Breathing system is an assembly of components which connects patient’s airway to anaesthesia machine through which controlled composition of gas mixture is dispensed. It delivers gas to the patient, removes expired gas and controls the temperature and humidity of the inspired mixture. It allows spontaneous, controlled, or assisted respiration. It may also provide ports for gas sampling, airway pressure, flow and volume monitoring.

Breathing systems have been classified by Conway and Mapleson.
Conway suggested a functional classification:
– Circuits requiring a CO2 absorber
– Circuits not requiring a CO2 absorber

William Mapleson designated varying arrangements of breathing system components (masks, breathing tubes, fresh gas flow inlets, adjustable pressure-limiting valves, and reservoir bags) as Mapleson A-E circuits.
Mapleson A: Arranged as FGF inlet, reservoir bag, APL valve, mask.
In this circuit, because the reservoir bag is between the FGF inlet valve and the APL valve, expired gas from the patient may re-enter the system and fill the reservoir bag during controlled ventilation. This is the most efficient system for spontaneous breathing as the FGF must only be equal to a patient’s minute ventilation to prevent rebreathing.

Mapleson B: Arranged as reservoir bag, FGF inlet, APL valve, mask.
In this circuit, the FGF inlet is closer to the APL valve, which helps prevent the rebreathing concern in the Mapleson A circuit as above during controlled ventilation.

Mapleson C: Arranged as reservoir bag, FGF inlet, APL valve, mask.
In this circuit, the arrangement is the same as the Mapleson B circuit. However, this circuit is shorter as it does not contain elongated corrugated tubing. This circuit also has the FGF inlet close to the APL valve to aid in preventing rebreathing.

Mapleson D: Arranged as reservoir bag, APL valve, FGF inlet, and mask.
In this circuit, the arrangement interchanges the FGF inlet and APL valve of the Mapleson A circuit. This system prevents rebreathing by directing FGF towards the APL valve rather than towards the patient during exhalation.

Mapleson E: Arranged as corrugated tubing, FGF inlet, and mask.
In this circuit, there is no reservoir bag and no APL valve. Given the inability to alter the pressure of the circuit, this is ideal for spontaneously ventilating neonates or paediatric patients where low-pressure ventilation is desired. The system prevents rebreathing, similar to the Mapleson D circuit.

Jackson Rees later modified the Mapleson E by adding an open ended bag, which has since become known as the Mapleson F.
Mapleson F: Arranged as APL valve directly connected to reservoir bag, corrugated tubing, FGF inlet, and mask.
The system prevents rebreathing similarly to Mapleson D by directing FGF towards the APL valve.

Dinamap continuously measures the systolic, diastolic and mean arterial pressure along with pulse rate, thereby providing a continuous monitoring of the blood pressure using the osscillitonometric principle of measurement.

The device loses accuracy towards the extremes of BP and is more accurate with systolic compared with diastolic pressure. In arrhythmias such as AF, the devices are also inaccurate due to the major fluctuations associated with the individual pulse pressure variations.

The manual BP device is still the gold standard for BP measurement and monitoring.

A higher frequency ultrasound comes with a better resolution of the digital image. Ultrasound with a frequency of 15 MHz is best used in imaging of superficial organs such as the thyroid gland, muscles, tendons and breasts whereas deep organs are better imaged using a lower frequency of 2-7MHz because of its ability for deeper penetration but lower resolution. These low frequency probes are also used to diagnose ascites, pleural effusions or can be used in echocardiography.

The US probe emits and then absorbs a reflected wave. Similar to brightness control, increasing the gain will amplify the return signal which is then attenuated by the tissue. This increases the signal to noise ratio.
A high frame rate, which basically means the number of times an image is updated onto the screen per second, improves the resolution of a moving 3D image which has become more accurate as the computing power has increased.

Widening of the image field can be obtained by altering the penetration depth which is obtained by changing the frequency of the US beam

Among the breathing circuits, the Lack circuit is the most efficient for spontaneous breathing.

An outer coaxial tube is present to deliver fresh air; exhaust air is routed to an inner tube, which is then delivered to a scavenging system. An expiratory valve is seen at the patient end, which is an advantage over other circuits. Moreover, the Lack circuit prevents rebreathing slightly greater than the alveolar minute ventilation at 4-5 litres per minute.

