------------------------------------------------------------------------------ TITLE: EVALUATION AND MANAGEMENT OF ASPIRATION SOURCE: Dept. of Otolaryngology, UTMB, Grand Rounds DATE: January 15, 1992 RESIDENT PHYSICIAN: Robert Hoffman, MD FACULTY: Byron Bailey, MD SERIES EDITOR: Francis B. Quinn, Jr., M.D. ------------------------------------------------------------------------------ "This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion." I. Introduction The larynx has three basic functions: protection of the tracheobronchial tree, respiration and phonation. The loss of the protective function of the larynx can lead to intermittent or persistent aspiration producing life threatening pulmonary disease. Fever, bronchospasm, and atelectasis may result from aspiration of small quantities of material. The effect on the lungs will vary according the amount of aspirate, the pH of the aspirate, and the underlying status of the pulmonary, cardiovascular and immune systems. When large amounts of material are aspirated, especially with a low pH, an intense bronchospasm is usually produced as well as severe injury to the pulmonary capillary endothelium and the epithelium of the distal airway. The resulting hypotension, hypoxia, hypercarbia and pulmonary edema may be fatal. The causes of aspiration are varied and require careful evaluation to determine the best treatment course. II. Anatomy and Physiology The normal swallowing mechanism is dependent upon rapid neuromuscular coordination of structures in the oral cavity, pharynx, and larynx during a brief cessation respiration. If the event does not occur in a synchronized fashion, there will be nasal reflux, choking, aspiration and regurgitation. This mechanism can be divided into three stages: oral stage, pharyngeal stage, and esophageal stage. Oral Stage: Oral preparation, the voluntary stage of the swallowing mechanism, involves the coordination of lip closure, rotary and lateral motion of the jaw, buccal tone, rotary and lateral motion of the tongue, and anterior bulging of the soft palate to narrow the oropharyngeal inlet. This serves to break food down to a consistency appropriate for swallowing and to mix it with saliva. Once food is formed into a bolus, it is held against the center of the palate immediately prior to beginning the swallow. The tongue then moves upward and backward propelling the bolus in the pharynx. Pharyngeal Stage: The pharyngeal stage starts when the bolus passes the faucial pillars and is a completely involutary action. The complex series of events which comprise this stage include: A. Velopharyngeal closure to prevent food or liquid from refluxing in the nose. B. Laryngeal elevation and anterior movement to carry the larynx up under the tongue and out of the path of the bolus, as well as to apply extrinsic stretch to the cricopharyngeal region. C. Laryngeal closure to prevent material from penetrating the larynx. This starts at the level of the vocal folds and progresses superiorly to the false cords, the epiglottis and aryepiglottic folds. True vocal cord closure is essential to airway protection during swallowing. Closure of the laryngeal vestibule to prevent entrance of food and liquid is performed by movement of the epiglottis. This is performed by a combination of three forces (1) the bolus pressure from above, (2) the downward pull of muscular forces such as the aryepiglottic muscle and (3) the combined pressures of the tongue base moving posteriorly and the larynx elevating. D. Pharyngeal peristalsis to clean the pharynx with a wave of contraction. This is a superior to inferior muscular contraction that begins at the nasopharynx with the superior constrictor and progresses to the hypopharynx with the inferior constrictor. The peristaltic wave clears residual material and applies back pressure to the bolus. E. Opening of the cricopharyngeal region. The cricopharyngeal valve or upper esophgeal sphincter is a musculoskeletal valve composed of the cricopharyngeus muscle, the lower fibers of the inferior constrictor and the upper fibers of the esophageal constrictor. At rest, the cricoid lamina touches the posterior pharyngeal wall thus maintaining the closure of the sphincter. The anterior and superior movement of the larynx stretches the muscular component of the sphincter and separates the cricoid lamina from the posterior pharyngeal wall. Relaxation of the cricopharyngeaus muscle increases compliance of the muscular portion to further allow passage of the bolus. Esophageal Stage: The esophageal stage involves active peristalsis from the top to the bottom. This stage concludes when the bolus passes through the lower esophageal sphincter. This is a circular muscular valve that opens to allow the passage of the bolus but is otherwise closed to prevent gastroesophageal reflux. III. Pathophysiology