Clinical Trial: Small Airway Involvement in Patients With Chronic Hypersensitivity Pneumonitis
Study Status: Recruiting
Recruit Status: Recruiting
Study Type: Interventional
Official Title: Evaluation of Small Airway Involvement in Patients With Chronic Hypersensitivity Pneumonitis and Its Impact on Exercise Limitation
Brief 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
Detailed Summary:
Hypersensitivity pneumonitis (HP) is a syndrome with variable clinical presentation, in which inflammation in lung parenchyma is caused by inhalation of organic antigens or specific low molecular weight substances in previously sensitized individuals. Systemic symptoms may or not be present. Chronic HP represents the final stage of this disease, where prolonged exposure to a particular antigen would lead to lung fibrosis. The list of new antigens is growing, but the main antigens responsible for this disease are exposure to mold and birds.
Not all exposed individuals develop HP. The pathophysiology involves initial exposure and a subsequent decrease in antigen tolerance. Genetic susceptibility can also modulate the immune response to a specific antigen.
There are no reliable epidemiological data on the incidence or prevalence of HP. Differences in the type of antigen sensitization, lack of standardized diagnostic criteria and underreporting are possible factors. In Mexico, one of the few population surveys showed an estimated incidence of 30 cases per 100000 inhabitants in 2 years (1988-1990); however, there are some bias that limit the extrapolation of data to other contexts.
The patient rarely associates the onset of symptoms with a relevant exposure, making it important to actively search for environmental factors against respiratory complaints. It is believed that intermittent exposure to an antigen, long-term exposure to a small load of antigen or a cumulative effect of multiple episodes of acute exposure can cause chronic HP. It is noteworthy that only a small proportion of patients with a single episode of acute exposure will develop chronic HP.
In chronic HP, the patient complains of dyspnea on exertion and dry cough
Sponsor: University of Sao Paulo General Hospital
Current Primary Outcome: Pletismography - forced expiratory volume in 1 second / forced vital capacity (FEV1/FVC) < 0.7, residual volume (VR) and VR/total lung capacity (TLC) values and changes with salbutamol [ Time Frame: One day visit ]
Original Primary Outcome: Same as current
Current Secondary Outcome:
- Air trapping in expiratory chest CT scans [ Time Frame: One day visit ]Expiratory / inspiratory mean lung attenuation ratio as a measure of air trapping
- Reactance and impedance of small airways through forced oscillation technique [ Time Frame: One day visit ]Reactance and impedance of small airways
Original Secondary Outcome: Same as current
Information By: University of Sao Paulo General Hospital
Dates:
Date Received: August 9, 2015
Date Started: September 2015
Date Completion: December 2017
Last Updated: October 24, 2016
Last Verified: October 2016
