Respiratory Rate. Disclosure: Research grants and honoraria from Masimo Corp

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1 Respiratory Rate Acoustic Monitoring Michael Ramsay MD Chairman, Department of Anesthesia Baylor University Medical Center President, Baylor Research Institute Professor, Texas A&M Health Science Center Clinical Professor, UT Southwestern Medical School Disclosure: Research grants and honoraria from Masimo Corp 1

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3 BREATH SOUNDS 3

4 Respiratory Rate An abnormal respiratory rate is a sensitive early indicator of critical illness A robust, reliable and patient acceptable method of remotely monitoring respiratory rate is necessary for telemonitoring of patients 3 Clinical Patterns of Unexpected Hospital Death 1. Hyperventilation Compensated Respiratory Distress (Sepsis, PE, CHF) 2. Progressive Unidirectional Hypoventilation (CO2 Narcosis) 3. Sentinel Rapid Airflow/SPO2 Reductions followed by Precipitous SPO2 Fall) Lynn and Curry, Patient Safety in Surgery 2011, 5:3 Lynn and Curry, Patient Safety in Surgery 2011, 5:3 4

5 Lynn and Curry, Patient Safety in Surgery 2011, 5:3 Lynn and Curry, Patient Safety in Surgery 2011, 5:3 Current Respiration Rate Monitors Physical assessment (intermittent) Transthoracic impedance Capnography (continuous) (continuous) Air Flow Sensors (continuous) Photoplethysmography (continuous) Acoustic Monitoring RRa (continuous) 5

6 Intermittent Human Observation Cannot be audited Should assess: Respiratory Rate; Pattern; Depth; Quality Difficult to distinguish CO2 narcosis from natural sleep Transthoracic Impedance Plethysmography The changing air volumes in the lungs alter thoracic impedance. Continuous monitor of respiratory rate Historically has been limited in detecting obstructed breathing Newer technology is more sensitive and more accurate and measues TV, MV and RR. Voscopoulos et al. Anesth Analg 2013;117:91 100) Anesth Analg 2013;117:91 100) 6

7 Airflow Sensors Sensors can detect airflow as expired air is warmer more humid and contains carbon dioxide. Temperature: Real-time infrared thermography. In the neonate respiration was monitored based on a 0.3 degree C to 0.5 degree C temperature difference between inspiration and expiration. Abbas et al. Biomed Eng Online 2011:10:93. Humidity: A miniature optical humidity sensor is placed on a face mask and measures water vapor of exhaled air. Mathew et al. Biomed Opt Express 2012;3:3325 Abbas et al. Biomed Eng Online. 2011;10:93. Capnography Capnography measures ventilation and provides a graphical waveform available for interpretation 7

8 Photoplethysmography 8

9 Photoplethysmography Derived Respiratory Rate RR oxi Continuous monitoring of respiratory rate, SpO2 and pulse rate. Derives respiratory rate from the variability in baseline of the plethysmogram The pleth variability index can predict fluid responsiveness in the mechanically ventilated patient Sensitive to movement artifacts and vasoconstriction Obstructed airflow affects pleth signal does this affect rate calculation? Entropy of Tracheal Sounds [Lu Y et al., Anesthesiology 2013; 118(30):1-9] [Lu Y et al., Anesthesiology 2013; 118 9

10 Period of Apnea [Lu Y et al., Anesthesiology 2013; 118 Acoustic Respiration Rate (RRa) Accurate > Easy-to-Use > Patient-Tolerant When used with other clinical variables, first-ever continuous and noninvasive monitoring of acoustic respiration rate (RRa) may help clinicians assess respiratory status and help determine treatment options Acoustic Monitoring How does it work? Acoustic signals are produced in the upper airway by the turbulent airflow that occurs during inspiration and expiration Signal conducted from the trachea through the muscle and skin in the patient s neck. Sensor captures acoustic breath sounds, respiration rate is calculated based on inspiration-expiration envelopes Respiratory pause is continually monitored for by counting from expiration to next inspiration (ie, the period of no airflow) 10

11 Potential Issues Study carried out in PACU with much ambient noise without affecting the signal interpretation Many study patients were morbidly obese with large neck circumference but good signals obtained. Diaphoretic patient caused sensor to become detached 11

12 RAM More Accurate RAM More Precise 12

13 Atkins and Mandel Anesth Analg 2014;XXX:00 00) Conclusions The Acoustic Monitor (Rra) rapidly detects changes in respiratory rate, demonstrates minimal bias, and when errors in rate occur, these do not persist. Apnea alarm after 30 secs Respiratory rate window 45 secs Atkins and Mandel Anesth Analg 2014;XXX:00 00) Acoustic Monitor compared to Instantaneous Respiratory Rate Atkins and Mandel Anesth Analg 2014;XXX:00 00) 13

14 Pediatric Study Patino et al Pediatric Anesthesia 2013;23: Pediatric Study Compared to nasal capnography RRa showed similar accuracy and precision but was better tolerated by pediatric patients Patient Tolerance of rainbow Acoustic Monitoring and EtCO2 in a Pediatric Post-Surgical Population Thirty-nine of 40 patients (97.5%) demonstrated good tolerance of the acoustic sensor, 25 of 40 patients (62.5%) demonstrated good tolerance of the nasal cannula 97.5% 62.5% rainbow Acoustic Monitoring Capnography Patino M et al. Pediatric Anesthesia

15 Snore Out Snore Out 15

16 Patient Safety Net 16

17 International Journal of COPD 2011: Lung Sounds > Provide vital information about health and disease > May be: Normal - healthy Adventitious continuous or discontinuous Continuous: Wheezes and Rhonchi Wheezes > Dominant frequency > 100 Hz > Duration > 100 millisecs > Caused by airway obstruction in the lung (asthma) 17

18 Rhonchi > Duration > 250 millisecs > Low pitched dominant frequency > 250 Hz Crackles > Short explosive discontinuous sounds > Duration < 100 millisecs > Produced by pressure equalization or sudden opening of closed airways in the lungs Normal Breathing 18

19 Wheeze Rhonchi Crackles 19

20 Spectrogram of Respiratory Cycle with Wheezing Breathing is Good 20