Development of a Tracheal Sound Sensor for Early Detection of Hypoventilation

Detailed Summary

An observational study will be conducted in 20 hospitalized surgical patients routinely managed with opioids for anesthesia and post-operative pain control. Trachea Sound Sensor measurements and reference respiratory measurements will be recorded and analyzed to develop diagnostic algorithms that produce a risk-index score that detects/predicts progression from mild hypoventilation, to moderate hypoventilation, to severe hypoventilation due to opioids and other medications that cause respiratory depression. Our current Trachea Sound Sensor (TSS) has a wired Sony commercial microphone integrated into a commercial pediatric stethoscope, coupled to the skin surface over the trachea at the sternal notch. The Trachea Sound Sensor will measure and record the sounds of air moving within the proximal trachea during inhalation and exhalation. The microphone signal will be converted into an accurate measurement of the patient's respiratory rate and tidal volume (during inhalation \& exhalation) over time, to determine the minute ventilation trend, breathing patterns, apnea episodes, and degree of snoring (due to partial upper airway obstruction). A commercial respiratory facemask and two pneumotachs (gas flow sensors) will also be used to accurately and continuously measure the patient's respiratory rate and tidal volume (during inhalation \& exhalation) to determine the minute ventilation trend, breathing patterns, and apnea episodes. TSS data and reference respiratory data will be collected prior to surgery with the patient breathing normally (baseline), in the Operating Room (OR) during the induction and maintenance of anesthesia, in the Post Anesthesia Care Unit (PACU), and on the general nursing floors of Thomas Jefferson University Hospital (TJUH). The sounds of air flowing through the proximal trachea will be correlated with the reference breathing measurements using signal processing methods to optimize the measurement accuracy of RR, TV, breathing pattern, apnea episodes, and degree of snoring. A commercial accelerometer may be coupled to the skin surface of the neck (with tape) to measure body position and activity level. The TSS and vital sign trend data will be analyzed to produce a Risk-Index Score every 30 seconds with alerts and alarms that warn the patient and caregivers about progressive Opioid Induced Respiratory Depression (OIRD).

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