Pharyngeal Manofluorography (Video-manometry): A Simple Quantification of the Modified Barium Swallow

(This text was prepared in June 1997 and taken in part from Probe-Based Studies, by J.R. Salassa and
K.R. Devault, in Diagnostic Test in Otolaryngology-Head and Neck Surgery, edited by D.E. Mattox, Ikaigaku-Shoin Medical Publisher, in press.)

Introduction

Several techniques have evolved in the evaluation of patients with suspected oropharyngeal swallowing dysfunction. The "modified barium swallow" (MBS), video swallowing fluoroscopy, has been well standardized and is currently the accepted standard procedure for clinical pharyngeal swallowing analysis. The MBS allows a two-dimensional view of: a) the anatomic structures of the mouth and throat at rest and during various functions; b) bolus kinetics; and c) the interrelationship of a and b. However, other than for timing of events, the clinical modified barium swallow remains largely subjective. Sophisticated computer programs to measure distances such as laryngeal elevation and cricopharyngeal opening are available but are time consuming and not widely used in clinical practice. Descriptive terms such as "mild," "moderate," and "severe," are used for subjective quantification. Such terms are not clearly defined for universal usage and are, therefore, meaningful only to the individual user group. The result is frequently a significant variation in interpretation between one reviewer and another. Pharyngeal manometry objectively quantifies pressure and timing measurements to pharyngeal function thus replacing subjective terms with objective numbers in mm Hg and seconds. Pharyngeal manometry alone, however, gives little clinically useful information. Without the exact known position of the sensor in relation to anatomic structures and the bolus, interpretation of pharyngeal manometry data is difficult. In patients with abnormalities in resting cricopharyngeus pressure, laryngeal elevation, palate closure, tongue function, and bolus transport, it is impossible to identify what pharyngeal manometry as a sole modality is measuring. The solution to this problem is to combine pharyngeal manometry with simultaneous video swallowing fluoroscopy, resulting in manofluorography or video-manometry. Manofluorography has been used successfully as a research tool, and with the introduction of commercially available units (e.g., the Kay Swallowing Workstation, Kay Elemetrics Corp., Lincoln Park, NJ), it is now moving into clinical practice.

Purpose Of The Modified Barium Swallow And Manofluorography

The spectrum of disease processes that result in oral pharyngeal dysphagia is enormous. With few exceptions the etiology of the dysphagia is either known or suspected prior to any study of oropharyngeal swallowing function. Furthermore the different etiologies of oropharyngeal dys-phagia often result in similar findings when examined by either a modified barium swallow or manofluorography. Information provided by either of these studies is therefore rarely diagnostic of a specific disease process but rather more clearly defines the specific areas of dysfunction, severity of disease, risk of complications, treatment modalities to be considered, and efficacy of treatment. The modified barium swallow and manofluorography should not be looked upon as a test which will define the etiology of the dysphagia but rather the treatment of the dysphagia.

Physiologic Basis For Manofluorography

Pressure as a measurement of pharyngeal forces

Bolus passage through the pharynx depends on gravity, pharyngeal shortening, and the propulsive forces of the pharynx. Pharyngeal manometry measures pressures in the pharynx, not pharyngeal propulsive forces. Propulsive forces require a directional measurement. This directional force can only be inferred in pharyngeal manometry by multiple pressure readings over distance and time, and/or correlation with bolus transient seen on video barium swallow. When pressure is used as a measurement of forces applied to the bolus, the difference between the biomechanics of liquids and solids must be understood. In simplified terms, pressure measurements within a liquid (moving) bolus are (almost) equal in all directions, whereas pressure measurements in a solid (moving) bolus are very directional-dependent. Thus, liquid intrabolus pressures reflect the force applied in the direction of bolus movement.

Circumferential and vertical pharyngeal dynamics

Circumferential and vertical dynamics in pharyngeal swallowing are equally important. The sequential circumferential pharyngeal forces are manometrically peristaltic. These circumferential forces are radially unequal with anterior posterior pressures exceeding lateral pressures. Vertical shortening is universal to "peristalsis" throughout the alimentary tract and is critical to normal effective bolus transport. Thyrohyoid shortening, laryngohyoid elevation, and the inferior movement of the tongue base are the structures most easily identified in pharyngeal shortening. Variabilities of these vertical movements and circumferential pressures, especially in dysphagic patients, present a major technical problem in pharyngeal manometry. This is because sensor spacings are at fixed vertical distances determined for normal subjects. Thus pharyngeal manometry only becomes meaningful with the addition of simultaneous video fluoroscopy to identify what and where pressures are recorded.