The Bain circuit prevents rebreathing at 160-200ml/kg per minute, and is a co-axial version of the Mapleson D circuit.

The Mapleson E circuit prevent rebreathing at a fresh gas flow (FGF) of approximately twice the patient’s normal minute volume. A modification of this, the Mapleson F, has a reservoir bag at the opposite end for the FGF. This circuit is appropriate for paediatric patients with a body weight less than 20 kg.

Electromagnetic waves are categorized according to their frequency or equivalently according to their wavelength. Visible light makes up a small part of the full electromagnetic spectrum.

Electromagnetic waves with shorter wavelengths and higher frequencies include ultraviolet light, X-rays, and gamma rays. Electromagnetic waves with longer wavelengths and lower frequencies include infrared light, microwaves, and radio and televisions waves.

Different electromagnetic waves according to their wavelength from shorter to longer are X-rays, ultraviolet radiations, visible light, infrared radiation, radio waves. X-ray among electromagnetic waves has the shortest wavelength and higher frequency with wavelengths ranging from 10*-8 to 10* -12 and corresponding frequencies.

The Drager Oxylog® 1000 is a pneumatically powered, time-dependent, volume-titrated emergency ventilator with a pressure limit. It is compatible with CD cylinder oxygen. The CD cylinder is a strong and lightweight cylinder usually composed of aluminium or Kevlar. The internal cylinder volume is 2 litres, and the pressure of a full cylinder is 230 bar. The volume of the full cylinder is determined by applying Boyle’s law: P1 × V1 = P2 × V2

Where:
P1= pressure of a full cylinder (230 bar)
V1= volume of oxygen at that pressure (2 litres)
P2= final pressure (1 bar), and
V2= volume of oxygen in the full cylinder.

Substituting values into the equation:

230 × 2 = 1 x V2
V2 = 460 litres. The flow of fresh gas is 4 litres/minute + 1 litre/minute required by the control, making a total of 5 litres/minute. The amount of time it takes for the cylinder to empty would be the total volume of oxygen in the full cylinder divided by the amount of oxygen expelled per minute: 460/5 = 92, meaning it would take 92 minutes for the cylinder to empty.

There are two types of defibrillators
AC defibrillator
DC defibrillator

AC defibrillator,
consists of a step-up transformer with primary and secondary winding and two switches. Since secondary coil consists of more turns of wire than the primary coil, it induces larger voltage. A voltage value ranging between 250V to 750V is applied for AC external defibrillator. And used to enable the charging of a capacitor.

DC defibrillator,
consists of auto transformer T1 that acts as primary of the high voltage transformer T2. Is an iron core that transfers energy between 2 circuits by electromagnetic induction. Transformers are used to isolate circuits, change impedance and alter voltage output. transformers do not convert AC to DC.

Diode rectifier composed of 4 diodes made of semiconductor material allows current to flow only in one direction. Alternating current (AC) passing through these diodes produces direct current (DC). Capacitor stores the charge in the form of an electrostatic field.

Capacitor is used to convert the rectified AC voltage to produce DC voltage but capacitors do not directly convert AC to DC.

Inductor induces a counter electromotive force(emf) that reduces the capacitor discharge value.

In step-down transformer primary coils has more turns of wire than secondary coil, so induced voltage is smaller in the secondary coil.

Direct laryngoscopy are performed using laryngoscopes and they can be classed according to the shape of the blade as curved or straight.

Miller, Soper, Wisconsin and Seward are examples of straight blade laryngoscopes. Straight blades are commonly used for intubating neonates and infants but can be used in adults too.

The tip of the miller blade is advanced over the epiglottis to the tracheal entrance then lifted in order to view the vocal cords.

The RIGHT-SIDED Macintosh blade is used in adults while the left-sided blade may be used in conditions that make intubation with standard blade difficult e.g. facial deformities.

The McCoy laryngoscope is based on the STANDARD MACINTOSH blade not Robertshaw’s. It has a lever operated hinged tip, which improves the view during laryngoscopy.

Polio blade is mounted at an angle of 120-135 degrees to the handle. Originally designed for use during the polio epidemic ​in intubation patients within iron lung ventilators, it is now useful in patients with conditions like breast hypertrophy, barrel chest, and restricted neck mobility.

