Alterations in Airway Dynamics following Inhalation of Ultrasonic Mist

Abstract

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 die with slight irritative cough but no change was observed in the values of WC, FEVl 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 died water and 5 percent saline mist. In addition there was slight increase in airway resistance in tbose 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. ltrasonic mist is commonly used in clinical U practice to increase the humidi6cation of the inspired air. The motive force for nebulization of liquids is the high frequency vibrational energy generated by a piezoelectric crystal, which in turn yields a mist, the volume output of which can be varied between 0.5 ml and 6.0 ml per minute.'s2 While the clinical applicatio~ of ultrasonic mist therapy and its beneficial effects are well recogni~ed,~ more recent studies reported by Cheney and Butlei' and Pflug and co-workers5 showed an increase in airways obstruction following inhalation of ultrasonic mist in patients with chronic obstruc