[Safety of sputum induction in interstitial lung disease]

Sputum induction (SI) is a safe and effective technique to study airway inflammation in asthma and chronic obstructive pulmonary disease (COPD). However, it has the potential to induce bronchospasm and fall in arterial oxygen saturation (SaO2) in some patients and the safety of the method in interstitial lung disease (ILD) has not been determined. The aim of this study was to examine the effect of SI procedure on spirometric results and SaO2 in patients with ILD.

We studied prospectively 59 patients (33 males, 26 females) with different ILD (36 - sarcoidosis, 16 - hypersensitivity pneumonitis, 7 - idiopathic pulmonary fibrosis). Sputum was induced by 4 sequential 5-minute inhalations of 5% saline solution and FEV(1), FVC and SaO2 were measured at 5, 10, 15 and 20 minutes of induction.

The procedure was well tolerated, and none of the patients experienced excessive bronchoconstriction, defined as a fall in FEV1 of > or = 20%. Nine patients (15%) had a fall in FEV1 of > or = 10% from the baseline; a drop in FVC of > or = 10% from the baseline was observed in 10 subjects. The mean (SD) maximum per cent fall in FEV1 was 6,3 +/- 4,4%, and in FVC - 6,4 +/- +/- 4,6%. The maximum per cent fall in FEV1 did not correlate with baseline FEV1% predicted (r = -0,099). SaO2 was measured in 42 patients. There was a very small fall in SaO2 at 5, 10, 15 and 20 minutes of induction, although statistically significant (baseline SaO2 = 96,7 +/- 1,9% vs 95,8 +/- 2,4%, p = 0,002; vs 96,1 +/- 2,2%, p = 0,0114; vs 95,7 +/- 2,4%, p = 0,0016; vs 95,9 +/- 2,0%; p = 0,0038, respectively). No significant relationship was found between fall in FEV1, FVC or SaO2 after induction and diagnosis or smoking history.

Sputum induction is safe and well tolerated in patients with ILD.