Infrared imaging identifies sleep apnea without disturbing patients

Sleep apnea is commonly diagnosed by measuring airflow through nasal pressure, temperature, and/or carbon dioxide, using sensors placed in the nose. The method can be uncomfortable and disturb sleep patterns, however. New research presented in October at the annual meeting of the American College of Chest Physicians suggests that remote infrared imaging can monitor airflow and detect abnormalities during sleep, without disturbing the patient.

In a preliminary trial, Dr. Jayasima Murthy, an assistant professor of medicine at the University of Texas Health Science Center in Houston, evaluated remote infrared imaging in 13 men and women without known sleep apnea. Researchers recorded the heat signals expired from patients' nostrils or mouth using an infrared camera during an hour of polysomnography.

To minimize any bias, airflow channels were recorded and analyzed separately. Results were then compared with those obtained through the conventional methods of sleep apnea diagnosis, including nasal pressure, nasal-oral thermistors, and capnography.

"The underlying principle of monitoring the relative changes in airflow based on the changing of the infrared heat signal is similar to that of the traditional thermistor," Murthy said. "The biggest difference is that the thermistor is placed in the subject's nostril, while the infrared camera is placed six to eight feet from the patient's head. This method allows us to have recorded data, so we can go back and extract the airflow data after the completion of the study, which we can't do with conventional sensors."

Murthy found that infrared imaging detected 20 sleep-disordered breathing events, compared with 22 events detected by the nasal-oral thermistor and 19 detected by nasal pressure. Given the outcome, researchers suggest that infrared imaging was in near-perfect agreement with conventional methods and represents a noncontact alternative to standard nasal-oral thermistors.

"The results from this study will greatly impact the development of this technology," he said. "While implementation of this technology for clinical studies is still far away, these early results are encouraging enough for us to pursue this further."

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