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When using contrast generic rhinocort 100mcg overnight delivery, image acquisition must be timed such that images are acquired when the blood pool saturation in the target structure is maximal generic rhinocort 100mcg. Various techniques exist to time the arrival of the contrast bolus in the arterial tree and initiate imaging 100 mcg rhinocort with mastercard. Evaluation of chest pain in patients with low to intermediate pretest probability of obstructive disease and ongoing symptoms (e discount 100mcg rhinocort. This is helpful for the mapping of pulmonary venous anatomy preprocedurally and to exclude pulmonary vein stenosis postprocedurally. Assessment of graft patency after prior bypass surgery may be feasible in select cases, although the study can be limited by artifacts related to calcification and surgical clips. It is also useful in the long-term follow-up of patients who have undergone prior aortic surgery or endovascular stenting. However, there are important risks associated with radiation and/or contrast exposure that must be weighed against the benefits of the study. Given the potential for contrast-induced nephropathy, patients with significant renal insufficiency (i. Patients with allergic reactions to contrast should be pretreated with diphenhydramine and steroids before contrast administration. A prior anaphylactic response to contrast is generally felt to be an absolute contraindication for intravenous iodinated contrast administration by many institutions. For younger patients with normal renal function without risk factors for contrast-induced nephropathy, contrast doses of up to 150 to 200 mL per 24 hours are generally well tolerated. Iodinated contrast is contraindicated in the setting of uncontrolled hyperthyroidism because of possible precipitation of thyrotoxicosis. Image quality will be significantly reduced because of respiratory motion artifact, if the patient cannot comply with breath-hold instructions. Effective dose is an estimate of the dose to patients during an ionizing radiation procedure and is expressed in millisieverts. Iodinated contrast media can cause renal ischemia by reducing renal blood flow or increasing oxygen demand and may also have a direct toxic effect on tubular epithelial cells. Prophylactic measures include saline hydration, use of low-osmolar agents, and sodium bicarbonate infusion, although the data for each of these measures remain somewhat controversial. The use of N-acetylcysteine has been shown to have no effect in slowing the progression of contrast-induced nephropathy. Coronary calcium scoring uses the observation that coronary calcium is a surrogate marker for coronary atherosclerotic plaque. Studies have shown that the complete absence of coronary artery calcium makes the presence of significant coronary luminal obstruction highly unlikely and indicates a very low risk of future coronary events. Men tend to have higher calcium scores, and individuals of either gender with renal insufficiency or diabetes mellitus tend to have higher coronary calcium scores. Contrast is not necessary because calcium is readily identified secondary to its very high x-ray attenuation coefficient (high H. However, with very low and very high scores, such interobserver variability has little clinical meaning. Therefore, there has to be a comparison of the individual data with a “normal” cohort in order to produce meaningful data, usually presented as a percentile distribution (e. However, not every atherosclerotic plaque is calcified, and even the detection of a large amount of calcium does not directly translate into the presence of significant obstructive coronary artery lesions. The test is most useful in intermediate-risk populations, in which a high or low score may reclassify individuals to a higher or lower risk group, respectively. Quantification of stenosis severity is often impossible in densely calcified arteries, whereas image quality is significantly degraded in patients with arrhythmias or tachycardia. When assessing the coronary arteries, noncalcified plaque appears as a low to intermediate attenuation irregularity in the vessel wall. Calcified plaques are bright, high-attenuation lesions in the vessel wall and may be associated with positive remodeling of the vessel. Densely calcified plaques are often associated with calcium blooming artifact, which can lead to overestimation of luminal stenosis severity. Certain characteristics of noncalcified plaque, such as positive remodeling, have been reported to predict atherosclerotic lesions at higher risk of developing subsequent acute coronary syndromes. Coronary stenoses are generally categorized as mild (<50% diameter stenosis), moderate (50% to 70% diameter stenosis), or severe (>70% diameter stenosis). This led to decreased functional testing, increased invasive angiography, and more focused treatment regimens for patients. Using a