Sir.—The article by Outwater et al1 in the May 1988 issue of AJDC was noted with great interest. This excellent report outlines the methods and techniques developed at Boston's Floating Hospital for delivering ribavirin (Virazole) during ventilation with the Healthdyne 102 ventilator (Healthdyne Inc, Marietta, Ga). Demers et al2 described alternative circuitry for use with pressure- and volume-preset ventilators.
Several differences between the circuitry employed by Outwater et al and the systems described by Demers and coworkers can be observed. Of particular significance is the presence of a one-way valve interposed between the ventilator and the junction of the ventilator's inspiratory tubing, and the outflow tube of the small-particle aerosol generator (SPAG) (Viratek, ICN Pharmaceuticals, Costa Mesa, Calif) in the configuration developed by Outwater and colleagues.
The purpose of the one-way valve at that position is to prevent retrograde flow from the small-particle aerosol generator to the