Mist Tent Therapy of Cystic Fibrosis

Cystic fibrosis is a hereditary disease of children, adolescents, and young adults. Until recently this disease, which involves the exocrine glands of the body, caused death at an early age. Now, thanks to early diagnosis1 and treatment: some children with cystic fibrosis may lead almost normal lives.3 A primary reason for the improved outlook for patients with cystic fibrosis has been improved methods for preventing and treating the pulmonary aspect of this disease. The pulmonary involvement is due to abnormal secretions which the mucus glands of the respiratory tract produce. These mucous secretions accumulate in the tracheobronchial tree. Airways are obstructed and air trapping results. Infection occurs in the stagnant mucus and may produce damage to the lining of the tracheobronchial tree. Progressive infection causes destruction of the bronchial walls and adjacent lung tissue. About 95 per cent of the overall problems in children with cystic fibrosis are due to the pulmonary involvement. One of the most effective therapeutic measures for preventing and treating the obstructive pulmonary lesion of cystic fibrosis is mist tent therapy used during sleeping ho~rs.~ The objective of such therapy is to wet and thin the bronchial secretions to facilitate their clearance from the respiratory tract. This is accomplished by the addition of small particles of water or of water containing mucolytic substances to the secretions at the site of their production or accumulation. Since the obstructive lesion starts in the smaller bronchi and bronchioles and progresses toward the larger bronchi, effective therapy requires use of a nebulizer which provides small mist particles which will deposit in the peripheral bronchial tree. This can be accomplished with both jet-type and ultrasonic nebulizers5 Of equal importance is the density of the mist inhaled. The surface area of the tracheobronchial tree at any age is measured in square meters. To wet and thin secretions covering such a large area requires deposition of a large amount of water, and this can only be accomplished by inhalation of a dense mist over a long (8-10 hour) period of time. Use of a mist tent during sleeping hours permits such therapy with a minimum of inconvenience for the patient. Many factors influence the water content of the air in a mist tent and the effectiveness of mist tent therapy (Table I). Condensation, rain-out and impaction of particles on the tent walls all reduce the water content of the air