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• 10 cm H2O in mmHG und kPa 10 cm H20 = 7,5 mmHg= 1 kPa   The average barometric pressure at sea level is equal to: 1 atmosphere 1000 cm of water 760 mm Hg 101.325 kPa 1 Bar 14.7 pounds per square inch.
• Nicht invasive Blutdruckmessung: Manschettenbreite Sphygmomanometer Richtig: Oberarmdurchmesser + 20% zu schmal: Werte falsch hoch zu breit: Werte falsch niedrig 5 Korotkoff-Phasen
• Arterielle Blutdruckmessung Die Resonanzfequenz ist die Eigenfrequenz, mit der das System oszilliert, wenn es von aussen nicht angeregt wird sollte  mindestens das zehnfache der Grundfrequenz des Messsignals betragen. Je näher die Resonanzfrequenz an der Frequenz des Messsignals desto ungenauer die Messung. direkt proportional zum Durchmesser des Schlauchs umgekehrt proportional zur Wurzel von: Compliance, Länge des Katheters und Dichte der Flüssigkeit im System Dämpfung durch: Luftblasen, Thrombus, weicher Katheter > erniedrigte Systole, erhöhte Diastole Silicontransducer reduzieren Dämpfung  Keine Dämpfung: 0; Optimale D.: 0,64 (von kritischer Dämpfung). Kritische D.: 1.0   D = 1 in critical damping, where no overshoot of the trace occurs, equilibrium at zero amplitude occur most quickly D is < 1 when a marked overshoot is followed by many oscillations  D is > 1 if an excessively delayed response occurs.   Erhöhte Resonanz (zB durch steifen Katheter): erhöht systole, erniedrigt Diastole 12-16 Hz (flüssigkeitsgefülltes Schlauchsystem inklusive Transducer) gewünscht: hohe Resonanzfrequenz ( sonst Überschlagung)  arterielle Blutdrucksysteme haben Resonanzfrequenz unter 40 Hz und benutzen die ersten 10 Oberschwingungen der Grundfrequenz (entsprechend der Herzfrequenz)  ideally should be stiff, non-pliant, less than 120 cm in length and of a 'large' diameter. Wheatstone bridge ist eine der Voraussetzungen für arterielle Blutdruckmessung   Kalibration  A two-point calibration prevent gradient drift. The values of 0 mmHg and 200 mmHg are within the physiological range of measurement and are therefore the most appropriate values. The establishment of the "zero" value is the concept of making hydrostatic measurements with fluid-filled systems relative to a reference value, usually atmospheric pressure (760 mm Hg), and then examining the change from that value.   Kalibration mittels Anwedung eines Rechtecksignals für den Drucktransducer  Englisch: natural frequency (Eigenfrequenz), fundamental frequency (Grundfrequenz)  
• Boyle's Law Druck eines Gases nimmt ab, wenn das Volumen zunimmt Druck und Volumen sind umgekehrt proportional Temperatur und Menge Gas sind konstant. Geschlossenes System. P1xV1=P2xV2
• Rotameter/ Flowmeter - niedrige Flüsse: laminarer Flow --> abhängig von Viskosität, Radius4 - hohe Flüsse: turbulenter Flow --> abhängig von Dichte, Radius2 - stetig konstanter Druck über der Kugel  
• Dampfdruck geschlossenes System, termodynamisches Gleichgewicht von Dampf und Flüssigkeit. nimmt mit zunehmender Temperatur zu Wasser siedet, wenn Dampfdruck den Umgebungsdruck übersteigt. --> in 8000 m Höhe schon bei 74C. Kochpunkt: Dampfdruck= Atmosphärendruck
• APL Valve = adjustible pressure limiting valve Drucklimitierung bis max. 60 cm H2O = 6 kPa 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  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.  
