Electrical interference can cause pacemakers and ICDs to malfunction.
Up to 0.1 mA.
Alternating current (AC) supplied at 50 Hz and 240 V.
Current may pass through an alternative route, causing electrical shocks and burns to the patient.
The pressure exerted by a vapor when in contact with and in equilibrium with its liquid phase within a closed system at a given temperature.
The flow of electric charge reverses direction periodically, producing a sine wave pattern.
F = Q/t.
The substance progresses from solid to liquid to gas at a given pressure.
By using a short, wide-bore cannula, raising the height of the giving set, applying a pressure bag, and warming the blood to reduce viscosity.
Inaccurate for continuous flow; over-reads at high flow rates and under-reads at low flow rates.
Solid, liquid, and gas.
Conditions where an external voltage appears on a part of equipment applied to the patient.
The heat required to convert 1 kg of solid at its melting point into liquid at the same temperature.
Joule per mole per kelvin (J mol−1 K−1).
It refers to the tetanic muscular contractions caused by AC at frequencies peaking at 50 Hz, making it difficult for a person to release their grip.
John Ritchie, a New Zealand anaesthetist.
Flow characterized by swirls and eddies, varying fluid velocity across the tube, and a non-linear relationship between pressure and flow.
A substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist.
The amount of energy given to a material to cause a 1 °C rise in temperature.
The amount of heat required to raise the temperature of 1 kg of a substance by 1 kelvin (or 1 °C).
To restore normal cardiac rhythm by delivering a burst of electrical energy to the heart.
Up to 0.5 mA.
The conditions of temperature and pressure where two of the three phases are in equilibrium.
Joule per kilogram (J kg−1).
Electronic sensors.
The saturated vapor pressure increases due to more molecules gaining sufficient energy to escape the liquid surface.
Pacemaker devices must be checked, and alternative pacing techniques should be available.
Opposition to the flow of direct current, represented by R and measured in ohms (Ω).
More complex structures have higher heat capacity due to more ways for molecules to vibrate.
To ensure that no safety hazard arises if a single fault occurs.
Joule per kilogram per kelvin (J kg−1 K−1).
Laminar flow and turbulent flow.
An oxygen failure alarm powered by falling oxygen pressures.
As oxygen pressure falls, the diaphragm's force reduces, allowing the valve to open and activate the whistle.
The specific temperature and pressure at which water can exist simultaneously in solid, liquid, and gas phases.
The states of a substance at different temperatures and pressures.
A system that shuts off the supply of all other gases apart from oxygen and air.
By measuring the pressure difference across a fixed orifice.
The amount of heat required to raise the temperature of 1 mole of the substance by 1 K (or 1 °C).
It acts as a resistance to flow and maintains laminar flow.
They are depolarized, essentially re-setting the electrical status of the heart.
To prolong the duration of current discharge.
0.5–1.0 MHz.
A 'floating circuit' where parts attached to the patient are isolated from the rest of the equipment.
In the mid-1960s.
At least 60 dB lasting for 7 seconds.
When oxygen pressure falls to 200 kPa.
It allows for minimal power loss over large distances.
Wright respirometer.
To measure gas flow using a constant orifice, variable-pressure method.
Flow (F) is the quantity (Q) of a liquid or gas passing a point per unit time (t).
Diathermy involves the deliberate application of tissue-damaging currents, and patients must be protected from contact with earth to prevent severe burns and leakage currents from faulty equipment.
To cut tissues and coagulate blood vessels.
Particles are arranged in a regular pattern or lattice with minimal spacing.
A constant pressure, variable orifice device used to measure gas flow.
Heliox, being less dense than air, lowers the Reynolds number, changing turbulent flow to laminar flow, which reduces the work of breathing.
Limit use to short bursts of less than 5 seconds and ensure the neutral plate is well adhered and far from the pacemaker.
In coulombs (C).
Fusion (melting).
Reynolds number > 2000.
20–50 J.
To prevent the 'R on T' phenomenon, which can trigger VF.