Adequate humidification is vital to maintain homeostasis of the airway. Heat and moisture exchangers conserve some of the exhaled water, heat and return them to inspired gases. Many heat and moisture exchangers also perform bacterial/viral filtration and prevent inhalation of small particles. Heat and moisture exchangers are also called condenser humidifier, artificial nose, etc. Most of them are disposable devices with exchanging medium enclosed in a plastic housing. For adult and paediatric age group different dead space types are available. Heat and moisture exchangers are helpful during anaesthesia and ventilatory breathing system. To reduce the damage of the upper respiratory tract through cooling and dehydration inspiratory air can be heated and humidified, thus preventing the serious complications. Moreover, they are the most appropriate humidification devices used for routine anaesthesia.

Gases can be bubbled through water to increase humidity. Passing gas through water at room temperature causes the gas to cool due to latent heat of vaporisation. The water bath can be heated. This improves the efficiency of the device and also reduces the incidence of bacterial colonisation.

Nebulisers use a venturi system which employs the Bernoulli effect. A gas at high flow passes through a constriction causing the gas to accelerate, reducing its potential energy allowing other gases or liquids to be entrained. This can include medications or in the case of humidification, water vapour. The size of the water droplet produced by nebulisation determines where in the airway it is deposited. Standard nebulisers produced droplets of 4 microns in diameter and these are deposited in the upper airway and trachea. Efficacy can be improved by passing the droplets over an anvil which further reduces particle size. The most efficient form of nebuliser is the ultrasonic nebuliser. Here a transducer immersed in water and vibrated at a frequency of 3MHz produces1-2micron droplets. These particles easily reach the bronchioles and provide excellent humidification.

Flowmeters measure the rate at which a specific gas, that the flowmeter has been calibrated for, passes through. This calibration is done at room temperature and standard atmospheric pressure with an accuracy of +/- 2%.

Reading the flowmeter is done from the top of a bobbin (the midpoint of a ball). Oxygen is the last gas to be added downstream to the mixture delivered to the back bar as a safety feature. This prevents delivery of a hypoxic mixture.

Inaccurate flow measurements occur when the bobbin sticks to the inside wall of the flowmeter. Stannic oxide has been used as a successful antistatic substance thus, reducing the aforementioned risk.

Carbon dioxide being easily delivered is found on some older machines, but those attached flowmeters are limited by a maximum flow of 500 ml /min. Thus avoiding the delivery of a hypercarbic mixture.

The principle by which a strain gauge works is that when a wire is stretched, it becomes longer and thinner, and as a result, its resistance increases.

A strain gauge, which is used in pressure transducers, acts as a resistor. When the pressure in a pressure transducer changes, the diaphragm moves, changing the tension in the resistance wire and thus changing the resistance.

Changes in current flow through the resistor are amplified and displayed as a pressure change measure.

A Wheatstone bridge, on the other hand, is frequently used to measure or monitor these changes in resistance.

Mapleson breathing system (or circuit) analysed five different arrangements of components of the breathing system:
Mapleson A – It is the most efficient for spontaneous respiration. The flow of fresh gas required is 70-85 ml/kg/min, i.e., approximately 5-6 lit./min fresh gas flow for an average adult.
Mapleson B and C – inefficient for both SV and PPV; requires gas flow of two to three times minute volume (100 ml/kg/min). Not commonly used but category C may be used for emergency resuscitation.
Mapleson D – efficient for PPV at gas flow equivalent to patient’s minute volume; the Bain’s circuit is a coaxial version of the Mapleson D
Mapleson E and F – for paediatric use; requires gas flow at two to three times the patient’s minute volume. The Mapleson F consists of an open-ended reservoir bag (Jackson-Rees modification).

Professor Mapleson classified non-rebreathing circuits based on the position of the APL valve, which controls fresh gas flow.

The Mapleson A (Magill) circuit is most effective in spontaneous breathing, requiring only 70-100 ml/kg (the patient’s minute volume) of fresh gas flow. The patient inhales fresh gas from the reservoir bag and tubing during inspiration. During expiration, the patient adds dead space gas (gas that hasn’t been exchanged) to the tubing and reservoir bag in addition to the fresh gas flow. At the patient’s end, alveolar gas is vented through the APL valve. During the expiratory pause, the fresh gas flow causes more gas to be released.

The Mapleson A is inefficient during controlled ventilation. Venting occurs during inspiration rather than during the expiratory phase, as it does during spontaneous ventilation. As a result, unless a high fresh gas flow of >20 L/minute is used, alveolar gas is rebreathed.

