Binder2

Procedure 1. Attach a disposable probe cover to the thermometer tip. 2. Gently pull the ear up and back to straighten the ear canal. 3. With the ear canal straightened, insert the probe tip and operate the thermometer. 4. Remove the thermometer from the ear canal and release the patient’s ear. The temperature reading is displayed on the screen. 5. With the thermometer above a correct waste container, press the probe cover release button to dispose of the used probe cover.Maintenance & Service ProceduresThe Genius 2 tympanic thermometer is recalibrated at predetermined intervals usuallyannually, or when a fault occurs using a checker/calibrator. This device has been developed tocheck the accuracy and automatically recalibrate the thermometer, if necessary.The accuracy of tympanic thermometers has been brought into question and the trust is movingaway from them and towards contact thermometry across all sites.

Contact ThermometersContact thermometers use a thermistor to measure resistance as the temperature changes. Oncethe probe is placed into a person's mouth, it heats up to the same temperature of the mouth, thethermistor inside also warms up/cools down, increasing/decreasing its resistance. Amicrocontroller measures the resistance and converts it into a temperature and displays it onthe screen. (eHow, 2012)ProcedureOral 1. Ensure that the oral probe (blue ejection button) and the blue probe well are installed. 2. Holding the probe handle with your thumb and two fingers on the indentations of the probe handle, withdraw the probe from the probe well. 3. Verify that the oral model icon is selected by observing the flashing head icon on the instrument’s display. If this icon is not flashing, press the Mode Selection button until the head icon appears. 4. Load a probe cover by inserting the probe into a probe cover and pressing the probe handle down firmly. The probe handle will move slightly to engage the probe cover. 5. With the Oral Mode indicator flashing, quickly place the probe tip under the patient’s tongue on either side of the mouth to reach the rear sublingual pocket. Have the patient close their lips around the probe. Sublingual Pockets 6. Hold the probe in place, keeping the tip of the probe in contact with the oral tissue throughout the measurement process. Rotating “walking” segments appear on the display, indicating that measurement is in progress. 7. The unit will beep three times when the final temperature is reached. The measurement site, temperature scale, and patient temperature will display on the LCD. The final temperature will remain on the display for 30 seconds.

8. If you cannot correctly measure the patient’s temperature in Normal Mode, the unit will automatically enter Monitor Mode.In this mode, measurement time is extended. Either repeat the temperature measurement inNormal Mode in the opposite sublingual pocket or keep the probe in place for three minutes inMonitor Mode. The thermometer will not beep to indicate a final temperature. Record thetemperature before removing the probe from the site, as the temperature reading is notmaintained in memory.9. After the temperature measurement is complete, remove the probe from the patient’s mouth. Eject the probe cover by firmly pressing the ejection button on the top of the probe.10. Return the probe to the probe well. The LCD display will go blank.Long-term continuous monitoring beyond three minutes is not recommended in the Oral Mode.Patient actions may interfere with accurate oral temperature readings. Ingesting hot or coldliquids, eating food, chewing gum or mints, brushing teeth, smoking, or performing strenuousactivity may affect temperature readings for up to 20 minutes after activity has ended.AxillaVerify that the axillary mode is selected by observing the correct flashing axillary icon on theinstrument’s display. If this icon is not flashing, press the Mode Selection button to select theAdult Axillary or Paediatric Axillary icon i. 1. With the correct axillary mode indicator flashing, lift the patient’s arm so that the entire axilla is easily seen. Place the probe as high as possible in the axilla. Do not allow the probe tip to come into contact with the patient until the probe is placed in the measurement site. Before this, any contact between the probe tip and the tissue or other material may cause inaccurate readings. 2. Verify that the probe tip is completely surrounded by axillary tissue and place the arm snugly at the patient’s side. Hold the patient’s arm in this position and do not allow movement of the arm or probe during the measurement cycle. Rotating “walking” segments appear on the display, indicating that measurement is in progress.

RectalEnsure that the rectal probe (red ejection button) and the red probe well are installed. Theinstrument will only operate in Rectal Mode when the red rectal probe and probe well areinstalled. Observe the flashing lower-body icon on the unit’s display 1. With the Rectal Mode indicator flashing, separate the patient’s buttocks with one hand. Using the other hand, gently insert the probe only 1.5 cm (5/8 in.) inside the rectum (less for infants and children). The use of a lubricant is optional. 2. Tilt the probe so that the tip of the probe is in contact with tissue. Keep the hand separating the buttocks in place, and hold the probe in place throughout the measurement process.Maintenance & Service ProceduresThe SureTemp 692 thermometer calibration is checked at predetermined intervals usuallyannually, or when a fault occurs using a Sure Temp Cal-Key, and the 9600 Plus CalibrationTester. The SureTemp thermometer should be in same room as the 9600 Plus CalibrationTester for approximately 30 minutes prior to testing to allow for thermal accommodation.Remove the probe from the thermometer well and clean it with a 70% isopropyl alcoholsolution and allow to air dry for at least five minutes. The probe should then be checked againstthe 3 temperature ranges 36˚C, 38.5˚C and 41˚C ensuring the temperature displayed on screen iswithin ±0.1˚C.If the device is out of calibration then it should be returned to the supplier. (Welch Allyn)Battery leakage could cause skin irritant, PPE to be used. Probe tips may be contaminated due toprobe covers not being used.

BibliographyeHow, 2012. eHow. [Online]Available at: http://www.ehow.com/how-does_5162287_electronic-thermometer-work.html[Accessed November 2013].Jamieson, E., 2002. Clinical Nursing Practices. 4th ed. Edingburgh: Churchill.Nursing Times, 2007. Nursing Times. [Online]Available at: http://www.nursingtimes.net/home/clinical-zones/assessment-skills/temperature/200193.article[Accessed November 2013].

Ophthalmoscopes & Otoscopes Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

OphthalmoscopesThe eye is a complex optical system which collects light from the surrounding environment,regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lensesto form an image, converts this image into a set of electrical signals, and transmits these signalsto the brain through complex neural pathways that connect the eye via the optic nerve to thevisual cortex and other areas of the brain. (Yale, 2013) Fig 1 –Anatomy of the Human Eye. (All About vision, 2014)An ophthalmoscope is an instrument used for inspecting the interior of the eye including theoptic disc, retina, retinal blood vessels, macula and choroid. Ocular diseases, neurologicalconditions and diabetic retinopathy may be detected using an ophthalmoscope.There are two types of Ophthalmoscope Direct & Indirect;Direct - A hand held device consisting of a handle containing the power source. Light which isemitted from a bulb in the head passes through the relevant filter, through a series of focusinglenses that can magnify up to 20 times, and is then reflected out of the head via an angled mirrorwith a hole in it. The hole in the mirror allows clinical staff to view light reflected back from theretina.Indirect – A headband worn by the clinician holds a light which shines into the patient’s eye.Magnifying lenses, either monocular or binocular, are also attached to the headband for theclinician to view through. The image allows a wider view of the inside of the eye and a betterview of the fundus, than a direct ophthalmoscope, especially useful if the patient has cataracts.Maintenance & Service ProceduresThere are no scheduled maintenance procedures for either type of ophthalmoscope, however,battery powered devices will need battery replacement, though this is not a scheduledprocedure and is only carried out when required. Mains powered devices do need an annualelectrical safety test, normally Class 2. Bulb replacement may be necessary, ensuring the correctbulb is selected (Keeler have adopted a policy of red base for rechargeable, blue base fordisposable battery operated). Heads are often damaged through being dropped, sometimesthey are repairable however, this can be awkward due to the small size and delicate nature ofthe internal components but may need replacing or scrapping depending on age.

