By investigating the change in phase at the same frequency under different level presentations it will be possible to symptoms 5 weeks pregnant cramps order 100mg clozaril visa predict the cancellation phase and level at these frequencies medicine zoloft cheap 50 mg clozaril with amex. These values will then be used to symptoms ibs purchase clozaril 100 mg without a prescription make the previously employed technique easier to treatment jokes cheap clozaril online american express perform. The second method of speeding up data collection is to use the change in phase from cancellation at one cochlea to predict the phase change at the contralateral cochlea. This technique may be possible, as it was noted in chapter 5 that the phase progression was very similar on the left and right side (especially at higher frequencies >4 kHz). The cross-talk signal processing cannot be performed with low enough latency within a windows, mac or android operating system. The participant could then be placed in a speaker array where tone detection, speech intelligibility and sound localisation measurements can be made with and without cross-talk cancellation. However, in those with severe conductive hearing loss there will be very little direct sound reaching the cochleae. This could potentially allow for somewhat greater delays since problems such as spectral ripples will not be an issue. A potential acceptable delay maybe 40 ms which is agreed as the target for the international telecommunication union as an acceptable delay in order to avoid significant “lip sync effect” (Galster 2010). The other method employs filters which divide the signal into channels and process them channel by channel. Both processing methods suffer from the same fundamental issue that as the spectral resolution is improved the temporal resolution is degraded. This means that if cross-talk cancellation was implemented there would need to be a trade-off between the number of filterbank channels which can be used to increase the accuracy of the cross-talk cancellation and the time it takes to perform this action. However, if an alternative method of filtering is used then it is possible to optimise the cancellation by placing filters are frequencies where there are large changes in cancellation level or phase. If this were to be used further research needs to be performed to investigate at what frequencies the filters are placed in order to achieve the optimum cross-talk cancellation within the given number of filters. It is likely there will be considerable variability between participants as this will need to be tailored to frequencies where there are large changes in level over a small frequency range. In addition to this, the filters must also be take account of the relative importance of the 101 relative importance of different frequency bandwidths in order understand speech (Apoux & Healy 2009). Khanna et al (1976) give possible explanations of looseness of the coupling between the vibrator and the skull as well as the underlying tissues not acting perfectly elastically. It is not clear if this was due to a change in jaw movement or if there were temporary changes in intracranial pressure which can occur when taking a deep breath (Bloomfield et al. Under normal conditions this results in the intracranial pressure being very tightly controlled with small changes in sitting and standing which are a result of increased venous drainage which is then compensated for via an increased arterial blood pressure (Williams 1981). The participant did not find any clear alteration in the quality of cross-talk cancellation. This is primarily because its signals pass though air with little signal degradation. However, the short wavelength means that it does not propagate well through soft tissues such as the head and body (Cho et al. Firstly, the easiest way to achieve low latency with little extra battery requirements would be to have a wired connection. However, this is unlikely to be a very acceptable to patients due to the aesthetic impact a wire would have. We have shown these psychoacoustic measurements can be performed to a high degree of accuracy. Future developments will focus on further reducing the time taken to collect measurements as well as making the psychoacoustic task easier to perform. Single-sided deafness and directional hearing: Contribution of spectral cues and high-frequency hearing loss in the hearing ear. On the number of auditory filter outputs needed to understand speech: Further evidence for auditory channel independence. Comparison of pseudobinaural hearing to real binaural hearing rehabilitation after cochlear implantation in patients with unilateral deafness and tinnitus. Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology, 32(1), pp. High-frequency hearing, tinnitus, and patient satisfaction with stapedotomy: A randomized prospective study. Effects of tensor tympani muscle contraction on the middle ear and markers of a contracted muscle. Vibration of the Head in a Sound Field and Its Role in Hearing by Bone Conduction. Hearing protection: surpassing the limits to attenuation imposed by the bone-conduction pathways. Spatial release from masking in normally hearing and hearing-impaired listeners as a function of the temporal overlap of competing talkers. A proposed relationship between increased intraabdominal, intrathoracic, and intracranial pressure. The effect of head-induced interaural time and level differences on speech intelligibility in noise. Informational and energetic masking effects in the perception of multiple simultaneous talkers. The Human Body Characteristics as a Signal Transmission Medium for Intrabody Communication. A comparison of the nonlinear response of the ear to air and to bone-conducted sound. The benefit of bilateral versus unilateral cochlear implantation to speech intelligibility in noise. Erratum: the role of head-induced interaural time and level differences in the speech reception threshold for multiple interfering sound sources. The role of head-induced interaural time and level differences in the speech reception threshold for multiple interfering sound sources. Journal of otolaryngology head & neck surgery = Le Journal d’oto-rhino-laryngologie et de chirurgie cervico-faciale, 38(1), pp. Bilateral bone-anchored hearing aid application in children: the Nijmegen experience from 1996 to 2008. Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology, 31(4), pp. Patient satisfaction with bilateral bone-anchored hearing aids: the Birmingham experience. Speech intelligibility with bilateral bone-anchored hearing aids: the Birmingham experience. Transmission of bone-conducted sound in the human skull measured by cochlear vibrations. Implications for contralateral bone conducted transmission as measured by cochlear vibrations. Long-term benefit perception, complications, and device malfunction rate of bone-anchored hearing aid implantation for profound unilateral sensorineural hearing loss. Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology, 31(9), pp. Understanding speech in noise after correction of congenital unilateral aural atresia: Effects of age in the emergence of binaural squelch but not in use of head-shadow. The mechanical point impedance of the human head, with and without skin penetration. Sound localization in subjects with impaired hearing, spatial-discrimination and interaural-discrimination tests. Bilateral Bone-anchored Hearing Aid: impact on quality of life measured with the Glasgow Benefit Inventory. Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology, 30(7), pp. Effects of ear-canal pressurization on middle-ear boneand airconduction responses. Bilateral Bone-Anchored Hearing Aids for Bilateral Permanent Conductive Hearing Loss: A Systematic Review. Measurement of vibration velocity pattern of facial surface during phonation using scanning vibrometer. Microstructures of the bony modiolus in the human cochlea: a scanning electron microscopic study. Binaural prediction of speech intelligibility in reverberant rooms with multiple noise sources.
Nevus sebaceus has been associated with a wide variety of neoplasms from trichoblastomas to symptoms jaw pain order clozaril 50mg amex basal cell Eichenfield L symptoms of appendicitis purchase genuine clozaril line, Esterly N treatment anemia discount clozaril 100 mg without prescription, Frieden medications similar to adderall 100mg clozaril with amex, eds. Includes the folparasitism from commensalism, in which the host derives lowing orders: no benefit but is not injured, and mutualism, where the • Siphonaptera: fleas relationship benefits both organisms • Anoplura: head and body lice • Host, in addition to providing a steady food source, pro• Pthiridae: crab louse vides warmth and shelter • Diptera: 2-winged flies, mosquitos, midges • Definitive host are those in which parasite becomes sexu• Hemiptera: true bugs ally mature and undergoes reproduction • Lepidoptera: butterflies, moths, and their caterpillars • Reservoir hosts are those in which parasites that are • Hymenoptera: ants, wasps, and bees pathogenic to other animals or to humans reside • Class Arachnida: a group of organisms with 8 legs and • Vector are agent by which a parasite is transmitted to the 2 body segments: cephalothorax and abdomen host. Tunga penetrans (chigoe flea) be killed • Tropical and subtropical regions of North and South • Two treatments 1 week apart are recommended America, Africa because nits hatch in 7 days • Intense itching and local inflammation • Causes tungiasis – Female sand flea, which burrows into human skin at the point of contact, usually the feet – Head is down into the upper dermis feeding from blood vessels – Caudal tip of the abdomen is at the skin surface – Nodule (usually on the foot) that slowly enlarges over a few weeks • Treatment – Occlusive petrolatum suffocates the organism – Lindane, dimethyl phthalate, or dimethyl carbamate 3. Xenopsylla cheopis (Oriental rat flea) • Plague (Yersinia pestis) • Endemic (murine) typhus (Rickettsia typhi) 4. Automeris io (family Saturniidae) • Vector for Chagas disease (American trypanosomiasis) • Io moth caused by Trypanosoma cruzi • East of the Rocky Mountains from Canada to Mexico • It is 15 mm long, dark brown in color • Feed on deciduous (broadleaf) trees and herbaceous • Reduviid bug ingests the trypomastigote while feeding on plants infected animals; it then divides and transforms in the gut • Yellow-green with red and white lateral stripes of the bug into metacyclic trypomastigotes • Urticating spines 2. Sibine stimulea (saddleback caterpillar) • Brown at both ends • Green around the middle “saddle blanket” • Purple-brown oval-spot “saddle” • Urticating spines along the sides and at the front and rear of the body 4. Hagmoth: brown with 9 pairs of variable-length lateral processes with urticating hairs 5. Formicidae: ants • Solenopsis (fire ant) – Alkaloid venom contains phospholipase and hyalurinidase – May be red or black and live in ground colonies – Sting by first biting the victim with their powerful set of pincer jaws and then swiveling and stinging in a circular pattern A – Pustules, burning itch 2. Vespidae: yellowjackets, hornets, paper wasps • Paper wasps build hives under the eaves of buildings • Yellow jackets are ground-nesting • Hornets reside in shrubs and trees 3. Fitzpatrick’s Dermatology in – Hair loss begins about 1 week after the tick is General Medicine, 8th Ed. Ixodes tick • Diagnosis: mites, eggs, larvae, or scybala on microscopic • Ixodes scapularis: eastern United States examination of lesional skin scrapings • Ixodes pacificus: in California • Nodular scabies • Ixodes ricinus: in Europe • Erythematous, firm nodules that persist for weeks to • Vector for months after treatment – Lyme disease (Borrelia burgdorferi) – Babesiosis – Anaplasmosis 2. Atlas of Emergency • Only the female of the species is capable of envenomating Medicine, 2nd Ed. Fitzpatrick’s Dermatology in General Medicine, • Light gray and leathery in appearance 8th Ed. All of the above • Eggs in host feces (dogs, fox, wolf) • Ingested by herbivores (cows) and penetrate bowel to 3. Sand flies are vectors in which disease(s): enter muscle, brain, and eyes, where they develop into A. Carrion disease • Viperidae family (pit viper) • Copperhead, rattlesnake, cottonmouth (water 6. Sleeping sickness tissue necrosis can develop at the site of the bite • Damage to vascular endothelium, hypotension 7. The red mite known to infest birds, reptiles, and mammyelin causing cell lysis, neutrophil chemotaxis, platelet mals and causes a characteristic dermatitis concentrated aggregation and activates complement. Latrotoxin-alpha is along lines of tightly fit clothing in campers and hikers is: the toxin in black widow venom. Ornithonyssus sylviarum They cause a pruritic eruption ofen along elastic lines of D. Xenopsylla cheopis has been considered the classic vector of endemic typhus which is caused by Rickettsia typhi and Rickettsia felis. While head and pubic lice are not clearly linked to the Br Med J 1988;296:489–491. Fitzpatrick’s Dermatology in General Medicine, latter organism is more likely to cause endocarditis. J Am Acad are flarial diseases carried by black fies and deer fies, Dermatol 2003;49:363–392. Hepadnavirus • Diagnosis • Clinical Pox Viruses • Confirmatory biopsy in some cases. The lesions may persist for 6 to 8 weeks or aches, and exanthem that appears after 2 to 4 days more (Fig. Sheep farmers, veterinarians – Pustule (8–9 days) confirms successful mainly affected vaccination • Clinical – Crust (12+ days) • Four to seven days incubation followed by 36-day – Scar (17–21 days) period with 6 clinical stages: each lasts 6 days • Systemic symptoms such as malaise, lymph• Lesions progress through several stages. They occur at adenopathy, myalgia, headache, chills, nausea, fatigue, sites of contact with infected animals or fomites and fever may appear at day 8. Satellite and secondary malaise, and fever lesions progress in the same fashion as the primary • Diagnosis lesion • Based on typical clinical skin lesion and a history of • Systemic symptoms occur late in the onset of the sheep exposure. It is confirmed by histological study disease, death occurs as a result of an overwhelming with or without electron microscopy toxemia, viremia, or septicemia • Histology varies depending on the stage of the lesion. Adult cases are usually due to of cells in the upper third of the stratum spinosum. Those • Use of corticosteroids has been linked with increased with a heterozygous gene mutation have a slowmortality er course of disease. She has systemic lupus erythemaparakeratosis, acanthosis, and papillated epithelial surtosus, which is well controlled with prednisone, 10 mg faces. She has no recollection of chickenpox as a child; thelium, you