Asthma affects 5–7% of the population of Europe and North America. It is characterised by recurrent shortness of breath, wheeze or cough caused by reversible narrowing of the airway lumen. The principal cause of increased airways resistance is contraction of smooth-muscle cells as a result of hypersensitivity to many different stimuli such as cold air, smoke, exercise and emotion, as well as antigens. Thickening of the airways by oedema and cellular infiltrates, as well as blockage of airways by mucus and secretions, also contribute. Wheeze is not an essential feature.

Asthma is sometimes classified into extrinsic and intrinsic, although treatment is the same.

Clinical Features

Acute Attacks

These may be fairly abrupt in onset and brief in duration (hours), or longer (a week or two). Longer severe attacks are called ‘status asthmaticus’ (p. 113). In an attack the patient feels tightness in the chest and both inspiratory and expiratory effort are difficult. There may be a cough that is initially dry but later becomes productive, particularly if there is infection. The patient usually sits up with an overinflated chest, an audible expiratory wheeze, using the accessory muscles of respiration. The respiratory rate may be little altered but the pulse is invariably rapid. Acute attacks are precipitated by specific allergens (e.g. pollens or house dust mite), exertion, cold air, a respiratory infection and β-blockers.

Recurrent Asthma

Mild asthmatics (particularly with extrinsic asthma) usually have normal respiratory function between attacks, but those with long-standing severe asthma tend to develop some degree of dyspnoea and persistent airways obstruction between acute attacks.

Investigation

Investigation includes chest X-ray (for regional collapse, pneumonia, pneumothorax) and measurement of ventilatory function (FEV₁ or PEFR, preferably at several times a day on several days at home) and the response to bronchodilators. Variability through the day, especially with a ‘morning dip’ in PEFR, is characteristic. Skin hypersensitivity tests performed by pricking standard allergens into the skin can help the patient recognise and avoid environmental precipitants. Bronchial reactivity may be more precise but should be tested only in carefully controlled conditions. Adrenaline (0.5 ml of 1 : 1000) must be available in case of acute anaphylactic reactions (p. 115).

Management of chronic asthma

The patient should be asked about precipitating factors, including upper respiratory tract infection, season (grass pollen and fungal spores), cold, exercise, food, house dust (contains the mite Dermatophagoides), smoke, emotion and drugs (e.g. aspirin, NSAIDs, β-blockers). Patients should be trained to use a peak flow meter reliably and to document values at home. Increasing morning dips provide an early warning of deterioration.

Most patients respond to simple therapy and may be controlled by:

• removing known allergies, e.g. feather pillows, cats
  
• inhaled short-acting β₂-agonists, e.g. salbutamol, as required – the response is a guide to severity
  
• inhaled corticosteroids in a regular regimen
  
• inhaled sodium cromoglicate (Intal)
  
• inhaled antimuscarinic preparations, e.g. ipratropium (Atrovent)
  
• theophylline preparations, given as a slow-release preparation at night to control overnight symptoms
  
• leukotriene receptor antagonists, e.g. montelukast, are used as add-on therapies in the prophylaxis of moderate asthma not controlled by the above therapies
  
• oral steroids may be required for exacerbations
  
• hyposensitisation is of value in only a small number of patients who demonstrate specific allergies.

Respiratory failure can be defined as a reduction in arterial PaO₂ below 8 kPa with a normal arterial PaCO₂ (hypoxaemic respiratory failure), or with an increase in arterial PaCO₂ above 6.6 kPa (hypercapnic respiratory failure).

NB The normal range for PaO₂ is about 10–13 kPa. Values of PaO₂ are lower in the elderly.

The PaO₂ may fall while the PaCO₂ remains normal. This may occur with alveolar parenchymal lung disease: infiltrations, fibrosing alveolitis and ‘pure’ emphysema. Much more commonly, both arterial gas levels are abnormal. This occurs with ventilatory failure.

Acute

• patients with normal lungs, with upper airways obstruction (e.g. croup and acute anaphylaxis) or mechanical failure (e.g. flail chest) or central nervous system depression of respiratory drive (e.g. sleep apnoea, drug overdosage, stroke)
  
• patients with abnormal lungs (e.g. asthma, chronic bronchitis)

Chronic

Usually in patients with abnormal lungs, especially COPD. These patients are particularly likely to develop acute failure if infection occurs.

In restrictive disorders, lung expansion is limited by:

• lung disease, such as fibrosis collapse, oedema, consolidation
  
• pleural disease, such as fibrosis, effusion or mesothelioma
  
• chest-wall disease, such as costospinal rigidity and deformity, or abdominal splinting by obesity, ascites or pregnancy
  
• neuromuscular disease, such as muscular dystrophy, myasthenia or phrenic nerve paralysis.

This usually occurs on a background of COPD.

