Background: Poor sputum clearance is a common problem encountered in intubated patients, which may cause airway obstruction, hypoxaemia, and increased risk of lower respiratory tract infection. This may result in longer intensive care unit (ICU) stay or even death. Dry powder mannitol has been shown to improve sputum clearance, and thus we developed a system to deliver it to intubated patients.
Methods: This delivery system consists of a standard adult manual ventilation bag, a one-way duck-billed valve, and a dry powder inhaler (Osmohaler™) contained within a delivery chamber to allow positive pressure ventilation, which in turn, is connected in series to an endotracheal or tracheostomy tube. The aerosol is delivered by compressing the ventilation bag in a reproducible manner to generate positive pressure airflow to disperse the powder into the tracheal tube. We tested the powder output and characteristics of the powder in vitro from two endotracheal tubes (7.0 and 8.5 mm in diameter, 300 mm in length), and two tracheostomy tubes (7.0 mm in diameter and 95 mm in length; 90 mm in diameter and 115 mm in length).
Results and conclusions: Approximately 50 to 60% of the loaded dose of dry powder mannitol is delivered to the distal end of the tracheal tubes for both 4 × 40-mg and 4 × 80-mg capsules. The fine particle fraction (particles smaller than 5 μm) ranges from 20 to 31% of the loaded dose. Powder was emptied from each 40- and 80-mg capsule within 5 ± 1 puffs and 6 ± 1 puffs, respectively. This delivery system has been shown to consistently deliver a very high dose of powder with a favourable fine particle fraction to the distal end of a number of tracheal tubes. This has the potential for a number of clinical therapeutic applications in critically ill patients.