Identification of swallowing disorders in early and mid-stage Parkinson's disease using pattern recognition of pharyngeal high-resolution manometry data.

BACKGROUND: Parkinson's disease (PD) can cause severe dysphagia, especially later in disease progression. Early identification of swallowing dysfunction may lead to earlier intervention. Pharyngeal high-resolution manometry (HRM) provides complementary information to videofluoroscopy, with advantages of being quantitative and objective. Artificial neural network (ANN) classification can examine non-linear relationships among multiple variables with relatively low bias. We evaluated if ANN techniques could differentiate between patients with PD and healthy controls. METHODS: Simultaneous videofluoroscopy and pharyngeal HRM were performed on 31 patients with early to mid-stage PD and 31 age- and sex-matched controls during thin-liquid swallows of 2 cc, 10 cc and comfortable sip volume. We performed multilayer-perceptron analyses on only videofluoroscopic data, only HRM data or a combination of the two. We also evaluated variability-based parameters, representing variability in manometric parameters across multiple swallows. We hypothesized that patients with PD and controls would be classified with at least 80% accuracy, and that combined videofluoroscopic and HRM data would classify participants better than either alone. KEY RESULTS: Classification rates were highest with all parameters considered. Maximum classification rate was 82.3 ± 5.2%, recorded for 2 cc swallows. Inclusion of variability-based parameters improved classification rates. Classification rates using only manometric parameters were similar to those using all parameters, and rates were substantially lower for the comfortable sip volumes. CONCLUSIONS & INFERENCES: Results from these classifications highlight the differences between swallowing function in patients with early and mid-stage PD and healthy controls. Early identification of swallowing dysfunction is key to developing preventative swallowing treatments for those with PD.

Electromyographic activity from human laryngeal, pharyngeal, and submental muscles during swallowing.

The durations and temporal relationships of electromyographic activity from the submental complex, superior pharyngeal constrictor, cricopharyngeus, thyroarytenoid, and interarytenoid muscles were examined during swallowing of saliva and of 5- and 10-ml water boluses. Bipolar, hooked-wire electrodes were inserted into all muscles except for the submental complex, which was studied with bipolar surface electrodes. Eight healthy, normal, subjects produced five swallows of each of three bolus volumes for a total of 120 swallows. The total duration of electromyographic activity during the pharyngeal stage of the swallow did not alter with bolus condition; however, specific muscles did show a volume-dependent change in electromyograph duration and time of firing. Submental muscle activity was longest for saliva swallows. The interarytenoid muscle showed a significant difference in duration between the saliva and 10-ml water bolus. Finally, the interval between the onset of laryngeal muscle activity (thyroarytenoid, interarytenoid) and of pharyngeal muscle firing patterns (superior pharyngeal constrictor onset, cricopharyngeus offset) decreased as bolus volume increased. The pattern of muscle activity associated with the swallow showed a high level of intrasubject agreement; the presence of somewhat different patterns among subjects indicated a degree of population variance.

Complications of translaryngeal intubation.

The human larynx is complex and serves multiple functions. Unfortunately, endotracheal tubes do not reproduce all these functions. They serve well as air passages but cannot do so without damaging the mucosa of the posterior larynx. It appears that complications secondary to airway problems in the operating room are decreasing as the use of oximetry and capnometry becomes routine. It is hoped that this reduction in complications will carry over into the chronic care setting as such monitoring becomes the standard after intubations. Compared with malposition of the tube, most of the other complications of intubation are minor. However, knowledge of the various complications can ensure avoidance of many and early detection and correction of others.

Laryngeal activity during swallow, phonation, and the Valsalva maneuver: an electromyographic analysis.