Clinical Presentation

• peripheral vasodilatation with headache, engorged veins in the fundi, warm hands and a bounding pulse, all caused by carbon dioxide retention
  
• varying degrees of agitated confusion, drowsiness and coma
  
• increasing cyanosis
  
• signs of right heart failure
  
• flapping tremor of the outstretched hands and papilloedema are late signs

NB Unfortunately, physical signs are a poor guide to the presence and degree of respiratory failure. It is therefore necessary to measure blood gases in all patients in whom the diagnosis is suspected.

Management

This consists of the measures used for COPD as given above, with the addition of controlled oxygen therapy. The danger to life in this situation is hypoxia, but, paradoxically, relief of hypoxia may make the situation worse by causing hypercapnia. Give oxygen at 24 or 28% by Ventimask (or other controlled technique) if the arterial PaO₂ or oxygen saturation is low, targeting oxygen saturation at 94–98% unless the patient is at risk of hypercapnia, when the target should be lower at 88–92%. Oxygen is given continuously until the acute situation (including infection and heart failure) has recovered. PaCO₂ is monitored. For chronic respiratory failure controlled oxygen can be given continuously at home with improvement in symptoms and an increase in life expectancy (Trials Box 11.1).

NB Sedatives are absolutely contraindicated.

Trials Box 11.1 Home Oxygen Therapy in COPD

A systematic review of the effect of domiciliary oxygen therapy in patients with COPD found that long-term home oxygen therapy improved survival in a selected group of COPD patients with severe hypoxaemia (arterial PaO₂ less than 8.0 kPa). Home oxygen therapy did not appear to improve survival in patients with mild to moderate hypoxaemia or in those with only arterial desaturation at night. (Cochrane Database Systematic Review 2005; (4): CD001744.)

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Indications for Respiratory Support and Mechanical Ventilation

If the PaCO₂ falls, conservative therapy should be continued and reassessed periodically. If the PaCO₂ rises, this indicates that the patient’s ventilation is inadequate and is the prime indication for non-invasive positive pressure ventilation using a full facial or nasal mask that delivers ventilatory support from a flow generator (Trials Box 11.2), or if this fails mechanical positive-pressure ventilation. Patients should be ventilated before they become exhausted. The final decision to ventilate a patient is determined mainly on the basis of respiratory function before the acute illness: if very poor, it may not be possible to wean the patient off the ventilator.

Trials Box 11.2 Non-invasive Positive Pressure Ventilation in Acute Respiratory Failure

A systematic review of non-invasive positive pressure ventilation (NPPV) in patients admitted to hospital with acute respiratory failure secondary to an exacerbation of COPD showed the benefit of NPPV as first-line intervention as an adjunct therapy to usual medical care in all suitable patients. The review concluded that NPPV should be considered early in the course of respiratory failure and before severe acidosis ensues, as a means of reducing the likelihood of endotracheal intubation, treatment failure and mortality. (Cochrane Database Systematic Review 2004; (3): CD004104.)

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This rare condition occurs following exposure to allergens such as certain foods, e.g. peanuts; drug therapy, e.g. penicillin; and insect stings. Clinical features range from mild with flushing of the face, pruritus and blotchy wheals, to severe with asthma, respiratory obstruction from oedema of the larynx (angioedema) and circulatory collapse.

Immediate treatment is with adrenaline (epinephrine) 0.5 ml of 1 : 1000 (1 mg/ml) solution, i.e. 500 μg given intramuscularly and repeated after 5 min if no improvement is observed. Oxygen, if available, is important early on. An intravenous fluid challenge is given if there is hypotension. Hydrocortisone takes several hours to act. It is given (after the first injection of adrenaline (epinephrine)) in a dose of 200 mg slowly intravenously or intramuscularly, with chlorphenamine 10 mg slowly intravenously or intramuscularly.

In patients with a history of anaphylaxis allergens should be identified and avoided. Most patients will wish to carry self-adminstration preassembled pens containing adrenaline (epinephrine) for intramuscular injection.

Hereditary angioedema is a rare condition caused by C₁ esterase deficiency (autosomal dominant). It gives rise to erythema, patchy oedema and colicky abdominal pain. It responds to danazol prophylaxis and fresh frozen plasma (or if available plasma derived C1 inhibitor) to correct the deficiency during attacks.

Community-acquired pneumonia affects approximately 5–10/1000 adults per year. One in 1000 requires hospitalisation, and mortality in these patients is around 10%.

Clinical Presentation

Symptoms of cough, sputum, pleurisy and dyspnoea are less common in the elderly.

Clinical findings include fever, tachypnoea, crackles and signs of consolidation. The likely causative agent cannot be predicted from clinical findings.