• Sauerstoffflasche Manometerdruck 138 Atmosphären/bar 
• Wärmeverluste Konduktion: Wärmediffusion in Folge eines Temperaturunterschieds Konvektion: Ortsveränderung von Teilchen, die Wärme mit sich führen Radiation: Strahlung Atmung: 10% (8% Verdunstung von Wasser und 2% Anwärmen der Luft)  
• Shunt Fraktion Qs/QT  = (CcO2-caO2)/(CcO2-CvO2) Qs: Shunted blood Qt: total pulmonary blood CcO2: End kappilläres O2 CaO2: arterielles O2 CvO2: gemischtes venöses O2     where the oxygen content comprises both the oxygen bound to haemoglobin and that dissolved in the plasma. This requires knowledge of the alveolar PO2, arterial oxygen saturation (SaO2) and the haemoglobin concentration.   The pulmonary end-capillary oxygen cannot be measured directly but it can be estimated from the alveolar air equation.  
• Pulsoxy Wellenlänge 660 (max. Absorption von Desoxy-Hb) +940 nm (Oxy-HB). Vergleich der Absorption des Lichts. Falsch niedrig:  Methylenblau  Methämoglobinämie Sulphonamides Cyclophosphamide Prilocaine ( via the metabolite O-toluidine) Chloroquine Bilirubin Nagellack, je nach Farbe (braun-rot)   Falsch hoch: Carboxyhämoglobin (for every 1% of circulating carboxyhaemoglobin the pulse oximeter over reads by 1%; cave: heavy smokers may achieve carboxy haemoglobin (COHb) levels as high as 15-20%) Nagellack   Kein Effekt: fetales Hb, Polycythämie     The pulse oximeter provides a continuous non-invasive measurement of the arterial oxygen saturation. The light emitting diodes (LEDs) produce beams of red and infrared light at 660 nm and 940 nm respectively, which travel through a finger (toe, ear lobe or nose) and are then detected by a sensitive photodetector. The light absorbed by non-pulsatile tissues is constant (DC), and the non-constant absorption (AC) is the result of arterial blood pulsation. The DC and AC components at 660 and 940 nm are then analysed by the microprocessor and the result is related to the arterial saturation. An isobestic point is a point at which two substances absorb a wavelength of light to the same degree. In pulse oximetry the different absorption profiles of oxyhaemoglobin and deoxyhaemoglobin are used to quantify the haemoglobin saturation (in %). Isobestic points occur at 590 and 805 nm, where the light absorbed is independent of the degree of saturation, and are used as reference points. Abhängigkeit vom Hb-Gehalt. The pulse oximeter is accurate to within +/- 2% in the range of 70% to 100% saturation, and below 70% the readings are extrapolated (hochgerechnet). Pulse oximeters average their readings every 10 to 20 seconds and thus they cannot detect acute desaturation events. Consequently, they are often referred to as 'lag' monitors, due to the time delay in identifying the desaturation episode.  
• laminarem Flow: Widerstand und Flussrate Druck=Flussrate x Widerstand Widerstand:   R = 8 η l/π r4      1/2 Atemwegsquerschnitt -> 16 facher Widerstand Flussrate: (Hagen-Poiseuille) q = flowP = pressure differencer = radius of the vesselη = viscosityl = length of tube. Halbierung des Radius: 1/16 des Ausgangsflow In laminar flow the flow profile is cone shaped and the gas in the centre of the tube travels twice as fast as the average velocity.  
• Turbulenter Strom:  proportional to:   the second power of tube radius (r2)   square root of the pressure gradient (√ΔP)     inversely proportional to:   tube length (l)  gas density (ρ).  Turbulenter Fluss: Reynold's Zahl > 2000 Kritischer Fluss : "Reynold's Zahl = 2000"    
• Druck = Kraft/Fläche Cave: Fläche = Kraft / Pi r2 daher:  Spritzendurchmessers verdoppelt -> 4fache Abnahme des nötigen Drucks
• Exponentialfunktion Zeitkonstanten: 1: 63% des Prozesses abgeschlossen 2: 87% 3: 95% The half-life is 69% of the time constant  Nach 5 HWZ ist der Prozess abgeschlossen .  