Aperature & GraticulesDifferent products use a combination of these filters and beams. Wide Angle Intermediate Macula Illuminates the largest area of Permits easier access through Designed specifically for fundus for the best possible an un-dilated pupil and in examination of the maculageneral diagnosis through a large peripheral examination. region of the fundus where Particularly useful in a larger beam would create pupil. paediatric examination. excessive pupillary reaction or patient discomfort. Slit Fixation Star or Cross Glaucoma Used primarily to determine Projects a graticule onto the Projects a graticule onto the retinal elevations and retina to assess the degree retina to assess the optic and direction of eccentric cup/disc ratio as an aid todepressions, but may also be used fixation, E.G. as a result of glaucoma diagnosis.to assess anterior chamber depth. macula degeneration.Filters Red Free Cobalt Blue Safety The red-free filter is used to Used in conjunction with The unique Keeler safetyexamine the blood vessels in fine fluorescein dye for the filter cuts out the ultra violet, visible blue and detail. By filtering out the red detection and examination of infrared wavelengths saidrays, blood vessels are silhouetted corneal scars and abrasions. to cause phototoxic retinal damage with prolonged black against a dark green background. exposure. (Keeler, 2013)

OtoscopesAn otoscope or auriscope is a handheld instrument used by medical professionals for examiningthe external auditory canal and tympanic membrane (ear drum). Anatomy of the Human Ear (Physics Class Room, 2012)Otoscopes consist of a handle and a head. The head contains a light source and a low powermagnifying lens. The otoscope has an attachment for disposable plastic ear speculums. Mostotoscopes have a movable magnifying lens to enable the medical professional to insert tools intothe ear to remove cerumen (earwax) etc. Another feature present in some otoscopes is a bulbthat allows the user to blow a small amount of air into the ear to observe the mobility of thetympanic membrane.Video OtoscopeA video-otoscope is a small endoscope connected to a digital camera for examining the outerand middle ear.Video-otoscopes are sometimes preferred by clinical staff as they provide a larger high qualityimage which, make diagnosis simple. The other main benefit of video-otoscopes is increasingthe patients’ understanding of their condition by showing the image clearly on the screen.Maintenance & Service ProceduresOtoscopes are repaired / serviced on request. The most common problems being batteriesrequire replacing, rechargeable batteries no longer holding charge, on average these arechanged every 2 years for lead acid, 4 years for lithium ion, light bulbs require replacing,ensuring the correct bulb is selected.Infectious material on the equipment or the speculum if the otoscope has not been cleaned orthe speculum disposed of. The possibility of battery leakage which could cause an irritation. Itwould be recommended that PPE should be worn.

BibliographyAll About vision, 2014. Human Eye Anatomy. [Online]Available at: http://www.allaboutvision.com/resources/anatomy.htm[Accessed December 2014].Keeler, 2013. Apature & Graticukes. [Online]Available at: http://www.dfv.com.au/prod_keeler_ophthalmoscopes.htm[Accessed December 2013].Physics Class Room, 2012. Physics Class Room. [Online]Available at: http://www.physicsclassroom.com/class/sound/u11l2d.cfm[Accessed December 2013].Yale, 2013. MedCell - Yale. [Online]Available at: http://medcell.med.yale.edu/histology/keyword.cgi?keyword=eye[Accessed December 2013].

Laryngoscopes Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

LaryngoscopesA laryngoscope is a hand held device which is inserted into the mouth and into the tracheawhilst depressing the tongue. It can be used to obtain a view of the larynx, or to facilitatetracheal intubation in critically injured or anaesthetised patients.A laryngoscope consists of a handle containing batteries which power a light bulb. The bulbhousing is mounted on a spring, and only illuminates when it is depressed. Disposable blades,coming in a variety of sizes to suit the patient 0 (Neonatal) to 4 (Adult), are then attached to thehandle on a pivot. The blade can then either be folded down for storage, or extended. Whenextended, the mechanism ensures the bulb is depressed illuminating it, the light then travelsdown fibre optic tubing to the end of the blade illuminating the trachea.A laryngoscopy is an examination of the larynx with a mirror (indirect laryngoscopy) or with alaryngoscope (direct laryngoscopy).The purpose and advantage of seeing inside the larynx is to detect tumors, foreign bodies, nerveor structural injury, or other abnormalities. Two methods allow the larynx to be seen directlyduring the examination. In one, a flexible tube with a fibre-optic device is threaded through thenasal passage and down into the throat. The other method uses a rigid viewing tube passeddirectly from the mouth, through the throat, into the larynx. A light and lens affixed to theendoscope are used in both methods. The endoscopic tube may also be equipped to suctiondebris or remove material for biopsy. Bronchoscopy is a similar, but more extensive procedurein which the tube is continued through the larynx, down into the trachea and bronchi. (Medical Dictionary, 2012) Diagram of a Laryngoscope being inserted. (WritePass, 2012)

Maintenance & Service ProceduresLaryngoscopes only require visual inspection and function checks. A functional check involveschecking and replacing batteries, ensuring bulb illuminates when depressed, fitting blade andensure bulb illuminates with blade locked in position., if the laryngoscope is fitted withrechargeable batteries the charger must also be inspected and undergo an electrical safety test.However, most Laryngoscopes used in the trust are now disposable.BibliographyMedical Dictionary, 2012. Medical Dictionary. [Online]Available at: http://medical-dictionary.thefreedictionary.com/laryngoscopy[Accessed December 2013].WritePass, 2012. WritePass. [Online]Available at: http://writepass.com/journal/wp-content/uploads/2012/12/Showing-rigid-laryngoscope-inserted-through-the-mouth-adopted-from-Nucleus-medical-media.jpg[Accessed December 2013].