The most common organism in UK studies of hospitalised patients is Streptococcus pneumoniae (approximately one-third of cases in which an organism is identified), followed by Chlamydia pneumoniae and Mycoplasma pneumoniae. Haemophilus influenzae, Legionella species, Chlamydia psittaci and Staphylococcus aureus account for most of the remainder. Gram-negative bacilli, Coxiella burnetii and anaerobes are rare. Viruses (including influenza) account for 10–15% of cases.

Investigations

Investigations are performed to establish the diagnosis and assess severity.

• Chest X-ray shows infiltrates. Computed tomographic (CT) scanning is more sensitive and may be useful in detecting interstitial disease, cavitation and empyema.
  
• Blood gases to assess severity and guide oxygen treatment.
  
• Blood count – white cell count > 15 × 10⁹/l suggests bacterial infection; white cell count > 20 × 10⁹/l or ≤ 4 × 10⁹/l indicates poor prognosis. Haemoglobin for haemolysis.
  
• Creatinine and liver function tests for underlying or associated renal or hepatic disease.
  
• Gram staining and culture of sputum – but cough is unproductive in one-third of patients, and negative results are common, particularly if antibiotics have been given.
  
• Blood culture.
  
• Pleural fluid, if present, should be aspirated for culture.

Management

• Oxygen – to maintain PaO₂ above 8 kPa and oxygen saturation > 92%.
  
• Antibiotics – the organism is usually unknown initially. Treatment is started immediately and should cover Streptococcus pneumoniae. In uncomplicated pneumonia, treatment is usually started with oral amoxicillin or a macrolide (erythromycin or clarithromycin). In severe pneumonia intravenous therapy is given, often using a combination of a macrolide (erythromycin) and a second- or third-generation cephalosporin (cefuroxime or cefotaxime). The choice of antibiotics should take account of local guidelines, which will take account of other factors, including the incidence of Clostridium difficile enteritis.
  
• Intravenous fluids may be required.
  
• Analgesia for pleuritic pain.

Pneumococcal pneumonia is the most common bacterial pneumonia. S. pneumoniae is a Gram-positive diplococcus. It affects all ages, but is more common in the elderly, after splenectomy, in the immunosuppressed, alcoholics, patients with chronic heart failure and those with pre-existing lung disease. It typically presents acutely with fever, pleuritic pain and rust-coloured sputum. It causes both lobar and bronchopneumonia. Treatment is with penicillin, or erythromycin in the penicillin-sensitive. A polysaccharide pneumococcal vaccine is available for those at high risk. It should be given at least 2 weeks before splenectomy and before chemotherapy.

Staphylococcal pneumonia produces widespread infection with abscess formation. It may complicate influenzal pneumonia, and this makes it relatively common during epidemics of influenza. It also occurs in patients with underlying disease, which prevents a normal response to infection, e.g. chronic leukaemia, lymphoma, cystic fibrosis. Flucloxacillin is the drug of choice, although increasingly Staphylococcus aureus is methicillin resistant (MRSA) and requires treatment wth vancomycin. Lung abscess, empyema and subsequent bronchiectasis are relatively common complications.

Legionnaire’s disease was first described in a group of American army veterans (legionnaires). The causative Gram-negative bacillus flourishes in the cooling waters of air conditioners and may colonise hot-water tanks kept at < 60°C. It begins as an influenza-like illness with fever, malaise and myalgia, and proceeds with cough (little sputum), dyspnoea and sometimes severe anorexia, marked confusion and coma. Diarrhoea and vomiting are common and renal failure may develop. Examination shows consolidation that usually affects both lung bases. X-ray changes may persist for more than 2 months after the acute illness. Erythromycin or ciprofloxacin are the antibiotics of choice, but the mortality remains high.

NB Legionnaire’s disease (and Mycoplasma pneumoniae or psittacosis) should be suspected in all patients who develop pneumonia that does not respond to standard antibiotics.

Mycoplasma pneumonia is caused by M. pneumoniae, the only mycoplasma definitely pathogenic to humans. The clinical picture resembles bacterial pneumonia, although cough and sputum are absent in one-third of cases.

Respiratory symptoms and signs and X-ray changes (patchy consolidation with small effusions) are usually preceded by several days of influenza-like symptoms. Polyarthritis occurs and may persist for months. Malaise and fatigue may persist long after the acute illness is over. The diagnosis is confirmed by a positive Mycoplasma-specific immunoglobulin M (IgM) titre. Erythromycin or tetracycline are the antibiotics of choice.

Psittacosis pneumonia is caused by Chlamydia psittaci. It is transmitted in the excrement of infected birds (the bird need not be ill). Headache, fever and dry cough may be accompanied by a rash and splenomegaly. Hepatitis, encephalitis, renal failure and haemolysis also occur. Treatment is with tetracycline or erythromycin.

