Breathing patterns and aerosol delivery: Impact of regular human patterns,and sine and square waveforms on rate of delivery

In vitro tests are commonly employed to assess nebulizer performance. Wheth er the square or sine waveforms employed during in vitro tests could alter the nebulizer performance compared to that observed when a patient breathes through the nebulizer is debatable. Accordingly, the aim of this in vitro study was to compare the rates of delivery from nebulizers with simulated h uman breathing patterns to those obtained with matching sine and square wav eforms. Regular human breathing patterns with tidal volumes (VT) of similar to 40, similar to 200, similar to 500, and similar to 800 mL were selected . Sine and square waveforms that matched the VT, peak inspiratory flow rate (PIF), breathing frequency (f), and inspiratory duty cycle (t(i)/t(tot)) o f the human breathing patterns were created with a breathing simulator. The rate of delivery of nebulized technetium-99m-labeled diethylenetriamine pe ntaacetic acid ((TC)-T-99m-DTPA) from two different jet nebulizer brands wa s determined. The rate of delivery was defined as the amount of the (TC)-T- 99m-DTPA deposited during 30 sec of nebulization on a filter placed between the nebulizer and the breathing simulator. The rate of delivery of (TC)-T- 99m-DTPA with the human breathing pattern was similar to that measured with the matching sine or square waveforms for either nebulizer. The configurat ion of the breath (PIF, V-T, f, t(i)/t(tot)) did, however, influence the ra te of delivery. In conclusion, the shape of the waveform, in other words, o ne resulting from a human breathing pattern, or a matching sine or square w aveform, did not influence the rate of (TC)-T-99m-DTPA delivery from a nebu lizer in vitro.