of Swallowing Disorders A. Disruptions in the oral stage Swallowing may be disrupted in this stage by preventing proper lip closure secondary to facial nerve dysfunction or structural damage to the orifice. Decreased range of motion of the jaw will inhibit the ability masticate and break food down to a consistency ready to swallow. However, reduced tongue control is the only one that can lead to aspiration. Bits of food may fall into the open airway before the pharyngeal swallow is triggered. Since the tongue is partly responsible for triggering the stimulus for the pharyngeal swallow, uncoordinated lingual movements can lead to a delay in triggering the reflex. This is characterized by loss of the bolus over the back of the tongue into the pharynx before the reflex is elicited. Where the bolus is directed depends on the patients position and the size, consistency and viscosity of the bolus. B. Disruptions of the pharyngeal swallow Neurologic or structural damage may also produce aspiration once the involuntary pharyngeal swallow is started. Reduced soft palate closure can result in reflux of food into the nose. Reduction in pharyngeal peristalsis unilaterally will result in food collecting on the damaged side. Bilateral reduction will cause food to be collected on both sides, the valleculae and the pyriform sinuses. Remaining residue may then be aspirated on inspiration following the swallow. Reduced laryngeal elevation will cause the larynx to sit lower in the neck where food can enter during the swallow. It will also prevent the epiglottis from moving posteriorly and folding over the airway. Elevation of the larynx also causes opening of the cricopharyngeal valve. A delay in opening of the valve will prevent food from entering the esophagus and allow aspiration to occur. C. Disruptions of the esophageal stage The presence of a large hiatus hernia or a nasograstric tube may allow reflux of gastric contents and possible aspiration. Patients may report a sensation of a ball in the throat at the level of the cricoid cartilage, regurgitation, heartburn, or a salty taste in the mouth. Partial or total esophageal obstruction often presents with dysphagia and intermittent aspiration. Acute onset is usually related to foreign bodies. Slowly progressive symptoms can be found in patients with esophageal webs, strictures, achalasia, narrowing related to collagen- vascular diseases or esophageal carcinomas. Cripharyngeal muscle dysfunction can be found in disorders of the central or peripheral nervous system, with myopathies, secondary to trauma or surgery, or may be idiopathic spasm. Symptoms may include a choking sensation occurring 1 to 2 seconds after swallowing, more difficulty swallowing liquids than solids and a delay in clearing the pharyngeal phase leading to aspiration. Zenker's diverticulum is a herniation of mucosa at the level of the upper esophageal sphincter. It presents most commonly in the sixth and seventh decades of life. As the sac enlarges, dysphagia becomes more severe and the patient begins to regurgitate undigested food. The patient may then develop recurrent aspiration and pneumonia. Tracheoesophageal fistulas, excluding the congentital variety, are most commonly encountered in patients with esophageal carcinomas. Four keystones of swallowing determine the severity of aspiration when it occurs. These are (1) the ability of the tongue to elevate and retract posteriorly over the laryngeal inlet, (2) intact sensory innervation of the larynx, (3) the ability of the larynx to maintain a pressure gradient with glottic competence and (4) intact function of the cricopharyngeal sphincter. Provided that two of these keystones remain intact, the degree of aspiration usually remains minimal. If more than two of these are affected, then aspiration will be a significant problem. IV. Evaluation of Aspiration A. Clinical evaluation Initial evaluation starts with a complete past and present medical history. Patients with a history of major neurologic or neuromuscular disease or patients who have had head and neck surgery present a different diagnostic situation than do generally healthy patients. Physical examination should include the traditional head and neck exam to rule an out undiagnosed tumor or infection. Indirect laryngoscopy provides essential information regarding inability to protect the airway secondary to lesions, inflammation or paresis. It should also include a careful exam of cranial nerve function and symmetry. A swallowing performance screen should also be performed with a 5 to 10cc bolus of water. The patient should be able to perform this without tipping the head back, drooling, choking, coughing, or delay. Neurologic disorders that present particular risks for aspiration can be classified by the anatomic region of the nervous system involved: - Central nervous