Anästhesie (Subject) / Physik (Lesson)

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• MRI MRI: 0,5-3 Tesla Magnetism is measured in tesla and the Earth's magnetic field is 0.5 - 1 gauss. 1 tesla is equal to 10,000 gauss. All ferromagnetic objects must stay outside the 50 gauss line  
• Cardiopulmonary exercise testing (CPX) The anaerobic threshold indicates the point at which anaerobic glycolysis begins to supplement aerobic metabolism, and represents the functional ability of the patient to cope with the extra metabolic demands of surgery. An anaerobic threshold of less than 11 ml/kg−1/min−1 (O2-Verbrauch) is associated with significantly poorer outcomes. Anaerobic threshold AT is a marker of the combined efficiency of the lungs, heart, and circulation. With increasing exercise, oxygen demand will begin to exceed supply. Therefore, muscle cells will begin generating ATP anaerobically. This produces lactic acid which will be buffered by circulating bicarbonate, resulting in an increased production of CO2. The VO2 (O2-Verbrauch) at the point at which this occurs
• Sauerstoffmessung Messung des O2-Partialdrucks (ggf Angabe in%):   Brennstoffzelle (galvanic oxygen analyser, fuel cell): Goldkathode und Bleianode. Braucht keine Stromversorgung. Die selbst erzeugte Spannung ist proportional zum O2-Partialdruck. Massenspektrometrie: Ionisation. Analyse nach Masse zu Ladung. Detektor der verschiedenen Ionen.  Polarographic oxygen analysers (or Clark electrode): Platinkathode, Silberanode. Braucht Strom.  Van Slyke apparatus   In paramagnetic analysis oxygen is attracted  to the magnetic field (paramagnetism) due to the fact that it has two unpaired electrons in orbit. Most widely used.          
• Henry's law The amount of gas dissolved in a solvent is proportional to its partial pressure above the solvent, at constant temperature.' 
• Glatte Mm. Visceral smooth muscle is characterised by the instability of its membrane potential and by the fact that it shows continuous, irregular contractions that are independent of its nerve supply. In general, smooth muscles contain few mitochondria and depend to a large extent on glycolysis for their metabolic needs. Smooth muscle responds to autonomic innervation mediated by noradrenaline (inhibitory potentials) and acetylycholine, which has an opposite effect.
• Blutdruck BLutdruck = SVR x CO
• pH   pH is the negative log to the base 10 of the hydrogen ion concentration (−log10[H+]). The normal plasma is 7.35-7.45, equating to a [H+] of 35-45 nmol/L. The measurement of the pH is performed using a glass pH electrode which responds to hydrogen ions (H+ ions) rather than oxygen or carbon dioxide. The glass electrode (measuring electrode) is a bulb made of pH sensitive glass holding a silver/silver chloride electrode in a buffer solution. The potential difference across the glass bulb depends on the pH difference between the inside and outside. The reference electrode (mercury/mercury chloride) is in contact with a potassium chloride solution (not hydroxide) via a membrane. This semi-permeable membrane reduces protein contamination from the sample. The blood sample (urine or cerebrospinal fluid) and the buffer are separated by the H+ ion sensitive glass. The buffer maintains a constant pH within the glass, but a gradient exists between the sample and the buffer solution, which gives a potential difference. Thus one electrode is in contact with the buffer the other is in contact with the sample. The two electrodes create a circuit and the potential difference can be measured and displayed on a meter. Both the glass and reference electrodes (not just the reference electrode) are maintained at 37°C. It produces a linear electrical output (not non-linear) of about 60 millivolts per unit pH.  
• Michaelis-Menten Kinetik Michaelis-Menten kinetics describes the reaction of substrate (S) and enzyme (E) to form product (P), via an enzyme substrate complex (ES). The kinetics are saturatable and therefore are initially first order (rate is proportional to substrate concentration), becoming zero order (rate independent of substrate concentration, that is, constant rate) as the enzyme's active sites become occupied. The constant Km is the concentration of substrate at half maximal reaction velocity, that is,  ½Vmax (not Vmax). The equation may be applied to drug absorption, elimination and distribution.
