Detection and assessment of sleep-disordered breathing with emfit mattress

Measuring respiratory effort during sleep is a demanding job. It needs intrathoracic pressure monitoring via nostril inserted catheter in the esophagus. Though the size and material of catheter are nowadays more comfortable than earlier, it is still quite invasive and cumbersome technique, and it does not suit for clinical use. It is known that mattress-type contactless sensors can be used to detect respiratory movements and overall cross-body movements. Beating heart produces mechanical activity called ballistocardiography (BCG), which can be assessed with Emfit (Electromechanical film transducer) mattress sensor too. These heart-related movements with increased breathing effort cause patterns called spiking in the mattress signal. We have studied esophageal pressure changes during this spiking and showed that this phenomenon appears when intrathoracic pressure decreases under -8 cmH2O. These increased breathing efforts quite often appeared together with loud snoring. That is why we have also studied the spectral content of Emfit signal using the power spectral density (PSD). Snoring epochs displayed a power increase in all frequency bands. This increase was best quantified using the power ratio between 60–100 Hz (BW3) and 16– 30 Hz (BW2). We have shown that this type of contactless sensors suits well for the screening of snoring, and the increased respiratory effort was visualized too. Mattress-type movement sensors are inexpensive and unobtrusive, and thus provide an interesting tool for sleep research.