Nebulisers Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

NebulisersIn medicine, a nebuliser is a drug delivery device used to administer medication in the form of amist inhaled into the lungs. Nebulisers are commonly used for the treatment of cystic fibrosis,asthma, COPD and other respiratory diseases. Nebulisers use oxygen, compressed air orultrasonic power to break up medical solutions and suspensions into small aerosol droplets thatcan be directly inhaled from the mouthpiece of the device . The proportion of the nebulisedsolution that reaches the lungs is approximately 12%, which is why nebulised doses of drugsare higher than those administered via an aerosol inhaler. (Nursing Times, 2013) Fig 1 - Airways (Asthma Foundation, 2016)Jet NebuliserThe jet nebuliser is the most common type used. There are three components:Compressor:This is the power source that pressurises (compresses) the air. This compressed air breaks theliquid medication down into tiny droplets (a mist) that you breathe in.Nebuliser chamber:This is a small plastic cylinder that you put the liquid medication into. A long, thin tube connectsthe compressor to the chamber and passes the compressed air through.Face mask or mouthpiece:This is the device you use to breathe the medication into your lungs. It attaches to the nebuliserchamber. A face mask fits over your nose and mouth and is usually held in place by a thin elasticstrap that goes around the back of your head. You breathe normally to get the medication intoyour lungs. If you use a mouthpiece, you place your lips around it to form a seal and breathe themedication in. (British Lung Foundation, 2013)

Ultrasonic Wave NebulisersThe technology inside an ultrasonic wave nebuliser is to have an electronic oscillator generate ahigh frequency ultrasonic wave which causes the mechanical vibration of a piezoelectricelement. This vibrating element is in contact with a liquid reservoir and its high frequencyvibration is sufficient to produce a vapor mist. As they create aerosols from ultrasonicvibration, instead of using a heavy air compressor, they are light-weight. Another advantage isthat the ultrasonic vibration is almost silent. (Tech-FAQ, 2014)Maintenance & Service ProceduresIt is important to carry out a full and thorough visual inspection looking for any damage or wearthat is likely to cause a fault in the future.The Clinical Engineering Department are only responsible for the compressor. The face mask,tubing and nebuliser chamber are all the responsibility of clinical staff and the users.A Visual inspection should be carried out to include body, mains lead, battery (if applicable),condition of mains power socket and a full rotational to listen for any loose parts inside the unit.It should then be functionally checked including the Mains switch neon / DC switch indicator,that the Compressor is not excessively noisy, the auxiliary power switch indicator lights andthat it Operates on auxiliary power, if applicable.Replace any inlet & outlet filters, and perform a dynamic flow and pressure measurement checkas per specification for the model being tested.Finally an electrical safety test should be performed.Issuing New NebulisersAcceptance checks are to be completed as normal but label as Chest Clinic (Clinic 2), althoughthe actual location is Clinical Engineering. Mark the box with the LCE File numberWhen clinical staff request a new nebuliser, note the ward or clinic and the patient NHS number.Take the nebuliser with the lowest LCE file number from the storeroom.Unless the service labels are out of date just issue the nebuliser. If they are out of date, createand complete a ‘Verified Safety and performance’ job first.First have the location changed from Clinical Engineering to the ward or clinic that hasrequested the nebuliser and complete a worksheet Job type - Issue Parts. Word the task‘Nebuliser issued to <location name> for patient NHS number <number>’. Copy this info into theequipment notes field add nebuliser as a part to ensure the cost is charged to the correct ward.E-mail Phillip Ward or Andrew Darlow with this information along with the file number so theyupdate the database.

BibliographyAsthma Foundation, 2016. Asthma Foundation. [Online]Available at: https://www.asthmafoundation.org.nz/your-health/living-with-asthmaBritish Lung Foundation, 2013. British Lung Foundation. [Online]Available at: http://www.blf.org.uk/Page/Nebulisers[Accessed December 2013].Nursing Times, 2013. Nursing Times. [Online]Available at: http://www.nursingtimes.net/nursing-practice/clinical-zones/respiratory/respiratory-procedures-use-of-a-nebuliser/200213.article[Accessed December 2013].Tech-FAQ, 2014. Ultrasonic Nebulisers. [Online]Available at: http://www.tech-faq.com/how-does-an-ultrasonic-nebulizer-work.html[Accessed December 2014].

Constant Positive Airway Pressure (CPAP) Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

Constant Positive Airway Pressure (CPAP)Sleep ApnoeaObstructive sleep apnoea (OSA) is caused by the muscles and soft tissue in the back of the throatcollapsing inwards during sleep. These muscles support the tongue, tonsils and soft palate (amuscle at the back of the throat that is used in speech).Once the muscles relax the airway in the throat can narrow or become totally blocked, thisinterrupts the oxygen supply to the body, which triggers the brain to pull you out of deep sleepso that the airway reopens and you can breathe normally. However, after falling back into deepsleep, further episodes of apnoea and hypo-apnoea can occur. Such events may occur more thanonce a minute throughout the nightObstructive sleep apnoea is a condition that causes interrupted breathing during sleep.There are two types of breathing interruption characteristics of OSA:  Apnoea – the muscles and soft tissues in the throat relax and collapse sufficiently to cause a total blockage of the airway; it is called an apnoea when the airflow is blocked for 10 seconds or more  Hypo-apnoea – a partial blockage of the airway that results in an airflow reduction of greater than 50% for 10 seconds or moreThe term 'obstructive' distinguishes OSA from rarer forms of sleep apnoea, such as central sleepapnoea. In central sleep apnoea, the airway is not blocked but the brain fails to signal themuscles to breathe due to instability in the respiratory control centre. This type is called centralsleep apnoea because it is related to the function of the central nervous system. (NHS, 2013)Continuous Positive Airway Pressure (CPAP)Moderate to severe cases of sleep apnoea may need to be treated using a type of treatmentcalled Continuous Positive Airway Pressure (CPAP). This involves using breathing apparatus toassist with breathing whilst sleeping.A mask is placed over your nose, which delivers a continuous supply of compressed air. Thecompressed air prevents the airway in your throat from closing.Normal Breathing OSA CPAP Therapy Airway is open Airway collapses Airway splinted open air flows freely blocked air flow air flows freelyFig 1 – CPAP Therapy (ResMed, 2013)

Earlier versions of CPAP often caused nasal dryness, nosebleeds and a sore throat. However, thelatest versions include a humidifier, a device that increases moisture, which helps to reducethese side effects.CPAP machines have a delay timer or an inbuilt ramping system. This allows the user to becomeaccustomed to a low pressure of air whilst falling asleep. The machine will then gradually buildup to the prescribed pressure after a set length of time.Auto-titration devices (such as the S8 Escape) are intelligent devices which can detect eventssuch as snoring, apnoea, hypo-apnoea and flow limitation. On detection of these events thepressure can be generated accordingly, meaning the pressure can be decreased in betweenevents making it much more comfortable for the patient.Unrestricted Device PressureInspiratory Flow response (PressureTime curve. Unchanged).Flattening Device pressureInspiratory flow response (Pressuretime curve, caused increasing dependingby the airway on the level ofnarrowing. flattening).Snore Inspiratory Device pressureflow time curve, response (Pressurecaused by snoring. increasing depending on the loudness of snoring.Apnoea Inspiratory Device pressureflow time curve, response (Pressurecaused by the increasing untilairway closing. termination of Apnoea).Fig 2 – CPAP Flow Pattern Detection (ResMed, 2013)Certain devices are able to record and log patient usage/compliance (Data Capable CPAP), thisenables the clinical staff to monitor how much the device is being used, study any flow limitingevents and assess how effective the treatment is. (ResMed, 2013)

Maintenance & Service ProceduresCPAP machines need to be serviced annually; they should be visually inspected. Any filtersreplaced and listening for any excessive noise from the motor. All tests and calibrations arecarried out using software supplied by ResMed that controls the flow generator and gives stepby step instructions on how to assemble the test equipment. The most important test is tocheck the output pressure of a CPAP, excessive pressure may cause distress to the patient asthey may struggle to exhale. Excessive output pressure may also harm the patient. Afterfunction testing and calibration an Electrical Safety Test should be carried out.BibliographyNHS, 2013. NHS. [Online]Available at: http://www.nhs.uk/conditions/sleep-apnoea/Pages/Introduction.aspx[Accessed December 2013].ResMed, 2013. ResMed. [Online]Available at: http://www.resmed.com/uk[Accessed December 2013].