• Wright respirometer  is a one way system used to measure the exhaled tidal volume and minute volume accuracy of +/- 5 to 10 The vane does 150 revolutions when one litre of gas passes through the respirometer, causing the pointer to rotate around a display. The inner display is calibrated in 1 litre divisions and the outer display is calibrated in 100 ml per divisions. A minimum flow of 2 litres per minute is required for the respirometer to function accurately, but it tends to over-read at high flow rates and under-read at low flows.
• Flow meter   Flowmeters measure the flow rate of a gas passing through them, and they are individually calibrated for that specific gas. Calibration is performed at room temperature and at atmospheric pressure. They have an accuracy of +/- 2%. The reading of the flowmeter is taken from the top of a bobbin or the midpoint of a ball. A safety feature of flowmeters is that oxygen is the last gas (not first) to be added (downstream) to the mixture delivered to the back bar. This prevents delivery of a hypoxic mixture. Flow measurements become inaccurate when the bobbin sticks to the inside wall of the flowmeter. Stannic oxide (Zinnoxid) has been used as an antistatic substance which prevents the build up of static electricity, reducing the risk of the bobbin sticking to the wall of the flowmeter.  Anaesthetic rotameters under-read high flow rates.    
• The mean arterial pressure of a patient is 90 mmHg (12 kPa) and the cardiac output is 5 L/minute. Which of the following values is the closest estimate of the power output of the left ventricle? The derived SI unit of power is the watt (W) which is equal to one joule per second (J/s). Peak cardiac power is derived from the product of the peak mean arterial blood pressure and CO divided by 451. CP = MAP × CO/451 = (90 × 5 / 451) = 0.997 W The cardiac power index (MAP × CI/451) is a strong independent haemodynamic correlate of in-hospital mortality in patients with cardiogenic shock.
• Severinghaus-CO2-elektrode Glaselektrode Silber/Silberchlorid Referenzelektrode  misst pH-Änderungen auf Grund von H+ Änderungen nach der Reaktion von CO2 mit Bicarbonatlösung CO2 permeable Membran trennt Plasmaprobe von Bicarbonatlösung 37°C Betriebstemperatur 2-3 Minuten Messzeit: Zeit für CO2-Diffusion durch Kunststoffmembran
• Temperatur   The SI unit of temperature is the kelvin, but Celsius and Fahrenheit are also recognised temperature scales. The corresponding points on different temperature scales are: Absolute zero is 0 kelvin, -273.15°C or -459°F Melting point of ice is 273 kelvin, 0°C or 32°F The boiling point of water is 373 kelvin, 100°C or 212°F. The triple point of water is the temperature at which water exists simultaneously in solid, liquid and gaseous states and corresponds to 273.16 K or 0.01°C. Mercury solidifies at -38.87°C, so is a liquid at -37°C. Messung: A thermocouple relies on the Seebeck effect, that is, the production of a potential difference (voltage) at the junction of two different conductors is proportional to the temperature. thermistor consists of a little bead of metal oxide semiconductor, the resistance of which falls exponentially (not linearly) as the temperature rises. The platinum resistance wire is a resistance thermometer and is based on the principle that the electrical resistance of a metal increases linearly with temperature. Liquid thermometers are non-electrical techniques for measuring temperature. They usually contain mercury, which expands as temperature increases, and moves up the calibrated tube of the instrument. Alcohol thermometers are used for measuring very low temperatures minus 70 to +78 degrees centigrade.    
• Nasal cannulae Nasal cannulae are an alternative method for the delivery of supplemental oxygen. Two prongs protrude 1 cm into the nose and are held in place by a head strap. There is increased patient compliance with nasal cannulae compared with face masks (eating and drinking is unrestricted). A flow rate of 2-4 litres per minute delivers approximately 28-36% oxygen. Flow rates greater than 4 l/min are uncomfortable and increase the drying effect and irritation to the nasal mucosa. The inspired oxygen concentration achieved is proportional to: The oxygen flow rate The patient's respiratory rate, inspiratory flow and tidal volume The volume of the nasopharynx. When the patient breathes through the mouth causing inspiratory flow, a Venturi effect is produced in the pharynx, which entrains the oxygen enriched air from the nose. Therefore, it is not necessary to request that patients breathe through the nose.
