6: Respiratory

Section 6 Respiratory

Edited by Anne-Maree Kelly

6.1 Upper respiratory tract 273

6.3 Community-acquired pneumonia 283

6.4 Influenza and emerging respiratory infections 293

6.5 Chronic obstructive pulmonary disease 298

6.6 Pneumothorax 303

6.7 Pleural effusion 307

6.8 Haemoptysis 311

6.1 Upper respiratory tract

Introduction

The upper respiratory tract extends from the mouth and nose to the carina. It comprises a relatively small area anatomically, but is of vital importance. Presenting conditions may be acute and potentially life-threatening, requiring immediate evaluation or treatment, although the majority of presentations are not life-threatening.

Urgent conditions requiring immediate attention or intervention are those likely to compromise the airway. Protection and maintenance of airway, breathing and circulation (the ABCs) take precedence over history taking, detailed examination or investigations. Possible causes of airway obstruction are listed in Table 6.1.1.

Table 6.1.1 Causes of upper airway obstruction

Non-urgent presentations include rash or facial swelling not involving the airway, sore throat in a non-toxic patient, and complaints that have been present for days or weeks with no recent deterioration. Pharyngitis and tonsillitis are common causes for presentation in both paediatric and adult emergency practice.

Triage and initial evaluation

Initial evaluation should be aimed at differentiating those patients needing urgent management to prevent significant morbidity and mortality, from those needing less immediate intervention. Triage must be based on the chief complaint and on vital signs, as the same clinical presentation may result from a range of pathophysiologies, e.g. stridor can be due to trauma, infection, drug reactions or anatomical abnormalities such as tracheomalacia.

Symptoms and signs of airway obstruction include dyspnoea, stridor, altered voice, dysphonia and dysphagia. Evidence of increased work of breathing includes subcostal, intercostal and suprasternal retraction, flaring of the nasal alae, as well as exhaustion and altered mental state. The presence of these signs may vary with age and accompanying conditions. Cyanosis is a late sign. Further examination will be directed by the presenting complaint and initial findings and includes:

• General appearance – facial symmetry, demeanour.

• Vital signs – temperature, heart rate, respiratory rate, BP, pulse oximetry.

• Head and face – rash, swelling, mucous membranes, lymphadenopathy.

• Oropharynx – mucous membranes, dental hygiene, tongue, tonsils, uvula.

Upper airway obstruction

Upper airway obstruction may be acute and life-threatening or may have a more gradual onset. It is essential that the adequacy of the airway is assessed first. Any emergency interventions that are required to maintain the airway should be instituted before obtaining a detailed history and examination. This may range from relieving the obstruction to providing an alternative airway.

Obstruction may be physiological, with the patient unable to maintain and protect an adequate airway owing to a reduced conscious state. Mechanical obstruction may be due to pathology within the lumen (aspirated foreign body), in the wall (angioedema, tracheomalacia) or to extrinsic compression (Ludwig’s angina, haematoma, external burns). Obstruction may be due to a combination of physiological and mechanical causes. A summary of potential causes of upper airway obstruction is provided in Table 6.1.1. Despite the plethora of possible causes, the initial treatment to secure the airway is the same.

Investigation

Investigations are secondary to the assessment and/or provision of an adequate airway. Once the airway has been assessed as secure, the choice of investigations is directed by the history and examination.

Endoscopy

Direct laryngoscopy by an experienced operator is the single most important manoeuvre in patients with acute upper airway obstruction. It may concurrently form part of the assessment, investigation or treatment. By visualizing the laryngopharynx and upper larynx the cause of the obstruction can be seen. Any foreign bodies may be removed or, if necessary, a definitive airway such as an endotracheal tube introduced. In the case of the stable patient with an incomplete obstruction this should only be attempted when there are full facilities available for intubation and the provision of a surgical airway. It may be more appropriately deferred until expert airway assistance is available.

Bronchoscopy may be required to assess the trachea and distal upper airway, but is not part of the initial resuscitation. It is more appropriate to transfer the stable patient to the operating suite or ICU for this procedure.