• LASER: light amplification by stimulated emission of radiation meistens Licht im sichtbaren (400-750 nm) und infraroten (750 nm-1mm) Bereich monochromatisches Licht/ monofrequent; konvergenter elektromagnetische Strahlung mit kl. Querschnittsfläche;  angeregte Atome aus dem Lasermedium senden Photone aus, welche zwischen einem Spiegel vor und zurückgestrahlt werden.  Energie hängt von der Frequenz des Photons ab:   E = hV Where: E is the energy of the photons h is Planck's constant V is the photon frequency.     Das Lasermedium bestimmt die Wellenlänge der elektromagnetischen Strahlung Das Lasermedium ist meist gasförmig, kann aber auch kristalin sein.   CO2 Laser: absorbiert durch Flüssigkeiten, Weichteilgewebe (da 90% Wassergehalt) > Schneiden von Gewebe, Koagulation Nd-Yag (Neodymium yttrium-aluminium-garnet): nahe infra-rot Lasern, > Dringt tief in Gewebe ein. Photokoagulation, Tumor Debulking, Tatoo, Pigmentläsionenentfernung Argon oder Krypton Laser: produzieren Licht im blau-grünen Bereich welches von rotem Gewebe maximal absorbiert wird > Ophthalmologie, Photocoagulation,  Dermatologie Heliumlaser Meiden von Lachgas wegen brandfördernder Eigenschaft. Volatile Anästhetika ok.   Augenschutz The eye is most susceptible to damage. Red and near-infrared light (400-1400 nm) can be focused up to 2×105 times greater intensity by the lens on to the retina. Most of the light is absorbed by melanin in the pigment epithelium just behind the photoreceptors and causes painless burns on the retina. Infrared light (>1060 nm) is particularly dangerous as it will not elicit the protective blink reflex due to its invisibility. Ultraviolet light (<400 nm) tends to be absorbed in the cornea and lens where it can produce burn injuries and cataracts at relatively low powers due to photochemical damage. Laser protective goggles are designed to wrap around the eyes and prevent inadvertent direct and indirect exposure to the eyes of the wearer. These goggles need to absorb light specific to the laser being used at the time.
• Ficksches Diffusionsgesetz Diff.rate [mol * s^-1] = Fläche * Koeffizient * (Konz.differenz (x) / Dicke der Membran)
• Hyperkaliämie, EKG Veränderungen fehlende p-Welle, verbreiterter QRS Komplex, Übergang QRS in T
• Methods for cleaning anaesthetic equipment can be classified into decontamination, disinfection and sterilisation     Decontamination removes macroscopic material. Disinfection kills most organisms but not spores. Sterilisation kills both organisms and spores and includes: Dry heat at 150° for 30 minutes Moist heat (autoclave) , Process times can vary from 30 minutes if at 1 atmosphere and 122°C to three minutes at 2 atmospheres at 134°C. Ethylene oxide (carcinogenic). For plastic: 2weeks exposure! Gamma irradiation (am verbreitetsten) Seventy per cent alcohol and pasteurisation at 100° for 5 minutes are both methods of disinfection.  
• SI Einheiten:     Meter Sekunde Kilogramm Ampere Kelvin Candela Mol Abgeleitet: Newton, Pascal, Joule, Watt, litre and Hertz. Newton is the unit of force; a force of 1 newton will give a 1 kilogram mass an acceleration of 1 metre per second per second (1 N = 1 kg/m-2) Litre is a unit of volume and is a 1000th of a cubic metre (1 litre = 0.001 m-3).
• Methods of measuring cardiac output include   Oesophageal Doppler Transthoracic impedance PiCCO NICO (Non Invasive Cardiac Output) Thermodilution Lithium dilution
• Cylinders of compressed vapours and gases have the following pressures when full at 15°C   Oxygen 13 700 kPa Entonox 13 700 kPa Medical air 13 700 kPa Carbon dioxide 5000 kPa (723 psi) Nitrous oxide 4400 kPa Cyclopropane 436 kPa.