Extrabolus, intrabolus, and resting pressures

Pharyngeal manometry can measure resting pressures, prebolus pressures, intrabolus pressures, and post bolus pressures. The principle of fluid mechanics can only be applied to liquid intrabolus pressures as previously mentioned. Liquid intrabolus pressures are generally quite low in the range of 4 to 12 mm Hg, compared to the significantly higher extrabolus after pressures of 90 to 110 mm Hg. It is therefore critical, especially in dysphagia patients, to accurately assess whether pressure readings are intrabolus or extrabolus pressures, whether they occur before or after the bolus passage, and the relationship of these pressures to the same anatomic site pressures at rest.

Equipment

Manofluorography requires the simultaneous display and storage of the standard fluoroscopic barium swallow with pressure measurements obtained from a transnasal pharyngeal catheter. The recent availability of such commercial systems (e.g., the Kay Swallowing Workstation) has enabled the meaningful clinical application of pharyngeal manometry.

The catheter specifications and design are of critical importance since a catheter with different designs will give different values. At present no standard catheter design has been accepted. Therefore, it is important to realize that normative data must be established for the specific catheter that is used. Proposed catheter standards are being published and are summarized as follows (Figure 1). The catheter should be 2 by 4 mm (or smaller, 1.5 by 3 mm) in diameter, ovoid, and 100 cm long. The catheter should be marked in centimeters with an anterior and posterior orientation. A slightly malleable, 3- to 4-cm length of catheter without sensors should remain beyond the most distal sensor. Solid state transducers should be used, and one sensor each should be placed at rest in three or four locations: cricopharyngeus, hypopharynx, and tongue base (esophagus for the fourth sensor). Sensor spacing should be 3 cm between cricopharyngeus and hypopharynx and 2 cm between hypopharynx and tongue base. The option of two sensors in the cricopharyngeus 1 cm apart enables measurements at the apex of laryngeal elevation in both normal persons and dysphagic patients without catheter adjustments. If an esophageal sensor is added, the location should be 3 cm below the (first) cricopharyngeal sensor. Unidirectional, in-line, posteriorly oriented sensors with the option of a single small circumferential sensor in the cricopharyngeus are currently preferred over circumferential sensors because of their small size and patient comfort.

Most of the currently used catheters are made by Gaeltec (Medical Measurements Inc., Hackensack, N J), Millar Instruments Inc. (Houston, TX), or Konigsberg (Pasadena, CA). All catheters must be calibrated prior to each use. With any of the available commercial systems, this calibration is a simple and quick procedure. Solid state sensors used in all of these catheters are very temperature sensitive and therefore should be calibrated at body temperature. In our clinical practice, however, we calibrate at room temperature, recognizing that base line 0 mm Hg in the calibration chamber may differ 3 or 4 mm Hg from the pharyngeal air column. Since all boluses are at room temperature, we feel body temperature calibration is unnecessary for clinical use.

Technique

Patients are asked to be fasting from solids for two to three hours prior to the study. A catheter is placed transnasally into the pharynx and cervical esophagus. Inspection of the nasal cavity will allow comfortable catheter placement through the most open side of the nose. Light topical anesthesia and vasoconstriction (Lidocaine/Neosynephrine) are preferred since this significantly reduces patient discomfort, increases patient tolerance, and decreases elevated pressures due to patient anxiety and discomfort. Placement of the catheter is similar to placing a nasogastric tube. In severely dysphagic patients, the concomitant use of small sips of water to facilitate catheter passage should be avoided for obvious reasons. For difficult patients, the fluoroscope can be momentarily turned on to ensure that the catheter is advanced into the esophagus and not the larynx, pharyngeal pouch or other postsurgical "dead end". The catheter is advanced approximately 27 cm, then adjusted under fluoroscopic guidance to ensure that all unidirectional sensors are facing posteriorly, and normal at rest vertical sensor placement (Figure 1). Sensor number 3, the cricopharyngeus should be 1 to 1« cm below the vocal cords. Sensor number 2 will then lay at or slightly above the bottom of the pharyngeal air column just above the arytenoids. Sensor number 1 (most proximal) will lay at the level of the epiglottis tip, and sensor number 4, the most distal, will lay in the cervical esophagus. Two problems arise in placing sensors. First, when patients with unusually long or short pharynxes are studied, adjustments must be made depending on the area of interest. For example, if the tongue base is of concern in a short pharynx patient, "normal" placement will put sensor number 1 behind the soft palate. The catheter must therefore be advanced deeper to record the tongue base. The second problem is the dysphagic patient with poor laryngeal elevation or palatal elevation. "Normal at rest" sensor placement assumes a slightly greater and a slightly earlier laryngeal elevation than, (palate), catheter elevation. If the cricopharyngeus region is of critical concern, catheter placement should be adjusted under fluoroscopic guidance to allow sensor number 3 to be 1 to 1« cm below the vocal cords (and thus in the middle of the cricopharyngeus) at the swallowing apex, i.e., maximum superior laryngeal elevation. The catheter is fixed to the nose with an adjustable bandage, (Suction Tube Attachment Device, Hollister Inc., Libertyville, IL), which easily allows minor catheter adjustments that may be necessary during the study.

