Sunday, February 18, 2007

Do videofluoroscopic swallowing studies show what happens during a meal?

In a word: No.

Understanding this is crucial to managing dysphagia appropriately. I would be all for video-ing just about everyone with dysphagia or suspected dysphagia if VFSS showed what happens at a meal. However, it does not -- it cannot.

Why not?

Most SLP’s recognize that a number of factors may differ between the video swallowing study and normal mealtime circumstances. As such, they (rightly) attempt to adjust these to be as close to the patient’s usual mealtime situation as possible. These factors include patient positioning (including head and body positioning), the patient’s mental status, bolus size/volume, and feeding rate. Most clinicians also recognize that a VFSS provides just a “snapshot” of how a patient is doing at that particular time, with a limited number of food and liquid trials. Unfortunately, these factors are often the only ones taken into account, so there seems to be a widespread belief that if these factors can be controlled for, the VFSS will at least closely resemble what happens during a meal.

However, this doesn’t take into account another set of factors, which cannot be modified. These have to do with the nature of the VFSS itself. The major ones are the bolus characteristics of barium, which are vastly different than those of plain food or liquid. Adding barium to food does not make the results of the VFSS closer to “what happens at a meal”; it just tells you how that patient swallows barium plus food (at that moment in time). Barium is heavier and denser than regular food or liquids, both bolus characteristics which are known to affect the physiology of the swallow. Add to that a different taste, mouth feel, and often viscosity, and it should be readily apparent why the barium bolus cannot be expected to closely resemble a regular food or liquid bolus.

Although many clinicians realize that there may be discrepancies between the results of a VFSS study and what is actually occurring at mealtimes, it has not stopped a large number of clinicians from elevating VFSS results to a level of near-infallibility -- the be-all-end-all of swallowing evaluation. See, for example, the “swallow scores” utilized in much of the VitalStim research: a numerical scale based on which textures/consistencies are “safe” according to VFSS. Or clinicians who change a diet based solely on VFSS performance, without regard to the patient’s clinical presentation.

I suspect that this underlying assumption -- that what happens on VFSS is equivalent to what happens when the patient is really eating/drinking -- is a large part of the heavy emphasis on obtaining VFSS on most (if not all) patients with suspected pharyngeal swallowing dysfunction. However, it has the potential to lead to inappropriate treatment decisions.


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