system Diffuse disorders: infection, increased intracranial pressure, degenerative disorders, seizures, CNS depression leading to stupor or coma Pyramidal system: motor neuron disease, syringomyelia, malformation, tumor, stroke Extrapyramidal system: myoclonus, chorea, tardive dyskinesia, dystonia, parkinsonism - Peripheral nervous system: Guillain-Barre syndrome, porphyria, laryngeal nerve injury - Neuromuscular junction: Myasthenia gravis, Eaton- Lambert syndrome, acute botulism - Myopathies: Polymyositis, progressive muscular dystrophy, metabolic myopathy, periodic paralysis B. Diagnostic Techniques A variety of techniques are available for visualization of the oropharynx during swallowing. These include manometry, scintigraphy, computerized axial tomography, ultrasonography, still x-rays, videofluoroscopy and magnetic resonance imaging. Still X-rays - Although still x-rays do not offer dynamic evaluation of swallowing, they clearly visualize the bony structures of the nasopharynx, oropharynx, laryngopharynx, the vertebrae, cartilage and the opened airway. CT scans and MRI - These studies are used to detect brain stem or cortical lesions which are common causes of dysphagia in patients with neurologic dysfunction. MRI is more sensitive in detecting brain lesions because it can obtain multiple plane images of the CNS and provides clearer imaging of the posterior fossa. Ultrasonography - This study offers real-time imaging of the oral cavity for evaluation of speech and swallowing. The transducer is placed beneath the chin and is rotated 90 degrees to obtain sagittal and coronal images of the tongue. This allows for excellent studying of the oral stage of swallowing by imaging the bolus placement, bolus transport, and initiation of the pharyngeal stage. Recording the images on videotape allows for frame-by-frame analysis. Scintigraphy - Scintigraphic examination uses radionuclide scanning during the ingestion of a radioactive bolus. The patient is placed in an upright 80 degree right anterior oblique position against a scintillation camera interfaced with a computer. A dose of Tc-99 sulfur colloid in 20cc water in then given to the patient. When the patient swallows, the camera records for approximately six seconds. Static images are then obtained at ten minutes following the swallowing. Scintigraphy may then accurately quantitate the percentage of ingested material passing below the larynx into the tracheobronchial tree and quantitate transit times. Videofluoroscopy can only estimate the amount aspirated. However, scintigraphy is not able to demonstrate the mechanism of swallowing and how the bolus enters the larynx. Pharyngeal manometry - Manometry measures pressure changes created by displacement of fluids moving through a tube. Pressure transducers with internal strain gauges are place inside a catheter which is then directed orally or transnasally through the pharynx into the esophagus. The system is then capable of measuring the amplitude of the pharyngeal peristalsis. It is best used in conjunction with videofluoroscopy since fluoroscopy ensures proper positioning of the sensors and simultaneous correlation with the sequential anatomic components of swallowing can be made. Diagnostically, it is best used to evaluate dysfunction of the pharyngoesophageal sphincter. Increased sphincter pressures will lead to a delay in the bolus entering the esophagus and possibly aspiration. Videofluoroscopy - This is the most commonly used procedure for the study of swallowing because it is able to depict the entire structure of the oropharynx and the passage of the bolus from the oral cavity to the esophagus in real-time. The standard barium swallow is designed to visualize the flow of a large bolus and focuses on the peristaltic motion of the esophagus as the bolus moves toward the stomach. It is designed to detect esophageal rings, webs, mucosal defects and inflammatory lesions of the esophagus. In a modified barium swallow, the focus is on the anatomy and physiology of the oropharynx. It is performed with the patient's speech pathologist present so that they can assess the patient's swallowing ability and construct a rehabilitation strategy. The patient is given small amounts of a barium preparation of varying consistencies from thin liquids, to paste, to a piece of cookie coated with barium. By varying the amounts and consistency of the contrast enables the examiner to determine which foods match the patient's swallowing physiology. V. Medical Management A. Initial approach After intractable aspiration is identified, aspiration prevention by nonsurgical measures is attempted. Pulmonary complications of aspiration are treated and aggressive pulmonary toilet is undertaken. Oral intake should be discontinued and an alternative route of alimentation instituted. Nutrition can be provided