• Paramagnetic analyser Paramagnetic gas analysers are very common in anaesthetic practise. They consist of two chambers separated by a pressure transducer. Changes in oxygen concentration are sensed by pressure changes on the transducer caused by an alternating magnetic field. Nitric oxide (NO) and nitrogen dioxide (NO2) are also strongly paramagnetic. Calibration is usually done with 100% nitrogen and 100% oxygen. Oxygen is attracted by magnetic fields (diamagnetic gases are repelled). A water trap (Wasserfalle) is required so as not to interfere with this very sensitive instrument 
• Reynold Zahl Übergang von laminarem in turbulenten Flow: Reynolds number = (Durchmesser x Dichte x Geschwindigkeit) / Viskosität > 2000  
• Diathermie zum schneiden und koagulieren. Hochfrequent: 1-3 MHz. Wechselstrom. schneiden: Wechselstrom-Sinuswelle.  koagulieren: gepulste Sinuswelle bipolar: keine Neutralelektrode. Frequenz fliesst von einem Schenkel der Pinzette durch das Gewebe zum anderen. Keine höheren Leistungen. Strom ist auf engen Bereich begrenzt. Vorteilhaft in NCH zur Schonung des umliegenden Gewebes. Höhere Stromdichte. 40 Watt (im Ggs zu monopolar: 400 Watt) Cardiac pacemaker: möglichst bipolar. The sensing electrode in a pacemaker may misinterpret diathermy current as intrinsic cardiac electrical activity and may subsequently fail to deliver a stimulus.
• EMG Frequenz und Spannung Frequenz 2 bis > 1000 Hz Spannung 10 mcV bis 80 mV
• EKG Frequenz 0,5-100 Hz Spannung 0,1-5 mV ECG electrodes consist of silver/silver chloride gel pads connected to shielded wires connected to an amplifier which has a frequency range of 0.05 to 100 Hz although this can be reduced to 0.5 to 40 Hz in some instances. Monitoring mode This mode has a frequency response of 0.5-40 Hz. All ECG monitors use filters to narrow the bandwidth in an attempt to reduce environmental artefacts. The high-frequency filters reduce distortions from muscle movement, mains current and electromagnetic interference from other equipment. The low-frequency filters help to provide a stable baseline by reducing respiratory and body movement artefacts. Diagnostic mode This mode monitors the ST-segment and there is a greater need for filtering of the signal. Thus, there is a wider frequency response range of 0.05-100 Hz. The high-frequency limit of 100 Hz ensures that tracings allow assessment of QRS morphology and tachyarrhythmias. The low-frequency limit allows representation of P and T wave morphology and ST-segment analysis. Mains frequency of 50 Hz can interfere but most amplifiers now have a notch filter at this frequency in their bandwidth. Electrode configurations Lead II is best for detecting arrhythmias.CM5 detects 89% of ST-segment changes due to left ventricular ischaemia.  (Right arm electrode on manubrium, left arm electrode on V5 and indifferent lead on left shoulder).CB5 is useful in thoracic anaesthesia. Right arm electrode over the centre of the right scapula and left arm electrode over V5.    
• EEG 1-60 Hz 1-200 mcV
• Sidestream Capnographs Sample: 50-250 ml/min
• Desfluran Vapor Siedepunkt (22,8C) nahe Raumtemperatur  > Erhitzen des Vapors für bessere Steuerbarkeit 39 C bei 2 Atmosphären (1550 mmHg)  
• Fick'sches Prinzip die totale Aufnahme oder Abgabe einer Substanz durch ein Organ ist gleich dem Produkt aus Blutfluss des Organs und arterio-venösem Konzentrationsunterschied der Substanz > Messung Cardiac Output, cerebral blood flow
• The marks found engraved on a nitrous oxide cylinder include   The test pressure (the highest pressure to which the cylinder has been subjected) and The dates that the tests were performed The chemical formula of the contents The weight of an empty cylinder of nitrous oxide (tare weight).
