Etiology of Allergic Alveolitis

(Great Britain—The Practitioner, March 1998, p. 200.) In susceptible persons, inhaled protein or spores can cause an immunologic response in the peripheral bronchioles and alveoli, leading to severe pulmonary fibrosis. This condition (allergic alveolitis) is usually caused by occupational exposures or close contact with birds, such as pets or racing pigeons. The most common form is farmer's lung, which results from inhalation of spores of thermophilic actinomycetes from moldy hay or mushroom compost. Industrial causes of allergic alveolitis include isocyanates (particularly in paint and polyurethane manufacture) and metal fumes, particularly cobalt. One term for the disease, “bird fancier's lung,” reflects its association with keeping parakeets or pigeons as a hobby. The allergen in avian cases appears to be avian IgA on droppings and the coating of feathers. Poultry farmers are not exposed to high levels of antigen because nonflying birds do not produce or disseminate sufficient levels. Allergic alveolitis develops slowly and is usually initially misdiagnosed as recurrent respiratory infection. Once the disease is suspected, serum levels of IgG antibodies confirm the diagnosis. Serum elevation of leukocytes and computed tomographic scanning of the lungs are usually also necessary to make the diagnosis. Management depends on limiting exposure to the allergen, improving lung function and treating acute episodes with steroids.

Travel Advice for Patients with Heart Disease

(Great Britain—The Practitioner, February 1998, p. 130.) In addition to routine immunization and advice about health aspects of travel, patients with heart disease have other specific requirements and considerations when undertaking trips. Dehydration precipitated by sweating and gastrointestinal upset may complicate diuretic therapy and impair cardiac function. Patients should be advised to weigh themselves daily to monitor fluid balance and to adjust fluid intake and diuretic therapy accordingly. Changes in diet may complicate sodium and potassium balance and contribute to problems with coagulation if vitamin K intake and absorption are compromised. In selected patients, beta-blocker therapy may reduce angina or arrhythmias resulting from anxiety or exertion. Patients receiving amiodarone therapy may experience photosensitivity and should be cautioned about avoiding sunburn. Unless there is a specific contraindication, patients should not be discouraged from traveling, provided appropriate measures are taken to anticipate and minimize the risk of complications.

Use of Antidepressant Medications

(Great Britain—The Practitioner, January 1998, p. 24.) Depression may affect one third of adults at some point and is a common issue in primary care. Although the newer anti-depressant medications are believed to have fewer side effects than traditional medications, more than one quarter of patients stop taking the newer medications, and at least 15 percent attribute their cessation of treatment to unacceptable side effects. When a patient with confirmed depression does not respond to antidepressant therapy, the dosage and the patient's compliance should be verified. Other factors to be considered include concomitant drug or alcohol abuse, or a co-existing mental condition such as post-traumatic stress disorder or anxiety. In cases of resistant depression, an increase in the dosage or a change to a different class of medication may be required. Some patients benefit from the addition of lithium to the antidepressant regimen, but this therapy requires careful monitoring.

Guidelines for Use of Oxygen Therapy

(Great Britain—The Practitioner, March 1998, p. 167.) Long-term oxygen therapy reduces mortality in patients with chronic hypoxemia related to conditions such as chronic obstructive pulmonary disease, asthma, interstitial lung disease, cystic fibrosis and pulmonary hypertension. Oxygen therapy should only be used in patients who do not smoke. Long-term oxygen therapy reduces pulmonary artery pressure, improves sleep quality, reduces secondary polycythemia and arrhythmias, and improves psychologic status. The treatment is usually prescribed for patients with a partial oxygen pressure (PaO₂) ranging from 55 to 62 mm Hg (7.3 to 8.0 kPa), particularly if there is evidence of peripheral edema, nocturnal hypoxia, pulmonary hypertension or secondary polycythemia. Therapy usually is given 15 hours daily for the remainder of the patient's life and requires regular monitoring of blood gases and other indicators. Oxygen concentrators are the most convenient method of providing long-term oxygen therapy at home. Other devices are available for ambulatory oxygen use. Traditional cylinders are often used for “short burst” oxygen therapy to relieve acute breathlessness or exacerbations of dyspnea associated with exercise.