by enteral route such as nasogastric tube, gastrostomy or jejunostomy or by parenteral hyperalimentation. After evaluation with a modified barium swallow by a speech pathologist, compensatory strategies can be undertaken. Patients with disorders of tongue function, a delay in triggering the pharyngeal swallow, or reduced laryngeal closure generally do best with a thickened liquid because they are able to control the bolus better and prevent splash into the pharynx before the pharyngeal swallow can be triggered. Patients with either unilateral or bilateral pharyngeal peristalsis disorders or reduced laryngeal elevation tend to do better with thin liquid consistencies that require less peristalsis and do not collect around the laryngeal inlet. Various postures can also make swallowing more efficient. Patients with reduced tongue control that is unilateral may do best to lean toward their stronger side in order to keep food on that side while they are chewing and swallowing. Patients who are not capable of moving the bolus posteriorly may benefit from tilting the head back during swallowing. Patients with a delay in triggering the pharyngeal swallow may tilt the head forward to widen the valleculae and put the epiglottis in a more protective position. Patients with a unilateral layngeal dysfunction may turn their head to the damaged side to increase laryngeal closure. This also closes the pyriform sinus and directs food down the stronger side. B. Gastroesophageal reflux The presence of a large hiatus hernia or a nasogastric feeding tube may allow reflux of gastic contents and possible aspiration. Reflux of gastric acid has also been associated with cricopharyngeal spasm. Evaluation may include a barium upper GI study or fiberoptic endoscopy. Initial management includes antacids after each meal and at night. Dietary recommendations are to avoid acidic and spicy foods, alcohol, smoking, caffeine, fatty foods, chocolates and meals before bedtime. Cigarettes and alcohol have been shown to relax the lower esophageal sphincter and thus increase esophageal reflux. If initial management fails, a histamine (H)2 blocker for a short course should be used. If the patient follows the dietary recommendations and does not respond to H2- blockers, further testing is indicated. These tests include fiberoptic endoscopy, pH probe, manometry, nuclear medicine scans and the Bernstein infusion test. Further treatment may include medications to stimulate esophageal contractions. Bethanechol which has cholinergic, parasympathetic actions and metoclopramide which is a dopaminergic-blocker have been used for this purpose. VI. Surgical Management Therapy for swallowing disorders is based on the understanding of the normal sequence of events in swallowing and how a patient's pathology deviates from that sequence. Surgical mangagement must then be tailored to correct the deficits. A. Laryngeal incompetence Tracheotomy - This is the most common method of dealing with copious, chronic aspiration. By using a cuffed tracheotomy tube, the airway can be secured through an independent external port. Substances that pass through the larynx will be kept from the trachea by the tracheotomy tube cuff. However, the major swallowing disorder associated with tracheotomy is aspiration. The pathophysiology of aspiration with tracheotomy is both mechancical and neurophysiologic. Decreased laryngeal elevation, esophageal obstruction by the cuff and increasing cuff pressures causing tracheomalacia and an ineffective seal are the mechanical effects of the tracheotomy tube. Desensitization of the larynx with loss of protective reflexes and uncoordinated laryngeal closure are its neurophysiologic effects. Therefore, tracheotomy is a short-term solution. Glottic prosthesis - A laryngeal stent can be used to obturate the larynx and prevent aspiration. After a tracheotomy is performed, stent can be placed endoscopically with percutaneous sutures to secure its position. The advantages include the ease of placement and reversibility. The disadvantages are leakage of fluid around an inefficient seal, scarring at the glottic level, and discomfort. Vocal cord augmentation - A symptomatic open glottic chink due to mechanical impairment, anatomic deficiency, or neuromuscular disability that is not accommodated for by the contralateral cord can be corrected. Teflon can be injected in the vocal cord via direct laryngoscopy producing medialization of the cord. This procedure is best done under local anesthesia. If medialization is necessary but there is some hope of return of function, gelfoam can be used. This provides medialization until the material is resorbed. In larger defects, augmentation with a cartilage implant can be performed. The technique was described by Meurmann in 1952 and there have been many refinements since. Glottic and