can expect to see which type of virus: results of a varicella titer are negative. Two-dose vaccination series over 6 weeks, delay work vomiting, fever, malaise, and abdominal pain since yesfor 4 weeks terday. The patient is presenting with a classic example of on a reverse transcriptase inhibitor to decrease the risk plantar wart (myrmecia). The signs and symptoms of nausea, vomiting, fever, therapy hepatomegaly, and jaundice are compatible with acute viral hepatitis. A newborn’s examination reveals purpuric macules and is transmitted via the fecal-oral route and common in papules on the entire body. Multinucleated giant cells ies the vaccine has demonstrated signifcant reduction D. A 60-year-old woman with history of diabetes mellitus are older or equal to 50 years old; therefore, the vaccine and hypertension presents with a painful erythematous would be indicated for use in this patient. The patient was most likely started on zidovudine, a has 9/10 pain and complains of trouble sleeping. Chronic suppressive therapy for herpes simplex infecpain medication tion can be achieved with any of the 3 agents. Acyclovir dosing for suppression is 400 mg 2 times daily or 200 mg tid-qid, while famcicloAnswers vir dosing is 250 mg 2 times daily. The patient is employed at a health care facility, infection (“blueberry mufn baby”) including purpuric and therefore required to have either serologic evidence macules, thrombocytopenia, hepatomegaly, and microof immunity to or a 2-dose vaccination series with varicephaly. Nonvaccination is not an option in this case given infected cells is “owl’s eye” basophilic intranuclear incluthe profession of the patient and the potential risk to her sions. Given recent studmumps or Candida skin test antigens: a novel immunotherapy ies demonstrating a signifcant decrease in incidence of for warts. Safety and immunogenicity sure to vaccinia virus: case definition and guidelines of data colof glycoprotein-D adjuvant genital herpes vaccine. Impact of suppressive antiviral applied immune response modifier for the treatment of external therapy on the health-related quality of life of patients with recurgenital warts. Polymorphisms in the genes for genital warts with imiquimod 5% cream followed by surgiherpesvirus entry. Association of p53 polymortions: epidemiology, pathogenesis, symptomatology, diagnosis, phism with skin cancer. Verrucous carcinoma of the foot assological and virological findings in patients with focal epithelial ciated with human papillomavirus type 16. Once, twice, or three times notherapy of warts with mumps, Candida, and Trichophyton daily famciclovir compared with acyclovir for the oral treatskin test antigens: a single-blinded, randomized, and controlled ment of herpes zoster in immunocompetent adults: a rantrial. J Cutan Med Surg controlled, dose-ranging trial of peroral valaciclovir for epi2003;7:449–454. New York: Oxford; podofilox gel in the treatment of external genital and/or perianal 2001. New York: prednisone for the treatment of herpes zoster: a randomized, Marcel Dekker; 2002. The pustules may rupture leaving with scarring contagious honey-colored crusts • Treatment: topical antibiotics, systemic antibiotics may be • Treatment: topical mupirocin indicated • Bullous impetigo is a toxin-mediated erythroderma Furuncles/Carbuncles (Fig. Periorificial and flexural accentuation may be • Clinical observed • Erythematous and irregular appearing linear streaks • Nikolsky sign present (extension of a blister resulting in the skin, extending from the primary infection site from lateral pressure to the border of an intact blister) toward regional lymph nodes. Streaks may tender and • Diagnosis: frozen section tissue analysis to exclude toxic warm. Due to inhalation of anthrax spores > nonspecific • Aerobes: (usually gram-negative organisms), ampicilsymptoms: low-grade fever and a nonproductive cough. Usually fatal • Intravenous immunoglobulin • Chest x-ray: widened mediastinum with hemorrhagic pleural effusions Actinomycosis • Gastrointestinal anthrax: due to ingestion of infected meat • Caused by Actinomyces israelii, a filamentous, anaerobic, products. Mainly affects the cecum gram-positive bacteria • Cutaneous anthrax: occurs 1 to 7 days after skin exposure > • Cutaneous disease includes cervicofacial disease (lumpy “Malignant pustule”: central area of coagulation necrosis jaw) or cutaneous mycetoma (Maduromycosis) (ulcer with eventual eschar), edema, and vesicles filled • Clinical: with bloody or clear fluid (actually not pustular) > • Cervicofacial—abscess with draining sinus, usually at ruptures to leave a black eschar and scar.