• Thermometer: Bourdonthermometer Druckmessuhr, verbunden mit Sensor, der eine kl. Röhre mit Quecksilber oder volatiler Flüssigkeit enthält.  Temperaturänderung > Druck- oder Volumenänderung erfasst durch die Bourdonuhr. Gemäss Gay-Lussac's  (Charles) Gesetz: bei konstantem Druck ändert sich das Volumen einer bestimmten Gasmenge direkt mit der absoluten Temperatur. Metall-Oxid-Thermistor kl. Tropfen Metalloxid; sein Widerstand fällt exponentiell mit steigender Temperatur.  oft in Wheatstonebrücke (Widerstandsänderungsmesser) verwendet Thermoelement mit Seebeck-Effekt An Verbindung zweier unterschiedlicher Metalle entsteht eine geringe Spannung, deren Grösse von der Temperatur an der Verbindungsstelle abhängt (zB Kupfer und Kupfer/Nickel(Konstantan)) Infrarot-Thermometer emmitierte Infrarote Strahlung ist direkt proportional zur vierten Potenz der Temperatur (Stefan-Boltzmann-Gesetz)     
• Charles law At constant pressure the volume of a given mass of gas varies directly with absolute temperature (Kelvin)V/T = k
• Dalton's law of partial pressure:  The pressure of a mixture of gases is equal to the sum of the pressures of all of the constituent gases alone. Mathematically, this can be represented as:   PressureTotal  =  Pressure1 + Pressure2 ... Pressuren
• Henry's law: At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
• Narkosetiefe- Messtechniken Monitoring the depth of anaesthesia and methods for detecting awareness during anaesthesia are numerous and include: The isolated forearm technique Lower oesophageal contractility Ocular microtremor Skin conductivity and R-R beat variability. Digital plethysmography Electromuscular monitoring Electroencephalogram and cerebral function monitoring  Evoked potentials. Clinical signs have been used to detect lightening of anaesthetic depth but these are unreliable. The presence of hypertension, tachycardia, sweating and lacrimation or PRST (that is, pressure rate sweat and tears) are worrying signs.
• Radioaktiver Zerfall Zerfall: exponentieller Prozess. Radioaktivität: Einheit: Becquerel  Definition: 'a given quantity of radioactive substance has the activity of one Becquerel if the disintegration of one nucleus occurs on average every second'. An α (alpha) particle consists of two protons and two neutrones, that is, a helium nucleus (not an electron). A β (beta) particle is an electron.  Gamma (γ) radiation Einteilung der ionisierenden Strahlen aus radioaktivem Zerfall in Alphastrahlung, Betastrahlung und Gammastrahlung mit deren steigender Fähigkeit, Materie zu durchdringen. Alpha- und Betastrahlung bestehen aus geladenen Teilchen und wechselwirken daher deutlich stärker mit Materie als die ungeladenen Photonen oderQuanten der Gammastrahlung. Entsprechend haben letztere ein deutlich höheres Durchdringungsvermögen.