To better understand the mechanisms of airway protection during swallow, the authors of this study performed an electromyographic (EMG) analysis on the thyroarytenoid (TA) and interarytenoid (IA) muscles during a variety of tasks. The tasks included high, low, and comfortable pitch phonation, the Valsalva maneuver, saliva swallow, and 5- and 10-mL water swallows. Raw EMG signals were analyzed to obtain root mean square data, which correspond to a relative magnitude of muscle activation. The data show that both TA and IA muscles generate a similar level of relative activation, with the greatest electrical activity observed during swallow tasks followed by the Valsalva maneuver and phonation. The duration, onset, offset, and pattern of activity during the swallowing tasks also showed close synchronization between the two muscles. These data can be used in designing therapy for voice disorders and pharyngeal dysphagia.

Resource utilization and patient morbidity in head and neck reconstruction.

Many papers have addressed the technical aspects of free tissue transfer in head and neck cancer patients. However, there has not been a critical assessment of the impact of free tissue transfer on resource utilization and patient morbidity compared with pedicle flap reconstructions. Two cohorts of patients derived from 245 consecutive reconstructions were tightly matched by age, site, stage, and histology, yielding 44 patient pairs differing in method of reconstruction. Patients undergoing free flap reconstruction spent more time in the operating room than those reconstructed with pedicled flaps (993 min vs. 777 min, P < 0.0001). The group with free flap reconstruction spent fewer days in the surgical intensive care unit and hospital (2 days vs. 2.5 days; 18.5 days vs. 22.6 days). This difference is attributed to the paucity of postoperative complications in the group with free flap reconstruction (fistula formation 4.5% vs. 21%, P < 0.04). These data indicate that the continued use of sophisticated reconstructive techniques in head and neck cancer patients is economically sound as assessed by patient morbidity and resource utilization.

Perioperative complications and risk factors in the surgical treatment of obstructive sleep apnea syndrome.

A retrospective review of 135 patients surgically treated for obstructive sleep apnea syndrome (OSAS) from 1982 to 1987 was performed to identify perioperative complications and potential risk factors. The incidence of complications was 13% (18/135). Airway problems comprised 77% (14/18) of these complications, resulting in one death. There were three postoperative hemorrhages and one postoperative arrhythmia. Comparison of the complication group versus the noncomplication group showed a statistically significant difference in the minimum oxygen saturation (66% vs. 79%) and apnea index (75 vs. 57) on the pre-operative sleep study and in the amount of narcotic administered intraoperatively. Patients with intubation complications tended to be heavier, whereas patients with extubation complications received significantly more narcotic analgesia intraoperatively. Risk for a perioperative complication was not related to age, type of obstructive symptoms, medical problems, or concurrent septoplasty/tonsillectomy. A protocol for perioperative airway management is presented.

Arytenoid adduction combined with Gore-Tex medialization thyroplasty.

OBJECTIVE: To describe the technique of combined Gore-Tex medialization thyroplasty with arytenoid adduction and to determine the long-term vocal outcome of patients treated for unilateral vocal cord paralysis with this procedure. STUDY DESIGN: A retrospective chart review and patient reevaluation for patients treated at The University of Iowa Hospitals and Clinics between May 1995 and June 1999. METHODS: The review addressed patient demographics, perioperative and long-term complications, and voice outcomes. Details of the surgical technique are provided within the manuscript. RESULTS: Seventy-two Gore-Tex medialization procedures were completed. Arytenoid adduction was included in 22 of these procedures. This subset of patients was compared with the patients treated with Gore-Tex alone. No major postoperative complications occurred in either group. Preoperative and postoperative voice and videostroboscopy data were available for 19 arytenoid adduction patients and 25 Gore-Tex alone patients. On a seven-point scale (6 [severely abnormal] --> 0 [normal voice]), the average patient rating of voice dysfunction improved from 4.2 to 1.6 (arytenoid adduction) and 4.5 to 2.8 (Gore-Tex alone). Maximum phonation time improved from 6.9 seconds to 16.7 seconds in the arytenoid adduction group. Subjective voice assessment employing the four-point GRBAS scale (3 [severely abnormal] --> 0 [normal]) identified average improvement from an overall grade of 2.1 to 0.8 arytenoid adduction and 2.2 to 1.5 in the Gore-Tex alone group. Improvement was identified in the vocal quality of breathiness from 1.9 to 0.2 (arytenoid adduction) and 1.9 to 0.9 (Gore-Tex alone). CONCLUSIONS: The combined technique of Gore-Tex medialization thyroplasty and arytenoid adduction provide functional results that appear to exceed the improvement attained with medialization alone.

