The mortality of untreated pulmonary embolism in patients with intermediate probability lung scans.

quiet, single room for the 24-h test period; studies were done at 1:00 PM and 1:00 AM, both in supine position with a closefitting face mask and nasal packing to ensure mouth breathing. Subjects inhaled nebulized saline solution (control) and citric acid, delivered by an ultrasonic nebulizer. The citric acid was dissolved in the saline solution, providing incremental concentra¬ tions from 0.3 to 360 mg/mL. The subject's cough was recorded with a lapel microphone attached to the clothing, and connected to a tape recorder. The cough threshold was defined as the concentration at which the subject coughed at least five times, provided he or she also coughed at subsequent higher concen¬ trations.3 The threshold concentration of citric acid was higher in patients than in control subjects during the day (25.1 [± 1.3] mg/mL vs 6.3 [±1.3] mg/mL; p < 0.01) and during the night (63.1 [±1.3] mg/mL vs 15.8 [±1.3 mg/mL; p < 0.01). Further¬