• Gaszylinder Medical gas cylinders are manufactured using molybdenum steel The ideal size for a cylinder fitted to the anaesthetic machine is size E. Oxygen cylinders range from size C to size J. Size C oxygen cylinders contains 170 litres, and as the size of the cylinder increases the volume of oxygen inside doubles each time. Thus a size D contains 340 litres, a size E contains 680 litres, and so on. Size J cylinders hold 6800 litres of oxygen. Nitrous oxide cylinders are available in sizes C to G and similarly the volume doubles as the size of the cylinder increases. Size C cylinders contain 450 litres of nitrous oxide; therefore size E cylinders must contain 1800 litres. Entonox is available in a wide range of cylinder sizes including D, G and J. Medical gas cylinders in the UK have the following colour codes: Oxygen has a black body with white shoulders. Nitrous oxide cylinders are French blue. Air has a grey body with black and white quarters on the shoulders. Entonox has a French blue body with white and blue quarters on the shoulders. Carbon dioxide cylinders are grey. heliox (79% He, 21% O2) in white cylinders with white/brown shoulders or as pure helium in brown cylinders The filling ratio is the weight of liquified gas introduced into a cylinder compared to the weight of water it would take to fill the same cylinder at 15°C. The filling ratio allows for some expansion due to heat, preventing possibly dangerous pressure increases. In the UK it is 0.75, but in warmer regions it will be 0.67. These cylinders undergo a number of tests. Every year each cylinder will undergo an endoscopic examination and a pressure test to 50% above that cylinder's usual working pressure. In addition, 1 in every 100 cylinders will undergo tensile and impact tests  
• BIS   intravenous anaesthetic agents (propofol, thiopental and midazolam) have a strong depressant effect on the BIS value inhalational agents propagate an intermediate depressant effect on BIS.  Opioids have little or no influence on the BIS at clinically relevant concentrations.  nitrous oxide and ketamine which deepen the anaesthetic, appear to have a paradoxical effect and increase the BIS value. Thus BIS monitoring should not be used when these two agents are in use BIS is not able to predict movement in response to a surgical stimulus some of which are spinal reflexes and not perceived by the cerebral cortex. Whilst BIS is used during cardiopulmonary bypass to measure depth of anaesthesia and an index of cerebral perfusion it cannot reliably predict subtle nor significant cerebral damage.  
• Paramagnetische Sauerstoffanalyse The electrons in the outer shell of an oxygen molecule are unpaired, thus it has paramagnetic properties and is attracted into a magnetic field. Since most other gases are weakly diamagnetic they are repelled by a magnetic field (nitric oxide is also paramagnetic). Null deflection is a crucial principle in paramagnetic analysers (reflected beam of light on two photocells) which gives very accurate results (typically 0.1%). Water vapour affects the readings and 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. As with most measurement instruments paramagnetic analysers must be calibrated before use. Im Gegensatz zu anderen Gasen wird Sauerstoff von einem starken magnetischem Feld angezogen. Wir benutzen diesen Paramagnetismus um schnelle, genaue Sauerstoffmessungen vorzunehmen. Ein konzentriertes Magnetfeld wird erzeugt, welches den vorhandenen Sauerstoff in dem stärksten Bereich des Magnetfeldes sammelt. Zwei mit Stickstoff gefüllte Glaskugeln hängen an einer Drehvorrichtung in diesem Magnetfeld. Ein Spiegel ist an der Mitte der Drehvorrichtung befestigt. Auf den Spiegel wird eine Lichtquelle gerichtet. Das reflektierte Licht wird auf ein Paar Fotozellen geleitet. Der vom Magnetfeld angezogene Sauerstoff verdrängt die mit Stickstoff gefüllten Kugeln, wodurch sich die Drehvorrichtung dreht. Diese Bewegung wird von den Fotozellen erfasst, die daraufhin ein Signal erzeugen.  Das von den Fotozellen erzeugte Signal wird an ein Rückführsystem geleitet. Das Rückführsystem leitet einen Strom durch ein an der Drehvorrichtung angebrachtes Kabel. Der hierdurch entstehende Motoreffekt sorgt dafür, dass die Drehvorrichtung in ihrer ursprünglichen Stellung verbleibt. Die Spannungsstärke im an der Drehvorrichtung angebrachten Kabel ist direkt proportional zur Sauerstoffkonzentration im Gasgemisch.
• Penaz technique  measure continuously the blood pressure in a finger  A cuff is placed on a finger which is attached to a pressure transducer and connected to a servo-controlled air pump. The cuff also incorporates a photocell and an infrared light-emitting diode, which acts as a photoplethysmograph. The servo-controlled air pump acts as a feedback mechanism, continuously inflating and deflating the finger cuff in order to maintain a constant photoplethysmograph output. Some perfusion of the finger occurs during the continuous cuff inflation (it is not negligible) but digital ischaemia may occur with prolonged use.