protocol similar to that used for coronary artery assessment (>1 mm slice thickness), the patency of both arterial and venous bypass grafts can be assessed. Occasionally, artifacts related to metallic clips can interfere with the assessment of distal anastomosis of an arterial graft (internal mammary or radial artery graft). This image is from a 68-year-old male, with recurrent chest pain, who is being considered for surgical intervention. Intramyocardial bridging can also be detected with high sensitivity, although the clinical significance of this relatively common finding is uncertain. Patients with prior myocardial infarction can have fibrous replacement of myocardium with or without calcification, ventricular wall thinning, aneurysm formation, and intracavitary thrombus. Ventricular dysplasia is characterized by fibrous and/or fatty replacement of myocardium, ventricular wall thinning and/or focal aneurysm formation, and ventricular cavity dilation with regional or global wall motion abnormalities. The pericardium appears as a thin structure (1 to 2 mm) surrounding the heart, usually visible with a small amount of adjacent epicardial/pericardial fat. Cardiac tamponade is better evaluated by echocardiography, because of its ability to provide hemodynamic assessment. A pericardial cyst will appear as a well-circumscribed paracardiac mass with characteristic water attenuation (H. Both primary neoplasms and, more commonly, metastatic neoplasms can be visualized in the pericardium. The ability to evaluate cardiovascular anatomy in multiple planes is often helpful for delineating cardiac morphology in congenital heart disease, particularly with regard to the relationship of the great vessels, pulmonary veins, and coronary arteries. Aortic intramural hematomas are believed to be caused by spontaneous hemorrhage of the vasa vasorum of the medial layer. They appear as crescent-shaped areas of increased attenuation with eccentric aortic wall thickening. Aortic aneurysm occurs when there is enlargement (≥150%) of the normal aortic caliber (usually >5 cm in the thoracic aorta and >3 cm in the abdominal aorta). Given the often tortuous course of a dilated aorta, it is important that these measurements be made in the true short axis of the aorta, because oblique cuts can result in erroneous overestimation. Quantitative measurements of an aortic aneurysm can be made for planning endovascular repair with a stent graft. These tend to be focal lesions of the descending thoracic aorta that appear as contrast-filled irregular outpouchings of the aortic wall. This modality is most sensitive for proximal (main through segmental branches) thrombi. Visualization of the valve leaflets, particularly the aortic valve, is feasible with newer generation scanners because of their improved temporal resolution.

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Faecal testing Elastase • proteinase produced by pancreatic acinar cells and remains un-degraded during gut transit order rhinocort 100mcg amex. Pancreolauryl test • Fluorescein dilaurate (an ester) is taken orally with a set diet order 100mcg rhinocort overnight delivery. Baseline biochemical tests Urinary 5-hydroxyindole acetic acid • 24h collection of urine for 5-hydroxyindole acetic acid (5hIaa) discount rhinocort 100mcg amex. Investigation • ambulatory 24h test that places a ph electrode through the nose to sit 5cm above the lower oesophageal sphincter generic rhinocort 100 mcg fast delivery. Investigation • Static test using a nasogastrically placed multiple channel, water- perfused catheter, which is gradually withdrawn during a series of wet and dry swallows. Intestinal transit studies • Intestinal transit is measured using 50 radio-opaque plastic markers inside a ph-sensitive gel capsule, swallowed by the patient and designed to release its contents in the terminal ileum. Anorectal manometry • Water-perfused catheter measures anorectal pressures to assess voluntary and involuntary sphincter squeeze pressures and refex responses to balloon distension in the rectum. Extra- and intra-hepatic cholestasis may cause raised aLp and results from benign or malignant dis- ease with or without raised bilirubin. Prothrombin time Test of plasma clotting activity and refects the activity of vitamin K- dependent clotting factors synthesized by the liver. In vitamin K defciency with normal liver func- tion, pT will return to normal within 18h of administration of parenteral vitamin K. Bilirubin In liver disease, a raised bilirubin is usually associated with other liver function abnormalities. Bilirubin may be conjugated or unconjugated, although in practice, this conjugation state only diferentiates congenital hyperbilirubinaemias. In Gilbert’s syndrome (the commonest benign cause of an isolated raised serum bilirubin), an elevated unconjugated bilirubin, which rises during fast- ing and mild illness, diagnoses the condition. The best investi- gations for an individual