Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1998-10-06
2001-01-30
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S586000
Reexamination Certificate
active
06179783
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to an apparatus, operation and method for measurement of blood pressure. In particular, this invention relates to an apparatus, operation and method for the detection, identification and characterization of sounds relating to either systemic or pulmonary blood pressure through the use of sonospectrography.
BACKGROUND OF THE INVENTION
Blood pressure is the force exerted by the blood against the inner walls of blood vessels. Blood pressure determination is an important diagnostic tool. The blood vessels that comprise the vascular system can be grouped into two main divisions, a systemic circuit and a pulmonary circuit. In the systemic circuit, high blood pressure may indicate the presence of arteriosclerosis or other vascular disease, while low blood pressure may indicate shock or blood loss. Detection and measurement of elevated pulmonary blood pressure is a key diagnostic indicator for a number of pulmonary diseases, such as: cystic fibrosis, pleuresy, lung pulmonary diseases, and pulmonary impedance. Early diagnosis of these diseases greatly assists in symptom mitigation and improved patient quality of life.
The systemic circuit includes the aorta and its branches that deliver oxygenated blood to all body tissues, as well as the companion system of veins returning blood to the right atrium. Freshly oxygenated blood received by the left atrium is forced into the systemic circuit by the contraction of the left ventricle. When the left ventricle contracts, the mitral valve closes, and the only exit is through the aortic valve into the aorta.
The peripheral nature of certain systemic circuit arteries in the body extremities allows for the traditional indirect measurement of the systolic and diastolic pressures with a sphygmomanometer blood pressure cuff. While this method is effective for many patients, use of the traditional blood pressure cuff on an extremity may be contraindicated for patients suffering from any number of problems including severe extremity trauma, or burns. In patients where use of the traditional blood pressure cuff is contraindicated, there is no reliable alternative method of monitoring blood pressure. This is extremely important in trauma patients where prompt detection of blood pressure changes are needed to counteract the effects of shock or large blood loss.
The pulmonic circuit provides for blood circulation from the right ventricle through the pulmonary valve into the pulmonary artery. The pulmonary artery extends upward and posteriorly from the heart, dividing into right and left branches which serve the right and left lungs, respectively. Within the lungs the right and left branches of the pulmonary artery divide repeatedly giving rise to arterioles that continue into the capillary networks associated with the walls of the alveoli. Gas exchange occurs as the blood moves through these capillaries, so that when the blood enters the venules of the pulmonary circuit, it is well oxygenated and poor in carbon dioxide. The pulmonary venules merge forming small veins, which in turn converge forming larger veins. Four pulmonary veins return oxygenated blood to the left atrium, thereby completing the pulmonic circuit.
None of the arteries of the pulmonic system are located in extremities and therefore measurement of pulmonic system pressure with a blood pressure cuff is not possible.
At present, the only reliable method for measuring pulmonic system blood pressure is through use of an invasive blood pressure catheter that is inserted directly into the pulmonary artery. This diagnostic procedure has a substantial degree of risk and is expensive, its use is thus generally seen as an unjustified procedure in patients without other symptoms.
The physician may attempt to detect and differentiate the abnormal sounds that occur with elevated blood pressure using traditional auscultation. Closure of the aortic and pulmonary semilunar heart valves generate a sound component that is in the audio frequency range. As the systemic or pulmonic blood pressure increases, the frequency components of the related heart valve also increase. This increased frequency audio component is not present in a healthy patient. However, aural detection of this frequency increase is extremely difficult because the physician must determine the absolute frequency of the audio component of the heart valve of interest. Additionally, the sounds are very weak and heavily contaminated with noise from other patient heart sounds, other normal patient body sounds and external ambient noise in the room. Further, the audio component of the aortic and pulmonary semilunar heart valves are heavily attenuated as they pass through the patient's chest and chest wall.
A need exists for a non-invasive, low cost and reliable means for determining systemic blood pressure in those situations where traditional means are contraindicated. A need also exists for a non-invasive, low cost and reliable means for determining pulmonary blood pressure.
DESCRIPTION OF RELATED ART
As mentioned, the sounds related to systemic and pulmonary heart pressure are difficult to discern. U.S. Pat. No. 4,528,690 to Sedgwick; U.S. Pat. No. 3,790,712 to Andries; and U.S. Pat. No. 3,160,708 to Andries et al. disclose relatively simple electronic stethoscopes as methods for amplification of the sounds in an attempt to raise the sub-audible components into the audible range. However, simple amplification of the entire frequency spectrum, as disclosed, does not help in determining the absolute frequency of the heart valve sounds, or in detecting the subtle changes of this frequency that occur with changes in blood pressure.
To this end, U.S. Pat. No. 4,594,731 to Lewkowicz and U.S. Pat. No. 5,347,583 to Dieken et al. disclose various forms of selective filtering or signal processing on the audio signal in the electronic stethoscope. Lewkowicz discloses a means for shifting the entire detected spectrum of sounds upward while expanding the bandwidth so that they are more easily perceived by the listener. Dieken et al. discloses an electronic stethoscope having a greater volume of acoustic space and thereby improving low frequency response.
The electronic stethoscope provides a moderate improvement over conventional methods of auscultation. However, information remains in audio form only and is transient; the physician is unable to visualize the data and either freeze the display or focus on a particular element of the signal retrieved. To accommodate that deficiency, the technique of phonocardiography, which is the mechanical or electronic registration of heart sounds with graphic display, is used. U.S. Pat. No. 5,218,969 to Bredesen et al.; U.S. Pat. No. 5,213,108 to Bredesen et al.; U.S. Pat. No. 5,012,815 to Bennett, Jr. et al.; U.S. Pat. No. 4,967,760 to Bennett, Jr. et al.; U.S. Pat. No. 4,991,581 to Andries; and U.S. Pat. No. 4,679,570 to Lund et al. disclose phonocardiography with signal processing and visual/audio output. U.S. Pat. No. 5,301,679 to Taylor; and U.S. Pat. No. 4,792,145 to Eisenberg et al. disclose phonocardiography with signal processing and visual display.
The process of phonocardiography as commonly known in the art, acquires acoustic data through an air conduction microphone strapped to a patients chest, and provides the physician with a strip chart recording of this acoustic data. The strip chart is generally created at a rate of 100 mm/second. As this method is generally used, with the exception of the created strip chart, data is not stored. Thus, it is not possible to manipulate and/or process the data post acquisition. In addition, phonocardiography does not provide the sensitivity needed to monitor softer physiological sounds such as the closure of the semilunar valves and blood flow through the circulatory system.
As previously noted, one problem in traditional auscultation is ambient noise from the room in which the examination is occurring, which reduces the signal-to-noise ratio of the sounds of interest. U.S. Pat. No. 4,672,977 to Kroll disclos
Aurora Holdings, LLC
Nasser Robert L.
Roberts Abokhair & Mardula LLC
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