• Transcutaneous oxygen measurement: Transcutaneous oxygen measurement provides a continuous measurement of the PO2 in the skin and capillaries, which approximates to the arterial PO2. If the skin is locally heated to 43-44˚C (not 35 ºC), the peripheral blood vessels dilate and the oxygen used in metabolism by the tissues underlying the skin surface is negligible compared with the total oxygen present in the capillaries. Therefore, the skin PO2 approximates to the arterial PO2. Oxygen diffuses through the skin (not impermeable) and the measuring electrode is therefore placed on the skin to measure the arterial PO2. The system forms a polarographic electrode, not a fuel cell. It has a platinum or gold cathode surrounded by a silver anode, which are in contact with an electrolyte solution retained by an oxygen permeable membrane. A temperature rise above 45ºC will cause a localized burn. Therefore, the skin temperature is measured by a thermistor, which controls the heater power and a second thermistor is used as a safety device that switches off the system in the event of a malfunction in the primary heating circuit. The electrode position should be moved every 3-6 hours (not hourly), which will reduce the risk of cutaneous burns.
• Sättigungsdampfdruck/ saturated vapour pressure (SVP)   ist der Druck der dampfförmigen Phase eines Stoffes, wenn die flüssigförmigen und dampfförmigen Phasen sich im Gleichgewicht befinden. It indicates the degree of volatility and agents with higher SVPs are more volatile and easier to vaporise than agents with lower SVPs. When the SVP equals the atmospheric pressure the liquid boils SVP von Volatilen wird üblicherweise bei der Standard Temperatur 20°C angegeben  
• Gas pipeline pressure A piped gas supply is made up of networks of pipes and sockets which distribute medical gases from a central source to the point of demand. In the United Kingdom only Oxygen Nitrous oxide (not nitric oxide) Medical air and Entonox are supplied by such systems. All pipeline gases are supplied at 4 bar (or 400 kPa).  Compressed air is supplied at 7 bar for power tools. Carbon dioxide and nitric oxide are usually only supplied in cylinders.
• Nernst Gleichung ...beschreibt die Konzentrationsabhängigkeit des Elektrodenpotentials eines Redox-Paares (Ox + z e− Red) Elektrodenpotential ° Standardelektrodenpotential Universelle oder molare Gaskonstante, R = 8,31447 J mol−1 K−1 = 8,31447 C V mol-1 K-1 absolute Temperatur (=Temperatur in Kelvin) Anzahl der übertragenen Elektronen (auch Äquivalentzahl) Faraday-Konstante, F = 96485,34 C mol−1 = 96485,34 J V−1mol−1 Aktivität des betreffenden Redox-Partners
• natural frequency/ fundamental frequency The natural frequency is the frequency at which the system is resonant. The natural frequency should be at least 10 times the fundamental frequency. (The fundamental frequency is the lowest frequency at which the system resonates. A harmonic is a multiple of this frequency). Natural frequency is: direkt proportional zum Katheter-Durchmesser umgekehrt zu der Quadratwurzel der Dichte der Flüssigkeit und der Quadratwurzel der Länge des Schlauches
• High frequency ventilation (HFV)   High frequency ventilation (HFV) uses small tidal volumes delivered at high frequencies, maintaining gas exchange without barotrauma or other deleterious effects of intermittent positive pressure ventilation (IPPV). It is defined as ventilation at four times the normal rate, and uses tidal volumes of 1-3 ml per kg. Conventional endotracheal tubes may be used. There are three modes used: High frequency positive pressure ventilation (HFPPV) High frequency jet ventilation (HFJV) and High frequency oscillation (HFO). The Hayek oscillator is a non-invasive form of ventilation that uses high frequency oscillation within a cuirass. The patient who requires ventilatory support does not have to be intubated as they are fitted into a cuirass, so that it covers them from the axilla to the lower abdomen. It is not connected directly to an endotracheal tube. The Hayek oscillator works by decreasing and increasing the pressure within the cuirass, causing inspiration and expiration respectively.  High frequency jet ventilation (HFJV) is a type of high frequency ventilation which can be delivered via a cannula Inserted through the cricothyroid membrane Placed within a bronchoscope or Incorporated near the distal end of an endotracheal tube. It cycles at 60 - 600 per minute and can generate tidal volumes up to 150 ml. It produces positive airway pressure of about 5 cm of water. In the emergency situation, a Sanders injector may be used to ventilate a patient via a cannula inserted through the cricothyroid membrane. It has also been used in surgery to correct a bronchopleural fistula and used to ventilate patients during bronchoscopy.  
