Development of a Tracheal Sound Sensor
Condition: Respiratory Insufficiency; Opioid Overdose; Hypoventilation
MeSH terms: Respiratory Insufficiency; Hypoventilation; Opiate Overdose
Study type: Observational

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).
    

Detailed description: 
      RTM's Trachea Sound Sensor (TSS) and data acquisition system will be used to measure and
      record the sounds of air movement within the trachea during inhalation/exhalation prior to
      surgery (baseline), and during management with opioid medications in the operating room (OR),
      post-anesthesia care unit (PACU), intensive care unit (ICU), and/or general nursing floor.

      The TSS will be adhered to the skin of the neck (within the sternal notch) to measure and
      record the sounds of air flowing through the proximal trachea during inhalation and
      exhalation. A commercial miniature accelerometer sensor may also be adhered to the skin of
      the neck and used to measure and record the patient's body position and activity level.

      In addition, research staff will intermittently measure and record each patient's respiratory
      rate (RR) and tidal volume (TV) prior to surgery (baseline), during anesthesia (OR), during
      anesthesia recovery (PACU), and during post-operative care (ICU or nursing floor) using a
      commercial research facemask and respiratory flow sensors (pneumotachs) hardwired to a data
      acquisition system and personnel computer (PC). One commercial pneumotach will accurately
      measure the patient's tidal volume during inhalation, and another commercial pneumotach will
      accurately measure the patient's tidal volume during exhalation.

      The concentration of oxygen in the inspired air delivered into the facemask will be tightly
      controlled, according to a physician's order and standard-of-care methods. The facemask and
      commercial ventilation measurement system was designed and tested in collaboration with Nick
      Rudolph from the company Hans Rudolph, Inc.

      Capnography will also be used to continuously measure and record the concentration of carbon
      dioxide within the facemask's air during inhalation and exhalation, using end-tidal
      measurements to estimate the concentration carbon dioxide in the alveoli and arterial blood.
      Hemoglobin oxygen saturation will be continuously measured and recorded using a commercial
      pulse oximeter and finger probe.

      In some of the study subjects, blood will be intermittently sampled from a radial artery
      catheter (previously inserted for clinical care) or a peripheral venous catheter and used to
      measure the levels of pH, oxygen, carbon dioxide, lactate and other analytes using a
      point-of- care meter. Blood may be sampled more frequently before and after an opioid bolus
      or a change in opioid dose. Blood will not be sampled from some of the study subjects because
      a radial artery/venous catheter were not available or functional for blood sample
      acquisition.

      Trend data will be used to develop a diagnostic algorithm with a risk-index score that
      detects/predicts progression from mild hypoventilation, to moderate hypoventilation, to
      severe hypoventilation due to opioids
    

Intervention name(s): Trachea Sound Sensor (TSS)
Intervention type(s): Device
Intervention description(s): Use the TSS and commercial vital sign monitors to develop a diagnostic algorithm that detects and predicts hypoventilation due to opioids and anesthetic medication
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        All patients scheduled for inpatient surgery at Thomas Jefferson University Hospital that
        would routinely receive opioids for their clinical care.