American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Jan 1999
Comparative StudyReconciling in vitro and in vivo measurements of aerosol delivery from a metered-dose inhaler during mechanical ventilation and defining efficiency-enhancing factors.
We attempted to resolve the discrepancies in reported data on aerosol deposition from a chlorofluorocarbon (CFC)-propelled metered-dose inhaler (MDI) during mechanical ventilation, obtained by in vivo and in vitro methodologies. Albuterol delivery to the lower respiratory tract was decreased in a humidified versus a dry circuit (16.2 versus 30.4%, respectively; p < 0.01). In 10 mechanically ventilated patients, 4.8% of the nominal dose was exhaled. ⋯ A lower inspiratory flow rate (40 versus 80 L/min; p < 0.001), a longer duty cycle (0.50 versus 0.25; p < 0.04), and a shorter interval between successive MDI actuations (15 versus 60 s; p < 0.02) increased aerosol delivery, whereas use of a hydrofluoroalkane (HFA)-propelled MDI decreased aerosol delivery compared with the CFC-propelled MDI. A MDI and actuator combination other than that designed by the manufacturer altered aerosol particle size and decreased drug delivery. In conclusion, aerosol delivery in an in vitro model accurately reflects in vivo delivery, providing a means for investigating methods to improve the efficiency of aerosol therapy during mechanical ventilation.
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Am. J. Respir. Crit. Care Med. · Jan 1999
Comparative StudySniff nasal inspiratory pressure. Reference values in Caucasian children.
Like in adults, normal values of maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax) span a large range in children, making interpretation of low values difficult. Recently, sniff nasal inspiratory pressure (Pnsn) was developed as a new noninvasive test of inspiratory muscle strength. In healthy adults, Pnsn is most often higher than PImax. ⋯ We conclude that Pnsn can be easily used to assess inspiratory muscle strength in children age 6 yr or more, providing values higher than PImax. Normal values are independent of age in girls, and can be predicted from age by a first-degree equation in boys. Being easy and noninvasive, Pnsn may prove useful to assess inspiratory muscle strength in children with neuromuscular disorders.