Non-invasive respiration monitoring by thermal imaging to detect sleep apnoea

Accurate airflow measurements are vital to diagnose apnoeas; respiratory pauses occurring during sleep that interrupt airflow to the lungs. Apnoea diagnosis usually requires an overnight polysomnography during which numerous vital signs are monitored, including respiratory rate and airflow. The current gold standard in respiration monitoring is a nasal pressure sensor which is placed inside the nostrils of the patient and through which the airflow is measured. Due to the contact nature of the sensor, it is often refused or removed during polysomnography, especially in the case of paediatric patients. We have found that around 50% of children refuse the use of nasal prongs due to its in-vasiveness, and of those that accepted it, 64% removed the sensor over the course of the polysomnography. We evaluated a non-contact method to monitor respiration by developing infrared thermal imaging, whereby temperature fluc-tuations associated with respiration are measured and correlated with airflow. A study was carried out on a sample of 11 healthy adult volunteers whose res-piratory signals were recorded over four simulated apnoea scenarios. The res-piratory signal obtained through thermal imaging was compared against the gold standard nasal pressure sensor. In 70% of cases, apnoea related events were well correlated with airflow sensor readings. In 16% of recordings the subject’s head position did not allow correct identification of the region of interest (i.e. the nostrils). For the remaining 14% of cases there was partial agreement between the thermal measurements and airflow sensor readings. These results indicate thermal imaging can be valuable as a detection tool for sleep apnoea, particularly in the case of paediatric patients.