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Describe basic diagnostic tools used in refractive surgery treatment centers for depression order clozaril 25mg, including topography symptoms nerve damage cheap 50 mg clozaril amex, pachymetry medicine and technology purchase clozaril overnight, and biometry; and interpret results medications vs grapefruit order 50mg clozaril fast delivery. Describe more complex types of refractive errors, including postoperative refractive errors following cataract surgery, keratoplasty, refractive surgeries, ectatic conditions, and irregular astigmatism. Explain basics of wavefront analysis, including ray tracing and dynamic skiascopy, and graphical representation of wavefront errors, including corneal and entire eye high-order aberration maps, point-spread function, and modulation-transfer function. Use different topographic maps and scales for different purposes (eg, screening, postoperative evaluation, detection of complications). Describe corneal biomechanics, including biomechanical responses to keratorefractive surgery, corneal healing after excimer laser procedures, corneal hysteresis, and corneal resistance factor. Describe the mechanism of action, indications, advantages, and potential complications of mitomycin C application in surface ablation. Describe the affect of corneal crosslinking on the biomechanical properties of the cornea, including its indications and how it can be combined with other refractive surgery procedures. Perform refraction techniques using trial lenses or phoropter for basic and more complex cases, including: a. Apply the basics of optics and optical principles of refraction and retinoscopy in the clinical setting, including higher order aberrations. Gather accurate information essential for preoperative evaluation of patients seeking refractive surgery, including: a. Use the keratometer to make corneal measurements in more complex patients (eg, prior corneal surgery or corneal disease), and correlate results with corneal topography maps, visual acuity, and quality of vision. Assist in developing patient care management plans for simple refractive errors (eg, myopia, hyperopia, regular astigmatism), and define the risks and benefits for each procedure. Describe and diagnose various types of refractive problems, including irregular astigmatism, and identify the best solution for each. Describe the most complex types of refractive errors, including postoperative refractive errors, postkeratoplasty, and refractive surgery. Describe the most advanced optics and optical principles of refraction and retinoscopy, including higher-order aberrations. List the indications for and interpret preoperative and postoperative diagnostic testing, including: a. Formulate informed diagnostic and therapeutic decisions based on patient information, current scientific evidence, clinical judgment, and patient expectations. Describe accommodative and nonaccommodative treatments of presbyopia, including: a. Develop patient care management plans for more complex cases (eg, mixed and irregular astigmatism, irregular corneas, combined refractive surgery procedures). Describe the basics of topography-guided, wavefront-guided, and optimized ablations as compared to standard ablations. Perform the most advanced objective and subjective refraction techniques using trial lenses or the phoropter, including: a. Contact lens refraction for more complex refractive errors, including modification and refinement of subjective manifest refractive error b. Utilize the most advanced optics and optical principles for refraction and retinoscopy, including higher order aberrations. Utilize the keratometer for detection of subtle or complex advanced corneal refractive errors. Fit contact lenses in patients with irregular corneas, irregular astigmatism, and following refractive surgery. Assist in advanced refractive surgeries, including topography-guided ablation, wavefrontguided ablation, and combined refractive surgeries. Encourage patients to actively participate in their own care by providing disease and treatment information, and counsel patients on how to prevent postoperative injury. Correct refractive error after surgeries, such as penetrating keratoplasty, deep anterior lamellar keratoplasty, and radial keratotomy. Formulate informed diagnostic and therapeutic decisions based on patient information, current scientific evidence, and clinical judgment: a. Collect data, analyze refractive outcomes, and develop personal nomograms based on data. Develop refractive surgery management plans in the context of other conditions (eg, dry eyes, herpes, keratoconus, postkeratoplasty, glaucoma, retinal disease, amblyopia). Perform under supervision 10 advanced refractive surgeries for complicated cases, including excimer laser enhancement procedures and topography-guided ablations for highly irregular corneas. Perform–if feasible–supervised femtosecond refractive surgical procedures, specifically three femto-Lasik procedures and three intracorneal ring segment implantation procedures using a femtosecond laser. Describe the anatomy of the retinal nerve fiber layer, optic nerve head, and visual pathway from the retina to the visual cortex. Describe the microscopic anatomy