Viral pneumonia in children is commonly due to the respiratory syncytial virus (RSV), so called as it is a respiratory virus which produces syncytium formation when grown in culture. Infection may be indistinguishable from acute bacterial bronchitis or bronchiolitis in children and infants. The presence of a skin rash supports the likelihood of RSV infection.

Acute viral pneumonia in adults is less common but occurs during epidemics of influenza. Fever, headache and myalgia are followed after a few days by dry cough and chest pain. Treatment is largely symptomatic (paracetamol, rest, fluids). Influenza vaccines are available for those at high risk. The most common cause of pneumonia during influenza epidemics results from secondary bacterial infection, the most serious being staphylococcal pneumonia. The viruses of measles, chickenpox and herpes zoster may directly affect the lung. The diagnosis is confirmed by a rise in specific antibody titre.

Aspiration pneumonia comes in two main varieties, differentiated from each other by the type of fluid aspirated and the circumstances in which it occurs.Aspiration of gastric contents may produce a severe chemical pneumonitis with considerable pulmonary oedema and bronchospasm (Mendelson syndrome). The acute respiratory distress and shock can be very rapidly fatal and very difficult to treat. It tends to occur in states of reduced consciousness such as general anaesthesia, drunks and when gastric lavage (for drug overdose) has been performed inexpertly.

Aspiration of bacteria from the oropharynx may follow dental anaesthesia and can occur in bulbar palsies. The bacteria, apart from Bacteroides, are nearly all penicillin-sensitive and amoxicillin (or ampicillin) with metronidazole are the antibiotics of choice until sensitivities of isolated organisms are known. Recurrent episodes occur in some oesophageal disorders, including hiatus hernia, stricture, achalasia of the cardia, and in patients with diverticula or pharyngeal pouch.

Recurrent bacterial pneumonia in the absence of chronic bronchitis arouses suspicion of:

• bronchial carcinoma preventing drainage of infected areas of lung
  
• bronchiectasis
  
• cystic fibrosis
  
• achalasia of the cardia, 25% of which present as chest disease, pharyngeal pouch and neuromuscular disease of the oesophagus, e.g. bulbar palsy, all producing aspiration
  
• hypogammaglobulinaemia and myeloma.

Opportunistic infection of the lungs occurs in patients immunosuppressed as a result of treatment, e.g. for myeloproliferative disorders or acquired immunodeficiency syndrome (AIDS, p. 343).

Aetiology

• aspiration (see above)
  
• bronchial obstruction, usually by carcinoma or a foreign body (especially peanuts and teeth)
  
• pneumonia partially resolved or treated, particularly when caused by the Staphylococcus, Klebsiella or Pneumococcus organisms

Clinical Features

There is a swinging fever and the patient is very ill. The sputum is foul and purulent and there is a high polymorph cell count. Clubbing may develop.

Investigation

Sputum is sent for Gram stain and culture, and blood for culture. Chest X-ray shows round lesions which usually have a fluid level, and serial X-rays monitor progress. It may be necessary to proceed to bronchoscopy to exclude obstruction and to obtain a biopsy and sputum trap specimen.

Treatment

Antibiotic therapy is given according to sensitivities and continued until healing is complete. Repeated postural drainage is started. In resistant cases, repeated aspiration, antibiotic instillation and even surgical excision may be required.

Bronchiectasis means dilatation of the airways. It only becomes of clinical significance when infection and/or haemoptysis occurs within these dilatated airways. Severe forms are now rare, especially in the young.

Aetiology

• following acute childhood respiratory infection, particularly measles, whooping cough or pneumonia
  
• cystic fibrosis
  
• bronchial obstruction predisposes to bronchiectasis (e.g. peanuts)
  
• tuberculosis has become less common as a cause
  
• congenital (rare): primary ciliary dyskinesia, e.g. Kartagener syndrome (bronchiectasis, sinusitis, situs inversus)

Clinical Features

• chronic cough, often postural
  
• sputum, often copious, especially with acute infections
  
• halitosis
  
• febrile episodes
  
• haemoptysis: may be the only symptom (‘dry bronchiectasis’) and is occasionally severe
  
• dyspnoea, coarse basal crepitations and wheeze
  
• cyanosis and clubbing
  
• loss of weight and cor pulmonale in advanced cases

Management

Stop smoking.

The object is to get rid of chronic sepsis. Twice-daily postural drainage will help empty dilated airways and decrease the frequency of further infections. Bronchodilators will often help improve clearance of sputum. Antibiotics, as for chronic bronchitis, are given for acute infections and exacerbations. Treatment is unnecessary in the absence of symptoms.

Surgery is rarely indicated unless there is uncontrolled bleeding because the disease is seldom limited to one or two lung segments. Patients with severe disease may develop respiratory failure.

Aetiology

Spontaneous Pneumothorax