Once the catheter is in place, standard modified barium swallow protocols are carried out and are very much dependent on patient tolerance and specific complaints. A full protocol is rarely needed. If the catheter is to be used for future tongue base or other biofeedback exercises, the distance at the nose is carefully recorded for future reference. At the end of the study the patient is advised to drink plenty of water and prune juice or given a K-phos soda laxative if constipation from the barium becomes a problem.

Interpretation

Although only the interpretation of manometry will be discussed, it should be remembered that fluoroscopic findings are far more important and account for more than eighty percent of relevant information obtained during manofluorography. The important manometric parameters include coordination, cricopharyngeal nadir, peak amplitude clearing pressures, intrabolus pressures and special circumstances.

1. Coordination ("Peristalsis")

Although the use of the term "peristalsis" is objectionable by some, this term most closely describes the rapid (less than one second), orderly, sequential, antegrade pressure wave that is generated during a normal pharyngeal swallow. The peak amplitude clearing wave pressures, c waves, are most easily identified to evaluate "peristalsis"(see Figures
1 and 2). It is important to remember, however, that normal pharyngeal "peristalsis" is not synonymous with normal pharyngeal swallowing. Clearing wave peak pressures represent after bolus events, and as such are more accurately termed "after bolus peristalsis". "After bolus peristalsis" is one measure of pharyngeal coordination. Bolus transient in relation to pharyngeal pressures is equally important. Preswallow bolus spillage and after swallow bolus residual are easily evaluated by video fluoroscopy without manometry. However, coordination of bolus head arrival after the cricopharyngeal nadir is most easily determined by manometry and is the second critical parameter of pharyngeal coordination.

2. Cricopharyngeal Nadir and Resting Pressures

The clinical usefulness of resting cricopharyngeal pressure measurements is so rare that precise maximal pressure measurements using slow pull-through techniques are no longer done. The resting pressure is relevant only as a base line reference point, for a given swallow and given cricopharyngeal sensor location. What is important, however, is the nadir, or lowest pressure of the cricopharyngeal sensor during the swallow and the relationship of this nadir to the bolus head. The nadir should be a negative number of -2 to -6 mm Hg using our system, and should occur prior to bolus head arrival. A negative nadir indicates normal cricopharyngeal segment relaxation and laryngeal elevation. It represents the best manometric parameter of pharyngeal shortening, laryngeal elevation. It also results in normal cricopharyngeal opening unless a fixed adynamic stricture is present. This nadir is sometimes visible, but unreliably measured on the video swallow as air in the cricopharyngeus prior to bolus arrival

3. Maximum Amplitude Clearing Pressures

Besides their importance in determining peristalsis, maximum amplitudes of the post swallow clearing waves are indicators of pharyngeal strength. These peak amplitude pressures of the tongue base, hypopharynx, and cricopharyngeus regions are simple, easily determined values that objectively quantify pharyngeal strength. The correlation of these peak amplitudes with subjective "impressions" determined by video-fluoroscopy is excellent. Terms such as mild, moderate, and severe can be replaced by objective numbers such as 60-75 mm Hg, 40-60 mm Hg, and <35 mm Hg, respectively. (Normal = 80-120 mm Hg.)