patient are established from history, examination, and basic biochemical parameters. Hepatitis B Acute infection with subsequent clearing of virus • hBsag appears in blood from 6–12 weeks after infection, then disappears. Acute infection leading to chronic hepatitis B • hBsag persists and indicates chronic carrier state. This dif- ferentiates obstructive from parenchymal liver disease to suggest further investigation and treatment. Non-invasive testing of liver fbrosis ® Transient elastography (Fibroscan ) • Stages liver disease by assessing stifness using the velocity of a vibration wave. Methods for obtaining tissue (risks and benefts) Percutaneous with or without ultrasound viewing (See Table 7. Minor complications Shoulder tip pain, minor intra-abdominal bleeding, or mild abdominal pain (up to 30%)—usually settles with analgesia. Menghini needles use suction, have a needle lower rate of complications, and allow more rapid biopsy, but they have a lower yield for tissue than Trucut (a cutting needle) Sample placed into 10% formalin (or into a dry pot to estimate dry weight of iron or copper or for culture) patient Nurse in supine position or right lateral for >6h, with regular Bp and pulse measurements (every 15min for 2h, every 30min for the next 2h, then hourly), with urgent medical review if any sign of deterioration If stable at 6h, the patient can be discharged home as long as s/he can return to hospital within 30min and have a responsible adult with him/her overnight Transjugular • Specialist technique carried out using fuoroscopic guidance. Gram stain and culture • Gram staining for early identifcation of bacteria and bacterial culture allow targeting of antimicrobial therapy. Protein • Using ascitic fuid protein levels to aid diagnosis is best achieved using the serum ascites albumin gradient (SaaG) by subtracting ascites albumin concentration from serum albumin concentration. Patient breathes in a nebulized aerosol of histamine (or methacholine) of i concentrations. Patient must remain in the department for 30min following the procedure to observe any delayed reactions. This fgure has been arbitrarily chosen to assess degrees of bronchial reactivity for ease of comparison and safety. It is important that personnel performing the test are able to recognize severe bronchospasm and that resuscitation equipment is available. Pitfalls • Bronchial hyperresponsiveness in asthma is not a static phenomenon and may vary widely from day to day. If using low-resistance syringe, this will fll automatically; otherwise aspirate gently. Then check for any metabolic compensation or for a combined respiratory and metabolic process. Pitfalls • If the sample is to be analysed in a laboratory with >5min transit time, it should be kept on melting ice to slow the metabolic activity of the cells. Arterial blood gas analysis or oxygen saturation in the assessment of acute asthma? Note: ensure the needle enters immediately above the rib to avoid the neurovascular bundle. Investigation of a unilateral pleural efusion in adults: British Thoracic Society pleural disease guideline 2010. Subject rates on a scale of 0–3 the chance that, as part of his usual life in recent times, he would doze in each of eight diferent situations. Pitfalls Limited by patient’s ability to read and comprehend the questionnaire and answer questions honestly. During a maximal exercise test, the patient should be able to achieve 85–90% of predicted maximum heart rate. Interpretation Useful in making the distinction between exertional dyspnoea 2° to lung dis- ease or fatigue 2° to cardiac dysfunction. In patients known to have asthma, exercise test is +ve in 75% of cases with a single treadmill run and 97% if the test is repeated in −ve responders. Complications • 2 Bronchospasm: usually easily reversed with an inhaled β - adrenergic agonist. Domiciliary diurnal variation of exhaled nitric oxide fraction for asthma control. Bronchoscope lubricated with 2% lidocaine gel and passed via nostril or mouth guard. Contraindications • Patients at risk of pulmonary and cardiovascular decompensation, e. British Thoracic Society guideline for diagnostic fexible bron- choscopy in adults. Take a history and examine the patient, with particular reference to cardiorespiratory disease and previous symptoms during fights. Managing passengers with stable respiratory disease planning air travel: British Thoracic Society recommendations Thorax 2011; 66(Suppl 1): i1– 30. Patients must perform the test with maximal efort each time, and the results should be similar for each of the three attempts. Interpretation Particularly useful in recognizing patients with narrowing of the central air- way (larynx and trachea). Narrowing at this site has the greatest efect on maximum expiratory fow and also on maximum inspiratory fow, giving rise to a characteristic appearance. Possible results Nijmegen score is the sum of 16 item scores and can range from 0 to 64.