Pathology

Some tests may be useful in guiding further management. These include full blood count, arterial blood gases, and throat swab and blood cultures. Those required will be guided by the clinical presentation. Initial treatment in the emergency department (ED) should not await their results.

Imaging

Neck X-rays

A lateral soft tissue X-ray of the neck is sometimes helpful once the patient has been stabilized. Metallic or bony foreign bodies, food boluses or soft tissue masses may be seen. A number of subtle radiological signs have been described in epiglottitis (Table 6.1.2).

Table 6.1.2 Radiological findings in adult epiglottitis

The ‘thumb’ sign	Oedema of the normally leaf-like epiglottis resulting in a round shadow resembling an adult thumb. The width of the epiglottis should be less than one-third the anteroposterior width of C4.
The vallecula sign	Progressive epiglottic oedema resulting in narrowing of the vallecula. This normally well-defined air pocket between the base of the tongue and the epiglottis may be partially or completely obliterated.
Swelling of the aryepiglottic folds
Swelling of the arytenoids
Prevertebral soft tissue swelling	The width of the prevertebral soft tissue should be less than half the anteroposterior width of C4.
Hypopharyngeal airway widening	The ratio of the width of the hypopharyngeal airway to the anteroposterior width of C4 should be less than 1.5.

Computed tomography

In the patient with a mechanical obstruction a computed tomography (CT) scan of the neck and upper thorax may be helpful in diagnosing the cause of the obstruction as well as the extent of any local involvement. It may aid in planning further management, especially if surgical intervention is indicated, for example for a retrothyroid goitre or a head and neck neoplasm.

Management

Management initially consists of securing the airway. This is discussed in more detail elsewhere in this book, but simple interventions include chin lift or jaw thrust and an oropharyngeal airway, or more sophisticated items such as the laryngeal mask, endotracheal tube or surgical airway. A surgical airway is rarely necessary in the ED, although it is important that equipment is always available and that the techniques have been practised. These include needle insufflation and cricothyrostomy. A number of commercial kits, such as the ‘Mini-trach II’ and the Melker Emergency Cricothyroidotomy Catheter Set, are available. Further management will depend on the underlying cause.

Trauma

Trauma to the upper airway may involve obstruction by a foreign body, blunt or penetrating trauma or thermal injury.

Foreign body airway obstruction

Foreign body aspiration is often associated with an altered conscious state, including alcohol or drug intoxication as well as cerebrovascular accident (CVA) or dementia. Elderly patients with dentures are at increased risk. Laryngeal foreign bodies are almost always symptomatic and are more likely to cause complete obstruction than foreign bodies below the epiglottis. If the obstruction is incomplete and adequate air exchange continues, care should be taken not to convert partial obstruction into a complete block by overzealous interference. Foreign bodies in the oesophagus are an uncommon cause of airway obstruction, but if lodged in the area of the cricoid cartilage or the tracheal bifurcation, can compress the airway, causing partial airway obstruction. Oesophageal foreign bodies may also become dislodged into the upper airway.

Management

The Heimlich manoeuvre or abdominal thrust is one recommended technique for dislodgement of a foreign body. The rescuer stands behind the patient, placing clenched fists over the patient’s upper abdomen well clear of the xiphisternum. A short, sharp upward thrust is made to force the diaphragm up and expel the foreign body. There is a risk of injury to internal organs and so this should only be done by rescuers who have been trained in the technique. Chest thrusts may be more effective in obese patients if the rescuer is unable to encircle the patient’s abdomen.

Chest thrusts are a similar technique that may be used in children or pregnant women, and back blows can be used in small children. Patients who are asymptomatic after uncomplicated removal of a foreign body should be observed for a time in the ED, and if they remain well may be discharged home.

In the unconscious patient direct laryngoscopy may be performed, with removal of the foreign body under direct vision with Magill forceps or suction.

