The objective of this study was to quantify the effect of lung emptying on the lung doses of aerosol drugs.

Thirty healthy adults were recruited. Their breathing profiles were recorded while inhaling through different emptied DPI devices without breathe-out and after comfortable or forced exhalation. The corresponding emitted doses and aerosol size distributions were derived from the literature. The Stochastic Lung Model was used to estimate the deposited doses.

In general, forceful exhalation caused increased flow rate and inhaled volume. Increased flow rate led to the increase of lung dose for drugs with positive lung dose-flow rate correlation (Symbicort, Bufomix). For drugs with negative correlation of lung dose with flow rate (all drugs except the above two) lung emptying caused increased, almost unchanged and also decreased lung dose. In this case the change in lung dose depended on the extent of inhaled volume increase, but also on the formulation (see Seebri vs Onbrez).

In conclusion, the change of lung dose depends on the degree of lung emptying, but it is also inhaler and drug specific. Forceful exhalation can help in increasing the lung dose only if the above specificities are taken into account. 

Table 1. Relative change of the lung dose as a result of forceful breathe-out in comparison to no breathe-out