During the past decade the mortality and morbidity due to pulmonary diseases ranked number 2 or 3, the current data projection suggests that COPD (Chronic Obstructive Pulmonary Disease) alone will be the third cause of death worldwide by 2020. Before a respiratory disorder can be treated, it has to be diagnosed. Currently a variety of respiratory diagnostic devices/systems exists. Spirometer is the most common and frequently used respiratory diagnostic device, whereas plethysmograph (Bodybox) and Impulse Oscillometer (IOS) are more sophisticated systems. We have developed a simple, portable, and inexpensive respiratory diagnostic device, Airflow Perturbation Device (APD), that can evaluate the respiratory resistance noninvasively and effortlessly. It is based on normal breathing with no effort from the subject beyond simple breathing into the APD for less than one minute. APD measures the respiratory pressure (in mmHg) and flow (Liter per second), the ratio of the respiratory pressure over respiratory flow is the resistance of the respiratory system (mmHg/L/s). APD has been favorably compared with spirometer, plethysmograph, and IOS. The respiratory resistance value is highly age dependent, it is fairly high for children and infants (60 - 3 mmHg/L/s) and assumes low values in adulthood (2.5-2 mmHg/L/s). We have evaluated the respiratory resistance values for over 3,000 normal subjects and those with a variety of pulmonary disorders such as asthma, COPD, Vocal Fold Dysfunction, etc. Since APD is an effortless and noninvasive pulmonary diagnostic device, it is in particular very attractive for young children and infants unable to do spirometry.
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