Introduction

Pneumonia is defined as an inflammatory process involving alveoli and terminal bronchioles and related to infectious agents. Infectious lung diseases and especially pneumonia are particularly serious in the elderly and represent the fifth leading cause of death in persons older than 65 years. Pneumonia is a major cause of hospitalization and about two of three patients hospitalized due to pneumonia are older than 70 years of age. The prognosis of pneumonia is severe, with a fatality rate reaching 50% in some series of nosocomial pneumonia.

Pneumonia should be differentiated from other lower respiratory tract infections and especially from acute bronchitis. Bronchitis is an inflammatory response of large bronchi with no involvement of the lung parenchyma. In contrast to pneumonia, bronchitis usually has a benign course, except in patients with chronic obstructive pulmonary disease who might suffer from deterioration of respiratory function.

Several factors may increase the risk of respiratory infection in the elderly (Table 47.1). During ageing, the body’s defences against infectious agents are less effective, especially cellular immunity. The ageing respiratory system is particularly exposed to risks of infection because of reduced effectiveness of cough and mucociliary clearance and due to microaspiration. Some lung diseases commonly encountered in the elderly, for example, chronic obstructive pulmonary disease, asthma and sequelae of tuberculosis, may facilitate the occurrence of respiratory infection and also some common situations in geriatrics such as diabetes mellitus, heart failure, neurological diseases, swallowing disorders, use of sedative drugs, especially antipsychotics, gastro-oesophageal reflux, protein–energy malnutrition and enteral nutrition or nasogastric tube. Aspiration of oropharyngeal secretions and microflora, food debris or gastric contents is frequently involved in lower respiratory tract infection in frail elderly people, especially among patients having a neurological disease, dysphagia and/or using psychotropic drugs. Pneumonia is the main specific cause of mortality observed in Alzheimer’s disease.

Table 47.1 Conditions that favour respiratory infections in the elderly.

Ageing

Pulmonary diseases: chronic obstructive pulmonary disease, asthma, past tuberculosis

Diabetes mellitus

Heart failure

Neurological diseases

Swallowing disorders

Use of sedative drugs, especially antipsychotics

Gastro-oesophageal reflux

Protein–energy malnutrition

Enteral nutrition, nasogastric tube

Causative Agents

A wide variety of infectious agents may be responsible for respiratory infections in the elderly. Their identification is often difficult in the acute phase of infection, especially in frail elderly patients.

Many bacteria might provoke pneumonia. Streptococcus pneumoniae should be a major concern because it is the bacterium most commonly involved in community-acquired pneumonia requiring admission to hospital and its mortality rate is very high among the elderly. Other bacteria frequently involved are Gram-negative bacilli (especially in cases of aspiration, hospitalization or prior antibiotic treatment) and Staphylococcus aureus. Legionella pneumophila is rarer but often severe with a high mortality rate among elderly patients. The involvement of anaerobic bacteria seems fairly common, especially in aspiration-related pneumonia. Other bacteria may be involved, such as streptococci, staphylococci, Enterobacteriaceae, Haemophilus influenzae and Mycoplasma pneumoniae. Multimicrobial pneumonias are common in elderly patients. Hospital-acquired respiratory infections (nosocomial) are often severe because of the resistance of causative bacteria to certain antibiotics and because of the vulnerability of the patients, often weakened by the diseases that brought them to hospital. Mycobacteria, especially M. tuberculosis, can determine a subacute or chronic respiratory infection. Aspergillosis may be responsible for an infection in the pulmonary sequelae of tuberculosis or lung abscess. Fungal infections of the lung are very rare and relate to subjects with severe immunosuppression.

Viruses may be involved in 10–30% of community-acquired acute pulmonary infection and often occur in an epidemic, particularly in institutions. The agents involved are influenza (including in patients who received vaccination), respiratory syncytial virus, parainfluenza influenza, rhinovirus and adenovirus.

Patients’ age and context of care are factors that influence the frequency of the agents responsible for pneumonia requiring hospitalization. In older patients, S. pneumonia, H. influenzae and respiratory viruses are more frequently observed than in younger adults, whereas Legionella, Mycoplasma and Chlamydia spp. are less frequent. In nursing home patients, aspiration pneumonia, Gram-negative enteric bacilli and multiple anaerobic agents are more frequently observed than in age-matched persons.