Functional magnetic resonance imaging using iron oxide particles in characterizing head and neck adenopathy.

OBJECTIVES: In lymph nodes harboring metastases the reticuloendothelial system is replaced by tumor cells and does not concentrate iron particles. This study assesses the value of contrast magnetic resonance imaging (MRI) using ultrasmall superparamagnetic iron oxide particles (Combidex, Advanced Magnetics, Inc., Cambridge, MA) to characterize and stage neck nodes. STUDY DESIGN: Prospective analysis of neck imaging by Combidex MRI, with correlation from pathological assessment of resected lymph nodes. METHODS: Nine patients underwent MRI and subsequent bilateral neck dissections (three), unilateral neck dissections (five) or fine-needle aspiration (one). Each case was evaluated for the number, location, MRI characteristics, and pathological assessment of lymph nodes. RESULTS: Forty-nine separate nodal levels were evaluated with both Combidex MRI and pathological assessment. The presence of metastatic nodal involvement among 45 levels was correctly assessed by the Combidex MRI (three false-negative results, one false-positive result; sensitivity, 84%; specificity, 97%). Analysis was possible for 101 of the individual lymph nodes identified by MRI that could be correlated with individual nodes pathologically examined. Combidex MRI assessment was correct for 99 nodes (one-false positive result, one false-negative result; sensitivity, 95%, specificity, 99%). Standard MRI interpretation without Combidex identified that 12 of 18 nodes (67%) that were greater than or equal to 10 mm (greatest dimension) contained tumor, whereas 9 of 83 nodes (ll%) that were less than 10 mm contained tumor. CONCLUSIONS: Combidex MRI provides functional information to characterize lymph nodes in the clinical staging of squamous cell carcinoma of the head and neck. The inability of MRI to identify small lymph nodes restricts the usefulness of this technique.

Esthesioneuroblastoma: the University of Iowa experience 1978-1998.

OBJECTIVE: Esthesioneuroblastoma is rare and the best treatment has yet to be defined. The purpose of this study is to analyze the natural history, treatment, and patterns of failure of esthesioneuroblastoma treated at one institution. METHODS: Between 1978 and 1998, 13 patients with esthesioneuroblastoma were identified using the University of Iowa Tumor Registry. All patients were staged according to Kadish criteria. Mean follow-up was 6.3 years. Six patients had 5 or more years of follow-up and four had follow-up exceeding 9.5 years. One patient was lost to follow-up at 36 months. RESULTS: No patients had Kadish stage A disease, five were stage B, and eight stage C. Overall actuarial 5- and 10-year survival rate was 61% and 24%, respectively. Disease-free survival rate at 5 and 10 years was 56% and 42%, respectively. Seven patients have died, three of intercurrent disease and three of disease progression, one with an unknown disease status. Six patients remain alive, three without evidence of disease and three have experienced a local or regional recurrence. Five patients who were initially controlled developed recurrence, three local only, one locoregional, and one regional and distant. Median time to failure was 96 months. All patients with follow-up exceeding 12 years have experienced either a local or regional recurrence. Survival after salvage therapy in these patients ranged from 3 to 12 years. CONCLUSION: Esthesioneuroblastoma has a long natural history characterized by frequent local or regional recurrence after conventional treatment. Successful retreatment can lead to prolonged survival.

Laryngeal cancer cost analysis: association of case-mix and treatment characteristics with medical charges.