Weigh Scales Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

Weigh ScalesIn a medical environment there are two main types of scales, patient weighing and fluidweighing.Patient WeighingThe patient's height and weight are recorded for several reasons;Diet Management. -The patient's ideal weight may be determined. The health care team willalso be able to monitor weight loss or gain.Observation of Medical Status - Taking the patient's height and weight may indicate that thepatient is overweight, underweight, or is retaining fluids (edema). The health care team canobserve changes in weight caused by specific disease processes and determine the effectivenessof nutrition supplements prescribed to maintain weight.Calculation of Medication Dosages - Drug dosage is often prescribed in relation to a patient'sweight when a specific blood concentration of the drug is desired. Larger doses may be requiredin a heavier person. (Nursing Fundamentals, 2012)Fluid WeighingAnother important function of weigh scales in the clinical environment is fluid measurement.Urine, vomit, diarrhoea, blood and other bodily fluids can be measured using fluid scales. It isimportant that users are aware that generally fluid scales are calibrated to water (1ml = 1g)care should be taken when measuring other fluids as they may be heavier.The Non-automatic Weighing Instruments Regulations (NAWI) 2000 state that from 1 January2003, where scales are first used for the 'determination of mass in the practice of medicine forweighing patients for the purposes of monitoring, diagnosis, and medical treatment', you willneed to ensure that the scales meet the requirements of these regulations.Equipment meeting these standards should bear the following;A green sticker (Metrology). This is the mark meaning legal for any use covered by theregulations.An accuracy class marking – this could be Class I, II, III or IIII.Class III scales will be labelled with the min/max weight and the scale interval.The verification scale interval is used for classification and verification of a weighinginstrument. This is the specification of the scale within the indicated range[1] & [2] below indicates a user selectable range. i.e. Seca 799 stand on column scales, aremarked: [1] Max 150Kg, e=0.1Kg, Min 2Kg [2] Max 200Kg, e=0.2Kg, Min 4KgSo with range [1] selected, between 2Kg to 150Kg the accuracy is +/- 100g & with range [2]selected, between 4Kg to 200Kg the accuracy is +/- 200g.See Appendix A for error allowances in Class III and Class IIII scales.

Medical scales are generally either class III or class IIII. Although class IIII instruments may besuitable for a limited number of applications such as monitoring for general health and fitness ina GP consulting room, it is recommended that only the higher precision class III machines areused in any medical establishment. Only metric instruments should be used, Failure to do socould result in an error if the wrong units are inadvertently used. This could result in incorrecttreatment doses being given to patients. (UKWF, 2011)The majority of weigh scales used in the hospital environment are electronic. Electronic scalesuse strain gauges, a length of resistive metal that stretches or compresses as a load is applied toit, attached to a load cell that deflects as a load is applied to it. As the metal stretches andlengthens the resistance increases, and when the metal compresses and shortens the resistancedecreases. The scales then calculate the weight applied from the change in resistance (Load Star Sensors, 2012)Maintenance & Service ProceduresAll stand-alone weigh scales on ULHT sites are certified by an approved external company(Autoweigh - Certified and verified by the National Weights and Measures Laboratory (SI1999503) and UKAS accredited) every 6 months to maintain accuracy. Scales that are incorporatedinto another piece of equipment such as, hoists, beds etc., are also certified by an externalcompany, however, some equipment with an inbuilt weighing facility, for example a Neonatalincubator, is checked during a routine service by the Clinical Engineering Department.Weigh scales must be tested with certified test weights at several points through the weighingrange. For most medical weighing applications, it should be possible to apply full load to thescale during calibration. Where this is not practical then a significant proportion should beapplied. A test certificate should be issued with readings before and after any adjustment ismade and a sticker applied identifying the date of calibration. (UKWF, 2011)On acceptance patient weigh scales should be inspected for conformity to the above directivesand regulations (CE mark, Green Metrology sticker, and class III minimum). They should also beaccompanied by a declaration of conformity. CEng protocol should be carried out, includingvisual inspection, calibration - ensuring any calibration weights used have a current and validcertificate of calibration. Clinical Engineering are responsible for electrically safety testing anymains powered scales on site.

BibliographyLoad Star Sensors, 2012. Load Star Sensors. [Online]Available at: http://www.loadstarsensors.com/technology.html[Accessed January 2014].Nursing Fundamentals, 2012. Nursing Fundamentals. [Online]Available at:http://www.brooksidepress.org/Products/Nursing_Fundamentals_II/lesson_4_Section_1.htm[Accessed January 2014].UKWF, 2011. United Kingdom Weight Federation. [Online]Available at: http://www.ukwf.org.uk/technical_information.html[Accessed January 2014].

Enteral Feed Pumps Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

Enteral Feed PumpsPatients with under-nutrition to a degree that may impair immunity, wound healing, musclestrength, and psychological drive cope poorly with modern medical and surgical interventionsand, on average, stay in hospital for approximately five days longer than the adequatelynourished, incurring approximately 50% greater costs. Hospitals should therefore aim toprovide at least adequate nutrition to all patients. In the majority, this can be achieved by thecatering services if they offer good food and care is taken to avoid missed meals and to providephysical help with eating, as necessary. However, even if these ideals are met, many hospitalpatients do not or cannot eat adequately. Some of these will benefit from oral supplements butothers will need active nutritional support. This can usually be provided by enteral tube feeding(ETF). (GUT, 2003)Enteral feeding refers to the delivery of a nutritionally complete feed containing protein,carbohydrate, fat, water, minerals and vitamins directly into the stomach, duodenum orjejunum. Fig 1- Gastrointestinal Diagram (Richards, 2012)Nasogastric (NG) tubesMost enteral feed is given into the stomach to allow the use of hypertonic feeds, higher feedingrates, and bolus feeding. Fine bore (5–8 French gauge) NG tubes are now used unless there is aneed for stomach aspiration, or administration of high fibre feeds or drugs via the tube. Largebore PVC tubes should be avoided as they irritate the nose and Oesophagus and increase therisks of gastric reflux and aspiration. They also need frequent replacement as they degrade oncontact with gastric contents. Polyurethane and silicone tubes last for at least one month.