• Tuben   Tracheal tubes can be made either of disposable plastic, or reusable red rubber. The tube size refers to the internal diameter in mm. The internal diameter (ID) is marked on the outside of the tube (some manufacturers also have the external diameter marked on the outside). Plastic tubes have a radio-opaque line running along their entire length, which allows their position to be identified on x rays. The bevel located at the end of the tube is usually oval in shape and is left-facing, 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 which increase the external diameter, making them wider for a given internal diameter. RAE (Ring, Adair and Elwyn) tubes are preformed and can be either north or south facing, and cuffed or uncuffed. The cuffed RAE tubes have one Murphy eye, whereas the uncuffed version has two eyes. Uncuffed tubes are mainly used in paediatric anaesthesia and two Murphy eyes ensure adequate ventilation, should the tube be too long. Tubusgrösse Kind: 4+Alter/4 (ID)  
• Spinalnadeln Yale and Quincke needles are cutting needles, whereas Whitacre and Sprotte needles are pencil point needles. 32G spinal needles are the narrowest currently available, but are not widely used. Pencil point needles are considered less traumatic than cutting needles, but electron miscroscopy has shown that both types of needles can cause trauma, albeit to varying degrees.
• resistivity = spezifischer Widerstand A material with low resistivity readily allows the movement of electric charge. The resistivity of a wire is determined on the atomic structure of the material itself. Metals are very good conductors of electricity because they have low coefficients of resistivity. Resistivity and conductivity are reciprocals of each other. Resistance: Is directly proportional to length of a conductor. Is inversely proportional to cross-sectional area of a conductor. Is directly proportional to the coefficient of resistivity of a conductor. The resistance of a wire increases with temperature but is less important than the chemical structure of the material itself.
• Strom in einem Stromkreis Spannungsunterschied (V) = Stromstärke (I) x Widerstand (Ω). What is the amount of current (I) in a circuit? zB Bei 2 Widerständen: I=V/(R1+R2)
• Gaschromatographie carrier gas, for example, helium, argon or nitrogen stationary phase: column of silica-alumina particles coated in wax (polyethylene glycol) or silicone oil.  
• Helium Helium is present in air and in natural gas. It is supplied as either heliox (79% He, 21% O2) in white cylinders with white/brown shoulders or as pure helium in brown cylinders. Helium has a lower density than nitrogen and oxygen. Therefore, during turbulent flow the velocity will be higher when heliox is used. This will reduce the work of breathing in patients with an upper airway obstruction such as a tumour. Its use in severe asthma and lower airway disease has also been suggested but at present is not commonly used.
• Entonox The British Oxygen Company (BOC), which manufactures Entonox, supplies a product datasheet. This states that Entonox can cause impaired folate metabolism through vitamin B12 inactivation and should be in no greater concentration than 100 parts per million in the general atmosphere. There are no reported adverse events in breastfeeding women and there is no definitive evidence to confirm or exclude the existence of a causal link between exposure to Entonox and infertility. Entonox is non-flammable but strongly supports combustion.
• electrocution Electrocution with 75 mA can cause ventricular fibrillation. The effects of electrocution depend on the duration of contact, the pathway of the current, the frequency and size of the current. A general guide: 1 mA - tingling pain 5 mA - pain 15 mA - tonic muscular contraction 50 mA - respiratory muscle paralysis 75 mA - ventricular fibrillation. Wet skin reduces the resistance to current flow and therefore increases the effects of electrocution. The higher the frequency, the less effects of electrocution on the body. The classes of equipment describe the method used to protect against electrocution: I. Basic protection II. Double insulated III. Safety extra low voltage. Equipment is also classified into types based on maximum leakage current. Only type CF equipments protect against microshock as they allow leakage currents of 0.05 mA per electrode for class I equipment and 0.01 mA for class II. Microshock is a small leakage current that can result in harm because of direct connection to the heart via transvenous lines or wires, bypassing the impedance of the skin can lead to ventricular fibrillation. Microshock current of 100 μA is sufficient to cause VF.