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Tzanck Test Used to diagnose viral disease (herpes simplex discount rhinocort 100 mcg visa, herpes zoster discount rhinocort 100 mcg on-line, and molluscum contagiosum) Technique involves scraping a fluid and base of vesicle or bullae onto a glass slide generic 100 mcg rhinocort fast delivery. Another common cause is nickel generic rhinocort 100 mcg free shipping, which is widely used in jewelry and in metal clasps on women’s underclothes. In podiatry, contact dermatitis is commonly due to the rubber found in the toe box of most shoes or the cement used to bind shoes together. Irritation contact dermatitis Nonimmunologic mechanisms, whereby a single exposure causes a reaction (i. The first contact causes no reaction, but the exposure sensitizes the skin to future exposures (i. Presentation 296 Irregular poorly demarcated patches of erythema and edema, on which are superimposed closely spaced vesicles, punctate erosions exuding serum, and crust. Increase aeration: Avoid shoes with plastic uppers, wear cotton or wool socks instead of synthetic ones, apply drying powders. Topical hydrocortisone cream for pruritus, in moderate to severe cases treat pruritus with oral meds (Benadryl, Atarax, Vistaril) Astringent soaks (Burow solution, Epsom salt). Moisturizing lotions may also be soothing and help with lichenification and fissuring. Topical Abx for secondary bacterial infections Atopic Dermatitis Dermatitis resulting from a hereditary predisposition to a lowered cutaneous threshold to pruritus. There is usually a positive family history of allergic rhinitis, hay fever, asthma, or migraine headaches. Atopic dermatitis is often exacerbated by sudden changes in temperature, humidity, and stress/anxiety, and females may have eruption just before their menstrual period. Infantile atopic dermatitis Usually starts at about 2 to 6 months and mostly seen on the face. In about half the infants, it clears up by age two and never returns; in the other half, it clears up and then reappears in late childhood or early teens (childhood atopic dermatitis). In about half of these individuals, the condition clears up in adolescence; in the remaining half, it persists into adulthood (adult atopic dermatitis). Adult atopic dermatitis As the person grows older, the rash usually seems to shrink and become localized. It can be found anywhere on the body but has a predilection for the flexures, front and sides of the neck, eyelids, forehead, face, wrists, and dorsum of the hands and feet. Presentation Irregular, often asymmetrical, poorly demarcated patches of erythema and edema, on which are superimposed closely spaced vesicles, punctate erosions exuding serum, and crust. Treatment Increase aeration: Avoid shoes with plastic uppers, wear cotton or wool socks instead of synthetic ones, apply drying powders. In moderate to severe cases, 298 treat pruritus with oral meds (Benadryl, Atarax, Vistaril). Astringent soaks (Burow solution, Epsom salt) will decrease inflammation and reduce weeping. Moisturizing lotions may also be soothing and help with lichenification and fissuring. Topical Abx for secondary bacterial infections Urticaria An allergic reaction resulting in transient pruritic wheals or small erythematous papules that erupt in minutes to hours and disappear usually within 24 hours or less. Lesions often have an associated bacterial infection, and treatment should include oral dicloxacillin or erythromycin in addition to topical corticosteroids. Presents as erythematous scaling plaques with exudation, crusts, and superficial ulcers. Symptoms include mild pruritus, pain, edema, and nocturnal cramps, and a painful ulcer may be present. Treatment Saline or Burow wet dressing, later topical corticosteroids Unna boot 301 Reduce edema (elevate leg, supportive stockings, leg muscle pumps). Dyshidrotic Eczematous Dermatitis (Dyshidrosis) A special vesicular type of hand and foot eczema associated with pruritus. There is a predilection for the sides of the fingers, palms, and soles of the feet. Presents as small vesicles deep seated (appearing like “tapioca”) in clusters, occasionally bullae. Later stages present with scaling, lichenification, painful fissures, and erosions. Emotional stress and ingestion of certain metals (nickel, cobalt, or chromium) have been suggested as possible precipitating factors. Most commonly seen in 303 those 20 to 50 years; in children, it is called “cradle cap. Treatment Antiseborrheic shampoos are the standard therapy for the scalp—1% selenium sulfate suspension (Selsun Blue), zinc pyrithione (Head and Shoulders, Zebulon), and tar derivatives (T/Gell). Consists of large ulcers with characteristic purple overhanging edges, which develop rapidly from pustules and tender nodules. Exact etiology is unknown; lesions occur particularly on lower legs, abdominal, and face. In the crusted stage, there are golden- yellow crusts that appear “stuck on” an erythematous base. Bullous impetigo presents as scattered thin-walled bullae arising in normal skin and containing clear yellow fluid without later becoming crusted. Cause Corynebacterium minutissimum Diagnosis Wood’s lamp will cause the area to fluoresce “coral-red. In the feet, it most commonly occurs between the third and fourth toes, resembles tinea. Treatment Oral erythromycin or tetracycline Relapses are common within 6 to 12 months. Spreads rapidly, and red streaking may be seen from the cellulitis toward the heart with swollen lymph glands nearest the cellulitis. Treatment Oral antibiotics Warm water soaks over the area of cellulitis to relieve pain/inflammation and hasten healing. Elevation and restricted movement of affected area 310 Folliculitis A superficial contagious bacterial infection of a hair folliculitis usually caused by S. Treatment involves applying moist heat to allow the lesion to come to a head and drain. Furuncle A contagious deep bacterial infection of a hair follicle usually caused by S. A furuncle, also known as a boil, is the result of a worsening case of folliculitis. Treatment involves applying moist heat to allow the lesion to come to a head and drain.