of the retina from inner to outer portions, with attention to the retinal ganglion cell layer and nerve fiber layer. Describe the fundamentals of Goldmann static, kinetic perimetry, and standard automated perimetry. Know basic principles of tonometry and aqueous outflow, and applications of tonometric data (eg, diurnal curve, peak and trough values). Describe the major features of primary open-angle glaucoma (high and low tension), angle-closure glaucoma, glaucoma suspects, and ocular hypertension. Describe the major risk factors for primary open-angle glaucoma and angle-closure glaucoma. Describe the steps in evaluating primary open-angle glaucoma and angle-closure glaucoma. Define glaucoma as a progressive neural degeneration of retinal ganglion cells, their axons and their connections to central visual centers. Describe the basic features of the major glaucomas: primary open-angle glaucoma, angleclosure glaucoma, exfoliative glaucoma, and pigmentary glaucoma. Describe principles and basic techniques of gonioscopy (3 or 4 mirror lenses) to evaluate angle structures. Know subtypes of angle-closure glaucoma (eg, pupillary block, plateau iris, lens-related angle-closure, and malignant glaucoma). Understand the principles of indirect ophthalmoscopy to evaluate the optic nerve and retinal nerve fiber layer. Describe major classes of glaucoma medications, their mechanisms of action, indications, contraindications, and side effects (topical and systemic). Describe the major results of large prospective clinical trials in addition to those appropriate to the practice region. Perform basic slit-lamp biomicroscopy (including peripheral anterior chamber depth evaluation, Van Herick test). When performing basic tonometry, recognize and correct artifacts, and know how to disinfect tonometer and check calibration. Recognize and evaluate angle structures, abnormalities, and appositional and synechial angle closure. Recognize the common features of the glaucomatous optic nerve including the significance of optic nerve head size, and perform stereo examination, using direct ophthalmoscope, fundus lens, and indirect lenses (ie, 60, 66, 78, or 90 diopter lens). Recognize typical features of glaucomatous optic neuropathy (eg, neuroretinal rim changes, disc hemorrhage, peripapillary atrophy). Recognize optic nerve features of disorders that cause visual field loss (eg, optic nerve head drusen, optic neuritis). Describe slit-lamp findings of secondary glaucomas (eg, iridocorneal endothelial syndrome, pigment dispersion syndrome, exfoliation syndrome, angle recession). Interpret visual field results for Goldmann kinetic perimetry and Humphrey or Octopus standard automated perimetry. Recognize ocular emergencies of acute angle closure, and blebitis/endophthalmitis. Know epidemiology of congenital glaucoma, primary open-angle glaucoma, exfoliation syndrome and exfoliative glaucoma, and angle-closure glaucoma. Recognize secondary glaucomas (eg, angle recession, inflammatory, steroid induced, pigmentary, exfoliative, phacolytic, neovascular, postoperative, malignant, lens-particle glaucomas, plateau iris, glaucomatocyclitic crisis, iridocorneal endothelial syndrome) with attention to appropriate pathophysiology. Describe the evaluation and treatment of complex secondary glaucomas (eg, exfoliation, angle recession, inflammatory, steroid induced, pigmentary, phacolytic, neovascular, postoperative, malignant, lens-particle glaucomas; plateau iris; glaucomatocyclitic crisis; iridocorneal endothelial syndromes; aqueous misdirection/ciliary block).
It does not matter whether the irritant is breathed in medications medicare covers cheap 50mg clozaril otc, aspirated or transported up the mucociliary escalator (see below) medications given for adhd generic 50 mg clozaril free shipping. The oesophageal sphincters alternately relax and then contract to medications vascular dementia buy clozaril in united states online allow food through – this is an involuntary or refiex action that occurs once the patient has voluntarily moved the food bolus to medications related to the female reproductive system buy cheap clozaril line the pharynx from the mouth. The sphincters also contract in a refiex fashion when there is distension of the stomach to keep stomach contents out of the oesophagus and ultimately the larynx/oropharynx. Gastroesophageal refiux is the syndrome whereby gastric contents spontaneously move back up the oesophagus into the pharynx. This can be due to mechanical problems with swallowing (see below), due to anatomical problems such as a hiatus hernia (where part of the stomach is above the diaphragm, thereby rendering the lower oesophageal sphincter ineffective), weak lower oesophageal sphincter (especially relative weakness when opposed by gravity when bending over or opposed by obesity) and gastric stasis (also known as gastroparesis, where the stomach fails to empty and move food along in a timely