Nasojejunal (NJ) tubesJejeunal feeding may be used if there are problems with gastric reflux or delayed gastricemptying. It should also be used in unconscious patients who have to be nursed flat. All NJtubes are fine bore (6–10 French gauge). Some have a shorter second lumen for gastricaspirationPercutaneous gastrostomy tubesIf enteral feeding is likely to be needed for periods of more than 4–6 weeks, a gastrostomy tubecan be inserted directly into the stomach through the abdominal wall, using relatively simpleendoscopic or radiological procedures. Gastrostomy tubes allow feeding without theinconvenience and discomfort of NG access, and patients receive more of their prescribed feed.Feed Pump Construction (GUT, 2003)The unit consists of a pump, pump holder, pole clamp and Class 2 figure 8 mains lead. Feedpumps control the amount of feed and the speed that it is infused into a patient. The feed isdelivered through a bag held on a drip stand down a giving set to the patient.The giving set is loaded into the pump, ensuring the tubing is in a straight line, and also that it isslightly stretched but not elongated (otherwise errors can be induced into the flow rate andvolume accuracy). The pump can then be set for continuous feeding with no target volume, orcontinuous feeding with a target volume (VTBI – Volume to be infused).Sensor Area Clamp Fixture Pump Mechanism Tube Sensor Fig 2 – Fresenius Applix Feed Pump (Fresenius, 2013)

Pump Mechanism Fig 3 – Pump Mechanism of an Applix Feed Pump (Fresenius, 2013)The giving set is inserted into the pump and clamped between the pumping mechanism anddoor. The motor turns at a set speed moving the pump mechanism, which in turn compressesthe tubing, which drives the feed through the giving set.The pump has three sensors, one to sense door shut, an optical sensor to detect installed givingset, and an ultrasonic sensor to detect air in the tubing. If set to continuous the pump will rununtil the feed bag is empty at which point the pump will alarm with a ‘line empty’ symbol, or if atarget volume has been set the pump will run until this volume has been reached at which pointthe pump will stop with the ‘target volume reached’ symbol flashing. The pump will alarm toindicate certain conditions: Low Battery, Line Empty, Air Detected, Upstream / DownstreamOcclusion, Incorrect Insertion of Giving Set, Pump Door Open, Pump Mechanism Blocked, andany System Faults (indicated by ‘EXX’ on the display screen).The pump holders do have a nurse call function, however, this function is not used. (Fresenius, 2013)Maintenance & Service ProceduresThe feed pumps are on contract to be serviced and repaired by the manufacturer, on returnthese pumps are given a basic check to ‘Work Instruction- Equipment returned from an externalprovider - Cdoc0001A’, which includes a visual inspection and a check to make sure the correctdocumentation and labelling is with the pump. A database has been set up to inform Dieteticswhich pumps have been sent away, a maximum of 10 at any one time, and when they are readyto be collected from the Clinical Engineering Dept.

BibliographyFresenius, 2013. Fresenius. [Online]Available at: http://www.fresenius-kabi.com/files/4137-2_nu_Applix_Smart_GB_V1.pdf[Accessed January 2013].GUT, 2003. Enteral Feeding. [Online]Available at: http://gut.bmj.com/content/52/suppl_7/vii1.long[Accessed January 2013].Richards, D. J., 2012. GI Disorders. [Online]Available at: http://drjoycerichards.com/digestive-diseases.htm[Accessed January 2013].

Intermittent Compression (DVT) Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

Intermittent Compression (DVT)Deep Vein Thrombosis (DVT) describes a condition where a blood clot (thrombus) forms in oneof the large veins in the body, usually in the lower limbs. These blood clots form when bloodflow is reduced due to surgery (muscles are relaxed, and there is no movement to stimulateblood flow), injury, inflammation, or lack of mobility during prolonged travel or sitting. Theblood clot can cause total or partial blockage. In itself the condition can be painful, causingswelling and tenderness of the affected limb, however, a more serious complication may arisewhen a part of the blood clot breaks free (Embolus). This embolus then travels around the bloodstream and can cause Pulmonary Embolism, a sudden blockage of a lung artery, which may befatal. DVT and pulmonary embolism together are known as venous thromboembolism (VTE). (DVT, 2012) Fig 1- Deep Vein Thrombosis (VasoCare, 2004)In order to aid in the prevention of a DVT occurring an intermittent compression device is used.Intermittent compression pumps replicate the physical effects of walking. When walking theblood flow is enhanced by the movement of the lower leg and the squeeze that is applied to theveins in the foot when weight is placed on it.A patient who's immobile for an extended period may have pneumatic compression garmentsprescribed to prevent DVT. Attached to a pump and applied to one or both legs, the garmentsare fabric wraps containing bladders that inflate intermittently to compress the legs and propelthe blood forward. Garments are available for use on the calves only or the thighs and calves. (DVT, 2012)

Flowtron universal PumpThe pump consists of an electronically controlled air compressor with associated air routingand alarm facilities. The operation of all the pumps features are driven by microcontrollersoftware.The key parts of the pump are as follows: • Compressor - This provides a flow of air to the pneumatic system, allowing inflation of the garments. The output of the compressor is fed to the motor and manifold assembly. • Motor and Manifold Assembly - This includes a rotary valve which routes the air pressure to the garments. The rotary valve also makes sure that as one garment is being inflated, the other garment is vented to the atmosphere. • Pressure Transducer - This provides the monitoring system with the means of accurately measuring the pressure fed to each garment. • Control Printed Circuit Board (PCB) - This PCB controls the compressor, the motor and manifold assembly, and the illuminated graphic LCD display panel. It also performs a continuous check of the operation and performance of the pneumatic circuit. In the event of a detected fault, the electronic monitoring system generates both visual and audible alarms. • Power Supply Printed Circuit Board (PCB) - In addition to generating the DC voltages for use in the pump, the PCB provides interfaces to the compressor and the optional battery pack. • Automatic Garment Recognition Facilities - The connector on the end of each pump hose set contains a sense coil which is connected to the control PCB, and is used to automatically recognise the type of garment fitted to the connector (foot garment, or single chamber calf garment). (ArjoHuntleigh, 2009)Maintenance & Service ProceduresThe Flowtron Universal pumps are serviced by the manufacturer (ArjoHuntleigh), if any faultsoccur collection of the pump is arranged and a replacement pump is supplied. Thesereplacement pumps are then checked to ‘Work Instruction Equipment returned from externalprovider– Cdoc0001A’. These checks include a visual inspection and a check to make sure all thecorrect paperwork has been sent with the device and that it has had an electrical safety test. Allrelevant labels/stickers should be on the device.

BibliographyArjoHuntleigh, 2009. Flowtron Service Manual. 1st ed. London: Flowtron.DVT, 2012. Prevent DVT. [Online]Available at: http://www.preventdvt.org/about/what-is-dvt.aspx[Accessed January 2013].VasoCare, 2004. VasoCare. [Online]Available at: http://www.vasocare.net[Accessed January 2013].