Blunt trauma

Laryngotracheal trauma is rare, comprising 0.3% of all traumas presenting to an ED. The upper airway is relatively protected against trauma as the larynx is mobile and the trachea compressible, and because the head and mandible act as shields. Blunt trauma may be difficult to diagnose, as external examination may be normal and there may be distracting head or chest injuries.

Mechanism

‘Clothesline injuries’ involve cyclists or other riders hitting fences or cables. Direct trauma from assaults, sporting equipment or industrial accidents also occurs. Suicide attempts by hanging may cause traumatic injuries to the neck as well as airway obstruction due to the ligature. ‘Dashboard injuries’ occur when seatbelts are not worn, with sudden deceleration resulting in hyperextension of the neck and compression of the larynx between the dashboard and the cervical spine.

Pathology

The most common laryngeal injury is a vertical fracture through the thyroid cartilage. Fractures of the hyoid bone and cricoid cartilage also occur, and may be found in cases of manual or ligature strangulation. The cricothyroid ligament and the vocal cords may be ruptured and the arytenoids dislocated. Complete cricotracheal transection may occur. Mortality rates depend on the location of the injury, ranging from 11% for isolated fractures of the thyroid cartilage to 50% for injuries involving the cricoid cartilage, bronchi or intrathoracic trachea. Asphyxiation is the most common cause of death in blunt laryngeal trauma. Up to 50% of patients sustaining significant blunt airway trauma have a concurrent cervical spinal injury.

Clinical

Tracheal or laryngeal injury should be suspected if aphonia, hoarseness, stridor, dysphagia or dyspnoea occur. Patients may present with complete obstruction or may deteriorate rapidly after arrival. There may be minimal external evidence of injury or the larynx may be deformed or tender, and there may be subcutaneous emphysema. It is important to check for associated head, chest and cervical spine injuries.

Penetrating trauma

Mechanism

Penetrating injuries may be secondary to assault or to sporting or industrial accidents. A focused history is mandatory.

Clinical

Penetration of the airway should be suspected if there is difficulty breathing, a change in voice, pain on speaking, subcutaneous emphysema or bubbling from the wound. This is often associated with great vessel or pulmonary injuries, and the patient may require an emergency airway procedure. Uncontrolled haemorrhage is a potentially life-threatening condition. Other causes include head and neck malignancies eroding vascular structures, or following radiotherapy. Uncontrolled haemorrhage may lead to exsanguination as well as compromising the airway, and requires prompt surgical intervention.

Management of blunt and penetrating trauma

Airway management with protection of the cervical spine is essential. Fibreoptic bronchoscopic intubation is preferable to minimize complications such as laryngeal disruption, laryngotracheal separation or the creation of a false tracheal lumen. Cricothyrostomy is relatively contraindicated because of the altered anatomy. Emergency tracheostomy may even be required, ideally performed in the operating theatre. Early ENT involvement is important, and indications for surgical exploration include airway obstruction requiring tracheostomy, uncontrolled subcutaneous emphysema, extensive mucosal lacerations with exposed cartilage as identified on bronchoscopic or laryngoscopic examination, vocal cord paralysis, and grossly deformed, multiple or displaced fractures of the larynx, thyroid cartilage or cricoid cartilage.

Investigations

Endoscopy

Endoscopy includes both laryngoscopy and bronchoscopy, performed in the operating theatre, as urgent surgical intervention may be required. Fuhrman et al. (see Further reading) suggest a classification system for the severity of blunt upper airway injury based on endoscopic and radiological findings (Table 6.1.3).

Table 6.1.3 Grading of blunt laryngeal injury

Grade	Endoscopic and radiological findings
I	Minor laryngeal haematoma without detectable fracture
II	Oedema, haematoma or minor mucosal disruption without exposed cartilage, or non-displaced fractures on CT
III	Massive oedema, tears, exposed cartilage, immobile cords

Infections

Infections may involve the upper respiratory tract directly or affect adjacent structures. They range from the common and trivial to the rare and potentially life-threatening. Croup and epiglottitis usually occur in children, but may be seen in adults. Acute respiratory infections are the most frequent reason for seeking medical attention in the USA, and are associated with up to 75% of total antibiotic prescriptions there each year. Unnecessary antibiotic use can cause a number of adverse effects, including allergic reactions, GI upset, yeast infections, drug interactions, an increased risk of subsequent infection with drug resistant Streptococcus pneumoniae and added costs of over-treating.

