 The study will terminate 60 minutes after the third aerosol administration. At that point, any further therapy will be at the discretion of the treating physician. Patients will be questioned about the occurrence of any side effects from levalbuterol treatment including palpitations, anxiety, nausea, vomiting or headache. Patients will also be questioned about the occurrence of any side effects from ipratropium, including dry mouth, dry eyes, and urinary retention. Patients will be withdrawn from the study at any point these side effects become intolerable to the patient or any time the patient so desires. Patients will also be withdrawn if they develop palpitations and have an ECG that demonstrates ventricular or supraventricular tachycardia. 