OBJECTIVES: To examine the relationship of various pretreatment case-mix characteristics and treatment modalities with medical charges incurred during diagnosis, treatment, and 2-year follow-up for patients with laryngeal cancer. DESIGN: Retrospective chart review and billing record analysis. METHODS: The charts and billing records of patients diagnosed with laryngeal cancer at the University of Iowa Hospitals and Clinics (UIHC) between January 1, 1991 and December 31, 1994 were reviewed. The independent variables included various pretreatment patient-mix and tumor characteristics (age, AJCC TNM clinical stage, smoking history, ASA class, and comorbidity as defined by Kaplan-Feinstein grade) as well as type of treatment. The dependent variables included total physician, office, and university hospital-based charges incurred during the pretreatment evaluation and 0- to 3-, 3- to 12, and 12- to 24-month billing periods after the initiation of cancer-directed therapy. Total 1-year and 2-year charges were also evaluated. Univariate and multivariate analyses were used to investigate the relationships between dependent and independent variables and to develop models predictive of management charges during the individual and total billing periods. RESULTS: Pretreatment charges showed no significant associations (P < .05) with any of the independent variables. Multiple regression analyses indicated that comorbidity, stage, and initial treatment modality were significant variables in one or more of the models predicting charges incurred during the 0- to 3-month, 3- to 12-month, total 1-year, and total 2-year billing periods. The models yielded R2 values for the total 1- and 2-year billing periods of 0.5246 and 0.5055, respectively. CONCLUSIONS: This work supports continued study of measures that may result in earlier detection of laryngeal cancer as a potential means of reducing management charges. These results also indicate that a more accurate method of stratifying the disease severity of laryngeal cancer patients for reimbursement purposes would include measurements of the severity of the index disease as well as comorbid diseases.

Blood transfusion as a risk factor for death in stage III and IV operative laryngeal cancer. The Department of Veterans Affairs Laryngeal Cancer Study Group.

OBJECTIVE: To evaluate the role of a blood transfusion in a patient population with head and neck cancer that was treated with combined therapy (surgery and radiation). DESIGN: Retrospective, nonrandomized end point study. Univariate and multivariate analysis of 24 variables, including transfusion status. SETTING: The Veterans Affairs Cooperative Study (Cooperative Studies Program 268). PATIENTS: Patients in the surgical arm of the study (166 patients) underwent surgery and postoperative radiation therapy for advanced (stage III and IV) laryngeal cancer. MAIN OUTCOME MEASURES: Identification of variables related to patient time to death. RESULTS: The univariate analysis identified age, clinical N (lymph node) class, primary tumor site, number of pathologically positive lymph nodes, extracapsular spread, pretreatment screening hematocrit, hematocrit and albumin level at 1 month after treatment, intraoperative fluids and units of blood, and total units of blood as significant (P < .05). The stepwise multivariate models identified independent significance in clinical and pathologic node status, hematocrits at both screening and 1 month, extracapsular spread, albumin level at 1 month, age, and primary site. The position of each variable within the individual regression models varied. CONCLUSIONS: Clinical N class or pathologic node status occupied the first position of predictive significance in all models. Blood transfusion status never retained independent significance in any multivariate assessment.

Head and neck liposarcoma. A histopathologic reevaluation of reported cases.