During spontaneous ventilation, the Mapleson D circuit is inefficient.

The oxygen concentration in a Hudson mask is insufficient to allow for adequate pre-oxygenation.

The following are the colour codes for medical gas cylinders:

Oxygen cylinder has a dark body with white shoulders.

Nitrous oxide is French blue. Air encompasses a grey body with dark and white quarters on the shoulders.

Entonox contains a French blue body with white and blue quarters on the shoulders.

Carbon dioxide barrels are grey in colour.

The nerve stimulators deliver a stimulus lasting for 1-2 milliseconds (not second) to perform nerve blockage.

There are just 2 leads (not 3); one for the skin and other for the needle.

Prior to the administration of the local anaesthesia, a current of 0.25 – 0.5 mA (not 1-2mA) at the frequency of 1-2 Hz is preferred.

If the needle tip is close to the nerve, muscular contraction could be possible at the lowest possible current.

Insulated needles have improved the block success rate, as the current is only conducting through needle tip.

Stimulus to the femoral nerve which is placed in the mid lingual line causes withdrawer of the quadriceps and knee extension, that’s the dancing patella ( not plantar flexion).

A thermocouple, or a thermal junction, is temperature measuring device consisting of a pair of dissimilar metal (bimetallic) wires or strips joined together. Typically, copper and constantan (an alloy of 55% copper and 45% nickel) are used. When there is contact between these metals, a small voltage is generated in the order of millivolts. The magnitude of the thermojunction electromotive force (emf) is proportional to applied temperature (the Seebeck effect). This physical principle is applied in the measurement of temperature. The electromotive force at the measuring junction is proportional to temperature.

Two wires with different coefficients of expansion, joined together, can be used as a switch for thermostatic control.

Semiconductors are NOT used in thermocouple. The resistance of the measuring junction of a thermocouple is irrelevant.

Two bonded wires of dissimilar metals, iron/constantan or copper/constantan, make up a thermocouple (constantan is an alloy of copper and nickel). At the tip, a thermojunction voltage is generated that is proportional to temperature (Seebeck effect).

All of the other connections are non-linear.

For a single compartment model, the relationship between a decrease in plasma concentration of an intravenous bolus of a drug and time is a washout exponential.

A sine wave is the relationship between current and degrees or time from a mains power source.

A sigmoid curve represents the relationship between efficacy and log-dose of a pure agonist on mu receptors.

The pressure of a fixed mass of gas and its volume (Boyle’s law) at a fixed temperature are inversely proportional, resulting in a hyperbolic curve.

A Wrights Respirometer measures the volume of air exhaled over the course of one minute of normal breathing

It is unidirectional and measures tidal volume and minute volume of gas flow in one direction. It is placed at the expiratory side (lower pressure than inspiratory side therefore lower chances of gas leaks)

Slits are arranged such that incoming gas will rotate the vane at a rate of 150 revolutions per litre of flowing gas

The Wright respirometer tends to over-read at high flow rates and under-read at low flows because of mechanical causes like friction and inertia and the accumulation of water vapour

The ideal flow for accurate readings is 2 L/min for the respirometer. The respirometer reads the tidal volume and minute volume with a ±5–10% accuracy within the range of 4–24 L/min.

There are different models of flowmeters determined by the applied pressure and its orifice. For instance, the watersight flowmeter functions through applying variable pressure, and it has a variable orifice. In contrast, the bubble flowmeter is operated using a constant pressure and orifice. Flowmeters such as rotameters, Heidbrink and Peak have a constant pressure but variable orifice. On the other hand, flowmeters including a simple pressure gauge, water depression, and pneumotachograph have a constant orifice but variable pressure.

Tracheal tubes are made of either disposable plastic or reusable red rubber.

The tube size refers to the internal diameter (ID) in mm which is marked on the outside of the tube (some manufacturers mark the external diameter on the outside).

Plastic tubes have a radiopaque line spanning the entire length of the tube, which allows their position to be identified on x-rays. The bevel located at the end of the tube is left-facing and oval in shape, which improves the view of the vocal cords during intubation.

Oxford tubes are L-shaped and have a bevel that faces posteriorly. They have thick walls that increase the external diameter, making for a wider internal diameter.