Non-specific upper airway infections

Upper airway infections are generally diagnosed clinically. Symptom complexes where the predominant complaint is of sore throat are labelled pharyngitis or tonsillitis, and where the predominant symptom is cough, bronchitis. Acute respiratory symptoms in the absence of a predominant sign are typically diagnosed as ‘upper respiratory tract infections’ (URTI). Each of these syndromes may be caused by a multitude of different viruses, and only occasionally by bacteria. Most cases resolve spontaneously within 1–2 weeks. Bacterial rhinosinusitis complicates about 2% of cases and should be suspected when symptoms have lasted at least 7 days and include purulent nasal discharge and other localizing features. Those at high risk for developing bacterial rhinosinusitis or bacterial pneumonia include infants, the elderly and the chronically ill. The antibiotic prescription rate for uncomplicated URTIs in the USA has been previously shown to be 52%, despite the fact that these infections are typically viral in origin and that antibiotic treatment does not enhance illness resolution nor alter the rates of these complications. Treatment should be symptomatic only.

Pharyngitis/tonsillitis

Sore throat is one of the top 10 presenting complaints to EDs in the USA. The differential diagnosis is large and includes a number of important conditions (Table 6.1.4). Pharyngitis has a wide range of causative bacterial and viral agents, most of which produce a self-limited infection with no significant sequelae. The major role for antibiotics in treating pharyngitis is for suspected group A β-haemolytic streptococcal infection (GABHS) or Streptococcus pyogenes. Timely use of appropriate antibiotics reduces the duration of symptoms by an average of 8 hours but increases the rate of adverse effects. Antibiotic use also reduces the incidence of suppurative complications such as otitis media, quinsy and retropharyngeal abscess. If given in the first 9 days they prevent the development of acute rheumatic fever. Antibiotics have not been shown to reduce the incidence of post-streptococcal glomerulonephritis, which is related to the subtype of streptococcus. Antibiotic therapy is also recommended for patients from the following groups: patients with scarlet fever, with known rheumatic heart disease, or from populations with high incidence of acute rheumatic fever, including some Aboriginal populations in Central and Northern Australia.

Table 6.1.4 Differential diagnosis of sore throat in the adult

Infective pharyngitis

Bacterial: Group A β-haemolytic streptococcus most common pathogen.

Diphtheria should be considered in patients with membranous pharyngitis

Viral: including EBV and HSV

Traumatic pharyngitis (exposure to irritant gases)

Non-specific upper respiratory tract infection

Quinsy (peritonsillar abscess)

Ludwig’s angina

Parapharyngeal and retropharyngeal abscesses

Gastro-oesophageal reflux

Oropharyngeal or laryngeal tumour

Up to 50% of pharyngitis in children is caused by GABHS, but only between 5% and 15% of adult cases. The most reliable clinical predictors for GABHS are Centor’s criteria. These include tonsillar exudates, tender anterior cervical lymphadenopathy or lymphadenitis, absence of cough and a history of fever. The presence of three or more criteria has a positive predictive value of 40–60%, whereas the absence of three or more has a negative predictive value of approximately 80%.

Rapid antigen tests are available which have sensitivities ranging between 65% and 97% but are not widely used. They may have a future role in deciding the need for antibiotics. Throat cultures take 2–3 days and may give false positive results from asymptomatic carriers with concurrent non-GABHS pharyngitis. The Infectious Diseases Society of America recommends cultures for children and adolescents with appropriate clinical criteria but negative rapid antigen testing. In adults, because of the lower incidence of streptococcal infection and lower risk of rheumatic fever, a negative rapid antigen test is considered sufficient. Despite the availability of a number of guidelines, there are still wide variations in the management of pharyngitis. Serological testing is not useful in the acute treatment of pharyngitis but is useful in the diagnosis of rheumatic fever.

