Small Airway Involvement in Patients With Chronic Hypersensitivity Pneumonitis
Status:
Completed
Trial end date:
2017-11-20
Target enrollment:
Participant gender:
Summary
Hypersensitivity pneumonitis (HP) is a syndrome with variable clinical presentation in which
lung inflammation is caused by inhalation of specific organic antigens or low molecular
weight particles in previously sensitized individuals. Systemic symptoms may or may not be
present. Chronic HP represents the final stage of the disease, caused by prolonged exposure
to a particular antigen, leading to pulmonary fibrosis. In chronic HP, pulmonary function
tests (PFTs) commonly present a restrictive ventilatory pattern, with decreased diffusion of
carbon monoxide (DLCO). Some patients can also have obstructive disorders with expiratory
flow limitation, due to obstruction of the small airways typically caused by bronchiolar
involvement in this pathology. However, PFTs are relatively insensitive for detecting small
airway involvement when there is concomitant interstitial fibrosis. First, conventional PFTs
may be normal in patients with small airway involvement, since they contribute to less than
30% of the total airway resistance. In addition, damage to the small airways in HP is
generally occurring parallel to areas of focal fibrosis - even when small airways are
involved, these regions can be completely ignored, since they are excluded from ventilation.
In summary, traditional PFTs are not sufficiently sensitive to detect diffuse small airway
involvement in these diseases. In these cases, other functional tests, such as forced
oscillation technique (FOT) and high resolution computer tomography (HRCT) scans of the chest
with expired studies, could be used for this purpose.
This will be a cross-sectional study, which will include the following evaluations in 28
patients with HP recruited from our clinic:
- Clinical variables: (A) demographic and anthropometric data; (B) Clinical data: Onset of
symptoms and time of diagnosis
C) Dyspnea score:
D) Smoking: * Current or former smoker * Smoking history (number of cigarettes smoked per day
and for how long);
- Spirometry with forced and slow maneuvers before and after bronchodilator (salbutamol);
- Plethysmography to measure lung volumes;
- Diffusion capacity of carbon monoxide (DLCO);
- High-resolution chest CT with expiratory scans;
- Six-minute walk test;
- Cardio-respiratory test using a maximal incremental treadmill.
- Forced oscillation technique (FOT).