Approach
OP is an inflammatory lung disease, so the general approach is to treat the inflammation. Corticosteroid therapy is the best option. The amount and length of treatment depend on the severity of disease and response to the medication. In some situations, OP can be monitored without treatment. Pulmonary rehabilitation and an exercise program are helpful after the initial phase.
Severity of OP is determined by shortness of breath, extent of radiographic involvement, and pulmonary function tests, such as diffusing capacity <50% predicted and oxygen desaturation <85% during a walking exercise.
Rapidly progressive OP
Rapidly progressive OP begins with a flu-like illness proceeding to rapid progression of shortness of breath and respiratory failure within a few days. The patient is admitted to the ICU, supported with mechanical ventilation, and given intravenous corticosteroid therapy. This disorder may also be referred to as acute fibrinous organizing pneumonia (AFOP).[57]
It is the author's experience that this type of OP is generally treated the same as acute interstitial pneumonia but requires high doses of corticosteroids and cyclophosphamide.
Cryptogenic OP
Corticosteroid therapy is the treatment of choice for cryptogenic OP. Oral prednisone is prescribed at a higher dose (i.e., 40-60 mg/day) and tapered over 6 months.[58]
Severity is determined by symptoms of shortness of breath, extent of radiographic involvement, and diffusing capacity of <50% predicted. A total of 6 months of treatment may be effective for most patients, although 1 year may be required. About 5% percentage of patients may require intermittent doses for 3 to 5 years and this does not appear to affect mortality or morbidity.[58]
Mild disease may respond to macrolide antibiotics.[59] However, present studies are all observational and macrolides in cryptogenic OP need to be investigated in clinical trials. Erythromycin was used successfully in 6 Japanese women, with 1 responding at 2 months and 5 responding at 3 months.[60] Clarithromycin was also used successfully.[59] Azithromycin may also be effective. Macrolides may be useful for prevention of recurrence.
Secondary OP
Drug-related OP is reversible with drug cessation and/or corticosteroid therapy, depending on the severity of the disease. If symptoms are not severe, the causative drug could be stopped and any improvement noted. However, if symptoms are moderate or severe, the causative drug should be stopped and corticosteroids started immediately.
Toxin-exposure OP can be treated by immediately avoiding all contact with the toxin and prescribing corticosteroid treatment.
Postradiation OP occurs in all regions of the lungs and will resolve without treatment or with corticosteroid therapy, depending on the severity of the OP.[22]
In postinfectious OP, the underlying infection either resolves on its own (some viral pneumonias) or is treated with appropriate antibiotics or antimalarials. Corticosteroid therapy is usually helpful and usually results in complete resolution.
When OP is associated with rheumatologic or connective tissue disorders, it is often responsive to corticosteroid therapy.
Failure of corticosteroid treatment
If prednisone is not effective or its dose cannot be weaned below 40 mg/day, azathioprine, and cyclosporine have been used with variable success as corticosteroid-sparing agents.[61]
In these situations, it is important to confirm that the primary process is OP (no honeycombing by high-resolution computed tomography scan) as many patients with seemingly corticosteroid-resistant OP do not have primary OP but have an underlying fibrosing process, such as interstitial pneumonia or nonspecific interstitial pneumonia, not responsive to corticosteroid therapy. Here, OP is a secondary inflammatory lesion, responsive to corticosteroid therapy.
Treatment of recurrent OP
OP may recur in up to one third of patients. The symptoms will be the same as the initial episode, and the radiograph usually has the same pattern, although new lung regions may become involved.
If an OP recurrence has been established with recurrent symptoms, recurrence of radiographic findings, and deteriorating diffusing capacity, prednisone is reinstituted at 20 mg higher than the dose at the time of recurrence. This new dose is given for 3 months, then tapered.[58] A second and third recurrence can be treated in the same way.
In very rare situations, lung transplantation may be necessary for patients who do not respond to treatment or have an unusual or hybrid form of OP.
Pulmonary rehabilitation
Rehabilitation is an important part of managing the mid-to-late phase of OP (after the initial few days of treatment, with the patient ambulatory and with improving symptoms and radiographic findings). It introduces an exercise program for improving muscle conditioning, muscle oxygen efficiency, and sense of well-being. Patients also receive guidance for an ongoing exercise program at home or at a commercial exercise facility.
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