fashion). Gastroparesis is particularly common in hospital patients because any severe illness will cause gastric dysmotility such that gastric emptying is slowed down. Head injury, therapeutic general anaesthetics or administration of sedative drugs, intentional or unintentional drug overdose, seizures, toxaemia from infection, cerebrovascular accidents or intracranial haemorrhage are just some of the many causes of deterioration in a patient’s level of consciousness. A cerebrovascular accident is the interruption of blood supply to part of a patient’s brain resulting in death of part of the brain and is very common. Mendelson’s syndrome of aspiration pneumonitis was first described in the postoperative course of patients receiving a general anaesthetic for obstetric conditions, where the twin problems were increased abdominal pressure forcing gastric contents (in a patient who was both non-fasting and, due to labour, suffering from gastroparesis) back past the lower oesophageal sphincter and the anaesthetic abolishing the sphincter’s tone and refiex contraction. A muscular disorder called achalasia, which is due to a disorder of smooth muscle in the wall of the oesophagus, can cause the lower oesophageal sphincter to fail with free refiux of gastric contents back up the oesophagus with the possibility of aspiration. Neurological causes can include upper motor neurone causes such as cerebrovascular accidents, tumours, hydrocephalus and rarer disorders such as motor neurone disease, Parkinson’s disease and multiple sclerosis just to name a few. These are called upper motor neurone lesions because they affect the nerve cells and transmitting nerve fibres that are above the lower motor neurone system. The lower motor neurone system is the nerve cell body, transmitting nerve fibre, the junction between the nerve fibre and the muscle and the muscle itself. This is basically located in the lower part of the central nervous system known as the brain stem, which lies between the cortex and the spinal cord. Lower motor neurone diseases include myasthenia gravis, general debility, malnutrition, hypophosphataemia (refeeding a starved patient can cause this), other electrolyte abnormalities and lesions such as bleeding/trauma/stroke to the brain stem. Pneumonia is the active infection of lung tissue by an infectious agent – which might be bacterial, viral, fungal or other rarer organisms – with resultant infiammatory changes. Pneumonitis is the sterile infiammatory changes in the lungs without the growth of infectious agents. The two can occur simultaneously or separately but aspiration pneumonia is usually preceded by aspiration pneumonitis. Aspiration pneumonia mostly involves bacterial infection, although a small subset may have fungal agents implicated. It is suggested that even common causes of community acquired pneumonia, such as the bacteria Streptococcus pneumoniae, Mycoplasma pneumoniae, and Haemophilus pneumophila and viruses such as adenovirus, respiratory synctial virus, infiuenza and parainfiuenza, usually colonize the oropharynx first before being aspirated down into the lungs to cause pneumonia. These include prolonged hospitalization, exposure to antibiotics, significant medical diseases (chronic heart or lung disease, diabetes, renal failure, liver disease), invasive (via a tube) ventilation and smoking. The defence mechanisms include coughing, active ciliary transport and immune reactions. The mucociliary escalator is the combination of the mucus lining that coats the airways and traps small particles (larger particles are usually deposited on the oropharynx or nasopharynx and are filtered out by the nostrils) in the airway, as well as bacteria, and the minute hairs that whisk the trapped small particles up the trachea to the vocal cords to be coughed out or swallowed. The immune reactions include humoral immunity, mediated by antibodies to the infectious agent, cellular immunity, mediated by cells such as T lymphocytes, and innate immunity, mediated by alveolar macrophages and secreted toxins within the alveolus (air sac). Weakening of these defences will increase the risks of acquired infection from aspiration of even these small amounts. Weakening can be done by things such as smoking, which impairs coughing and the mucociliary escalator. The mucociliary escalator can also be impaired by general anaesthetics, viral or bacterial infections, and even intubation for ventilation. Cough can be impaired by anything that affects respiratory muscle strength such as chronic obstructive lung disease, or any factor that depresses the level of consciousness, or lower motor neurone disease. Drugs such as chemotherapy to treat cancer or immunosuppressive drugs such as steroids to treat overactive immune systems can all weaken the humoral and cellular immune systems. A myriad of diseases can also damage the immune system, ranging from diabetes through heart failure to autoimmune diseases where