4. Intrabolus Pressures

The third, perhaps most important, and yet most difficult, manometric pressures to evaluate are intrabolus pressures. Liquid intrabolus pressures are indicators of, but are not synonymous, with, intrabolus propulsive forces, assuming antegrade movement. Elevated intrabolus pressures indicate outlet obstruction. However, the opposite, outlet obstruction results in elevated intrabolus pressures, may not be true for two reasons. One, if the structures doing the pushing (tongue base, hypopharynx) are so weak they are incapable of generating elevated intrabolus pressures, or two, coordination is lacking and bolus movement is not antegrade. The amplitude and sequential timing of the peak clearing pressures are therefore important to assess prior to determining intrabolus pressures. In the presence of weak but coordinated driving forces (i.e., decreased clearing wave peak amplitudes and decreased laryngeal elevation, as is commonly seen in many dysphagic patients), the evaluation of outlet obstruction is difficult.

How to reliably measure intrabolus pressure is a difficult and unsettled problem that further confuses the issue. Intrabolus head pressures are slightly lower than tail pressures in normal patients. In patients with normal driving forces, but outlet obstruction, this difference is exaggerated, creating an intrabolus "ramp" effect. This "ramp" may be reduced to normal in patients with decreased driving force, even in the presence of outlet obstruction. The "ramp" effect should always be looked for when evaluating intrabolus pressures. Calculating total pressure over time from bolus head to bolus tail, has also been investigated in an effort to quantify intrabolus forces (pressures). However, we have found these calculations unreliable in dysphagic patients with weak driving forces since patients may compensate for decreased intrabolus pressures with increased duration resulting in normal pressure-time calculations. Also, bolus head and tail determinations are often difficult in these patients with high bolus residuals. Assessing mid-intrabolus pressure either by distance using fluoroscopy, or by timing using manometry, is also a possibility and is the author’s current preference. Reduced intrabolus pressures are the result of either decreased driving forces or gross dys-coordination. Applying the principles learned in cardiac catheterization for valve dysfunction, high intrabolus pressure gradients occur across an obstruction. Intrabolus pressure gradients across the cricopharyngeus are presently being investigated to determine outlet obstruction.

5. Special Circumstances

Perhaps the greatest value of pharyngeal manofluorography is in the presence of abnormal anatomy. Surgically altered pharynges, cervical osteophytes, pouches and a variety of extrinsic obstructions, all create situations where normal anatomic structures and manometric recordings are absent or distorted. For these special circumstances, simultaneous fluoroscopy and manometry complement each other to give a clearer understanding of functional pharyngeal swallowing mechanics.

Case Report

Patient History

A 67-year-old female was referred for a 25-year history of difficulty swallowing pills and solids. By chewing her food very finely she has maintained normal dietary choices, normal duration of meal times, and no weight loss. She rarely choked on liquid or solids, (FOSS stage II). The main reason for referral was that she could not swallow pills. Pills would stick in her throat similar to other large particulate substances. This has been lifelong. Because of a new diagnosis of Crohn's Disease, she was required to swallow whole, time-released capsules and could not crush them as she had done in the past. A liquid barium esophagram showed a prominent cricopharyngeal bar.

Manofluorography

Fluoroscopy showed a persistent narrowing at the cricopharyngeus due to a prominent cricopharyngeal bar. There was a delay in emptying of the hypopharynx that was greater for solids than liquids. Solids would require a second or third swallow to clear the bolus. A one-centimeter barium tablet would not pass the cricopharyngeus region. The remainder of the fluoroscopic findings appeared normal although there was some concern of "mild" tongue base weakness.

Manometry, (see figure 2), demonstrated normal tongue base and hypopharynx clearing pressures, normal cricopharyngeus nadir ( laryngeal elevation), and normal coordination. Liquid intrabolus pressures were elevated to 40 mm Hg (normal 4-12 mm Hg) and demonstrated a classic "ramp" effect. The intrabolus pressure gradient across the cricopharyngeal bar was markedly elevated to 33 mm Hg (normal 5-10 mm Hg). In summary, the manofluorography findings reveal normal pharyngeal performance with the exception of an obstructing cricopharyngeal bar.

Treatment and Results

The patient underwent a cricopharyngeal myotomy and was relieved of her pill and solid dysphagia.

Conclusions

Pharyngeal manofluorography is a clinically useful tool that should not routinely replace the standard modified barium swallow. Its use should be selective for difficult or unusual patients. In these patients, establishing treatment plans, whether surgical or non-surgical, is often greatly facilitated by the addition of manometry to the video swallow. Manometry quickly and simply adds a crucial objective parameter to swallowing evaluations when done both before and after treatment. Manofluorography provides important additional information to the modified barium swallow that does not define the etiology of dysphagia but rather the therapy of the dysphagia.

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