommended maximum accepted concentrations in the UK, over an 8-hour time-weighted average, are:

1.  100 particles per million (ppm) for nitrous oxide
2.  50 ppm for enflurane
3.  50 ppm for isoflurane
4. 10 ppm for halothane

A. conduction is the most important phenomenon B. convection is decreased when the air adjacent to the body is warm C. radiation is decreased by aluminium foil blankets D. respiration equals 30% of the total heat loss E. sweating is decreased when the relative humidity increases

A. FALSE B. TRUE C.TRUE D. FALSE E. TRUE

The major cause of loss is radiation, accounting for roughly 60% of the total. Radiative loss is proportional to the difference between the fourth powers of the room wall (i.e., ambient) and skin temperatures. Being a shiny surface the aluminium sheet reflects radiant heat and reduces the heat loss by radiation by as much as 90%.

The remaining loss is largely convective, which is proportional to the difference between skin and air temperatures multiplied by the square root of airspeed. Hence, the warmer air prevents heat loss by convention.
Respiratory evaporative loss contributes only approximately 10% to the total and cutaneous evaporative loss remains relatively small except during sweating. However, evaporative loss from within surgical incisions can be substantial.
Conductive loss is dependent on the temperature of surfaces the patient comes in direct contact with during anaesthesia.

High relative humidity means the air is already saturated with water. This leads to a slowing of the evaporation of sweat from the skin.

A. determining the dew point B. a wet and dry bulb thermometer C. cooling a known volume of air D. absorption of water by a hair E. measuring barometric pressure

A. TRUE B. TRUE C. TRUE D. TRUE E. FALSE

Measurement of humidity:

Regnault’s (dewpoint) hygrometer: The dew point is the temperature to which air must be cooled to become saturated with water vapour. When cooled further, the airborne water vapour will condense to form liquid water (dew). At this temperature, the gas is fully saturated with water, hence both the water content and the relative humidity at any other temperature can be ascertained from a vapour pressure table.
Hair gets longer when it wet and the property is used in measuring ambient humidity with help of hair hygrometer.

Wet and dry bulb hygrometer: A system using two thermometers, one with a wet and the other a dry bulb. Air movement over the wet bulb causes evaporative cooling, generating a difference in temperature readings. This difference relates to the rate of airflow over the wet bulb and the relative humidity. Tables are used to look up the relative humidity from the two temperatures.
Absolute humidity is measured by weighing all moisture removed from a gas by cooling or chemical desiccants. This method is extremely accurate but takes many hours and is mainly used to calibrate other hygrometers.
Mass spectroscopy: Mass spectroscopy can be very accurate but only if condensation does not occur in the sample line. This is the best technique for assessing “in-circuit” humidity, as it can assess breath by breath changes.
Humidity transducers: Transducers are available in which the electrical conductivity of a membrane changes with water vapour

A. ultrasound B. dye dilution C. plethysmography D. thermal dilution E. electromagnetism

A. TRUE B. FALSE C. TRUE D. FALSE E. FALSE

The auscultatory or Korotkoff method of measuring BP has been the traditional approach for measuring SBP and DBP
ULTRASOUND is the basis of many non-invasive BP measurement machines especially in presence of A-V fistula and obesity. These devices measure the absolute local BP waveforms by applying an ultrasound transducer to the skin above an artery.
Plethysmography measures changes in volume in different areas of your body. It measures these changes with blood pressure cuffs or other sensors. Penaz finger cuff method is based on this technique. Recently, photoplethysmography (PPG) has been proposed as a continuous, non-invasive approach to BP estimation that can be integrated into wearable devices.
Thermal dilution and electromagnetic monitors are used for cardiac output measurement.

A. right ventricular performance
B. position of the patient
C. intra-abdominal pressure
D. mean airway pressure
E. competence of the tricuspid valve
Explanation: The venous system of the human body including the SVC has a poor muscular framework and the intraluminal pressure is easily affected by extraluminal forces like mean airway pressure, external compression (tumors, lymph nodes, aneurysm).
The superior vena cava is a valveless structure. This allows the pressure in the right atrium to be conducted upwards into the right internal jugular vein. Any change in RA or RV in cases of the incompetence of tricuspid valve pressure is reflected in SVC pressure.
Elevated intrathoracic pressures, as a result of trans-diaphragmatic Intra-abdominal pressure transmission, have been demonstrated to erroneously increase the central venous pressure.
Changes in the position of the patient, mean airway pressure and PEEP significantly alter the pressure in the central venous system including SVC.