Presented at the 2013 AAPM Annual Meeting « Back

The Use of a Respiratory Volume Monitor in the Assessment of Obstructed Breathing and Postoperative Apnea

Jenny E. Freeman, MD, jfreeman@respiratorymotion.com¹, Edward George², Jordan B. Brayanov, PhD¹, C. Marshall MacNabb, MS1, Eunna Cho¹, Diane Ladd, DNP³, Michael J. Lalli, BSE¹, Christopher Voscopoulos², (1) Respiratory Motion, Inc., Waltham, Massachusetts, (2) Brigham & Women’s Hospital, Harvard Medical School, Boston, Massachusetts, (3) Midland Internal Medicine, Midland, Michigan

Introduction: Respiratory assessment to prevent complications associated with opioid pain management in post-operative patients continues to present significant challenge, particularly in patients with obstructive sleep apnea. A non-invasive, continuous Respiratory Volume Monitor (RVM) was developed to provide quantitative measurements of Minute Ventilation (MV), Tidal Volume (TV) and Respiratory Rate (RR). Methods: Real-time, impedance-based RVM data (ExSpiron, Respiratory Motion, Inc., Waltham, MA) acquired from six thoracic electrodes and spirometry data (SpiroAir-LT, Morgan Scientific, Haverhill, MA) were collected simultaneously during normal and simulated obstructed breathing in eight ambulatory volunteers. RVM performance vs. spirometry was evaluated and obstructed breathing patterns characterized. RVM data were also collected from two orthopedic patients with diagnosed obstructive sleep apnea 1) pre-operatively and 2) in the PACU within 20 minutes following administration of the first post-operative dose of narcotic (PCA hydromorphone). All subjects were studied in IRB approved protocols. Results: In the eight volunteers, RVM derived TV readings were highly correlated with spirometry (r>0.96) and decreased from normal values of 1329ml ±117ml to 197ml± 4.53ml during obstructed breathing (approaching physiologic dead space), p<0.0001, (Fig. 1). In two post-operative patients, RVM measurements of TV and MV decreased following narcotic administration and demonstrated periods of apnea (Fig. 2), although oxygen saturations remained above 96%. Conclusions: RVM data demonstrated decreased measurements of MV and TV due to obstructed breathing in both experimental and clinical settings. RVM has potential utility in defining inadequate ventilation to assist in narcotic pain management and improve patient safety, especially in patients at risk for airway obstruction.

Funding: This study was funded by Respiratory Motion, Inc.

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