an overactive immune system actually attacks the body. Finally, inhaled toxins (such as asbestos and those in cigarette smoke), viral infections and starvation can damage the innate immune systems. The inhalation into the lungs of sterile stomach contents causes Mendelson’s syndrome. This is a chemical injury to the lung tissue caused by the acidic nature of the stomach fiuids – as outlined above it was first described in pregnant patients in labour undergoing emergency operative deliveries under general anaesthetic. The acidic nature of the stomach fiuids usually keeps such fiuids free of organisms. However, the use of anti-ulcer therapy, particularly in ventilated patients often allows the stomach contents to become colonized with the same organisms as the oropharynx. Other factors may also increase the chances of such colonization, including use of enteral feeds (common in intensive care units), gastroparesis or small bowel obstruction. Such colonization increases the risk of pneumonia in the event of aspiration of stomach contents, although, of course, most aspiration episodes involve oropharyngeal secretions that are already colonized with such organisms. Aspiration of particulate matter such as undigested or semi-digested food will increase the likelihood of pneumonia, and, in particular, lung abscesses, developing and has been suggested to increase even the severity of pneumonitis. It may also be totally silent clinically – 63% of patients with known aspiration have been found to have no symptoms/signs (Warner et al. However, it was also suggested in the same study that those that did acquire symptoms were more likely to need more intensive support, such as ventilation and antibiotics, and were more likely to die. Symptoms that might be seen after an aspiration episode include cough, wheeze, fevers or chills, rigors, breathlessness or chest pain. Signs that might be elicited include temperatures, wheeze, crackles, bronchial breathing, reduced chest expansion, fast (often shallow) respirations, hypotension or cyanosis (a blue tinge to the skin). Bronchial breathing is where the breath sounds heard at the peripheries of the lung sound like those heard through the stethoscope over the centre of the lung. This is best noticed by observing that normally there is a small gap between the inspiratory noise and the expiratory noise at the periphery – in bronchial breathing there is no such gap. Simple testing may show a low oxygen level in the blood – low arterial or transcutaneous saturations – or radiological signs such as atelectasis (collapse) or consolidation. The natural tendency is for aspirated material to go down the right side of the tracheobronchial tree into the right lower lobe because the right main bronchus is straighter and more in alignment with the trachea. Therefore, radiological and clinical signs tend to be best seen at the right base/lower zones. In simple terms, the principles of management of an acute episode of aspiration are as follows. The patient should be placed either head down to facilitate drainage of the fiuids or in the lateral recovery position to try to minimize further aspiration. The witness should call for help, preferably trained help such as medical officers or nursing staff. Chest radiographs may or may not be obtained, either as a baseline or to show the pneumonitis. If the patient produces sputum, samples should be taken and sent off to culture organisms. If impairment of gas exchange is severe enough, the patient may be moved to the intensive care unit and ventilation, either invasive via an endotracheal tube or non-invasive via a mask, may be initiated. Of course, further assessment is indicated once the patient’s clinical condition stabilizes to lessen the risk of a repeat episode of aspiration (see Chapters 7, 8 and 14). Aspiration can also lead to airway obstruction from laryngeal oedema (or foreign object such as a ‘steak bolus’). It can also be a cause of an asthma attack (in those who are susceptible, especially asthmatics) or even a chronic cough. It can be associated with lung abscess, which can be the endpoint of a necrotizing pneumonia caused by a virulent (or more vicious) organism or due to obstruction of the airway to a part of the lung by foreign material (such as food), or even a chronic interstitial fibrosis (Irwin, 1999). I will briefiy outline the principles of medical management of aspiration pneumonia. Surgery or thoracocentesis (drainage of the pleural/chest cavity by needle or operating telescope) may even be indicated. Otherwise, symptoms, signs, treatment and investigation are much as for aspiration pneumonitis. It can be very difficult to distinguish aspiration pneumonitis from pneumonia in the short term – with the passage of time, the difference will usually become clearer. It is also less associated with infection – nasal tubes do cause sinusitis, but parenteral feeding lines become infected much more commonly.