Brief History
Several research studies have had subjects swallow when an IOPI tongue bulb was in their mouth. In these studies, the IOPI was set to the "Peak" function, so it recorded the highest pressure achieved during the brief compression of the tongue bulb that occurred during the swallow. Although there were good reasons, initially, to be somewhat skeptical about the interpretation of such pressure readings, this measurement has now been made in several studies from different laboratories. The findings have generally been consistent, and suggest the following observations:
- peak readings are reasonably consistent when a person swallows the same food or water "stimulus" several times.
- different research groups using the IOPI have found average swallowing pressures in normal adults that are a surprisingly large portion of a person's maximum pressure, i.e. 30-50%.
- swallowing pressure is higher for viscous foods than for water.
- the presence of a pressure-sensing bulb in the mouth does not change the basic patterns of bolus flow, as determined by videofluoroscopic analysis, so such swallows may be regarded as physiologically normal.
Potential for Clinical Use
There is currently little information in the research literature about how differences in peak swallowing pressure, measured with the IOPI, are related to swallowing disorders. There are, however, at least two clinical questions that potentially could be answered by this measurement:
- If the "effortful swallow" technique is used to help a patient with a swallowing problem, determining that the effortful swallow does in fact produce a swallowing pressure that is significantly higher than the habitual swallow establishes the fact that the patient understands what is meant by "effortful swallow," and has the ability to produce a higher pressure. Keep in mind that it is possible that the habitual swallow is actually an "effortful swallow" that the patient has learned to cope with their swallowing problem, in which case having the patient try an effortful swallow will not actually raise the swallowing pressure.
- If a patient with a swallowing problem produces a peak swallowing pressure that is clearly within the normal range, it would be obvious that a weak tongue, per se, is probably not the main cause of their problem. Perhaps the cause is more related to tongue control.
Recording Swallowing Pressure Over Time
The IOPI has a Data Out port that provides a continuous voltage representing pressure. If a laboratory or clinic has a computer system having a data acquisition system that can digitize, display, and record this voltage, it would be possible to study these swallowing pressures in detail. Much needs to be learned, but it is possible that research on swallowing pressure waveforms obtained from patients with various swallowing problems could lead to better diagnosis and treatments.
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