In hospital-acquired pneumonia (nosocomial), S. aureus, Pseudomonas aeruginosa and enteric Gram-negative bacteria are frequently observed, in addition to resistance to antibiotics. Also, pneumonia might be encountered in patients recently treated with antibiotics, together with complex and/or resistant germs including polymicrobial infection.

Clinical Presentation of Pneumonia in the Elderly

The classical features of acute lobar pneumonia with general malaise, frank hyperthermia, cough and chest pain are rarely complete in the elderly: initially, fever and cough are absent in 30–40% of cases. In many cases, the picture is not typical, with a gradual onset of less marked signs leading to a delayed diagnosis. Elders with pneumonia usually have several respiratory or non-respiratory symptoms, but each of them might be missing. Respiratory symptoms comprise cough, productive or not, purulent sputum, dyspnoea, chest pain and haemoptysis. Non-respiratory symptoms usually comprise fever, anorexia, chills and sweats.

Examination of the patient can show the following findings: tachypnoea (respiratory rate >30 min−1) tachycardia (heart rate >110 min−1), fever and hypothermia. Classic auscultatory findings (localized crackles) are very suggestive of the diagnosis of pneumonia, but they may be absent or poorly recognized, because they are very discrete or because of hypoventilation or insufficient cooperation of the patient. The existence of wheezing indicating bronchial obstruction is common.

Other clinical presentations of pneumonia are possible. Severe sepsis with shock, hypotension, cold and clammy skin, altered consciousness and hypothermia should call for an examination of the lungs. Intestinal symptoms are sometimes prominent: abdominal pain, nausea, vomiting, paralytic ileus and diarrhoea. There can also be an isolated delirium or cardiac events such as onset of arrhythmia (atrial fibrillation) or heart failure.

Certain clinical presentations can suggest a specific aetiology. The flu syndrome with headache, diffuse myalgia, arthralgia, pharyngitis and rhinorrhoea orients towards a viral aetiology, especially in an epidemic context. The context of weight loss in recent weeks or months should prompt a search for tuberculosis.

Differential Diagnosis of Lower Respiratory Tract Infection

Diseases whose clinical presentation can mimic that of pneumonia are numerous, and are outlined below.

Bronchitis

Bronchitis is frequently misdiagnosed as pneumonia. Acute bronchitis shares many symptoms with pneumonia, especially productive cough with purulent sputum. Usually, marked general signs are infrequent and there are no localized crackles. Classically, it is important to distinguish acute bronchitis from pneumonia (Table 47.2) because antibiotics are not indicated for bronchitis occurring in persons free from chronic obstructive pulmonary disease. In fact, in elderly subjects, the distinction between these two entities is sometimes difficult in the initial stage of infection. Indeed, in some subjects with pneumonia, temperature might be normal fever and may be missed and pulmonary auscultation might be difficult. Also, performing a chest radiograph is an important element in differentiating the two diseases. However, it is almost impossible to obtain a chest CT for every outpatient with symptoms of respiratory infection. A more feasible strategy consists in obtaining a chest radiograph 2–3 days after the beginning of the treatment in every patient with a suspected diagnosis of pneumonia: at present, the absence of a chest image suggestive of pneumonia should lead to the consideration of other diagnoses.

Table 47.2 Main findings in bronchitis and pneumonia.

	Bronchitis	Pneumonia
Marked asthenia, fever >38.5 °C, chills, tachycardia	Infrequent	Frequent
Cough	Yes	Yes
Increased respiratory rate at rest	Infrequent (except in COPDa)	Frequent
Lung auscultation	Normal or diffuse wheezes	Localized crackles/wheezes
Leukocytosis	Normal or slightly increased	Normal or increased
Chest radiograph	Normal	Opacity or opacities, pleuritis (may be normal at a very early stage)
Chest computed tomography (CT)	Normal	Lung parenchymal opacities, pleuritis
Deterioration of a pre-existing condition	Infrequent (except in COPD)	Frequent

aCOPD, chronic obstructive pulmonary disease.