Neisseria gonorrhoeae is an uncommon cause of pharyngitis and may be asymptomatic. It is seen in persons who practise receptive oral sex. It is important to correctly diagnose N. gonorrhoeae pharyngitis, both for appropriate treatment and because of the need to trace and treat contacts. Ceftriaxone 125 mg i.m. as a single dose is the recommended treatment for uncomplicated pharyngeal gonorrhoea, and consideration should be given to concomitant treatment for chlamydia if this has not been ruled out. HIV is an unusual cause of pharyngitis but should be considered in high-risk populations. The acute retroviral syndrome may present with an Epstein–Barr virus (EBV) mononucleosis-like syndrome.

Most patients with pharyngitis are managed as outpatients. Airway compromise is rare, as the nasal passages provide an adequate airway. Some patients who are toxic or dehydrated may need admission for i.v. hydration and antibiotics. High-dose penicillin remains the drug of choice for streptococcal pharyngitis. The role of oral, i.m. or i.v. steroids remains controversial, but they may be useful in relieving airway obstruction and reducing the duration of symptoms.

Quinsy/peritonsillar abscess

Peritonsillar infections occur between the palatine tonsil and its capsule. Peritonsillar cellulitis may form pus and progress to abscess formation. Cellulitis responds to antibiotics alone, but differentiating between the two and identifying those that require drainage may be difficult clinically. Peritonsillar abscesses occur most commonly in males between 20 and 40 years of age. Symptoms include a progressively worsening sore throat, fever and dysphagia. On examination the patient may have a muffled ‘hot potato’ voice, trismus, drooling, a swollen red tonsil with or without purulent exudate, and contralateral deviation of the uvula. Complications include airway obstruction and lateral extension into the parapharyngeal space. GABHS is the most common organism associated with quinsy, but others include Staphylococcus aureus, Haemophilus influenzae and anaerobic species such as fusobacterium, peptostreptococcus and bacteroides. Treatment generally requires admission for i.v. penicillin and metronidazole. Clindamycin may be used as an alternative. Needle aspiration in experienced hands can be useful, but has a 12% false negative rate and carries the risk of damaging the carotid artery. Formal surgical drainage may be necessary.

Ludwig’s angina

Peripharyngeal space infections have become rare in the post antibiotic era but, of these, Ludwig’s angina or cellulitis of the submandibular space remains the most common. It was first described by Wilhelm Fredrick von Ludwig in 1836, and at that time was usually fatal because of rapid compromise to the airway. With prompt treatment, including i.v. antibiotics, the mortality rate has declined to less than 5%. Clinical features include toothache, halitosis, neck pain, swelling, fever, dysphagia and trismus. Ludwig’s angina is classically bilateral. Infection may spread rapidly into adjacent spaces, including the pharyngomaxillary and retropharyngeal areas and the mediastinum. Ludwig’s angina is related to dental caries involving the mandibular molars, or it may be associated with peritonsillar abscess, trauma to the floor of the mouth or mandible, and recent dental work. Cultures are usually polymicrobial and include viridans streptococci (40.9%), Staph. aureus (27.3%), Staph. epidermidis (22.7%) and anaerobes (40%) such as bacteroides species. Treatment necessitates admission and careful airway management. This may include endotracheal intubation, as abrupt obstruction can occur. Surgical drainage is indicated if the infection is suppurative or fluctuant. The i.v. antibiotics of choice are high-dose penicillin plus metronidazole or clindamycin.

Other abscesses

Parapharyngeal abscesses involve the lateral or pharyngomaxillary space. Presentation and treatment are similar to those of Ludwig’s angina, from which they may develop. As well as the complications of Ludwig’s angina, including airway obstruction and spread to contiguous areas, there is the added risk of internal jugular vein thrombosis and erosion of the carotid artery, which has a mortality of 20–40%.

