Both the local and systemic defence mechanisms are altered in old age. There is impairment of cough and other respiratory reflexes. Mucociliary function of the respiratory tract is depressed and the clearing of aspirated particles is delayed. The immunological defences involving different cells including the lymphocytes and macrophages are altered. There is decreased phagocytosis and microbial killing by the macrophages. Both antigen presentation and cytokine production are impaired.
In view of the impairment of both non-immunological and immunological mechanisms, the chances of occurrence of respiratory infections are increased and their resolution delayed.
In addition to the above listed factors which predispose to disease occurrence, there are several other variables which influence the clinical spectrum and behaviour of different respiratory diseases. The cumulative effect of exposure to different disease-producing agents which has taken place in the preceding years, becomes manifest. Tobacco smoking, occupational and environmental exposures are important examples of some of these exposures. Similarly, the presence of comorbid conditions such as diabetes mellitus, hypertension and other cardiovascular diseases, presence of gastrointestinal and neurological illnesses affect the occurrence and management of respiratory diseases.
Pneumonias: Pneumonia is the most frequent respiratory infection of old age. The factors predisposing to respiratory infection have been listed earlier. Pneumococcal pneumonia is perhaps the commonest form of community acquired pneumonia. Nosocomal pneumonias in hospitalized patients occur due to Klebsiella and other Gram negative bacilli or sometimes, staphylococci.
Haemophilus influenzae, influenza, other viral and mycoplasma pneumonias are also common especially in patients with chronic obstructive pulmonary disease (COPD). Both viral and bacterial pneumonias constitute an important cause of increased morbidity and mortality.
Diagnosis of pneumonia is suspected from the clinical picture of fever, increased malaise, fatigue and weakness, cough with or without sputum production and/or hemoptysis. Diagnosis is established on presence of polymorphonuclear leucocytosis and chest roentgenological findings. Sputum should be examined by Gram’s staining and culture. If sputum is not available, or patient shows poor (or no) response to treatment, bronchoscopic examination or other invasive procedures may be required to obtain material for microbiological investigations.
Treatment is administered with antibiotics and other supportive measures. Choice of antibiotic depends upon the causative organism which is either established or suspected. Empirically, a combination of amoxycillin and clauvulanic acid or macrolides are preferred for community acquired infections. Second generation cephalosporins or quinolones may also be used. For nosocomal pneumonias, parenteral antibiotics are required. A combination of an aminoglycoside and a second or third generation cephalosporin is used until a microbiological guidance becomes available. Treatment is required to be reviewed every 48 hours or so.
Tuberculosis: Old age is particularly susceptible to tuberculosis. It is mostly reactivation of a previously quiescent tubercular focus due to a recent insult or impairment of immunological defences which causes active tuberculosis. Primary tuberculosis due to reinfection may also occur. Symptoms are relatively fewer and physical examination nonspecific. Tuberculin test cannot be relied upon in view of its being positive in over 50 percent of healthy population of this country. Moreover, it is frequently negative in old age even in the presence of an active disease.
Diagnosis of tuberculosis is generally made on clinical features and roentgenological appearances of upper lobe infiltrates with/without cavitation, or a diffuse miliary pattern. Sputum, if available, offers the best choice for diagnosis. Smear examination if repeated thrice, is likely to be positive in upto 60 percent of patients with active tuberculosis. Many a patients either do not produce sputum or are unable to cough it out. Bronchoscopy is helpful in such cases and examination of bronchial secretions offers an additional positivity of about 20 to 30 percent. Transbronchial lung biopsy is of great help in patients with diffuse miliary disease.
Tuberculosis is managed on similar lines as in any other case. The initial intensive phase involves administration of four potent drugs (isoniazid, rifampicin, pyrazinamide and ethambutol) for two months followed by four months of isoniazid and rifampicin. Aminoglycosides such as streptomycin and amikacin are avoided in old age. Similarly, ethambutol dosage should not be high and duration not prolonged for fear of ocular toxicity. It may not always be easy to monitor for visual field defects in old age.