Burns, incorrect positioning of the neutral plate, ignition of flammable skin preps, and inadvertent activation of the diathermy probe.
Burns, ignition of flammable materials, interference with electrical components, precipitation of VF, and electrocution.
Because they have low reactance at high frequencies (e.g., 1.5 mHz) and can conduct, while mains electricity at 50 Hz has high reactance and will not be conducted.
A dimensionless number that predicts the onset of turbulent flow, calculated as velocity of fluid × Density × Tube diameter / Viscosity.
Monophasic and biphasic.
A dynamic equilibrium forms when the number of particles escaping the liquid equals the number rejoining it.
A magnetic flux.
The bobbin rises in a tapered glass tube as flow increases.
Up to 0.01 mA.
The technology of using the flow characteristics of a liquid or gas to perform operations similar to mechanical or electronic systems.
Macroshocks occur due to the passage of current from one part of the body to another, such as from lightning or direct contact with a live instrument.
Latent heat is given out to the surroundings.
Hagen–Poiseuille equation.
A magnetic field.
Water's melting point decreases with pressure.
A device that changes one form of energy into another, typically into an electronic signal for interpretation and recording.
Bandwidth filters, high or low pass filters, notch filters, and amplitude filters.
The heat required to convert 1 kg of liquid at its melting point into vapour at the same temperature.
Particles jiggle about, have no fixed form, and are free to move without a regular structure.
It is connected to the earth at the mains transformer, making its electrical potential 'neutral' with the earth.
The velocity above which the flow of a fluid within a tube is likely to change from laminar to turbulent.
Electricity would flow through the earth wire to earth, preventing a shock to the user.
A gas that is below its critical temperature.
Viscosity and density of the fluid.
Only at the surface of the liquid.
Vaporisation of the liquid phase from the skin surface causes cooling, rendering the area numb.
Because steam contains latent heat, which releases more energy upon condensation.
To transfer electrical energy between circuits through electromagnetic induction.
The difference in the size of the input signal and the amplified signal, measured in bels or decibels.
AC is significantly more dangerous than DC; AC can cause tetanic muscular contractions and is particularly dangerous to the heart, while DC typically results in a single muscle contraction.
Live wire (brown), neutral wire (blue), and earth wire (green and yellow).
1 atmosphere.
To store and rapidly discharge energy.
The pressure exerted by particles that escape from the surface of a liquid.
Anti-static flooring that has high impedance to mains electricity.
360 J.
It stores charge and consists of two conducting plates separated by an insulating material.
They block conduction of low-frequency currents while allowing conduction of high-frequency diathermy currents.
To avoid fluctuations in the delivery of the volatile agent.
Energy (e) = ½ C v².
It blocks DC (high resistance) but passes AC (low reactance) as the plates get alternately charged and discharged.
Positive anode and negative cathode, connected by a conductive electrolyte.
The ability of differential amplifiers to reject signals that are common to both leads while amplifying varying signals.
It protects people from exposure to the full current of mains electricity in faulty appliances.
0–5 mA causes tingling.
No, it depends only on temperature.
It inhibits the build-up of static electricity.
The kinetic energy of particles overcomes intermolecular forces, causing the lattice to break up.
To resist a change in electric current.
Charge (q) = Capacitance (C) × Voltage (v).
The ratio of the number of coils of each circuit around the transformer core.
It predicts laminar flow.
Through high frequency AC passing through tissues of high impedance.
Gas particles are very far apart, move in rapid random motion, and completely fill any container.
A fundamental equation in electronics represented as V = i × r, where V is voltage, i is current, and r is resistance.
It refers to heat used to overcome the attraction of inter-molecular bonds during phase changes.
E = ½QV or E = ½ c V².
It increases with increasing frequency.
The melting point increases with pressure.
Oxidation occurs at the anode and reduction at the cathode.
It is a damped sinusoidal wave where current flows in one direction only.
It allows 1 ampere of current to flow when a potential of 1 volt is applied across it.
They have high reactance to AC (block AC) and low resistance to DC (pass DC).
