Hypoxemia in young asthmatics with mild airway obstruction by methacholinechallenge

We studied 12 asymptomatic conscripts affected by bronchial asthma to evalu ate the level of hypoxemia and its relationship with bronchial obstruction induced by methacholine (Mch) challenge, Arterial blood samples were obtain ed before and immediately after bronchial challenge. The range of decrease of forced expiratory volume/forced vital capacity x 100 in 1 second of expi ration (FEV1), the absolute value reported as a percentage of the baseline value, after Mch challenge was from 21% to 36%. The mean decrease of arteri al oxygen tension was 27 mm Bg (from 11.4 to 39.8 mm Hg), the mean decrease of hemoglobin saturation was 3.53% (from 0.4 to 7.2), and the mean increas e of alveolar-arterial gradient for oxygen was 28.2 mm Ng. We found a signi ficant correlation between the prechallenge and postchallenge differences o f arterial oxygen tension and FEV1 (DFEV1P), which was expressed as a perce ntage of the predicted value. In conclusion, the Mch challenge seems to be a safe test, and the decrease of arterial oxygen tension can be sufficientl y predicted by DFEV1P.