(McClatchy-Tribune Information Services) -- Using computer algorithms and infrared imaging, Houston researchers have created a test for sleep apnea that detects the common but potentially serious disorder without a tangle of sensors attached to the patient's body during sleep.

The creation of a University of Houston computer scientist and a University of Texas Health Science Center at Houston doctor of sleep medicine was recently studied in patients at Memorial Hermann Hospital and found to be just as accurate at diagnosing sleep apnea as the traditional sensor-laden method, known as polysomnography.

"This could mark a major change in the way we diagnose sleep apnea," says Dr. Jayasimha Murthy of UT-Houston's division of pulmonary critical care sleep medicine, one of the investigators. "All the sensors used in traditional diagnosis can disturb sleep and contribute to patient anxiety. With this, we hope to 'unwire' subjects during sleep studies."

The new test, which the researchers describe in the November issue of the journal Sleep, is the first of its kind to diagnose sleep apnea using "non-contact technology." A thermal infrared camera about 8 feet away collects information based on airflow throughout the sleeping patient's nostrils.

Sleep apnea, which is characterized by temporary breath interruptions during sleep, affects 24 percent of men and 9 percent of women. It is associated with a number of health problems, including hypertension, heart disease and stroke.

It occurs when the muscles in the throat, soft palate and tongue relax during sleep, sagging and narrowing the airway, which blocks the windpipe and cuts off oxygen to the lungs. In a cycle typically repeated hundreds of time a night, the sleeper rouses from slumber to gasp for air, then falls back asleep. The awakening is usually so brief the sleeper doesn't remember it.

The only way to diagnose the condition is with a sleep study, during which the patient must sleep wearing more than 20 sensors, usually hooked up to the head, nose, legs, arms and chest. Ioannis Pavlidis, a UH computer science professor and co-developer of the test, says it's not exactly "like paying a short visit to the doctor in the morning and walking away with a prescription."

The new test retains some of the sensors, but doesn't require any in the most obtrusive area, the nose. In the test, the infrared imaging captures patients' unique thermal signature, a product of the cooler atmospheric air taken into the nostrils and the warmer air exhaled. Computational algorithms process the readings.

The test also provides a wealth of information not previously accessible, says Pavlidis.

"In contrast to the traditional one-dimensional methods, this new method is multi-dimensional," says Pavlidis. "We can see how airflow is distributed locally throughout the extent of the nostril. We get multiple values, rather than a single one, for each nostril at every point in time, which makes a lot of difference when it comes to appreciating subtle pathology."

Pavlidis and Murthy studied 27 subjects, 13 with a history of sleep apnea and 14 without, during two hours of sleep at Memorial Hermann's sleep disorders center. The study showed a high degree of agreement in data returned from traditional polysomno- graphy and the new test.

Pavlidis and Murthy said their next study will look at subjects during a full night of sleep.

Dr. Shyamsunder Subramanian, a Baylor College of Medicine professor of medicine and sleep specialist, called the test "a good breakthrough, preliminary but very exciting." But he said it's unclear whether it will eventually replace polysomnography except in severe cases "because it doesn't provide some of the information polysomnography does about sleep airflow's subtle effect on brain activity."

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