supraglottic laryngeal closure - Glottic closure was described by Montgomery in 1975. The technique is performed through a median thyrotomy. The mucosa of the vocal cords is stripped bilaterally and a figure of eight suture is placed to close the glottis. The procedure was modified by Sasaki to include a sternohyoid muscle flap interposed into the subglottic region to provide a better seal. The advantage of this technique is separation of the air and food passages with a permanent tracheotomy. The disadvantages are that the patient cannot phonate and the seal occasionally pulls apart if the vocal cords are functional preoperatively. Though the procedure is potentially reversible, laryngeal webs are difficult to remove and the vocal cords may not function properly following reversal. - Supraglottic closure was described by Habal and Murray in 1972. Through a pharyngotomy incision, an incision is made around the perimeter of the epiglottis, aryepiglottic folds, arytenoids and interarytenoid area. The epiglottis is then folded over the arytenoids and the mucosa is closed with absorbable suture. This enables the patient to use an uncuffed tracheotomy tube. The patient is unable to talk but the procedure is potentially reversible. Brookes described a modification of this technique which leaves a small opening in the posterior laryngeal inlet and a cricopharyngeal myotomy is performed. This allows the patient to phonate through the inlet. Laurian described another technique in which a small opening is left on the lateral aspect of the closure. -Laryngeal diversion Lindeman described a procedure to separate the air and food passages without damage to the laryngeal structures. In this procedure, the trachea is mobilized with care to avoid injury to the recurrent laryngeal nerves. The trachea is then transected between the second and third tracheal rings or at the level of the existing tracheostomy. The distal portion is brought out and sewn to the neck skin. A small opening is then made in the esophagus at the level of the proximal tracheal stump. The edges of the esophageal opening are then sewn to the proximal trachea in an end to side anastomosis. Baron and Dedo adapted a blind pouch technique by inverting the subglottic mucosa with interrupted sutures then oversewing the stump with a running suture. Patients cannot phonate after the procedure but laryngeal function can easily be assessed by indirect laryngoscopy or modified barium swallow. The procedure can then be reversed when laryngeal function has returned. Indications for these procedures have been published by Gilbert and Eisele. Patients with intractable aspiration that have failed conservative management with nasogastric or gastrostomy tube, NPO status and aggressive pulmonary toilet should be considered for these procedures. Eisele prefers the tracheoesophageal diversion procedure because the anastomosis allows secretions and oral intake to drain into the esophagus without pooling. Gilbert prefers the subglottic closure technique because it is relatively simple and does not require any surgical opening into the pharynx. He reported no complications related to the proximal stump in his study. These techniques have been described in patients with life-threatening chronic aspiration as young as two months old. -Laryngectomy This procedure provides a permanent cutaneous tracheostome and a permanent separation of the airway and food passage. It eliminates phonation, the possibility of reversal and involves the morbidity of and extensive surgical procedure. B. Cricopharyngeal myotomy When cricopyaryngeal muscle dysfunction is due to a systemic disorder, maximal medical treatment of the disorder should be used prior to surgery. A cricopharyngeal myotomy is performed through a left lateral neck incision. The larynx and upper esophagus are reached by retracting the thyroid lobe medially and the carotid sheath laterally. The recurrent laryngeal nerve can be identified as it crosses the inferior thyroid artery and then traced superiorly until its insertion. In some cases a large bougie can be inserted orally into the esophagus. The myotomy is then performed posteriorly near the midline. It is extended superiorly to include the lower one third of the inferior constrictor muscle and inferiorly to include 1 cm. of the circular esophageal muscle fibers. The wound is then closed over a drain. Zenker's Diverticulum - The surgical approach is identical to that used in the cricopharyngeal myotomy. Once the sac is identified and its juncture with the hypopharyngeal mucosa is identified, the neck is clamped and the diverticulum is excised. A cricopharyngeal myotomy is then performed. ---------------------------------------------------------------------------- BIBLIOGRAPHY Blitzer, A, et al. 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