Alterations in Airway Dynamics following Inhalation of Ultrasonic Mist

¹ Instructor in Medicine, Baylor College of Medicine; Medical Director of Inhalation Therapy, Ben Taub General Hospital, Houston
² Professor of Medicine and Chief, Pulmonary Disease Section, Department of Medicine, Baylor College of Medicine

In three separately designed studies, ultrasonically nebulized mists of distilled water, normal saline and 5 percent saline were administered to normal healthy subjects and patients with chronic obstructive pulmonary disease (COPD). The normal subjects reacted to the inhalation of distilled water and 5 percent saline with slight irritative cough but no change was observed in the values of FVC, FEV_1.0, airway resistance and pulmonary compliance following inhalation of any of the mists. The patients with COPD, however, complained of increased cough and wheezing with distilled water and 5 percent saline mist. In addition there was slight increase in airway resistance in those patients who tolerated the ultrasonic mist poorly, especially when 5 percent saline aerosol was used. These side effects of mist inhalation in the COPD patients were generally of short duration and could be reversed with inhalation of isoproterenol (Isuprel) combined with coughing and raising of sputum. Further, subjective tolerance of inhaled mist by the COPD patients was better and increase in airway obstruction less marked when the ultrasonic mist was inhaled at nebulizer outputs below 3.0 ml/min; at 6.0 ml/min output from the nebulizer, the ultrasonic mist was visually very dense and patients were unable to breathe the same comfortably. It is therefore suggested that patients with COPD receiving ultrasonic mists for any reason be closely monitored and the quantity of the inhaled mist adjusted to a suitable therapeutic level, preferably below 3.0 ml/min nebulizer output, which is comfortable for the patient.