Retropharyngeal abscesses are more common in children under 5 years of age. In adults they often result from foreign bodies or trauma. Presenting symptoms and signs include fever, odynophagia, neck swelling, drooling, torticollis, cervical lymphadenopathy, dyspnoea and stridor. Lateral neck X-rays show widening of the prevertebral soft tissues and sometimes a fluid level. CT of the neck may help in determining the extent and in differentiating an abscess from cellulitis. MRI, if available, is more sensitive than CT in assessing soft tissue infections of the head and neck, but demonstrates cortical bone poorly. Treatment requires admission, airway management and i.v. antibiotics, and may include surgical drainage.

Epiglottitis

Epiglottitis is becoming an adult disease, although in adults there is significantly less risk to the airway than in children. The incidence of adult epiglottitis has remained relatively stable at 1–4 cases per 100 000 per year, with a mortality of 7%, but this may change over the next 10–20 years as vaccinated children grow into adolescents and adults. Acute adult epiglottitis is often referred to as supraglottitis because the inflammation is not confined to the epiglottis, but also affects other structures such as the pharynx, uvula, base of tongue, aryepiglottic folds and false vocal cords. H. influenzae has been isolated in 12–17% of cases, and the high rate of negative blood cultures may reflect viral infections or prior treatment with antibiotics in cases that present late. Strep. pneumoniae, H. parainfluenzae and herpes simplex have also been isolated. Epiglottitis may also occur following mechanical injury such as the ingestion of caustic material, smoke inhalation, and following illicit drug use (smoking heroin).

Sore throat and odynophagia are the most common presenting symptoms. Drooling and stridor are infrequent. Factors shown to be associated with an increased risk of airway obstruction include stridor, dyspnoea, sitting upright, and short duration of symptoms. A number of X-ray changes have been described in epiglottitis, which are listed in Table 6.1.2. Management requires admission and i.v. ceftriaxone or cefotaxime. The role of steroids and nebulized or parenteral epinephrine (adrenaline) is controversial. Chloramphenicol may be used in patients with cephalosporin sensitivity. Most adults can be treated conservatively without the need for an artificial airway.

• The role of steroids in acute pharyngitis/tonsillitis and quinsy.

• Reaching a uniform approach to the use of antibiotics in adult pharyngitis.

• The role of intubation, steroids and nebulized or parenteral epinephrine (adrenaline) in adult epiglottitis.

Further reading

Alcaide ML, Bisno AL. Pharyngitis and epiglottitis. Infectious Disease Clinics of North America. 2007;21:449-469.

American Heart Association. Guidelines for cardiopulmonary resuscitation and emergency cardiac care. Circulation. 112, 2005. Supplement

Ames WA, Ward WMM, Tranter RMD, et al. Adult epiglottitis: an under-recognized, life-threatening condition. British Journal of Anaesthesia. 2000;85:795-797.

Atkins BZ, Abbate S, Fischer S, et al. Current management of laryngotracheal trauma: case report and literature review. Journal of Trauma. 2004;56:185-190.

Atkins BZ, Abbate S, Fischer S, et al. Current management of laryngotracheal trauma: case report and literature review. Journal of Trauma. 2004;56:185-190.

Bisno AL, Gerber MA, Gwaltney JM, et al. Infectious Diseases Society of America. Practice guidelines for the diagnosis and management of group A streptococcal pharyngitis. Clinical Infectious Disease. 2002;35:113.

Centor RM, Witherspoon JM, Dalton HP, et al. The diagnosis of strep throat in adults in the emergency room. Medical Decision Making. 1981;1:239-246.

Cicala RS. The traumatized airway. In: Benumof JE, editor. Airway management: principles and practice. Mosby-Year Book: St Louis; 1996:736.

Cooper RJ, Hoffman JR, Bartlett JG, et al. Principles of appropriate antibiotic use for acute pharyngitis in adults: Background. Annals of Internal Medicine. 2001;134:509-517.

Del Mar CB, Glasziou PP, Spinks AB. Antibiotics for sore throat. Cochrane Database of Systematic Reviews. (4):2006. CD000023. DOI: 10.1002/14651858.CD000023.pub3. Accessed December 2007

Fuhrman GM, Stieg FH, Buerk CA. Blunt laryngeal trauma: Classification and management protocol. Journal of Trauma. 1990;30:87-92.

