Drug – bio-affecting and body treating compositions – In vivo diagnosis or in vivo testing – X-ray contrast imaging agent
Reexamination Certificate
1999-11-18
2002-10-08
Jones, Dameron L. (Department: 1619)
Drug, bio-affecting and body treating compositions
In vivo diagnosis or in vivo testing
X-ray contrast imaging agent
C424S009400, C424S009100, C424S001110
Reexamination Certificate
active
06461589
ABSTRACT:
FIELD OF THE INVENTION
The invention is directed to standardized, viscosity-modified, edible formulations for use with dysphagic patients and methods to gauge the viscosity of modified foods using the standardized formulations. The formulations described herein can so combined with a radio-opaque agent to facilitate improved dynamic fluoroscopic imaging of the oropharynx, hypopharynx, etc.
BACKGROUND OF THE INVENTION
The oropharyngeal physiology involved in a normal swallow is an exceedingly complex series of coordinated actions. A host of very different medical conditions, both physical and neurological in nature, can alter normal swallowing. For example, patients suffering stroke, Alzheimer's disease, amyotrophic lateral sclerosis, or traumatic brain injury can exhibit abnormal swallowing. In many instances, the abnormal swallow can and does cause aspiration of food material, both liquids and solids, into the lungs. This is especially prevalent (and life-threatening) in bed-ridden patients. Aspiration of foreign material into the airways leads to increased morbidity in hospitalized patients and can lead to pneumonia. Abnormalities in the human swallow, whether or not the condition results in aspiration of foods, is called dysphagia.
A normal human swallow can be separated into four semi-distinct phases: 1) oral preparation; 2) the oral phase; 3) the pharyngeal phase; and 4) the esophageal phase. Patients who have suffered a stroke, traumatic brain injury, or neuromuscular disorder (such as MS or ALS) have an increased risk of aspiration, and may have difficulty with either the oral phase, the pharyngeal phase or both. For instance, weak and/or uncoordinated muscle movement when chewing or in the initial oral phase of swallowing can cause food to fall into the pharynx and into the open airway before the completion of the oral phase. Or impaired propulsion can result in residue in the oral cavity, valleculae, or pharynx after the swallow, when the residue may be inhaled into the trachea. Or a delay in the onset of the pharyngeal swallowing response can result in food falling into the airway during the delay when the airway is open. Or reduced peristalsis in the pharynx can leave residue in the pharynx after the swallow is completed that can fall or be inhaled into the airway. Additionally, laryngeal or cricopharyngeal dysfunction can also lead to aspiration because of decreased closure of the airway during swallowing. Any of these conditions, or a combination of these conditions, can lead to aspiration of food into the airways.
To detect and evaluate patients who have dysphagia or are at risk of developing dysphagia, speech pathologists currently employ a roughly standard procedure for initially evaluating a patient's swallow. A bedside swallow exam performed by most speech pathologists first evaluates the patient's medical history, respiratory status, level of responsiveness, and level of cognitive impairment, if any. Evaluating swallowing can be especially difficult in patients with moderate to advanced cognitive impairment due to the inability of the patient to understand and to follow instructions.
A physical examination of the oropharynx is then performed. The muscles involved in mastication, the lips, the tongue, and the palate are examined. The position of the patient when tested (prone, seated, standing) is noted as this can have a profound effect on the swallowing mechanism. The patient's empty mouth (“dry”) is evaluated. The patient is then asked to swallow one or more thin liquids, thick liquids, pureed textured, and/or solid textured foods to evaluate the swallow mechanism. In particular, the speech pathologist looks for a host of telltale signs of dysphagia such as gurgling, impaired vocal quality post-swallow, coughing, nasal regurgitation, and multiple swallows, as well as any visible signs that may indicate risk for aspiration.
While the standard bedside swallow exam to screen patients is beneficial for evaluating patients at risk for dysphagia, it sheds very little light on the whether the patient is actually aspirating and even less light on where in the swallow cycle the defect arises. Many patients, due to concomitant neurological defects, will silently aspirate, giving no indication during the bedside exam as to their condition. Aspiration in dysphagic patients, however, can be detected using a modified barium swallow fluoroscopic examination. Videofluoroscopy of the swallow mechanism is performed regularly to elucidate more clearly the anatomical or neurological deficit causing the dysphagia.
Dynamic fluoroscopic evaluation of the swallow, however, is not without its attendant difficulties and shortcomings. For instance, the imaging compositions conventionally used for fluorscopic exams are thick suspensions of barium sulfate. Barium is employed because of its large X-ray absorption cross-section, which makes it radio-opaque. The use of barium sulfate suspensions as a radiological contrast medium has a number of drawbacks. A first drawback is that conventional barium sulfate suspensions generally have either poor adhesion to the walls of the oropharynx or too much adhesion. These compositions, having been initially designed to image the gastrointestinal tract, have not been altered much if any, for use in imaging the mouth and throat. If the walls of the oropharyngeal tract are not sufficiently coated with the contrast agent, an X-ray image cannot be generated; there simply isn't enough contrast to visualize the relevant structures. Conversely, if the suspension is made thicker to encourage adhesion, the thick, chalky suspension actually coats the mouth and throat and physically alters the movement of the muscles used for swallowing. Consequently, the image generated is not necessarily indicative of the true swallow response exhibited by the patient. Further, total clearance of material from the oropharyngeal and esophageal cavities would be a useful visual cue to determine whether the function of these structures is within normal limits. If the oropharynx is coated with too much contrast agent, the dense X-ray cross-section creates a complete opacity in the resultant X-ray exposure, which does not provide sufficient detail of the structures involved in swallowing. A complicating factor is the taste and chalky texture of barium suspensions, which makes them generally unpleasant to hold in the mouth and to swallow. Substances that are more food-like in taste and texture would more likely elicit a more representative swallow response.
See, for example, U.S. Pat. No. 4,020,152 to Heitz, which describes barium titanate and barium zirconate X-ray contrast agents. This patent specifically notes that it is quite difficult to generate fluoroscopic images of the oropharyngeal cavity. Heitz states that patients have great difficulty in holding a mouthful of contrast medium at the very back of their throats for a long time without swallowing. When the patient swallows the barium sulfate suspension, it slides over the mucous membranes, often without leaving sufficient contrast agent in place to generate an image. Heitz believes the lack of adhesion is due to the saliva covering the walls of the oropharynx, which substantially reduces the adherence of a barium sulfate suspension. As a result, radiological examination of this key physiological intersection, the junction where aspiration occurs, is difficult and often leads to only mediocre imaging. Failure to generate a clean radiological image of the swallow leads to imprecise diagnosis and treatment.
Moreover, once a patient has been diagnosed as having dysphagia and is known to be aspirating foods, some compensatory treatment must be implemented to prevent further aspiration. One method widely employed is to alter the consistency (i.e., the viscosity) of liquid foods. Thickened liquid foods are thought to inhibit aspiration by providing greater mechanical resistance to the muscles involved in swallowing and providing greater “mouthfeel” to the patient. See, for example, U.S. Pat. No. 5,932,
DeWitt Ross & Stevens S.C.
Jones Dameron L.
Leone, Esq. Joseph T.
Wisconsin Alumni Research Foundation
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