Blow-by as potential therapy for uncooperative children: an in-vitro study

Blow-by, a common form of nebulizer therapy, in which the device is held away from a child's face, has been dismissed as ineffective because studies have demonstrated incremental aerosol drop-off with increasing distances from the face. Many of these studies do not take into account differences among nebulizer systems. Using common, commercially available nebulizer systems, we defined the interaction of system components (nebulizer type, face mask configuration, and compressor characteristics) on aerosol delivery with and without blow-by.

A pediatric model consisting of a ventilated mannequin fitted with a filter (inhaled mass), and 3 commercial nebulizer/compressor/face mask systems (Pari Sprint, Respironics Sidestream, and Salter 8900) were used to nebulize budesonide (1.0 mg/2 mL) at 0, 2, and 4 cm from the face. Inhaled mass and the deposition on face, eyes, and mask were measured using high-performance liquid chromatography and reported as a percent of nebulizer charge.

At 0 cm, inhaled mass for the Pari, Respironics, and Salter systems was 5.33%, 1.14%, and 3.50%, respectively; at 4 cm from the face, inhaled mass decreased to 1.83%, 0.13%, and 1.14%. Facial (1.12%, 0.63%, and 2.94%) and eye (0.35%, 0.12%, and 0.68%) deposition varied significantly. Pari compressor/nebulizer flow rate was lower than Respironics and Salter (3.5 L/min vs 5.7 L/min and 5.9 L/min), resulting in longer run time (7.7 min vs 4.0 min and 5.3 min).

At 4 cm, the Pari system delivered more drug than Respironics at 0 cm, suggesting adequate therapy during blow-by for some systems. Our results indicate that pediatric aerosol delivery is a strong function of the nebulizer system as a whole, and not simply a function of blow-by distance from the face or nebulizer efficiency. In uncooperative children, blow-by can be an effective means of drug delivery with the appropriate nebulizer system.