Frantz TD, Rasgon BM, Quesenberry CP. Acute epiglottitis in adults. Journal of the American Medical Association. 1994;272:1358-1360.

Gonzales R, Bartlett JG, Besseer RE, et al. Principles of appropriate antibiotic use for treatment of acute respiratory tract infections in adults: Background, specific aims, and methods. Annals of Emergency Medicine. 2001;37:690-697.

Gonzales R, Bartlett JG, Besser RE, et al. Principles of appropriate antibiotic use for treatment of nonspecific upper respiratory tract infections in adults: Background. Annals of Emergency Medicine. 2001;37:698-702.

Gonzales R, Steiner JF, Sande MA. Antibiotic prescribing for adults with colds, upper respiratory tract infections and bronchitis by ambulatory care physicians. Journal of the American Medical Association. 1997;278:901-904.

Howes DS, Dowling PJ. Triage and initial evaluation of the oral facial emergency. Emergency Medicine Clinics of North America: Oral-Facial Emergencies. 2000;8:371-378.

Hurley MC, Heran MKS. Imaging studies for head and neck infections. Infectious Disease Clinics of North America. 2007;21:305-353.

Linder JA, Chan JC, Bates DW. Evaluation and treatment of pharyngitis in primary care practice: the difference between guidelines is largely academic. Archives of Internal Medicine. 2006;166:1374-1379.

McCollough M. Update on emerging infections from the centers for disease control and prevention: commentary. Annals of Emergency Medicine. 1999;34:110-111.

Minard G, Kodak KA, Croce MA, et al. Laryngotracheal trauma. American Surgeon. 1992;58:181-187.

Nemzek WR, Katzberg RW, Van Slyke MA, et al. A reappraisal of the radiologic findings of acute inflammation of the epiglottis and supraglottic structures in adults. American Journal of Neuro Radiology. 1995;16:495-502.

Richardson MA. Sore throat, tonsillitis, and adenoiditis. Medical Clinics of North America: Otolaryngology for the Internist. 1999;83:75-84.

Schamp S, Pokieser P, Danzer M, et al. Radiological findings in acute adult epiglottitis. European Radiology. 1999;9:1629-1631.

Scott PMJ, Loftus WK, Kew J, et al. Diagnosis of peritonsillar infections: a prospective study of ultrasound, computerized tomography and clinical diagnosis. Journal of Laryngology and Otology. 1999;113:229-232.

Stewart MH, Siff JE, Cydulka RK. Evaluation of the patient with sore throat, earache, and sinusitis: an evidence based approach. Emergency Medicine Clinics of North America: Evidence Based Emergency Medicine. 1999;17:153-188.

Steyer TE. Peritonsillar abscess: diagnosis and treatment. American Family Physician. 2002;65:93-96.

Thierbach AR, Lipp MDW. Airway management in trauma patients. Anesthesiology Clinics of North America. 1999;17:63-82.

Victorian Medical Postgraduate Foundation. Therapeutic Guidelines: Antibiotic Version 12, 2006.

6.2 Asthma

Anne-Maree Kelly

1 Asthma is a major health problem worldwide, resulting in significant morbidity and mortality.

2 Asthma is characterized by episodic bronchoconstriction and wheeze in response to a variety of stimuli.

3 Features suggesting an increased risk of life-threatening asthma include a previous life-threatening attack, previous intensive care admission with ventilation, and having required a course of oral corticosteroids within the previous 6 months. Behavioural and adverse psychosocial factors have also been implicated in life-threatening asthma, including non-compliance, obesity and psychiatric illness.

4 Attacks vary in severity from mild to life-threatening, and may develop over minutes.

5 Clinical features supported by bedside pulmonary function tests and pulse oximetry are reliable guides to the severity of attacks.

6 Oxygen, β-adrenergic agents and corticosteroids are the mainstay of therapy.

7 Hospital admission is essential if pretreatment PEFR or FEV₁ is less than 25% of predicted, or post-treatment levels are less than 40% of predicted.