Head and neck liposarcoma is an extremely rare tumor. As with all rare lesions there is a void in the literature regarding tumor activity and treatment response. It is difficult to make rational treatment plans and advise patients as to probable treatment response and prognosis. To obtain as much information as possible from available data we have reviewed the world literature and reevaluated the descriptive histopathologic findings and treatment response of reported cases. Seventy-six cases have been reported since 1911. We added another case and then reclassified the previously reported lesions according to a current histopathologic system (well-differentiated, myxoid, round-cell, and pleomorphic lesions). We assessed tumor activity and treatment response by histopathologic tumor type. Paralleling tumor activity in other anatomic regions, all patients with myxoid and well-differentiated tumors did well; all were alive at the end of follow-up, eight of eight and 11 of 11, respectively (average follow-up, 5.7 and 4.8 years). This is compared with a 50% mortality rate in the round-cell and pleomorphic groups by the end of 2 years, (two of three and six of 11 patients alive, respectively). The likelihood of recurrence correlated with extent of tumor removal, and metastatic disease was identified almost exclusively with the tumor of the round-cell and pleomorphic variants. Surgical excision remains the primary treatment modality, while radiation and chemotherapy appear to be of limited utility.

Blood use in head and neck tumor surgery. Potential for autologous blood.

Recent increased concern regarding the risks of homologous blood transfusion led us to examine the use of blood products for head and neck tumor surgery. Major head and neck surgical procedures at three University of Washington (Seattle)-affiliated hospitals during 1987 were reviewed. Seventy-seven patients were identified. Parameters studied included the following: tumor site and stage, prior treatment, surgical procedure, preoperative and postoperative hematocrit values, estimated blood loss, operative and postoperative blood product use, and operative time. Data were grouped by procedure. Maxillectomy/midface procedures showed the highest average estimated blood loss (1037 mL) and the highest average blood use (1.5 units), followed by composite resections (883 mL and 0.8 units) and laryngectomies (724 mL and 0.9 units). When the data were subgrouped, larynogopharyngectomy (1450 mL and 4.0 units) and composite resection with mandibular swing (1300 mL and 1.0 units) showed the highest blood loss and blood product use. In the assessable groups, previous administration of radiation did not make a significant difference in blood loss or procedure time. However, blood loss correlated well with procedure time in all groups. The great majority of patients met all requirements to function as blood donors (84%). Sixty-five percent of patients met all criteria and used less than 2 units of blood, making autologous blood a reasonable option for the majority of patients with head and neck tumors.

Free-tissue transfer reconstruction of midfacial and cranio-orbito-facial defects.

OBJECTIVE: To review our results using free-tissue transfer to reconstruct midfacial and cranio-orbito-facial defects. DESIGN: Case series. SETTING: The University of Iowa Hospitals and Clinics, Iowa City. PATIENTS: Fourteen of 21 patients had defects that resulted from ablative oncologic surgery; six had severe mid-facial trauma; and one had Romberg's disease. INTERVENTIONS: Four latissimus dorsi, 11 rectus abdominis, three scapula, and four forearm free-tissue transfer flaps were used. MAIN OUTCOME MEASURES: Adequate flap separation of vital structures (intracranial contents and carotid artery) from the sinonasal or oropharyngeal cavities; restoration of palatal competence, oral diet, and speech intelligibility; maxillary dental rehabilitation; aesthetic results; complications; and the patient's return to social activities outside the home after surgery. RESULTS: The intracranial contents (six cases) or carotid artery (four cases) were protected from sinonasal or oropharyngeal contamination by the reconstructive flap in all cases in which this was required. Functional closure of the palate with the flap or a prosthesis was possible in 12 of the 13 patients with a palatal defect; seven of these 13 patients have had full maxillary dental rehabilitation. Twenty patients take an oral diet. Sixteen patients have normal or easily understood speech. Fourteen patients engage in social activities outside the home, and eight have returned to full-time employment. No vascular flap failures occurred in this series. CONCLUSIONS: The use of free-tissue transfer flaps is a safe and effective technique for repairing large midfacial and cranio-orbito-facial defects resulting from ablative oncologic surgery or trauma.

Spindle cell lipoma of the parotid: fine-needle aspiration and histologic findings.

A 47-year-old man presented to the otolaryngologist with a 7-year history of a mass of the cheek. Fine-needle aspiration revealed foci of spindled cells admixed with abundant fat and myxoid material. A diagnosis of spindle cell lipoma was rendered on the resected specimen. The cytologic findings of spindle cell lipoma of the parotid gland as seen by fine-needle aspiration are presented along with the histologic correlates.

