To the Editor: The delivery of lidocaine via small-volume nebulizers (SVN) can be used as topical anesthesia for use during flexible bronchoscopy in infants and children. Although the SVN is small and easy to use, the rate of nebulization at different gas flow rates is not well known. Since the total amount of nebulized lidocaine delivered to pediatric patients in relation to time and flow rates is important to prevent lidocaine toxicity (1), we recently conducted an in vitro study that evaluated the rate of nebulization of lidocaine with differential oxygen flow rates. Five SVNs (Misty-Neb Nebulizer, Allegiance, IL) were studied. Each SVN was filled with 5 mL of 4% lidocaine and connected to a pediatric facemask. The SVN was connected to the dispensing oxygen at flow rates of 2, 3, 4, 5, 6, 7, 8, and 10 L/min, respectively. The dispensing oxygen was temporarily stopped at 5-min intervals and the lidocaine was allowed to settle in the SVN to measure the residual volume. On the basis of the results of this study (Fig. 1), the amount of lidocaine nebulized at different oxygen flow rates and time periods can be estimated. This information may be used to limit the possible maximum lidocaine delivered to the patient by adjusting gas flow rates and reducing time exposure. Other brands of SVN may need separate calibration, as this study only examined one particular brand.Figure 1: Rate of nebulization of lidocaine with varied oxygen flow rates.Ban Ch. Tsui, MD, MSC, FRCP(C)) Stephan Malherbe, MB, ChB, MMed, FCA(SA)