Use of the respiratory magnetometer in diagnosis and classification of sleep apnea

Seventeen patients with sleep apnea were studied with reference to the frequency and duration of apneic episodies, the mechanism of the apnea and the extent to which oxygen saturation was depressed by the apnea. In all patients, esophageal pressure was recorded simultaneously with respiratory magnetometer records of rib cage and abdominal motion. Thermistor records from the nose and mouth indicated the presence of apnea. Nine patients had purely obstructive apnea and eight a mixture of central and obstructive apnea. In all instances the magnetometer records alone permitted distinction between obstructive and central apnea. Inspiratory efforts against an occluded airway produced a very different pattern of motion when compared to unobstructed breathing or to central apnea. We propose that magnetometer monitoring of thoracoabdominal motion indicates upper airway obstruction reliably and provides a noninvasive and thus more acceptable alternative to esophageal pressure recording for detecting upper airway obstructive apnea.