A preliminary study of the prognostic role of electromyography in laryngeal paralysis.

Confidence in the reliability of laryngeal electromyography to predict recovery is critical if this tool is to be used to select the type and timing of surgical intervention. The characteristics of electromyography of 14 patients with unilateral vocal fold paralysis were assessed to determine which factor or combination of factors would be most useful in determining prognosis. We examined the duration, amplitude, waveform morphology, root-mean-square, and time interval from onset to electromyography recording. The results supported the concept that electromyography recordings are valuable in determining prognosis if performed before 6 months and preferably within 6 weeks of onset of laryngeal paralysis. A positive prognosis for laryngeal recovery was indicated when the following electromyography features were present in the immobile vocal fold: (1) normal motor unit waveform morphology, (2) overall electromyography activity characterized by a root-mean-square value greater than 40 microV in any one task, and (3) no electrical silence during voluntary tasks. On the basis of this criteria our overall correct prognostic rate was 89%.

Incidence of deep venous thrombosis and pulmonary embolism in otolaryngology-head and neck surgery.

OBJECTIVE: Postoperative deep venous thrombosis and pulmonary embolus are major causes of morbidity and mortality in patients undergoing surgical procedures. In contrast to other surgical fields, the incidence of these life-threatening conditions has not been studied in our specialty. The purposes of this study were to elucidate the incidence of deep venous thrombosis and pulmonary embolus in patients after otolaryngologic operations and to identify specific risk factors that may contribute to the development of these conditions. METHODS: A retrospective analysis was done of 12,805 total operations on adults done by the Department of Otolaryngology at our institution from January 1987 to December 1994 to determine the number of patients in whom postoperative deep venous thrombosis and pulmonary embolus developed. Patients in whom a postoperative thromboembolic event developed after an otolaryngologic surgical procedure were identified by the medical records department with use of an abstracting database. This search cross-referenced disease-specific codes for otolaryngologic procedures with the codes for deep venous thrombosis and pulmonary embolus to identify the 34 patients in this report. Results (rounded to the nearest decimal point) were then categorized according to the different subspecialties within otolaryngology, and appropriate statistical analysis tests were performed on the resulting data. RESULTS: Thirty-four patients with postoperative deep vein thrombosis were identified during the study period, for an overall incidence of 0.3%. Of these 34 patients, 24 also had a pulmonary embolus for an overall incidence of 0.2%. The incidence of deep venous thrombosis (and pulmonary embolus) in the subspecialties was as follows: head and neck surgery, 0.6% (0.4%); otology/neurotology, 0.3% (0.2%); head and neck trauma and plastic surgery, 0.1% (0.1%); and general otolaryngology, 0.1% (0.04%). Only the patient's age and the presence or absence of pneumatic compression devices were identified as independent risk factors for the development of a thromboembolic event. CONCLUSIONS: Postoperative pulmonary embolus is a rare occurrence in the field of otolaryngology-head and neck surgery. When it does occur, it causes significant morbidity and increases the cost of care for that patient. We discuss our approach to categorizing patients into low-, intermediate-, and high-risk groups, as well as prophylaxis against pulmonary embolus.

Cost-identification analysis in oral cavity cancer management.