RAE (Ring, Adair, and Elwyn) tubes are preformed and can either be north or south facing and cuffed or uncuffed. The cuffed RAE tubes have one Murphy eye, whereas the uncuffed has two Murphy eyes. Uncuffed tubes are primarily used in paediatric anaesthesia and the two Murphy eyes ensure adequate ventilation- should the tube be too long.

Mapleson classified breathing systems into A, B, C, D and E. Jackson-Rees subsequently modified the Mapleson E by adding a double-ended bag to the end of the reservoir tubing, creating the Mapleson F. A Mapleson E or T-piece does not have a reservoir bag.

A Mapleson A system is a very efficient system for use during spontaneous ventilation. However, it is not suitable for use with patients less than 25 kg, due to the increased dead space at the distal / patient end. This system can be modified into a Lack system or coaxial Mapleson A, where the fresh gas flows through an outer tube (30 mm) and exhaled gases flow through the inner tube (14 mm).

The adjustable pressure limiting valve (APL) or expiratory valve allows exhaled gas and excess fresh gas to leave the breathing system. It is a one-way, adjustable spring-loaded valve, and gases escape when the pressure in the system exceeds the valve opening pressure. During spontaneous ventilation a pressure of less than 1 cm of water (0.1 kPa) is needed when the valve is in the open position (not 2 cm of H2O).

The reservoir bag is highly compliant and when over inflated, the rubber bag can limit the pressure in the system to about 40 cm of H2O.

This is due to the law of Laplace, which states that the pressure will fall as the radius of the bag increases:

Pressure = 2 x tension/radius.

Carbon dioxide (CO2), is a carbonic gas made up of two dissimilar atoms, namely one carbon atom and two oxygen atoms. Capnography is a technique used to measure carbon dioxide during a respiratory cycle, and it consists in calculating the concentration of the partial pressure of CO2, through the absorption of the infrared light, namely that CO2 absorbs infrared radiation at a wavelength of 4.28 µm.

End-tidal CO2 (ETCO2), referring to the level of the carbon dioxide released at the end of an exhaled breath, is required to be continuously monitored, especially in ventilated patients, as it is a sensitive and a non invasive technique that provides immediate information about ventilation, circulation, and metabolism functions. ETCO2 is normally lower than the arterial partial pressure and varies between 0.6 and 0.7 kPa.

There are two methods used to measure carbon dioxide. The sidestream capnometer method samples gases at a set flow rate (150-200 mL/min) from a sampling area through small diameter tubing, and the mainstream analyser method that uses a direct measurement of the patient exhaled CO2 by a relatively large and heavy sensors. Sidestram method allows the analysis of multiple gases and anaesthetic vapours comparing to the mainstream method that does not allow the measurement of other gases.

The potential difference (amplitude) and bandwidth frequencies of bioelectric signals are typical.

These are the following:

ECG: A bandwidth of 0.5-50 Hz is usually sufficient in monitoring mode, but a typical diagnostic bandwidth is 0.05-150 Hz (up to 200 Hz) with a typical voltage range of 0.1-4 millivolts (100-4000 microvolts).
EEG has a frequency range of 0.5-100 Hz and a voltage range of 0.5-100 microvolts.
EMG has a frequency range of 0.5 to 350 Hz and a voltage range of 0.5 to 30 millivolts.

Prior to display, these small signals will need to be amplified and processed further.

Ambient pressure has no effect on a volatile agent’s saturated vapour pressure (SVP). At a temperature of 20°C, the SVP of sevoflurane is approximately 21 kPa, or 21% of atmospheric pressure (100 kPa).

The SVP of sevoflurane remains the same when the ambient pressure is doubled to 200 kPa, but the output of the vaporiser is halved, now 21 percent of 200 kPa, equalling 10.5 percent. The vaporiser’s output has increased to 1%, but the partial pressure output has remained unchanged. The splitting ratio will not change because it is determined by temperature changes.

Calculations can be made as follows:

Vaporizer output % (ambient pressure) = % volatile (calibrated) x 100 kPa calibrated pressure/ambient pressure
2% = 2% (dialled) × 100/100
2% of 100 = 2 kPa

Altitude, pressure 50 kPa
4% = 2% (dialled) × 100/50
4% of 50 = 2 kPa

High pressure at 200 kPa
1% = 2% (dialled) × 100/200
1% of 200 = 2 kPa

Sevoflurane has a boiling point of 58°C and, unlike desflurane (which has a boiling point of 22.8°C), does not need to be heated and pressurised with a Tec 6 vaporiser.