Patient Warming & Cooling Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

Patient Warming & CoolingPatient WarmingTo ensure proper function of cells, tissues and organs, core body temperature needs to be stable& between 36.5°C - 37.5°C. However, there are occasions when the body is unable to regulatethe core temperature and hypothermia occurs when core temperature drops, or hyperthermiaoccurs when core temperature rises. Hypothermia is a fairly common yet serious conditionwhich increases the chances of mortality by up to 100% due to increased oxygen consumptiondue to shivering. This increase in oxygen demand places a strain on the heart, potentiallycausing arrhythmias and coagulopathy. (Van Rensburg, 2011)Hypothermia is defined as any body temperature below 35.0 °C (95.0 °F). It is subdivided intothree different degrees,  Mild 32–35 °C (90–95 °F);  Moderate, 28–32 °C (82–90 °F)  Severe, 20–28 °C (68–82 °F)The signs and symptoms vary depending on the degree of hypothermia;MildSymptoms of mild hypothermia may be vague with sympathetic nervous system excitation(shivering, hypertension, tachycardia, tachypnea, and vasoconstriction). These are allphysiological responses to preserve heat. Cold diuresis, mental confusion, as well as hepaticdysfunction may also be present. Hyperglycemia may be present, as glucose consumption bycells and insulin secretion both decrease, and tissue sensitivity to insulin may be blunted.ModerateLow body temperature results in shivering becoming more violent. Muscle discoordinationbecomes apparent. Movements are slow and labored, accompanied by a stumbling pace andmild confusion, although the person may appear alert. Surface blood vessels contract further asthe body focuses its remaining resources on keeping the vital organs warm. The victim becomespale. Lips, ears, fingers and toes may become blue.SevereAs the temperature decreases, further physiological systems falter and heart rate, respiratoryrate, and blood pressure all decrease. This results in an expected HR in the 30s with atemperature of 28 °C (82 °F). Difficulty in speaking, sluggish thinking, and amnesia start toappear; inability to use hands and stumbling is also usually present. Cellular metabolicprocesses shut down. Below 30 °C (86 °F), the exposed skin becomes blue and puffy, musclecoordination becomes very poor, walking becomes almost impossible, and the person exhibitsincoherent/irrational behavior including terminal burrowing or even a stupor. Pulse andrespiration rates decrease significantly, but fast heart rates (ventricular tachycardia, atrialfibrillation) can occur. Major organs fail. Clinical death occursHypothermia is a recognised and common occurrence during surgery, with estimates suggestingthat up to 70% of un-warmed patients may be hypothermic on admission to the recovery room.Patients who develop perioperative hypothermia can experience a number of complications,

including a greater chance of heart problems, higher rates of infection and increased blood loss.Patients experiencing perioperative hypothermia may need a longer stay in hospital.If the patient's operation lasts longer than 30 minutes, or if their operation is shorter than thisbut they are at higher risk of hypothermia or its complications, they should be kept warmthroughout the operation using forced air warming (and their temperature measuredthroughout surgery).Rewarming can be achieved using different methods;  Passive external rewarming involves the use of a person's own heat generating ability through the provision of properly insulated dry clothing and moving to a warm environment. It is recommended for those with mild hypothermia.  Active external rewarming involves applying warming devices externally such as warmed forced air (a Bair Hugger is the commonly used device @ ULHT). It is recommended for moderate hypothermia.  Active core rewarming involves the use of intravenous warmed fluids, irrigation of body cavities with warmed fluids (the thorax, peritoneal, stomach, or bladder), use of warm humidified inhaled air, or use of extracorporeal rewarming such as via a heart lung machine. Extracorporeal rewarming is the fastest method for those with severe hypothermia. (FAW, 2013)Forced air warming consists of a heating element, and a fan to draw air in through the unit pastthe heating element warming the air and through to the garment. Air temperature is monitoredat the outlet and fed back to the device to keep the temperature stable.A control panel allows temperatures to be set at one of four settings; Ambient, 32°C, 38°C and43°C.Patient blankets come in various designs so that the most appropriate one for the condition orprocedure may be used, each blanket has an equal spread of perforations to ensure an even heatis applied all over the skin and there are no hotspots.Neonatal WarmingNew born babies are at risk of hypothermia especially if they are premature. Babies lose heatsoon after birth by evaporation (Amniotic fluid evaporating from the skin), conduction (cominginto contact with cold objects, cloths, trays etc.), convection (air currents in which cold airreplaces the warm air around the baby) and radiation (heat radiation from the baby to colderobjects in the vicinity).There are a range of patient warmers available for neonatal care, incubators, radiant heatersand heated mattresses.Baby Warming Mattress - The mattress is water based, with the water being kept at 37°C. Thepremature or new born baby is placed in the ‘baby nest’, a soft mattress cover which is locatedon top of the water mattress (KanMed, 2012)Radiant Heater - The radiant warmer is intended for warming baby changing tables and formaintaining the body temperature of infants. The built-in ceramic radiator has very goodradiation properties and generates invisible infrared radiation in the region of 3 μm. The skinvery readily absorbs this radiation spectrum and the patients’ skin colour is not altered.The Ceratherm 600-2 is the device used at ULHT, it has 4 heat output settings, which can beindividually set in the range 25%-99%.

The heating output can be set in accordance with actual requirements using the four heatoutput settings (1 – 4). Level 1 = 25% Level 2 = 50% Level 3 = 75% Level 4 = 99%Patient CoolingAfter a cardiac arrest or conditions involving embolisms it may be necessary to inducehypothermia ( Therapeutic Hypothermia) in a patient to prevent tissue damage due to lack ofblood flow. Examples of when this is likely are;  Cardiac arrest,  Strokes,  Birth Asphyxia,  During Brain Surgery,  Traumatic Brain Injuries  Traumatic Spinal Injuries.Additionally patient cooling may be used in any condition whereby the patient has a hightemperature, infection etc. and is suffering from hyperthermia.Therapeutic Hypothermia can be induced by either invasive or non-invasive methods. Theinvasive method involves placing a catheter into the inferior vena cava (large vein that carriesde-oxygenated blood from the lower half of the body into the right atrium of the heart) and acold saline solution being injected in. The non-invasive methods involve garments that are indirect contact with the skin that are able to be cooled by passing refrigerated water throughthem. Another new cooling blanket is the EMCOOLS® pad, which consists of multiple coolingelements that are filled with a combination of graphite/water and placed directly on the skinsurface. (Resus Central, 2010)Maintenance & Service ProceduresThe Bair Hugger is serviced every six months or 500 hours use by an external provider. If a unitis sent into the department a visual inspection can be carried out. The hose needs to beinspected and checked it is attached securely as does the main unit to the base.If the hose is replaced due to damage or sensor fault codes, temperature settings need to becalibrated using Alt mode 1. However, the Bair Hugger is sent back to the manufacturer forrepair in most cases.

BibliographyFAW, 2013. Forced Air Warming Facts. [Online]Available at: http://www.fawfacts.com/[Accessed January 2014].KanMed, 2012. KanMed. [Online]Available at: http://www.kanmed.se/Kanmed-Babywarmer-en-US.aspx[Accessed Febuary 2014].Resus Central, 2010. Resusitation Central. [Online]Available at: http://www.resuscitationcentral.com/hypothermia/cooling-techniques/[Accessed Febuary 2014].Van Rensburg, 2011. Hypothermia. [Online]Available at:http://www.rcsed.ac.uk/fellows/lvanrensburg/classification/commonfiles/hypothermia%20trauma%20patient.htm,[Accessed January 2014].

