THE MEASUREMENT OF FLUID DEPOSITION IN HUMANS FOLLOWING MIST TENT THERAPY

Abstract

Mist tent therapy is used in the treatment of cystic fibrosis to deposit fluid droplets in the terminal airways of the lung. It is assumed that water deposited in the peripheral airways thins the secretions and facilitates their clearance from the lung. The distribution of inhaled mist was assessed by labelling aerosol from an ultrasonic nebulizer with technetium 99m and measuring the distribution of radioactivity in a subject who breathed the aerosol in the mist tent. Subjects breathed from the tent for 1 hour after which the total uptake of fluid was measured by a scintillation probe and its distribution with a rectilinear scanner. Three different ultrasonic nebulizers were used. In some studies 10% propylene glycol in water was used as the nebulizing fluid. In six healthy adults and eight patients with cystic fibrosis, less than 5% of the activity nebulized and distributed in the tent entered the body. Of this, 90% of the inhaled radioactivity initially lodged in the nasopharynx and rapidly appeared in the stomach. Very little activity was detected over the lungs. These results indicate that very little aerosol fluid from a mist tent is directly deposited in the terminal airways of the lung.