• Sterilisation   Moist heat kills all organisms and spores. It should be applied at 122°C at 1 atm for 30 minutes 126°C at 1.5 atm for 10 minutes, or 134°C at 2 atm for three minutes to sterilise non-heat sensitive surgical instruments. Steam is used to increase the temperature so dry heat needs to be at a higher temperature for a longer time, for example, 160°C for one hour, to have a similar effect to moist heat. Dry heat is used to sterilise glassware and powders. Steam at low pressure and 80°C will only disinfect instruments, and it does not destroy spores. The addition of formaldehyde will cause sterilisation, and is used to sterilise heat sensitive equipment such as cannulae. Gamma irradiation is emitted from a cobalt-60 source or an electron accelerator, and is an expensive but effective means of sterilising plastics prostheses. Cellulose filtration is used to sterilise heat sensitive fluids but it may not remove viral particles. The most effective known method of sterilising "high risk equipment" is to autoclave at 121°C for 30 minutes with 1N NaOH, clean rinse with water and then subject the equipment again to routine sterilisation. Effective prion decontamination relies upon protein hydrolysis or reduction or destruction of protein tertiary structure. Routine autoclave, gamma irradiation chlorine and ethylene oxide sterilisation techniques are ineffective in destroying all prions.  
• Tracheostomy tubes Tracheostomy tubes are curved and are designed to be inserted through a stoma cut into the second to fourth tracheal rings. They are supplied with an introducer for insertion and have wings attached to the proximal tube allowing it to be secured with a cotton tie. A standard 15mm (diameter) connector is located at the proximal end of the tube. The tip of the tubes are usually cut square rather than bevelled, which is to reduce the risk of obstruction against the tracheal wall. Fenestrated tracheostomy tubes have a window cut into the greater curvature which channels air towards the vocal cords allowing the patient to speak (nach Entfernung der Innenkanüle). Deflating the cuff on the tube reduces airway resistance and improves weaning. Metal tracheostomy tubes are used when long term intubation is necessary and they are made of non-irritant silver which is bactericidal (not bacteriostatic). Metal tubes are uncuffed (not cuffed) and have an inner tube that can be removed allowing regular cleaning.
• body plethysmograph The body plethysmograph is a large box that is used to measure lung volumes and pressures, airways resistance and the pulmonary blood flow. Boyle's law is used to calculate the functional residual capacity (Druck ist umgekehrt proportional zum Volumen)   The double application of Boyle's law measures air trapped in diseased parts of the lungs, which may be missed using the helium dilution technique.
• Pulsoxymetrie: Fehlmessungen Inaccuracy of the pulse oximeter saturation (SpO2) may be caused by: Movement artifact Electrical interference (for example, diathermy) Venous congestion (for example, tricuspid regurgitation and atrial fibrillation make the points for prediction extremely difficult as there is disparity between the points of maximal and minimal absorption) Coloured nail varnish leads to an increase in the non-pulsatile component, resulting in a lesser sensitivity to the pulsatile component Arterial saturations below 50%. Carboxyhaemoglobin causes the SpO2 to read falsely high, and methaemoglobin (and bilirubin) cause the SpO2to read falsely low Methylthioninium chloride (formerly known as methylene blue), which is used to identify sentinel lymph nodes, may temporarily decrease the SpO2 for several minutes following intravenous injection.
• Wärmeverluste   Heat can be lost from the body by five recognised methods: Conduction (5%): durch Temperaturdifferenz Respiration (10%) Convection (15%) durch Temperaturdifferenz oder Gebläse Evaporation (20%) Verdunstung Radiation (50%). Heat lost through radiation is the most important source (not convection). Radiation losses are greater when the amount of exposed surface is high and it increases when there is a large temperature differential. The vasodilation associated with anaesthesia increases radiation heat loss.  
