Pursuant to 37 CFR 1.71(e), this patent document contains material which is subject to copyright protection and the owner of this patent document reserves all copyright rights whatsoever.
In the late 1980's NIRS was determined to be useable to noninvasively assess skeletal muscle oxygenation (SmO2) in patients with heart failure by comparing light absorption at 760 nm and 800 nm as indicia of hemoglobin-myoglobin oxygenation. Wilson, J. R. et al.; Noninvasive Detection Of Skeletal Muscle Underperfusion With Near-Infrared Spectroscopy In Patients With Heart Failure; Circulation, 80(6), Pages 1668-74 (1989). Since then, NIRS has been studied for use in measuring oxygenation concentration as well as other physiological variables and analytes in various organs and tissues of the body. In contrast to typical pulse oximetry, which generally measures oxygen in the flowing blood, NIRS can be used to measure whether or not enough oxygen is being delivered to meet the metabolic demand of a particular organ or tissue (e.g., skeletal muscle, heart, brain, etc.).
NIRS has been studied for use in monitoring the oxygen content of certain body tissues during and following cardiopulmonary resuscitation (CPR). In one such study, regional cerebrovascular oxygen saturation (rSO2) was monitored by placing an infrared light-emitting probe on the patient's forehead after arrival in the hospital emergency department. Patients who survived for one week had significantly higher median rSO2 on arrival than nonsurvivors. Also, patients who arrived while undergoing CPR without spontaneous circulation had lower median rSO2 than patients who arrived after restoration of spontaneous circulation (ROSC). Patients with ROSC who went on to survive for one week had a higher rSO2 on arrival than patients with ROSC who did not survive for one week. These investigators concluded that low rSO2 after cardiac arrest was associated with a higher mortality and that non-invasive monitoring of cerebrovascular oxygen saturation by NIRS could potentially be useful in prognosticating outcomes for patients following cardiac arrest. Mullner, M., et al., Near Infrared Spectroscopy During And After Cardiac Arrest—Preliminary Results; Clinical Intensive Care, Vol. 6, No. 3, Pages 107-11 (1995).
In a more recent study, patients who had experienced out-of hospital cardiac arrest followed by ROSC were monitored by an NIRS StO2 monitor and by an end-tidal carbon dioxide (ETCO2) monitor. ETCO2 had previously been established and an indicator of ROSC or rearrest. Downward trends in StO2 were observed prior to each rearrest and rapid increases in StO2 were noted after ROSC. The StO2 data showed less variance than the ETCO2 data in the periarrest period. The investigators concluded that a decline in StO2 level may correlate with rearrest and, thus. may be useful as a predictor of rearrest in post-cardiac arrest patients. A rapid increase in StO2 was also seen upon ROSC and may be a better method of identifying ROSC during CPR than pauses for pulse checks or ETCO2 monitoring. Frisch, A., et al.; Potential Utility of Near-Infrared Spectroscopy in Out-of-Hospital Cardiac Arrest: An Illustrative Case Series; Prehospital Emergency Care, Vol. 16, No. 4: Pages 564-570 (2012).
Additionally, investigators have explored the use of a subcutaneously implanted NIRS device in combination with an Implanted Cardioverter Defibrillator (ICD). In this study, NIRS oximetric measurements were used, in combination with electrical monitoring by the ICD, to distinguish between the onset of a ventricular arrhythmia requiring defibrillation and mere electromagnetic interference or artifacts resulting from erroneous double counting of the electrocardiographic T-wave as an R-wave, ICD lead failure, or other electrocardiographic aberrancies. Bhunia, S. K. et al., Implanted Near-Infrared Spectroscopy For Cardiac Monitoring; Proc. SPIE 7896, Optical Tomography and Spectroscopy of Tissue IX, 789632 (2011). [http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=733147]
The prior art has included a number of NIRS devices that are positionable at various locations on the patients skin, or subcutaneously below the skin, to measure physiological properties or concentrations of analytes (e.g., pH, temperature, oxygen tension, oxygen saturation, partial pressure of oxygen, partial pressure of carbon dioxide, hemoglobin concentration, water concentration, hematocrit, glucose concentration, presence of biomarkers, etc.) in underlying organs or tissues. Some but not necessarily all examples of such devices are described in U.S. Pat. No. 5,931,779 (Arakaki, et al.); U.S. Pat. No. 6,212,424 (Robinson); U.S. Pat. No. 6,990,364 (Ruchti et al.); U.S. Pat. No. 7,245,373 (SoIler, et al.); U.S. Pat. No. 7,613,489 (Myers); U.S. Pat. No. 7,647,092 (Motz et al.); U.S. Pat. No. 8,277,385 (Berka et al.); U.S. Pat. No. 8,346,329 (Xu et al.); U.S. Pat. No. 8,406,838 (Kato) and U.S. Pat. No. 8,649,849 (Liu et al.) as well as United States Patent Application Publication Nos. 2014/0135647 (Wolf II); 2014/0024904 (Takinami); 2013/0225955 (Schenkman, et al.) and 2011/0184683 (SoIler et al.), the entire disclosure of each such patent and patent application being expressly incorporated herein by reference. Also, examples of such devices are currently marketed as CareGuide™ Oximeters (Reflectance Medical, Inc., Westborough, Mass.); INVOS™ Somatic/Cerebral Oximetry Monitors (Covidien Respiratory and Monitoring Solutions, Boulder, Colo.); Reveal LINQ™ Insertable Cardiac Monitoring Systems (Medtronic Corporation, Minneapolis, Minn.); FORE-SIGHT ELITE® Cerebral Oxygen Monitors (CAS Medical Systems, Inc., Branford, Conn.) and EQUANOX™ Cerebral/Somatic Tissue Oximetry Devices (Nonin Medical, Inc., Plymouth, Minn.). Some if not all of these NIRS devices utilize specialized apparatus and/or signal processing techniques (e.g, “background subtraction”) to minimize or eliminate spectral effects from skin, bone or other intervening tissue that resides between the location of the NIRS device and the organ or tissue of interest.
In the past, certain devices have been positioned within the esophagus adjacent to the heart to monitor or image the heart from a vantage point that has minimal intervening tissue between the device and the heart. For example, endoesophageal stethoscopes and pulse monitoring probes have been advanced into the esophagus and used to monitor a patient's heartbeat, examples of which are described in U.S. Pat. No. 4,409,986 (Apple et al.); U.S. Pat. No. 4,331,156 (Apple, et al.). Also, ultrasound probes have been inserted into the esophagus and used for transesophageal echocardiography, examples of which are described in U.S. Pat. No. 8,641,627 (Roth et al.); U.S. Pat. No. 8,172,758 (Harhen); U.S. Pat. No. 6,884,220 (Aviv et al.) and U.S. Pat. No. 6,471,653 (Jordfald, et al.).
Additionally, United States Patent Application Publication No. 2013/0231573 (Zeng et al.) describes the insertion of a near-infrared spectroscopy probe through the working channel of a bronchoscope and the use of such probe to for endobroncheal Raman spectroscopic analysis of lung cancer tissue.
Given that NIRS and other forms of optical spectroscopy used for measuring the physiologic status of living tissue (broadly termed “Physiologic Spectroscopy” (PS)) are a potentially valuable tool for monitoring cardiac tissue or a subject's blood at specific locations in emergency and critical care situations, it is desirable to develop new optical spectroscopy monitoring devices and methods which are useable for obtaining optical spectrographic measurements from cardiac tissue or from blood located within the chambers of the heart or great vessels (e.g., pulmonary artery, aorta, etc.), and other tissues within the vicinity of the esophagus, the trachea or the main bronchi.