The objectives of this study were to investigate potential relationships between pretreatment patient-mix characteristics, treatment modalities, and costs generated during the pretreatment work-up, treatment, and 1-year follow-up periods for patients with oral cavity cancer (OCC). Another objective was to identify potential areas for cost reduction and improved resource allocation in the management of OCC patients. Using a retrospective cohort of 73 patients with OCC, pretreatment patient-mix characteristics and treatment modalities were evaluated in relation to university-based charges incurred during the pretreatment evaluation, treatment, and 1-year follow-up periods. Simple regression and stepwise multiple regression analyses were used to develop predictive models for cost based on independent variables, including age, AJCC TNM clinical stage, smoking history, American Society of Anesthesiologists (ASA) class, comorbidity as defined by the Kaplan-Feinstein grade and treatment modality. The dependent measurements included all physician, office, and hospital charges incurred at the University of Iowa Hospitals and Clinics during the pretreatment evaluation, treatment, and follow-up periods, as well as the total pretreatment through 1-year follow-up management costs. Independent variables that were identified as being significantly associated with treatment costs included T classification, N classification, TNM stage, unimodality versus multimodality treatment, and the Kaplan-Feinstein comorbidity grade. Age, smoking status, and ASA class were not significantly associated with costs. The majority of the OCC management costs were incurred during the treatment period. The most substantial decreases in management costs for OCC will be realized through measures that allow identification and treatment of disease at an early stage, in which single-modality treatment may effectively be used. Resource allocation for OCC should support the investigation of measures through which the diagnosis and treatment of OCC at the earliest possible stage is facilitated. The presence of comorbid illness is a significant component in the determination of management costs for OCC and should be included in analyses of resource allocation for OCC. The singular diagnosis of OCC encompasses a wide range of patient illness severity, and diagnosis-related reimbursement schemes for OCC treatment should optimally differentiate between early and advanced stage disease.

Medialization laryngoplasty with expanded polytetrafluoroethylene. Surgical technique and preliminary results.

Symptomatic unilateral laryngeal paralysis may be treated successfully by a wide variety of surgical techniques. These techniques share the concept that stabilization of the paralyzed vocal fold in a median position will improve glottic function. Medialization laryngoplasty with expanded polytetrafluoroethylene (ePTFE) incorporates the general principles of established medialization procedures, yet is unique in its simplicity. The technique does not require special instrumentation, employs incremental adjustment of vocal fold position, and utilizes an implantable material with a long history of patient safety. We describe this new technique and report on the outcome of our first 16 patients treated. No surgical or implant-related complications have occurred. Voice results were measured from preoperative and postoperative video and voice recordings by four independent observers using a standardized assessment tool. Voice grade and breathiness were evaluated on a four-point scale (0 = normal and 3 = abnormal, extreme). The mean overall grade improved from 2.3 +/- 0.6 to 1.1 +/- 0.6, and breathiness from 2.0 +/- 0.8 to 0.4 +/- 0.4. The technique is simple, the implant material has been in clinical use for decades, and the voice results are good to excellent.

Pharyngeal pressure analysis by the finite element method during liquid bolus swallow.

The human pharynx is unique, acting as a complex interchange between the oral cavity and the esophagus, and between the nasal cavity and the lungs. It is actively involved in the transport of food and liquid, producing the forces that guide the bolus into the upper esophagus and away from the adjacent larynx and lungs. This study developed a biomechanical computer model of the human pharynx, utilizing a finite element method (FEM). Control 2-dimensional cine computed tomography images were obtained during 10-mL barium paste swallows at 8 levels extending from the tongue base to the cricopharyngeal level in order to encompass the entire pharynx. Three-dimensional finite element models of the pharynx were reconstructed from the geometric information obtained from the images at each level. Using an inverse dynamic approach with the addition of known tissue properties, we analyzed the 8 models under estimated pressure histories during swallow. Within each model, changes in the cross-sectional intraluminal area were calculated and compared with the area from the computer-generated FEM model. Area matching allowed estimation of intraluminal pressure gradients during swallow. The estimated pressure gradients were distributed through a range from 10 to 55 mm Hg, varying from one region to another and showing different patterns for the upper 4 levels and the lower 4 levels. The contraction velocity for the upper 4 levels was much higher than that for the lower 4 levels. The higher contraction velocities and pressure gradients in the upper levels are consistent with the bolus velocities required for efficient swallow.