Suction Units Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

SuctionSuction may be used to clear the airway of blood, saliva, vomit, or other secretions so that apatient may breathe. Suctioning can prevent pulmonary aspiration, which can lead to lunginfections. In surgery suction can be used to remove blood from the area being operated on toallow surgeons to view and work on the area, also thoracic suction which is low flow to ensureno tissue damage is caused whilst removing fluid from body cavities post-surgical procedures. (Heikal, 2012)A motor is used to drive a piston which by use of valves or a diaphragm creates a vacuum in thevacuum chamber. This creates a vacuum in the tubing, which is connected to the collectioncanister which acts as a reservoir, creating a vacuum at the patient tubing end. Some suctionunits have a pressure transducer which senses the pressure and displays the information on anLED display. The amount of suction is controlled via a regulator, and discarded air is vented viaan exhaust. Both bacterial and hydrophobic filters may be used to prevent any liquid oraspirated material from contaminating the pump mechanism, Abbott disposable liners have anantibacterial filter built into the lid, other machines require a filter to be fitted in line with thesuction tubing as with the SAM 12 & 14 suction pumps. Some models also have a float valvewithin the receptacle which causes an occlusion should the contents reach full capacity. Vacuum Connector Patient InletUser Interface Patient TubingCanister Holder Release Arm Canister Battery Door Fig 1 – Laerdal Suction unit (Laerdal, 2013)

Maintenance & Service ProcedureThe suction unit should have a visual inspection, looking for signs of damage to the canister ortubing cracked canisters may affect pressures due to leaks, kinked tubing would cause thesuction to fail completely. Routing of all tubing should be inspected to ensure users haveassembled correctly after changing the canister or lining and that the correct tubing has beenused. The exhaust/bacterial filter should be inspected and changed as necessary. If the pump isfitted with an internal hydrophobic filter this should be changed yearly.A pressure monitor must be connected to the unit at the patient end to check the suctionpressure is within specification at various settings, flow checks then need to be carried out byconnecting a mechanical flow gauge to the patient tubing or by connecting directly to the pump.Unit is then tested for electrical safety.BibliographyHeikal, D., 2012. Heikal Clinic. [Online]Available at: http://heikalclinic.com/clinic/medical-eqiupment/[Accessed Febuary 2014].Laerdal, 2013. Laerdal Suction. [Online]Available at: http://www.laerdal.com/gb/LSU[Accessed Febuary 2014].

Light Sources & Headlamps Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

Light Sources & HeadlampsLight sources are needed in the clinical environment for a variety of reasons, but they all servethe same basic purpose which is to illuminate an area, object or body cavity during procedures.The International Electro-technical Commission (IEC) has created the document IEC 60601-2-41– Particular requirements for the safety of surgical luminaires and luminaires for diagnosis, 2000to establish norms and guidelines for the characteristics of surgical and examination lights tosecure safety for the patient as well as lower the risk to a reasonable level when the light is usedaccording to the user manual. Some of the standards for surgical light-heads are as follows.  Homogenous light - The light should offer a good illumination on a flat, narrow or deep surface in a cavity, despite obstacles such as the surgeons head or hands.  Lux - The central luminance cannot exceed 160,000 lux and should not be lower than 40,000 lux  Light field diameter - The D50 should not exceed 50% of d10 diameter.  Colour rendition - For the purpose of distinguishing true tissue colour in a cavity, the colour rendering index (Ra) should be between 85 and 100.  Backup possibility - In case of interruption of the power supply, the light should be restored within 5 seconds with at least 50% of the previous lux intensity, but not less than 40,000 lux. Within 40 seconds the light should be completely restored to the original amount of lux.The light source may form part of a video or endoscopic stack, be a stand-alone unit often usedin ENT procedures, be attached to a microscope providing illumination to the area underinvestigation, the light is usually transmitted via a fibre optic cable to the lens end of a scope oralso provide illumination via a surgeon’s headlamp.High-Intensity Discharge LampsHigh Pressure Sodium (HPS), Metal Halide, Mercury Vapour and Self-Ballasted Mercury Lampsare all high intensity discharge lamps (HID Compared to fluorescent and incandescent lamps,HID lamps produce a large quantity of light from a relatively small bulb). HID lamps produce light by striking an electrical arc across tungsten electrodes housedinside a specially designed inner glass tube. This tube is filled with both gas and metals. The gasaids in the starting of the lamps. Then, the metals produce the light once they are heated to apoint of evaporation.Fibre OpticThe light in a fiber-optic cable travels through the core by constantly bouncing from thecladding (mirror-lined walls), a principle called total internal reflection. Because the claddingdoes not absorb any light from the core, the light wave can travel great distances. Fig 1 - Fibre Optic Cable (How Stuff Works, 2001)

Light source intensity is either adjusted manually via a dial or slider on the unit or if a cameraand processor are attached. The camera & processor monitors the amount of light at the scopeend and adjusts the intensity automatically.Different wavelengths of light are needed for different procedures;Auto Fluorescence Imaging (AFI) is based on the detection of natural tissue fluorescenceemitted by endogenous molecules (fluorophores) such as collagen, flavins, and porphyrins.After excitation by a short-wavelength light source, mucosal tissue emits a green fluorescence. Adifference in the intensity of this fluorescence is seen between healthy and unhealthy tissue.These colour differences in fluorescence emission can be captured in real time duringendoscopy and used for lesion detection or characterisation.Narrow Band Imaging (NBI) is a powerful optical image enhancement technology thatimproves the visibility of blood vessels and other structures on the bladder mucosa. This makesit an excellent tool for diagnosing bladder cancer during cystoscopy.White light is composed of an equal mixture of wavelengths. The shorter wavelengths onlypenetrate the top layer of the mucosa, while the longer wavelengths penetrate deep into themucosa. NBI light is composed of just two specific wavelengths that are strongly absorbed byhaemoglobin.The shorter wavelength in NBI is 415 nm light, which only penetrates the superficial layers ofthe mucosa. This is absorbed by capillary vessels in the surface of the mucosa and shows upbrownish on the video image. This wavelength is particularly useful for detecting tumours,which are often highly vascularised. The second NBI wavelength is 540 nm light, whichpenetrates deeper than 415 nm light. It is absorbed by blood vessels located deeper within themucosal layer, and appears cyan on the NBI image. This wavelength allows a betterunderstanding of the vasculature of suspect lesions. (Olympus, 2014) Fig 2 – Absorption of Narrow Band Illumination (Olympus, 2014)Maintenance & Service ProceduresA visual inspection, cleaning any ventilation grilles, lenses & filters should be carried out. Lamphours need to be checked and the lamp replaced if necessary (without touching the lens of thelamp), and the lamp hours counter reset. Light sources that use HID lamps require a scheduledlamp change, usually at approximately 500 hours of use. Lamps should be discarded by lettingthe xenon gas escape, if applicable, and disposing the body of the lamp in the correct bin. Anysafety features need to be checked, such as, a lamp door safety lock, which prevents the unitoperating, unless closed. Functional checks need to be carried out ensuring that the light outputis not pointing into a direction that anybody is standing as damage to eyes could occur. The unitthen needs to be tested for electrical safety.

BibliographyHow Stuff Works, 2001. How Stuff Works. [Online]Available at: http://computer.howstuffworks.com/fiber-optic2.htm[Accessed Febuary 2014].Olympus, 2014. Olympus - Narrow Band Imaging. [Online]Available at:http://www.olympus.co.uk/medical/en/medical_systems/applications/urology/bladder/narrow_band_imaging__nbi_/narrow_band_imaging__nbi_.html[Accessed Febuary 2014].