When the emergency oxygen flush is pressed, 100% oxygen is supplied from the common gas outlet. This gas bypasses BOTH flowmeters and vaporisers. The flow of oxygen is usually 45 l/min at a PRESSURE OF 400 kPa.

There is an increased risk of pulmonary barotrauma when the emergency flush is pressed, especially when anaesthetising paediatric patients.

The inappropriate use of the flush causes dilution of anaesthetic gases and this increases the possibility of anaesthetic awareness .

The body of the Entonox cylinder is usually blue (occasionally white), with blue and white shoulders. Entonox contains a 50:50 mixture of oxygen and nitrous oxide, with a full cylinder pressure of 13700 KPa (137 bar). The cylinder is equipped with a two-stage pressure regulator for safe operation.

The cylinder body and shoulder of nitrous oxide are (French) blue.

In today’s anaesthetic workstations, carbon dioxide cylinders are no longer used.

The body of an oxygen cylinder is black, with a white shoulder.

The white Heliox (21 percent oxygen and 79 percent helium) cylinder has a brown and white shoulder. The administration of this gas mixture, which is less dense than air, is used to reduce turbulence (stridor) of inspiratory flow in patients with upper airway obstruction.

Electrocautery, also known as diathermy, is a technique for coagulation, tissue cutting, and fulguration that uses a high-frequency current to generate heat (cell destruction from dehydration).

The two electrodes in bipolar diathermy are the tips of forceps, and current passes between the tips rather than through the patient. Bipolar diathermy’s power output (40-140 W) is lower than unipolar diathermy’s typical output (400 W). There is no earthing in the bipolar circuit.

A cutting electrode and a indifferent electrode in the form of a metal plate are used in unipolar diathermy. The high-frequency current completes a circuit by passing through the patient from the active electrode to the metal plate. When used correctly, the current density at the indifferent electrode is low, and the patient is unlikely to be burned. Between the patient plate and the earth is placed an isolating capacitor. This has a low impedance to a high frequency current, such as diathermy current, and is used in modern diathermy machines. The capacitor has a high impedance to current at 50 Hz, which protects the patient from electrical shock.

High frequency currents (500 KHz – 1 MHz) are used in both unipolar and bipolar diathermy, which can cause tissue damage and interfere with pacemaker function (less so with bipolar diathermy).

The effect of diathermy is determined by the current density and waveform employed. The current is a pulsed square wave pattern in coagulation mode and a continuous square wave pattern in cutting mode.

Medical gas cylinders are made up of molybdenum steel but not cast iron. They are checked and assessed at a regular interval.

At least one cylinder in each hundred are tested for tensile, pressure, smash, twist and straightening.

Nitrous Oxide cylinders contain a mixture of liquid and vapour at a pressure of approx. 4500 kPa or 45 Bar. Carbon dioxide cylinder contain gas at the pressure of 5000kPa.

The filling ratio is the ratio of mass of liquified gas in the cylinder to the mass of water required to fill the cylinder at the temperature of 15ºC. In the united kingdom, filling ratio of liquid nitrous oxide is 0.75. The cylinders are usually attached to the anaesthetic machine. As nitrous oxide is an N-methyl-d-aspartate receptor antagonist that may reduce the incidence of chronic post-surgical pain.

The electrons in the outer shell of an oxygen molecule are unpaired, thus it has paramagnetic properties and is attracted into a magnetic field.

It utilizes null deflection -True
Null deflection is a crucial principle in paramagnetic analysers (reflected beam of light on two photocells) which gives very accurate results (typically 0.1%).

It can be used to measure the concentration of diamagnetic gases – False
Since most other gases are weakly diamagnetic they are repelled by a magnetic field (nitric oxide is also paramagnetic).

Can measure gases dissolved in the blood – False
For accurate analysis the sample gas must be dried before passing into the analysis cell, for example, by passage through silica gel. Therefore, they are unsuitable to measure gases dissolved in blood.

Does not require calibration – False
As with most measurement instruments paramagnetic analysers must be calibrated before use.

E) The readings are unaffected by water vapour – False
Water vapour affects the readings hence for accurate analysis the sample gas must be dried before passing into the analysis cell, for example, by passage through silica gel. That is why they are unsuitable to measure dissolved blood gases.