Introduction

The prevalence of asthma varies significantly between regions across the world. In Australasia, New Zealand and the UK it is thought to affect about 20% of children and 10% of adults. Sufferers tend to present to emergency departments (ED) when their usual treatment plan fails to control symptoms adequately. The respiratory compromise caused can range from mild to severe and life-threatening. For these patients the main role of the emergency physician is therapeutic. Other reasons for patients with asthma to attend EDs include having run out of medication, having symptoms after a period of being symptom and medication free, and a desire for a ‘second opinion’ about the management of their asthma. For this smaller group the primary role is one of educating about the disease, of planning an approach to the current level of asthma symptoms, and of referral to appropriate health professionals, e.g. respiratory physicians or general practitioners.

Epidemiology

Asthma is a major health problem in many countries, resulting in significant morbidity and mortality. The cost in terms of long-term medications and lost school and work days is difficult to quantify, but would run to millions of US dollars annually. Australasia, the UK and North America have a greater prevalence of asthma than the Middle East and some Asian countries. There is also considerable geographical variation in severity, with Australasia reporting the highest proportion of severe disease. The reason for this geographical variation is unclear, but may relate in part to ethnicity, rural versus metropolitan environment, and air pollution. A number of epidemiological studies suggest that the prevalence and severity of asthma is slowly increasing worldwide.

Pathophysiology

Asthma is characterized by hyperreactive airways and inflammation leading to episodic, reversible bronchoconstriction in response to a variety of stimuli. Traditionally, it has been divided into extrinsic (allergic) and intrinsic (idiosyncratic) types.

Extrinsic asthma is initiated by a type I hypersensitivity reaction induced by an extrinsic allergen. IgE-mediated activation of mucosal mast cells results in the release of primary mediators (histamine and eosinophilic and neutrophilic chemotactic factors) and secondary mediators including leukotrienes, prostaglandin D₂, platelet-activating factor and cytokines. These result in bronchoconstriction via direct and cholinergic reflex actions, increased vascular permeability and increased mucous secretions.

In contrast, intrinsic asthma is initiated by diverse non-immune mechanisms, including respiratory infections (in particular viruses), drugs such as aspirin and β-blockers, pollutants and occupational exposure, emotion and exercise.

The morphological changes in asthma are over-inflation of the lungs, bronchoconstriction, and the presence of thick mucous plugs in the airways. Histologically there is thickening of the basement membrane of the bronchial epithelium, oedema and an inflammatory infiltrate in the bronchial walls, increased numbers of submucosal glands and hypertrophy of bronchial wall muscle.

Pathophysiologically the effects of acute asthma are:

• Increased physiological dead space.

• Respiratory muscle fatigue.

• Intrinsic positive end-expiratory pressure secondary to hyperventilation with air trapping.

There is increasing evidence that there are different phenotypes of both acute and chronic asthma. For acute asthma, a rapid onset may be closer to anaphylaxis in pathology, with minimal inflammation, and may respond more quickly to treatment.

Clinical assessment

History

Asthma is characterized by episodic shortness of breath, often accompanied by wheeze, chest tightness and cough. Symptoms may be worse at night, which is thought to be due to variations in bronchomotor tone and bronchial reactivity. Attacks may progress slowly over days or rapidly over minutes.

Features in the history indicating a significant risk of life-threatening asthma include a previous life-threatening attack, previous intensive care admission with ventilation, requiring three or more classes of asthma medication, heavy use of β-agonist therapy, repeated ED attendances, and having required a course of oral corticosteroids within the previous 6 months. It has been identified that behavioural and psychosocial features increase the risk of life-threatening episodes of asthma. These include non-compliance with medications, monitoring or follow-up, self-discharge from hospital, psychiatric illness, denial, drug or alcohol abuse, obesity, learning difficulties, employment or income problems, domestic, marital or legal stressors and major tranquillizer use. These should be sought in order to more accurately assess risk and plan management.

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