• Gasmessungen volatile anaesthetic agents  electron capture detector Infrared absorption analysers are commonly used  mass spectrometry quartz crystal oscillation  ultraviolet absorption (for halothane)    oxygen  Paramagnetic analysers    inorganic gases (nitrous oxide or oxygen) katharometer detects changes in thermal conductivity of the gas by measuring the change in electrical resistance of a heated wire placed in the gas flow    
• Röntgen Röntgenstrahlung = elektromagnetische Wellen mit Photonenenergien: 25–35 kV bei der Mammografie (weiche Strahlung) 38 und 120 kV bei den übrigen Körperregionen (harte Strahlung) Je weicher die Strahlung (niedrige kV-Werte), ein um so größerer Anteil der Strahlung wird vom Gewebe absorbiert > feinste Gewebeunterschiede auf dem Röntgenfilm jedoch hohe Strahlenbelastung Röntgenstrahlung kann durch zwei verschiedene Vorgänge entstehen: durch starke Beschleunigung geladener Teilchen (meistens Abbremsung oder Ablenkung von Elektronen) – das ist die Bremsstrahlung, deren Spektrum kontinuierlich ist, und durch hochenergetische Übergänge in den Elektronenhüllen von Atomen oder Molekülen. Das ist die charakteristische Röntgenstrahlung. Sie weist stets ein Linienspektrum auf. Beide Effekte werden in der Röntgenröhre ausgenutzt, in der Elektronen zunächst von einer Glühwendel (Kathode) aus beschleunigt werden und auf die Anode treffen, in der sie stark abgebremst werden. Dabei entsteht Röntgenstrahlung (Bremsstrahlung, mit insgesamt rund 1 % der eingestrahlten Energie) und Wärme (rund 99 %). Außerdem werden durch Elektronenstöße Elektronen aus den Schalen der Metallatome herausgeschlagen. Die Löcher in den Schalen werden durch andere Elektronen aufgefüllt, wobei charakteristische Röntgenstrahlung entsteht. K: Kathode (Elektronenquelle), A: Anode (Elektronenziel), X: Röntgenstrahlung, Uh: Heizspannung, Ua: Beschleunigungsspannung
• Kraft, Energie: Definitionen Kraft in Newton = mass x length/time2. Masse x Beschleunigung Druck x Fläche Arbeit/ Distanz   Energy in joules (J) =  force × length (m) (1 J = N.m). Energy is also a function of pressure (Pa) and volume (V) : (1 J = 1 Pa.m3). Energy may also be defined as work or power (W) × time (s), for example, 1 J = W.s. The formula ½ mass × velocity2  is for measuring kinetic energy.
• Grahamsches Gesetz Die Geschwindigkeiten  v , mit denen Gase durch eine poröse Wand (Transfusion) oder aus sehr feinen Öffnungen in einer dünnen Wand (z.B. Effusion aus einer Kapillare) diffundieren, sind der Quadratwurzel aus ihren Molgewichten M umgekehrt proportional
• ToF Watch single pulses: 0,1-1hz. Supramax Stimulation (20-60 mA für Erregung aller Mukelfasern des Nervens). TOF: 4x2 Hz. Widerholbar nach 10-15 sec Double burst:  2kurze tetanische Stimulationen (zB 50 Hz für 60 ms) mit 750 ms Abstand    Post tetanic count: 5 s tetanus  (50-100 Hz) followed by 20 pulses at 2 Hz• Shows fade response earlier than train of four• Used under deep paralysis to estimate time to recovery  
• humidification Medical gases are dry and failure to humidify the inspired gas will cause: Drying of the respiratory mucosa with ciliary dysfunction Mucous thickening with plugging of airways, atelectasis and reduced gas exchange mucosal keratinisation and ulceration. Humidification of inspired gases also reduces heat loss by avoiding the latent heat of vaporisation within the trachea and by warming the gases. The absolute humidity in the proximal trachea is 34 g/m3 where the air is fully saturated at 34 ºC. In the alveoli the absolute humidity is 43 g/m3, which is fully saturated air at 37 ºC. The ideal water droplet size is approximately 1 ìm (micron), which is small enough to be deposited in the alveoli. Droplets <1 ìm tend to be stable and therefore inspired and expired without deposition. Larger droplets of 20 ìm or greater tend to collect in the breathing system, and 5 ìm droplets tend to be deposited in the trachea. In the ultrasonic nebuliser water drops onto a plate which vibrates at 2 Mz and can achieve 100% saturation.
• Kraft Kraft= Masse x Beschleunigung

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