Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
2000-02-28
2003-09-02
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S322000, C600S323000, C600S328000
Reexamination Certificate
active
06615064
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a non-invasive device and method for analyzing the concentration of blood components, including oxygen saturation, bilirubin, hemoglobin, oxyhemoglobin, glucose, hormones and a variety of drugs.
2. Description of the Prior Art
Analysis of blood components is regularly required in hospitals, emergency rooms, doctors' offices, and in patients' homes (in the case of blood glucose analysis for example), for a variety of diagnostic purposes and to monitor therapy. In most cases, blood is obtained by venipuncture or finger prick, which raises small but important concerns regarding pain and the potential for transmission of infectious disease, such as viral hepatitis and human immunodeficiency virus (HIV) infection. The pain associated with blood drawing often inhibits patient compliance with prescribed blood testing, leading to potentially dangerous consequences of undiagnosed disease. Also, the need for trained technicians to draw and handle blood contributes to the high cost of medical care. Furthermore, blood testing procedures take time, which often delays diagnosis. Finally, for practical reasons, blood testing can be done only at intervals, providing only “snap-shot” data regarding the blood component of interest. Under some circumstances, as for example during the assessment of blood losses due to gastrointestinal hemorrhage or during the assessment of the response to hemodialysis, to the treatment of diabetic ketoacidosis, or to the treatment of acute intoxications, it would be desirable to monitor the concentration of one or more blood components continuously.
Blood tests are often performed in “panels;” that is, a number of tests is run on a single drawn blood sample. However, there are also clinical circumstances in which only a single or a small number of tests are required, or when a single test must be performed repeatedly over time. In such cases, noninvasive tests that do not require blood drawing would be particularly useful.
An example of a currently available noninvasive test is pulse oximetry, which measures the adequacy of saturation of arterial blood hemoglobin with oxygen. Mendelson Y.,
Pulse Oximetry: Theory and Applications for Noninvasive Monitoring, Clinical Chemistry
38:1601-7, 1992; Hanning C D, Alexander-Williams J M.,
Pulse Oximetry: A Practical Review, BMJ
311:367-70, 1995; Severinghaus J W and Kelleher J F.,
Recent developments in pulse oximetry, Anesthesiology
76:1018-38, 1992; Corenman et al., U.S. Pat. No. 4,934,372; Edgar et al., U.S. Pat. No. 4,714,080; Zelin, U.S. Pat. No. 4,819,752; and Wilber, U.S. Pat. No. 4,407,290. Oximeters have become indispensable for screening patients for life-threatening hypoxemia and for monitoring patient safety during procedures such as surgery and childbirth. Oximeters reliably report the relative arterial oxygen level (percent of the maximum that can be carried by the available hemoglobin), but they cannot measure absolute oxygen content of the blood, because their readings are independent of hemoglobin concentration.
In pulse oximeters, light produced by two light-emitting diodes (LEDs) at approximately 660 nm (red) and 940 nm (infrared) are alternately passed through the subject's finger, toe, or ear (or other well-perfused tissue), and the transmitted light is measured by a rapidly-responding photodetector. The light that is not transmitted to the photodetector is absorbed by the finger or is scattered out of the range of the photodetector. The amount of absorbance depends on tissue density and the amount and character of the blood (venous and arterial) that is present in the light path. At each of the two wavelengths, the resulting time-varying measurement of light intensity for the wavelength, termed “photoplethysmography,” is roughly inversely proportional to finger volume, which varies with the arterial pulse.
Changes in absorbance (A) are caused by changes in the amount of blood present in the light path, assumed to be primarily changes in the amount of arterial blood due to the arterial pulse. Because absorbance of oxy-hemoglobin differs for light at the two wavelengths, a ratio of change in absorbance of red to change in absorbance of infrared light can be used to measure oxy-hemoglobin percentage. In practice, transmittance (T=10
−A
) is measured from each of the photoplethysmograms, absorbance (A=log 1/T) is calculated, and the change in absorbance with the arterial pulse is calculated for each wavelength studied. A ratio of the two changing absorbances is then computed, and after inconsistent data points are discarded, the ratios are averaged to yield an average ratio of red/infrared absorbance change. The average ratio is then multiplied by a correction factor, which has been empirically determined for each instrument by comparison with oxy-hemoglobin levels measured by a co-oximeter in arterial blood samples in normal subjects with varying levels of oxyhemoglobin produced as a result of breathing gases with varying fractions of inspired oxygen (FiO
2
).
Commercial pulse oximeters used to measure the amount of arterial blood oxygen saturation (SaO
2
) are available from the following manufacturers: BCI International, Biochem International, Inc., Criticare Systems, Inc., Datascope Corp., Datex Instrumentation Corp., Gambro Engstrom A.B., Invivo Research, Inc., Kontron Instruments, Life Care International, Inc., MSA, Medical Research Laboratories, Minolta Camera Co., Ltd., Nellcor-Puritan-Bennett, Nippon Colin Co., Ltd., Nonin Medical Systems, Inc., Ohmeda, Inc., Palco Labs, PhysioControl, Respironics, Inc., Sensor Medics Corp., Siemens Medical Systems, Inc., Novametrics Medical Systems, Inc., Simed Corp. and Spectramed, Inc.
Pulse oximeters can be controlled with various software packages, including those made by EMG Scientific. Signal processing apparatus, such as that disclosed in U.S. Pat. No. 5,490,505, can be used to process the signals generated by a pulse oximeter.
Prior designs of pulse oximeters used to measure arterial oxygen saturation are well known. For example, U.S. Pat. No. 4,653,498 to New, Jr. et al. (1987) describes a display monitor for use with a pulse oximeter of the type wherein light of two different wavelengths is passed through body tissue, such as a finger, an ear or the scalp, so as to be modulated by the pulsatile component of arterial blood therein and thereby indicates oxygen saturation. Similarly, U.S. Pat. No. 4,621,643 (1986), U.S. Pat. No. 4,700,708 (1987) and U.S. Pat. No. 4,770,179 (1988), all to New, Jr. et al., describe disposable probes for use with pulse oximeters.
U.S. Pat. No. 5,810,723 to the same inventor as the instant application, which issued on Sep. 22, 1998 from copending application Ser. No. 08/759,582, is entitled Non-Invasive Carboxyhemoglobin Analyzer. In that patent an apparatus and method is disclosed which allows the non-invasive monitoring of a subject's carboxyhemoglobin level, thereby allowing the detection of possible carbon monoxide poisoning. The subject breathes oxygen to lower his reduced hemoglobin level to approximately 0%, thus allowing the detection and differentiation between oxy- and carboxyhemoglobin by modification of a conventional pulse oximeter.
Noninvasive monitors of bilirubin are also available, especially for following the course of neonatal jaundice. See Linder N, Regev A, Gazit G, Carplus M, Mandelberg A, Tamir I, Reichman B., Noninvasive determination of neonatal hyperbilirubinemia: standardization for variation in skin color;
Am J Perinatology
11:223-5, 1994. Usually, the absorbance by a body part of light near the peak absorption of bilirubin is monitored. Bilirubinometers are generally calibrated by comparison with measured blood bilirubin in the infant to be monitored. Without such calibration, the varying amounts of tissue and blood in the light path limits the accuracy of the measurements. Thus, at least one blood sample is required.
Examples of other blood tests that are oft
Essential Medical Devices, Inc.
Patterson Belknap Webb & Tyler LLP
Winakur Eric F.
LandOfFree
Non-invasive blood component analyzer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Non-invasive blood component analyzer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-invasive blood component analyzer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3058901