NIBP - Electronic Steven Lewis Clinical Engineering United Lincolnshire Hospital Trust

NIBP ElectronicThe measurement of blood pressure is important in the diagnosis and monitoring of a widerange of clinical conditions. Traditionally, blood pressure is measured non-invasively using theauscultatory technique (Korotkoff sounds) with the pressure in the cuff measured using amercury sphygmomanometer. This consequently became, and still is recognised as, the ‘goldstandard’. However, environmental concerns regarding mercury mean that there is no long-term future for these devices. These concerns have led to the imposition of bans in someEuropean countries and supply in the UK is now restricted to healthcare use. It is thereforerecommended that consideration be given to the selection of mercury-free products when theopportunity arises.Electronic NIBP monitors measure Systolic pressure (the pressure within the artery walls as theheart contracts and pumps blood into the circulatory system), and Diastolic pressure (thepressure within the heart and circulatory system at rest). The model recommended for use atULHT is the Omron HEM-907.The majority of non-invasive automated blood pressure measuring devices currently availableuse the oscillometric method. The oscillometric method relies on detection of variations in pressure oscillations due toarterial wall movement beneath an occluding cuff. Empirically derived algorithms areemployed, which calculate systolic, mean arterial (MAP) and diastolic blood pressure.Manufacturers develop their own algorithms by studying a population group and may havevalidated the stated accuracy by performing a clinical trial.Some automated devices may use an electronic auscultatory method. These devices incorporatea microphone in the cuff and apply sound-based algorithms to calculate the systolic anddiastolic blood pressure. (EBME, 2009)Automated blood pressure measurement devices, have become increasingly popular because oftheir ease of use.Automated (spot-check) NIBP monitoring devicesThese make single measurements of blood pressure with some incorporating heart rate. Thisincludes an electronic monitor with a pressure sensor, a digital display and an upper arm cuff.An electrically-driven pump raises the pressure in the cuff. Devices may have a user-adjustableset inflation pressure or they will automatically inflate to the appropriate level, usually about30mmHg above an estimated systolic reading. When started, the device automatically inflates,then deflates the cuff and displays the systolic and diastolic values. The majority calculate thesevalues from data obtained during the deflation cycle, but there are some that use data from theinflation cycle. The pulse rate may also be displayed. These devices may also have a ‘memory’facility which stores the last measurement and previous readings.Spot-check NIBP monitorsThese make single measurements and often incorporate additional vital signs monitoring.They are designed for routine clinical assessment and are now popular for clinic and generalward use.There may be an option to measure additional vital signs, such as oxygen saturation in thefinger pulse (SpO2) and body temperature.

Automatic-cycling non-invasive blood pressure (NIBP) monitorsThese make repetitive measurements at set time intervals and often incorporate vital signparameter alarms. They are designed for bed-side monitoring in a clinical environment. This issimilar to the spot-check NIBP monitor, but with the addition of an automatic-cycling facility torecord a patient’s blood pressure at set time intervals where repetitive monitoring of patientsand an alarm function is required. These devices may incorporate the ability to measureadditional vital signs. The alarm limits can usually be set to alert nursing staff when one or moreof the measured patient parameters exceed the pre-set limits.Ambulatory NIBP monitoring devicesThese are designed to record the patient’s blood pressure at pre-defined intervals over a 24-hour period during normal activities and store the data for future analysis. This includes anupper arm cuff and an electronic monitor with a pressure sensor and an electrically-drivenpump that attaches to the patient’s beltWrist deviceThis includes an electronic monitor with a pressure sensor, an electrically-driven pumpattached to a wrist cuff. Function is similar to the automated (spot-check) device above.Finger deviceThis includes an electronic monitor and a finger cuff such as in the BMEYE B.V. - Nexfin Model 1Syncope Patient Monitor. Uses oscillometric, pulse-wave or plethysmographic method(measuring changes in volume of a part or organ or whole body usually resulting fromfluctuations in the amount of blood it contains) for measurement.In the Omron HEM 907 pressure is measured by means of a transducer, which works by havingtwo semiconductor plates separated by an insulator, changes in pressure causes one of thesemi-conductor plates to move varying the capacitance. The systolic, diastolic, MAP (MeanArterial Pressure), and pulse rate are displayed. The system has a bleed valve which slowlyreleases pressure at a set rate for measurement, and a rapid release bleed valve which operatesautomatically should an over inflation occur. Inflation pressure can be selected using thecontrol dial on the front of the unit or set to automatic.In Patients experiencing, muscle tremors, abnormal heart rhythms, those with cardiacarrhythmias, pre-eclampsia and certain vascular diseases, weak pulse or very low bloodpressure due to shock, some automated blood pressure devices may fail to obtain a reading andwill either indicate an error code or give unreliable results. Because of these reasons theIndependent Advisory Group on Blood Pressure Monitoring in Clinical Practice hasrecommended that calibrated, non-mercury devices, which do not rely on oscillometric method,are made available in all clinical areas.The blood pressure recorded may be influenced by behavioural factors that are related to theeffects of the observer on the patient, such as ‘white-coat hypertension’.The patient should be discouraged from talking and moving during the measurement phase asthis can cause the blood pressure to vary and may interfere with the detection method.The height of the cuff in relation to the heart affects the blood pressure measurement. If the cuffis placed above the level of the heart, then lower pressures are recorded, whilst placing the cuffbelow the heart leads to higher pressure readings. Incorrect cuff size is a major source of error;an under-sized cuff tends to over-estimate blood pressure, while an over-sized cuff may under-

estimate. This is especially critical when measuring blood pressure in children. Cuffs should bemarked to indicate the correct size for the patient’s limb. The cuff should be placed on the arm with the centre of the bladder over the brachial artery;cuffs should be marked to facilitate this. Users should note that the tubing is not a reliableindicator for positioning the cuff, particularly when using the same cuff on left and right arms.The standard BS EN 1060-1 [5] considers the optimum bladder size to be: width 40% of limbcircumference, length 80% to 100% of limb circumference at the centre of the range for eachcuff size. The limb used for the blood pressure measurement should be properly supported. (DoH, 2012) Fig 1- Correct placement of BP Cuff (NICE, 2013)Maintenance & Service ProceduresAll blood pressure measuring equipment should be regularly checked and calibrated inaccordance with the manufacturer’s instructions, Clinical Engineering recommend at leastannual checks or twice a year for aneroid devicesCuffs, hoses and tubing connectors should be checked as excessive air leakage from damage orgeneral wear and tear may reduce the accuracy of the readings. The device should be tested forleaks this can be done by attaching a test chamber to the monitor and building the pressure inthe chamber and monitoring the amount of pressure lost over time, or to inflate the cuff to acertain pressure and monitor the pressure lost over a set amount of time. CEng protocol statesa value of no greater than 12mmHg over 60 seconds.Both disposable (single patient use) and re-usable cuffs are available. Re-usable cuffs should becleaned in accordance with the manufacturer’s instructions, ensuring that cleaning fluid doesnot enter the cuff bladder or hoses. Over pressure vent test needs to be carried out to ensurethe unit vents should an over pressure event occur which could injure the patient. Initialinflation pressures need to be checked for accuracy using a calibrated pressure monitor.The unit should then be tested for electrical safety.