No abstract

No abstract

To evaluate the efficiency and distribution of ultrasonic nebulized versus instilled surfactant in the treatment of surfactant deficiency at varying degrees of maturation, twin or triplet lamb fetuses were delivered at 125 to 137 d gestational age and received nebulized natural surfactant (Neb Only), instilled surfactant followed by a second instilled dose (Inst/Inst), instilled surfactant followed by nebulized surfactant (Inst/Neb), or no surfactant (Control). The lambs were ventilated for 6 h. Twenty-eight lambs were categorized into two groups (low compliance versus moderate compliance) based on initial physiologic lung characteristics. Efficiency of deposition of nebulized surfactant directly correlated with the compliances and ventilatory efficiency indices measured at 15 min of age. The low-compliance group (Low Comp) had significantly lower efficiency of surfactant deposition (7.6 +/- 1.6%) than did the moderate-compliance group (Mod Comp) (23.4 +/- 2.5%) (p < 0.01). Overall, instilled surfactant had a reasonably homogeneous distribution, whereas nebulized surfactant had a less homogeneous distribution, except for the Low Comp, Inst/Neb group, which had a distribution pattern similar to that for instilled surfactant. The potential for nebulized surfactant therapy for respiratory distress syndrome (RDS) may be limited by the nonhomogeneous nature of ventilation in the preterm lung.

Mucociliary function is a primary defense mechanism of the tracheobronchial airways, and yet the response of this system to an inhalational hazard, such as ozone, is undefined in humans. Utilizing noninvasive techniques to measure deposition and retention of insoluble radiolabeled particles on airway mucous membranes, we studied the effect on mucus transport of 0.2 and 0.4 ppm ozone compared with filtered air (FA) in seven healthy males. During 2-h chamber exposures, subjects alternated between periods of rest and light exercise with hourly spirometric measurement of lung function. Mechanical and mucociliary function responses to ozone by lung airways appeared concentration dependent. Reduction in particle retention was significant (P less than 0.005) (i.e., transport of lung mucus was increased during exposure to 0.4 ppm ozone and was coincident with impaired lung function; e.g., forced vital capacity and midmaximal flow rate fell by 12 and 16%, respectively, and forced expiratory volume at 1 s by 5%, of preexposure values). Regional analysis indicated that mucus flow from distal airways into central bronchi was significantly increased (P less than 0.025) by 0.2 ppm ozone. This peripheral effect, however, was buffered by only a marginal influence of 0.2 ppm ozone on larger bronchi, such that the resultant mucus transport for all airways of the lung in aggregate differed only slightly from FA exposures. These data may reflect differences in regional diffusion of ozone along the respiratory tract, rather than tissue sensitivity. In conclusion, mucociliary function of humans is acutely stimulated by ozone and may result from fluid additions to the mucus layer from mucosal and submucosal secretory cells and/or alteration of epithelial permeability.