• Atom- Aufbau   Kern: Positiv geladene Protonen, neutrale Neutronen (ergeben zusammen die Massenzahl und haben in etwa pro Teilchen die gleiche Masse) Hülle: negativ geladene Elektronen ( geringes Gewicht) Positronen und Elektronen sind etwa gleich gross Wassertoffatom: 1 Proton (Ordnungszahl = Protonenzahl)   
• infrared analysers can be used to measure the following gases: Gases with molecules that contain at least two dissimilar atoms absorb radiation in the infrared region of the electromagnetic spectrum. Therefore, carbon dioxide, nitrous oxide and all of the halogenated volatile anaesthetic agents can be measured using infrared absorption analysers. Oxygen, nitrogen, helium and the inert (or noble) gases do not absorb infrared light and cannot be measured using this technology. Oxygen is measured using the paramagnetic, galvanic or polarographic method.
• Kathetergrössen Intravenous and intra-arterial cannulae: standard wire gauge (SWG or G). old imperial unit (which requires metric conversion). urinary or chest drain,  Double lumen tracheal tube: French gauge (FG) catheters. circumference.   Single lumen tubes: internal diameter.  
• arterial pressure waveform, Information derived from:   Heart rate myocardial contractility: The slope (Steigung) of the upstroke of the wave reflects myocardial contractility represented by the derivative: dP/dt. Change of pressure with regard to change in time. Systolic, diastolic and mean arterial pressure: MAP can be determined by integrating a pressure signal over the duration of one cycle. The mean pressure is then given by the value of this integral divided by time oder SBD+2xDBD/3 Stroke volume can be calculated by integrating the area under the curve from the beginning of the upstroke to the dicrotic notch (entsprechend der Systole). If this is multiplied by the heart rate, then cardiac output can be estimated. Position of the dicrotic notch (zwischen Systole und Diastole) on the down stroke. A low dicrotic notch is seen in hypovolaemic patients. Slope of the diastolic decay indicates resistance to outflow. A slow fall is seen in vasoconstriction.  
• Capnography Capnography relies on the principle of infrared absorption. Carbon dioxide is made up of two dissimilar atoms and absorbs infrared radiation at a wavelength of 4.28 μm. End-tidal CO2 is normally 0.6-0.7 kPa lower than the arterial partial pressure. Mainstream analyser is located within the patient's breathing system and therefore increases dead space but allows rapid analysis. It does not allow analysis of other gases Sidestream analyser consists of a small diameter tubing that samples gases at 150-200 mL/min. It can cause sampling delay but multiple gases and anaesthetic vapours can be analysed from the same sample. Capnography is the measurement and pictorial display of the inspired and expired carbon dioxide partial pressure. A heated wire is used to generate the infrared light. The gas mixture is introduced to a sapphire chamber, where filtered infrared light (filtered to produce a beam of 4.28 micrometres) is passed through it. As the amount of carbon dioxide in the gas mix increases, the amount of infrared light passing though the gas mix decreases.This is a utilisation of Beer's law. The infrared light passing through hits a sensor, and the signal generated is analysed. Carbon dioxide absorbs infrared (IR) light maximally between the wavelengths of 4.2-4.4μm (4.26μm being optimal). Nitrous oxide absorbs IR light between the wavelengths 4.4-4.6μm (very close to that of CO2) and less strongly at 3.9μm. Carbon monoxide maximally absorbs IR light at a frequency of 4.7μm. The volatile agents have strong absorption bands at 3.3μm and throughout the ranges 8-12μm.  Collision broadening Oxygen does not absorb IR light, however, O2 molecules collide with the CO2 molecules interfering with absorption. This broadens the absorption band (so called collision or pressure broadening). Ninety five per cent oxygen can cause a 0.5% fall in measured CO2. Nitrous oxide causes a more significant inaccuracy of 0.1% per 10% nitrous oxide. Water vapour also absorbs IR light and can cause absorption band overlap, collision broadening and partial pressure dilution effects. The use of water traps and water permeable tubing helps minimise inaccuracies. Modern gas multi-gas analysers compensate for collision broadening.   Capnograph has four phases: sectrets of anaesthesia 185
• What do blood gas analysers directly measure? Blood gas analysers contain electrodes which measure the pH, and partial pressure (or tension) of oxygen and carbon dioxide. Base excess, the bicarbonate concentration and standard bicarbonate are derived from measurement of the pH and PCO2.
