Effect of face mask dead volume, respiratory rate, and tidal volume on inhaled albuterol delivery.

Introduction: Pediatric patients often require metered-dose inhaler (MDI) with holding chamber (HC) to overcome lack of coordination when receiving inhaled therapy. In infants and young children unable to use a mouthpiece, it is necessary to use a mask interface. We compared the effect of varying mask static dead volume (SDV), respiratory rate (RR), and tidal volume (VT) on albuterol captured at the mouth opening (ACMO) in an in vitro model.

Methods: An Aerochamber Max(R) without and with three mask sizes (SDV of 10, 36, 85, and 200 ml, respectively) was connected in series to a filter holder and breathing simulator. ACMO was measured at VTs = 36, 72, 145, and 290 ml and RR of 12 and 24. Each experiment comprised 10 puffs run for six respiratory cycles each. Albuterol was quantified via spectrophotometry at 276 nm. A P-value of 0.05 was considered significant.

Results: Increasing VT increased ACMO (all SDVs and RRs). Adding SDV decreased ACMO, except for the small mask at VTs = 145 and 290 ml at RR = 12. Increasing SDV decreased ACMO, except at VT = 36 ml (all masks) and VT = 72 ml (small = medium) at RR = 12 and VT = 36 ml (small = other and medium > large) at RR = 24. Increasing RR increased ACMO for all SDVs at VTs = 36 and 72 ml, but not for VTs = 145 and 290 ml, except for no and large mask at VT = 145 ml.

Conclusion: In general, decreasing SDV, increasing VT, and increasing RR increase ACMO. Early transition from face mask to mouthpiece should be considered in children receiving albuterol via MDI with HC.