There is a 3 mm connector that Generally buy rhinocort 100mcg visa, it is accepted that facemasks with reservoir feeds oxygen directly into the reservoir bag and also a bags probably deliver an F O between 0 buy generic rhinocort 100 mcg. During I 2 however rhinocort 100 mcg low cost, in reality there is likely to be considerable varia- inspiration buy rhinocort 100 mcg with mastercard, the reservoir bag, with its 15 mm aperture, tion around these values due to leak between the mask provides a greater proportion of inspiratory gas. Best amount is entrained through the 10 mm port, which has results will be achieved by using an O2 fow rate adequate a higher resistance to fow. During exhalation, this process for the patient’s needs such that the reservoir bag empties is reversed until the reservoir bag is full. Subsequent by no more than a third during inspiration and by achiev- exhalate then leaves via the 10 mm port only. I 2 moves up and down with respiration so that a patient’s It is also possible to ventilate patients briefy by occluding respiratory effort can be visualized and respiratory rate can the 10 mm port with a digit, with additional volume being easily be measured (Fig. Very high capacity oxygen delivery devices (capacity >2500 ml) Babies tolerate facemasks poorly and whilst small nasal cannulae are available, oxygen is frequently delivered in an incubator or via a head box or tent. Oxygen is fed into the bar at one end and escapes through perforations in the bar where it is in close proximity to the patient. There are many different designs 212 Equipment for the inhalation of oxygen and other gasses Chapter | 7 | A Fluid accelerates here Entrained fluid B Driving fluid A Constant admixture (A+B) A B Figure 7. Oxygen bar used for patients undergoing expense of potential energy; as a result, the pressure distal eye surgery under local anaesthesia. Numerous manufacturers produce single-use clear A Venturi can also be attached to a T-piece (Fig. Adjustable Venturi devices are also available are used on a short-term basis in recovery areas during (Fig. The segment of 22 mm by adjusting the size of the air entrainment aperture, diameter corrugated tubing has a volume of 56 ml, a 214 Ward’s Anaesthetic Equipment Figure 7. A section of wide-bore tubing (b), connects it to a close-ftting facemask (c), that has two one-way valves in the body of the mask. Humidifcation and oxygen monitoring maximal inspiratory gas fow in order to maintain the same units can be added to the system (Fig. This has 216 Equipment for the inhalation of oxygen and other gasses Chapter | 7 | the advantage of doing away with the work of breathing areas where temperature is liable to fall below 0°C. The frst breaths from such a cold cylinder are In addition to supplying supplemental oxygen, brief predominantly oxygen, but as the cylinder empties a periods of low-level positive pressure ventilation may be hypoxic mixture may be delivered. The demand valve consists of a sensitive rubber providing synchronized intermittent mandatory bi-level diaphragm that is deformed by negative pressure gener- ventilation. The sensing diaphragm can be manually depressed to test the Metered sources of oxygen and air integrity of the system. This ventional loose ftting mask (aerosol mask) or high fow allows the cylinder to be kept warm inside the ambulance nasal cannulae systems (Fig. This model also incorporates a ‘push to test’ feature that can be used for manual insuffation if desired. Helium is less dense than Entonox oxygen and nitrogen, and hence is more likely to fow in The physical properties, storage and supply of this 50 : 50 a laminar fashion in narrow airways, reducing the amount mixture of oxygen and nitrous oxide (N2O) are described of less effcient turbulent fow (and the majority of transi- in Chapter 1. Additionally, this allows faster diffu- used for the self-administration of Entonox during labour sion of oxygen and carbon dioxide in the distal parts of and for short painful procedures such as fracture reduc- the lung. Published literature describes the use of Heliox tion, drain removal or dressing changes. However, staff must obstruction is less convincing, leading Cochrane reviewers be aware that Entonox cylinders should not be stored in to conclude that Heliox therapy has little to offer in the 217 Ward’s Anaesthetic Equipment Face mask Exhalation valve Corrugated Safety valve hose Spring Diaphragm 2nd stage pressure 1st stage reduction reduction (atmospheric) Sensing diaphragm Non- interchangeable cylinder valve and yoke Push rod 2nd stage 1st stage Filter Gas cylinder (tilting type) valve valve Figure 7. Soft silicone Flexible cover with diaphragm ‘push to test’ feature Connecting Tilt valve 4bar rod Entonox Filter and expiratory valve single use patient unit Filter Expiratory valve flap Connection to mask or mouthpiece Figure 7. However, the evidence for its effcacy in these latter condi- tions is unclear; most have not been investigated in clinical trials and many are based upon case reports or small series. Those in due to increased fows through the upper generations of medical use tend to be divided into type A and type B on the bronchial tree. It could be with an adequate reservoir combined with a leak-free adapted to accommodate ten or more sitting patients. Humidifcation of Heliox may also be points to prevent build-up of electrical charge, an essential important for longer-term use. The device pressing the chamber with air whilst the occupants breathe consists of a 2L reservoir bag attached to the inlet of an oxygen via a tightly ftting facemask (Fig. Heliox is sometimes administered to ventilated patients, Lightweight and portable equipment has been developed especially children, via the air inlet of a ventilator. By facilitating adminis- tration, this should in due course allow a more defned Divers face several problems when breathing underwater role for Heliox therapy to be characterized in both non- at increased atmospheric pressure. The Type A hyperbaric chamber at the former Royal Hospital, Haslar (courtesy of Royal Navy and Qinetiq Ltd). A balanced frst-stage regulator situated on the physiologically inert, but at high pressure it is forced tank reduces gas pressure to 10 atm. If ascent is too rapid, through an intermediate hose to a second regulator on the bubbles of N2 form causing decompression sickness mouthpiece where it is balanced to the pressure of the (’the bends’), which is potentially fatal. When the diver exerts a slight 50 m or more, N2 causes narcosis by an unknown negative pressure on the regulator at the start of inspira- mechanism (rapture of the deep). Safety is of paramount importance: tanks mixtures: to increase the amount of time that they may are visually inspected annually and subjected to a hydro- stay at depth without the need for decompression stops static test procedure every 5 years and the resistance offered when ascending, to reduce the risk of decompression sick- by each regulator, accuracy of instruments and integrity of ness by decreasing the amount of dissolved nitrogen in the hoses are checked regularly. Nitrogen may be par- a pinhole orifce in the proximal end of the high-pressure tially or completely replaced by helium, which is not nar- hose, which prevents injury from a failing hose should cotic and reduces the work of breathing at very high it rupture. For very deep dives, the oxygen content of the Military, cave and specialist divers may choose to use a diving gas may be as low as 1%. The expired oxygen is recycled back into the (‘bail out bottles’) or up to 15 L for deeper or longer reservoir bag, which is supplemented by additional oxygen 222 Chapter | 7 | Equipment for the inhalation of oxygen and other gasses from the high-pressure supply. Use of mixed gasses may dioxide have been used, but are unreliable, as internal allow deeper dives using a closed circuit system, with elec- valves tend to ice up before the soda lime begins to warm tronic monitoring of gas levels to ensure that their levels up and work. Weighing ing and expertise is required to dive safely with such 3–7 kg in total, they comprise light titanium cylinders equipment. All systems Mountaineering are checked and tested for several hours in a ‘cold room’ Mountaineers require oxygen to facilitate climbing at very at −20°C before an expedition, paying particular attention high altitude or to manage medical emergencies. Non-invasive evaluation of oxygen delivery The clinical evaluation of the ventilation in acute respiratory using nasal prongs. Lancet Development of aerosol drug sequential gas delivery versus ‘fow 1984;1:1427–31. Effect 223 Ward’s Anaesthetic Equipment of helium-oxygen (Heliox) gas an overview of its applications, 30. Components 225 The respirable gas inlet mechanism is housed at one end Safety features incorporated into and the non-rebreathing valve at the other. This is ftted to the inlet of a device that is easily portable and that does not rely on the self-infating bag. When the bag is squeezed, the a source of pressurized gas or electricity for its operation. This prevents the escape of gas back number of different manufacturers marketing these through the inlet. Although there self-infating characteristic causes fresh gas from the have been a plethora of designs from the frst ‘Ambu bag’ respirable gas inlet to be indrawn.