Cutting mode uses an alternating sine wave pattern, while coagulation mode uses a pulsed sine wave pattern.
ECG monitoring is paramount.
It states that fluid pressure decreases in regions where flow velocity increases, maintaining constant total energy.
Changes in composition and temperature, specifically the increase in average kinetic energy of the particles.
In farads (F).
Triple point.
Block AC (high reactance) and pass DC (low resistance).
They can step up or step down the voltages of alternating current.
Higher temperatures increase the proportion of particles with sufficient energy to evaporate.
By acting as filters, often using differential amplification to reject common signals.
Bipolar diathermy is safer than monopolar diathermy.
The temperature remains constant even though heat is still being applied.
Shoes have a high resistance (200,000 Ω), which increases the total resistance encountered by the current, reducing the magnitude of current that can flow through the body.
100–400 watts.
It describes how a pressure drop induced by increased fluid velocity through a narrow orifice can entrain a second fluid.
To break a circuit or sound an alarm if a stray current above a set limit is detected flowing to earth.
Using the equation e = ½ c V².
A device that can store charge, consisting of two conducting plates separated by an insulator (dielectric).
To protect people from the effects of faulty insulation by providing a path for electricity to flow to the ground.
A microphone, which converts sound energy into an electrical signal.
Fluid moves steadily, flow rate is greatest at the center, a pressure difference must exist, and flow is directly proportional to this pressure difference.
It can change with temperature and stretch, which is exploited in electrical thermometers and transducers.
The amount of heat energy absorbed (or released) by a substance as it changes phase at a given temperature.
5000 V d.c.
Current is passed between two probes within a modified pair of forceps, heating tissues between them.
It decreases with increasing frequency.
Non-sparking switches and plugs.
Total opposition to current flow in an alternating current circuit, made up of resistance and reactance.
The process where particles of a liquid move to the vapor state at any temperature.
The process where a solid changes directly to a vapor without going through the liquid phase.
By the ratio of pressure to flow.
Solid carbon dioxide (dry ice) changing directly to CO2 vapor at normal atmospheric pressure.
150 J.
It provides a path for electricity to flow to the ground instead of through a person, reducing the risk of electric shock.
Opposition to the flow of alternating current caused by inductance and capacitance, rather than resistance.
The tendency of a fluid jet to stay attached to an adjacent curved surface, affecting gas flow distribution in the lungs.
The process where liquid particles gain enough energy to overcome residual forces and become a gas.
Regular checks and maintenance of equipment.
611.73 Pa (0.006 atm).
A collection of galvanic cells that convert stored chemical energy into electrical energy when part of an electrical circuit.
An amplifier makes the input signal larger for easier interpretation, rather than changing it from one form to another.
Current flows in alternating directions, completing one cycle in approximately 10 ms.
Because more energy is required to overcome the intermolecular bonds to liberate a gas.
Reynolds number < 2000.
Farads (F).
Use of an isolated patient circuit and an isolating capacitor.
Electrical equipment is classified by its protection from mains electricity and allowable leakage current into Class I (earthed), Class II (double insulated), and Class III (battery-operated).
Flow is proportional to the pressure drop and radius to the power of 4, and inversely proportional to the length of the tube and viscosity of the fluid.
Approximately 40 watts.
The boiling point increases with pressure.
Allows current to flow in one direction only.
A measure of the performance of the system, comparing the amount of noise introduced to the signal.
It lowers the electrical threshold for successful defibrillation, allowing lower energy levels to be used and reducing the risk of burns and myocardial damage.
It interferes with pulse oximetry, ECG, and oesophageal Doppler.
Microshocks occur due to the passage of current directly to the myocardium, often from small leakage currents through central lines or pacing wires.
To ensure the current density is low enough to prevent injury and burns.
273.16 K.
Only trained personnel should deliver shocks, ensure all personnel are standing clear, maintain and check the defibrillator regularly, and have dry surroundings.
Because biological signals are often very small and need to be amplified for display.
Unwanted signal that is amplified along with the desired signal.
The net inward force experienced by particles at the surface due to surrounding particles.