Exacerbation of Chronic Obstructive Disease

Exacerbation of chronic pulmonary obstructive disease (COPD) might also be confounded with pneumonia. Exacerbation of COPD is defined by the worsening of cough, expectoration and/or dyspnoea and is easily recognized when COPD has been previously diagnosed. When the diagnosis of COPD has not been established, it is usually suspected by the association of smoking and a history of chronic bronchitis and dyspnoea. Exacerbations can be provoked by non-infectious causes, but also infectious causes including acute bronchitis or pneumonia. Antibiotics are indicated in severe exacerbations defined by an increase in dyspnoea and sputum purulence and volume, and also in exacerbation occurring in severe COPD with chronic respiratory failure.

Heart Failure and Pulmonary Embolism

Heart failure associated with other infectious diseases (endocarditis, urinary tract infection) or a non-infectious disease responsible for fever may be confounded with pneumonia. Plasma brain natriuretic peptide (BNP) determination helps to distinguish dyspnoea related to heart diseases (BNP >300 pg ml−1) from that related to lung diseases. In elderly people, it is fairly common to observe concomitantly heart failure and pneumonia. Pulmonary embolism can share symptoms with pneumonia such as fever, cough, chest pain and dyspnoea. The normal lung fields on chest radiograph, the context favouring venous thromboembolism or the presence of clinical signs of venous thrombosis suggest the diagnosis of pulmonary embolism. The pulmonary infarction secondary to pulmonary embolism leads to signs shared with those of pneumonia and is very often the site of secondary infection.

Cancer and Other Diseases of the Lungs

Lung cancer can be revealed by a respiratory infection. Massive loss of weight and marked anorexia, the persistence of the radiological image at 12 weeks after the infectious episode and high exposure to tobacco or asbestos are points that must lead to the consideration of the diagnosis of lung cancer and require bronchoscopy and/or a chest CT scan. Other diseases affecting the lungs can manifest the presentation of a lower respiratory tract infection: drug-related pneumonia (amiodarone, carbamazepine), lipid pneumonia (inhalation of a paraffin-based laxative), Wegener’s granulomatosis, Churg–Strauss disease and other autoimmune diseases (rheumatoid arthritis, Sjögren’s syndrome, coeliac disease). In these situations, the outcome after antibiotic treatment is not the same as that observed during a respiratory infection, which leads to consideration of these diagnoses and that of an infection resistant to prescribed antibiotics.

Hospitalization and Further Investigations in Elderly Persons with a Suspected Diagnosis of Community-Acquired Pneumonia

Facing suspected pneumonia, physicians must quickly answer two questions:

Should the patient be referred to hospital?
Are additional tests required?

The answers to these questions depend on the severity of the disease, the patient’s frailty and the context of care, and guide the type of treatment for the pneumonia.

Referral to Hospital of an Elderly Person with Suspected Pneumonia

There are three main reasons that prompt referral to hospital.

First, the diagnosis of pneumonia is unclear and a severe disease is also suspected, such as pulmonary embolism or heart failure. In these conditions, the use of blood tests, ECG and chest X-ray is mandatory in order to select appropriate management.

Second, the diagnosis of pneumonia is likely, but conditions to treat the patient in their usual context of life (home or nursing home) are not fulfilled. This applies not only for the administration of anti-infective treatment but also for general support of care such as help with activities of daily living, prevention of pressure sores and dehydration and for appropriate follow-up.

The third reason is related to the severity of pneumonia. This can be assessed using simple tools such as the CRB-65 scale (Table 47.3) or the pneumonia severity index (PSI). The scores given by these scales are indicators of mortality rates and can be used to identify low-risk patients who can be treated at home. Stratification of the risk given by the PSI is more precise than that given by the CRB-65. The CRB-65 is a simplified version of another scale, CURB-65, which contains an additional item related to plasma urea and is not suitable for the clinical assessment of patients without blood testing. Although the CRB-65 seems to be simpler, mental status requires the use of another scale, the Abbreviated Mental Test score, which includes 10 more items. The PSI items that can be obtained clinically are listed in Table 47.4

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