An 8-year-old boy with cystic fibrosis has copious, tenaciou…

An 8-year-old boy with cystic fibrosis has copious, tenacious, purulent secretions. He is receiving 2.5 mg albuterol every 4 hours and dornase alfa (Pulmozyme) once a day. Laboratory results on a sputum sample indicate the patient has a Pseudomonas infection. Which of the following is most appropriate?