Improving portable inhalation therapy through real-time assessment of patient pulmonary state

Metered-dose inhalation therapy is the method of choice for a number of respiratory conditions including asthma and bronchitis. Correct use of the metered-dose inhaler (MDI) has been the subject of much research. Devices have been developed to assist with training in their proper use and to enhance the effectiveness of MDI therapy. However, all lack patient pulmonary state assessment. We have approached the development of an improved portable MDI device by focusing on the total system elements that contribute to a smart inhalation therapy device. Components of such a system should include assessment of the patient's therapeutic state, tracking of drug usage, and also include physician-modified alarm thresholds. Therapeutic state is best assessed with end-expiratory CO₂ measurements augmented by inspiratory and expiratory flow efforts. Drug usage monitoring needs to include the time history of drug administration. Physician-modified alarms should allow configuration of the smart inhaler to account for patient condition so that appropriate alarm limits can be established; for example, raising the CO₂ alarm threshold for patients with chronic lung disease.