Design of a PDA-based Asthma Peak Flow Monitor System

Recent study indicates that one of the important reasons that asthmatic condition could not be effectively controlled is that patients could not comply with the prescription of physician. One possible reason for this is that the conventional approach for physician to monitor the symptoms of asthmatic patients is based on the daily peak expiratory flow records of the patient. Because of the chronic essence of asthma, a long-term patient monitoring would be the necessary step to control the asthmatic condition. However, the asthmatic patients often stop following the prescription of physician once their symptoms of asthma are largely improved. This often leads to deterioration of treatment efficacy or even the patient's death. The main purpose of this study is to design an asthmatic peak expiratory flow monitor that is based on a personal digital assistant (PDA) and internet communication. Such a system would improve not only the communication between the asthmatic patients and physician but also the symptom of asthmatic patients. The device developed in this study is based on a Windows CE-based PDA. The peak expiratory flows (PEF) of asthmatic patient are converted into analog signals via a pneumotachometer (ADInstruments Inc., Sydney, Australia). These analog signals are digitized by a microcontroller and transferred to PDA by a serial interface (RS-232). The PEF data of asthmatic patients can be either stored in the database of PDA or synchronized with the computer in the office of physician to update the data through the internet or wireless local area network (LAN). The physician can also use the software program developed from this study to send short message to patients. Therefore, communication between the patients and physician not only will not be limited by time and distance, but also can achieve the goal of monitoring and improvement of patients' symptoms.