Comparison of bronchial responsiveness to ultrasonically nebulized distilled water (UNDW), methacholine, and ultrasonically nebulized distilled cold water (UDCW) in patients with sulfur mustard gas-induced asthma

OBJECTIVE To evaluate bronchial challenges using three different stimuli as screening tools for bronchial hyper-responsiveness in sulfur mustard gas-induced asthma. DESIGN Randomized, cross-over clinical study. SETTING University hospital. PATIENTS Eighteen veterans with mustard gas-induced asthma and 18 normal veterans as the control group. INTERVENTION Pulmonary function tests and inhalation challenges with ultrasonically nebulized distilled water (UNDW), methacholine, and ultrasonically nebulized cold water (UNDCW) were performed on all patients and subjects. RESULTS Six mustard gas-induced asthmatic veterans did not respond to a 20% in FEV(1) after distilled water (13.3%), and two of them (11.11%) did not respond with distilled cold water; all responded with methacholine. Only one healthy subject developed a PC20 FEV(1) after methacholine but did not with both distilled water and distilled cold water challenges. The asthmatic patients were sensitive to distilled water with a median PD20 of 7.24 +/- 3.83 ml (range 2.54 ml to 15.83 ml), and sensitive to cold water with a median PD20 of 6.42 +/- 6.24 ml (range 1.92 ml to 25.15 ml). The median PC20 methacholine was 1.90 +/- 1.88 mg/ml (range 0.14 mg/ml to 6.20 mg/ml). In patients with a positive response to the distilled water challenge test, no significant correlation was found between PC20 of methacholine and PD20 of distilled water (Rho = -0.34, p = 0.25), whereas in patients whose responses to distilled cold water (DCW) were positive, PD20 of distilled cold water (DCW) correlated well with PC20 of methacholine (Rho = -0.69, p = 0.006). CONCLUSION Overall, the methacholine challenge test is the best method to distinguish these asthmatic patients from normal subjects in this study. When compared to the methacholine challenge, although the airway response to ultrasonically nebulized distilled cold water test was somewhat less sensitive, it may be used as a simple, fast, inexpensive, and relatively reliable method to predict the absence of asthma in sulfur mustard gas-induced asthma.