Effect of salbutamol and inhaled sodium cromoglycate on the airway and neutrophil chemotactic activity in "fog"induced bronchospasm

Bronchial responsiveness to ultrasonic "fog" in occupational asthma due to low molecular weight chemicals

BACKGROUND

In a previous work we have demonstrated that the use of an indirect stimulus such as ultrasonically nebulized distilled water (UNDW, "fog") challenge, in addition to methacholine, in the assessment of occupational asthma due to TDI improves our ability in detecting sensitized subjects.

OBJECTIVE

In the present study we aimed to determine the validity of "fog" in the assessment of occupational asthma induced by various low molecular weight substances.

METHODS

Fourty subjects exposed to low molecular weight substances with work-related respiratory symptoms underwent methacholine, UNDW and specific bronchial challenge tests. Diagnosis of occupational asthma was made in 20 of 40 patients who developed bronchoconstrictive responses to the specific challenges (reactors). Sensitivity and specificity of UNDW alone, of methacholine alone, and of the combination of the two tests were determined at two different cutpoints of PD20FEV1 of methacholine, with the results of the specific challenge as the "gold standard".

RESULTS

Frequency and severity of bronchial hyperresponsiveness both to UNDW and to methacholine were significantly higher in reactors than in nonreactors. Ultrasonically nebulized distilled water had higher specificity (80% versus 60%) but lower sensitivity (65% versus 75% to 90%) than methacholine. As compared with methacholine alone, the combination in series of the two challenges (both challenges positive) substantially improved specificity (85% versus 60%).

CONCLUSIONS

In conclusion, in the assessment of low molecular weight chemical-induced asthma diagnosed with the specific challenge as the "gold standard," UNDW challenge proves more specific than methacholine for occupational asthma, but it is considerably less sensitive. The combination of the two challenges results in very high sensitivity and high specificity for occupational asthma, therefore, although further investigations are required for the definitive diagnosis, it should be regarded as a useful means to confirm objectively a suggestive history.

Bronchial responsiveness to ultrasonic fog in occupational asthma due to toluene diisocyanate

To determine the validity of ultrasonic nebulization of distilled water (UNDW, "fog") in comparison with methacholine challenge, in the assessment of toluene diisocyanate (TDI) asthma, we evaluated 75 subjects exposed to TDI with work-related respiratory symptoms. Subjects were submitted to bronchial challenge with methacholine at first, thereafter to UNDW inhalation and to specific challenge with TDI. The diagnosis of TDI-asthma was made in 30 of 75 patients (40 percent) who developed a bronchoconstrictive response to the specific challenge (reactors). Sensitivity and specificity of UNDW alone, methacholine alone, and of the combination of the two tests were determined with the results of the specific challenge with TDI as the "gold standard." Both frequency and severity of bronchoconstrictive response to UNDW (FEV1 decrease > or = 15 percent) and the degree (PD15 FEV1) and frequency of bronchial hyperresponsiveness to methacholine were significantly higher in TDI reactors than in nonreactors. The UNDW had higher specificity (82.2 percent vs 51.1 percent) but lower sensitivity (40 percent vs 76.7 percent) than methacholine. The combination in parallel (positivity of any of the two challenges) of methacholine and UNDW challenge did not change sensitivity to a great extent (80 percent vs 76.7 percent), whereas combination in series (positivity of both challenges) had considerably greater specificity (86.7 percent vs 51.1 percent) than methacholine alone. We conclude that in the assessment of TDI-asthma, the validity of UNDW challenge alone is limited since it is insufficiently sensitive. Instead, combining UNDW and methacholine challenge when methacholine is positive improves our ability in identifying subjects with TDI-asthma diagnosed with the specific challenge. This procedure constitutes a first objective confirmation of a suggestive history of TDI-asthma that is useful for clinical purposes. However, especially for medicolegal purposes, the definitive diagnosis requires the specific challenge.

Inhaled furosemide prevents both the bronchoconstriction and the increase in neutrophil chemotactic activity induced by ultrasonic "fog" of distilled water in asthmatics

Inhaled furosemide has been shown to prevent bronchoconstriction induced by inhalation of ultrasonic nebulization of distilled water (UNDW) in bronchial asthma. To evaluate whether inhaled furosemide also prevents the increase in serum neutrophil chemotactic activity (NCA) observed during UNDW bronchoconstriction, we measured NCA during UNDW challenge without (control) and immediately after inhalation of furosemide (40 mg) or placebo (saline) in 10 asthmatics responsive to UNDW, in a randomized, double-blind study. NCA was assessed by measuring the maximal distance reached by neutrophils in a filter when challenged with the subject serum in a Boyden chamber ("leading front"). UNDW inhalation produced a significant increase in NCA in each subject. Gel filtration chromatography on S400 column indicated that the NCA released were 600 to 700 kD. Saline had no effect on bronchoconstriction nor on NCA increase induced by UNDW in nine patients. Furosemide did not change baseline FEV1, but it prevented bronchoconstriction and NCA increase in nine patients. In the whole group the maximal decrease in FEV1 after UNDW was -31.1%, SEM 4.7 after saline and -7.5%, SEM 5.2 after furosemide, p less than 0.001, the maximal increase in NCA after UNDW was +52.9%, SEM 9.2 after saline and +3.8%, SEM 3.1 after furosemide, p = 0.001. These results indicate that inhaled furosemide prevents both the bronchoconstriction and the NCA increase induced by UNDW inhalation in most asthmatic patients. This finding adds support to the suggestion that furosemide acts on mast cells.