• Laryngoskope Straight blade laryngoscopes include the following types - Miller, Soper, Wisconsin and Seward. are designed to be advanced over the epiglottis. Curved bladed laryngoscopes are designed so that the tip is placed into the vallecula. Macintosh, polio and McCoy. standard Macintosh blade used in adults is the right-sided version Polio blade The blade is mounted at 120-135 degrees to the handle. This equipment was originally designed to facilitate intubation in patients encased within iron lung ventilators during the polio epidemic. It is also useful in patients with barrel chest, restricted neck mobility or breast hypertrophy. These blades are more popularly used in conjunction with a short 'stubby' handle  McCoy laryngoscope is based on the standard Macintosh blade (not Robertshaw's), with a lever operated hinged tip, which can improve the view at laryngoscopy  
• Doppler   The normal hearing range for an adult human is between 15 Hz and 20,000 Hz. Ultrasound is produced by the piezoelectric effect of crystals when a voltage is applied across. A two-dimensional image is produced by B-mode ultrasound, not an A-mode. An A-mode ultrasound displays the reflected ultrasound pulses from a single line scan and simply detects a range of tissue boundary. Findet noch Verwendung um zu Prüfen, ob Nasennebenhöhle flüssigkeitsgefüllt ist. The Doppler effect describes the apparent change in frequency caused by the movement of an object in relation to the source. It can be used to measure cardiac output (flow) in the oesophageal Doppler probe. The Doppler equation is the principle behind the transoesophageal echo: V= Cfd/2ft(Cos è) where: V is the flow velocity C is the speed of sound in body tissue (which is 1540 m/s) Ft is the frequency è is the angle between sound beam and flood flow fd is the Doppler frequency shift. Remember The cosine 0° = 1 and Cosine 90° = 0 increasing the angle will increasing the velocity. decressing the frequency will increase the velocity velocity is directly dependent on frequency shift  
• Scavenging systems Scavenging systems are designed to maintain a vapour free theatre environment.  They consist of a collection system, delivery tubing (30 mm - to avoid confusion with ventilatory tubing which is 15 or 22 mm), reservoir and disposal system. Active scavenging is more reliable and achieves higher flow rates than passive scavenging. Active scavenging can achieve flow rates up to 130 L/min. Maximum positive pressure that can be transmitted to the patient is 1 kPa. Filter   Activated charcoal absorbs only volatile anaesthetic agents (not N2O). Soda lime canisters absorb carbon dioxide and are used in circle breathing systems, they are not involved in scavenging anaesthetic gases. Resistance to exhalation is not increased by scavenging systems Passive systems are cheaper but they are not quantifiably more reliable than active systems.   Adequate ventilation is required in areas where anaesthetic gases are present, and the legally required minimum air supply to each area is: Operating theatres 0.65 m3 / second Anaesthetic rooms 0.15 m3 / second Preparation rooms 0.1m3 / second. Recovery rooms require 15 air changes per hour In the United Kingdom the maximum accepted concentration in the operating room: nitrous oxide 25 particles per million ppm   2 ppm for any volatile anaesthetic agent.  However, the long term exposure limit  nitrous oxide 100 ppm (8 hour TWA reference period),  isoflurane, desflurane and sevoflurane 50 parts per million  halothane 10 parts per million        
• EKG: Do normal electrocardiogram (ECG) configurations include the following?   The S-T segment should not deviate from the isoelectric line by more than 1 mm. T wave inversion may be a normal finding in V1 to V3, but is always abnormal if they are inverted in V4 to V6. The T waves should always be positive in leads I and II but may be negative in leads aVL, aVF and III. Q waves should not exceed 0.04 seconds in duration or have a depth greater than 25% of the height of the ensuing R wave. The presence of Q waves signifies infracted myocardium or certain cardiomyopathies however, Q waves in leads III and aVR can be ignored.  
