Flowmeter Could Diagnose Breathing Disorders

R&D DIGEST

Researchers have designed a disposable flowmeter to detect sleep-related breathing disorders, such as snoring and sleep apnea. The device could also be used to identify breathing problems in patients with chronic obstructive pulmonary disease and other lung ailments. And it could improve the detection of sleep disorders in children.

The compact pneumotachograph measures ventilation during sleep or when in a sleep-like state. It can provide measurements in infants and others with smaller airways, and assess airflow in each nostril. Because the flowmeter is disposable, infections won't be transmitted between patients.

The concept for the flowmeter originated during the severe acute respiratory syndrome (SARS) epidemic in China. It was developed to monitor patients in general wards and intensive-care units in hospitals.

According to device inventor Hartmut Schneider, MD, PhD, the high accuracy of the airflow meter will help doctors find disorders in situations where they previously went undetected. Schneider is an assistant professor at The Johns Hopkins University School of Medicine.

“The current standard in diagnosing breathing disorders during sleep is based on technologies from the late 1990s and, more importantly, it's based on the classification of recordings from the obese male population,” says Schneider. Doctors are now seeing many more women and children who have sleep-related breathing disorders. But the criteria aren't well defined. “An accurate measurement of airflow and ventilation would help us to detect a breathing disorder and define it with a higher accuracy.”

The current prototype consists of a recording unit and a disposable measurement unit. When a patient exhales, the air is expired to the disposable unit, which can be configured to be mounted in-line with ventilator tubes or masks. The recording unit has microelectromechanical pressure transducers that provide a sensitive and stable flow signal. The unit then calculates the difference between total and static pressures to determine the air velocity and flow rate.

Schneider thinks the flowmeter will evolve in the same way that diabetes glucose measurement devices have changed over time. He envisions its use by both patients in the home and clinicians in hospitals.

The finished device may be a small mask about the size of a clown's nose, and the electronic module may be as small as a USB key. The sensor and recording unit could be placed in the mask with thin wire connecting it to an external electrical power source. Production costs are anticipated to be low, so manufacturing a disposable device should be feasible.

The team is working to improve flow measurement accuracy and the signal-to-noise ratio. It also plans on developing an electronics module that attaches directly to the flow sensor. It's also possible that the device could have a wireless interface.

Other potential changes to the flowmeter include implementing a pulse oximeter that can be mounted on the nose or forehead to monitor oxygenation. The researchers are exploring the use of onboard software algorithms that measure upper-airway obstruction from a continuous airflow signal recorded during sleep.

Key Technologies Inc. (Baltimore), a development company, is a coinventor of the device.

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