Small airway dysfunction in chronic hypersensitivity pneumonitis.
BACKGROUND AND OBJECTIVE
Lung biopsies from patients with hypersensitivity pneumonitis (HP) have demonstrated small airway (SA) involvement, but there is no information concerning SA function in HP, and it is unknown whether pharmacological treatment could modify its function. SA function in patients with chronic HP using ultrasonic pneumography (UPG) and impulse oscillometry (IOS) was explored. We also compared initial results with those obtained after 4 weeks of standardized treatment with azathioprine and prednisone.


METHODS
The study group consisted of adults with recent diagnoses of HP. All patients completed UPG, IOS, spirometry, body plethysmography, single-breath carbon monoxide diffusing capacity (DLCO ) and the 6-min walk test (6MWT). The fraction of exhaled nitric oxide (FENO ) was obtained to assess eosinophilic airway inflammation. Measurements were taken at diagnosis and after 4 weeks of treatment.


RESULTS
A total of 20 consecutive patients (16 women) with chronic HP participated in the study. Median age was 50 years (interquartile range (IQR): 42-54). At diagnosis, the UPG phase 3 slope was abnormally high, consistent with maldistribution of ventilation. For IOS, all patients had low reactance at 5 Hz (X5) and elevated reactance area (AX) reflecting low compliance, and only eight (40%) patients had elevated R5 (resistance at 5 Hz (total)) and R5-20 (resistance at 5 Hz-resistance at 20 Hz (peripheral)) attributed to SA resistance. In contrast, FENO parameters were within normal limits. After treatment, forced vital capacity (FVC), the 6-min walk distance and the distribution of ventilation showed significant improvement, although DLCO did not.


CONCLUSION
Patients with chronic HP have SA abnormalities that are partially revealed by the UPG and IOS tests. Lung volumes, but not gas exchange, improved after treatment with azathioprine and prednisone.
['Guerrero Zúñiga|Selene|S|0000-0003-1890-2849', 'Sánchez Hernández|Julia|J|', 'Mateos Toledo|Heidegger|H|', 'Mejía Ávila|Mayra|M|', 'Gochicoa-Rangel|Laura|L|', 'Miguel Reyes|José Luis|JL|', 'Selman|Moisés|M|', 'Torre-Bouscoulet|Luis|L|']
D000403:Airway Resistance D000542:Alveolitis, Extrinsic Allergic D000893:Anti-Inflammatory Agents D001379:Azathioprine D001682:Biological Availability D001944:Breath Tests D005260:Female D006801:Humans D008168:Lung D008297:Male D008875:Middle Aged D009991:Oscillometry D010991:Plethysmography D011239:Prednisolone D012129:Respiratory Function Tests D013147:Spirometry D013990:Tidal Volume D000070857:Walk Test
hypersensitivity pneumonitis bird fancier's lung interstitial lung disease pulmonary function test