Surfactant therapy for the treatment of neonatal respiratory distress syndrome has led to increased survival and less morbidity in preterm infants (1). We conclude that surfactant nebulization during HFV improves lung function in rabbits with severe respiratory failure, without improving distribution, but with less effects on blood pressure and cerebral blood flow, when compared with surfactant instillation. Cerebral blood flow decreased with a maximum of 27% (10-37%). Nebulization did not affect blood pressure. Instillation resulted in a drop of mean arterial blood pressure of 17% (8-31%), and an even more pronounced drop in cerebral blood flow of 39% (18-57%). Surfactant deposition after nebulization was 9.8%. Both treatments resulted in nonuniform distribution. Partial arterial CO 2 tension decreased after instillation from 6.1 kPa (5.3-7.1 kPa) to 4.8 kPa (3.9-5.6 kPa), and during nebulization, after an initial rise, it decreased from 6.3 kPa (5.3-7.4 kPa) to 4.9 kPa (4.4-5.6 kPa). We found that after instillation partial arterial O 2 tension increased from 7.0 kPa (95% confidence interval, 6.3-8.0 kPa) to 34 kPa (16-51 kPa), and during nebulization from 7.0 kPa (6.0-9.0 kPa) to 46 kPa (27-58 kPa). Six other rabbits did not receive surfactant (control, HFV only). Technetium-99m-labeled surfactant (Alveofact, 100 mg/kg of BW) was nebulized or instilled ( n = 6 each). HFV was applied: frequency = 8 Hz, mean airway pressure = 12 cm H 2O, amplitude = 100%, fraction of inspired O 2 = 1.0. Therefore, severe respiratory failure was induced by lung lavages in 18 rabbits. The aim of this study was to compare the effect of surfactant nebulization versus instillation during HFV on lung function, surfactant distribution, and cerebral blood flow. We hypothesize that the combination of HFV and surfactant nebulization may benefit lung deposition of surfactant and consequently, lung function. High frequency ventilation (HFV) has been shown to improve lung aeration. However, efficiency of nebulization is low, and lung deposition seems to depend on lung aeration. Surfactant nebulization improves lung function at low alveolar doses of surfactant.
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