• Niere: Messung GFR und Blutfluss The ideal glomerular filtration marker should be: Non-toxic to the human body Measured accurately by chemical or physical means Freely and evenly diffusible throughout the extracellular fluid (ECF) compartment Unable to enter the intracellular fluid (ICF) compartment Removed from the blood only by filtration in the kidney, and Not reabsorbed into the blood from the renal tubules or other parts of the urinary system. Creatinine is endogenous and is freely filtered by the glomerulus, but is also secreted by the proximal tubule. Thus, creatinine clearance systematically overestimates GFR. This overestimation is approximately 10% to 40% in normal individuals, but is greater and more unpredictable in patients with chronic kidney disease. The gold standard method of inulin clearance requires an intravenous infusion and timed urine collections over a period of several hours making it expensive and burdensome. Inulin is in short supply and difficult to mix and maintain as a solution. Para-aminohippuric acid (PAH) is freely filtered by the glomerulus and any left in the peritubular capillaries is secreted into the proximal convoluted tubules. This marker is used in the measurement of renal blood flow.
• oxygen concentration delivered to the patient with venturi mask The air entrainment ratio is 1:9 (1 litre of 100% oxygen from the central source entrains 9 litres of air from the atmosphere). The flow rate of 100% oxygen is 6L/minute.   The air:oxygen entrainment ratio can be determined using the formula: 100% − FiO2 = air/oxygen entrainment ratio FiO2 − 21% The entrainment ratio is already known. Substituting the values in the equation: x = FiO2. 100 − x = 9 x − 21 100 − x = 9(x − 21) 100 − x = 9x − 189 10x = 289 x = 289/10 x = 28.9% The total flow received by the patient can also be calculated: Total flow = source gas flow + source gas flow × entrainment gas ratio In this example: Total gas flow = 6 + (6 × 9) = 60 L/minute.  
• ohm elektrischer Widerstand (Ohm) = Spannung/ Strom = Volt/ Ampere The ohm is the resistance which allows one ampere of current to flow under a potential difference of one volt.  
• Farad   Ein Kondensator mit einer Kapazität von einem Farad (F) kann durch das Aufladen auf eine Spannung von einem Volt (V) eine Ladung von einem Coulomb (C) speichern: Capacitance (farad) = Ladung / Spannung . Anschaulich beschreiben kann man diesen Zusammenhang auch durch: Ein Kondensator, der durch einen Strom von einem Ampere in einer Sekunde auf eine Spannung von einem Volt aufgeladen wird, hat eine Kapazität von einem Farad. Ein Kondensator, der durch eine Ladung von einer Amperesekunde (einem Coulomb) auf eine Spannung von einem Volt aufgeladen wird, hat eine Kapazität von einem Farad.  
• coulomb Elektrische Ladung Ein Coulomb ist definiert als die elektrische Ladung, die innerhalb einer Sekunde durch den Querschnitt eines Drahts transportiert wird, in dem ein elektrischer Strom der Stärke von einem Ampere fließt:  
• Impedanz Wechselstromwiderstand When resistance is dependent on frequency it is called impedance.
• CO2-Analyse CO2 absorbs infrared radiation at a wavelength of 4.3 micrometres 
• vacuum insulated evaporator (VIE)     Up to 1500 litres of liquid oxygen is stored at a temperature of -150 to -170°C and at a pressure of 5-10 atmospheres. (kritische Temperatur O2 −118 °C) Evaporation of the liquid oxygen requires heat (latent heat of vaporisation) and this is taken from the mass of liquid oxygen within the VIE, thus the low temperature is maintained. The VIE is positioned on a weighing balance which measures the mass of the liquid. A resupply of fresh liquid oxygen is pumped from a tanker into the vessel. A safety valve is located in the VIE that opens at 1700 kPa and allows oxygen gas to escape into the atmosphere. The pressure in the VIE increases when there is a reduced demand for oxygen. A pressure regulator maintains the pressure of the gas entering into the pipeline at 400 kPa.    

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