IOPI Northwest

Pressure as a Measure of Strength

Measuring the maximum pressure that a person can produce by squeezing a compliant bulb in order to estimate the strength of the tongue, lip, or hand was a completely novel idea when the IOPI was patented. Since that time, many research studies have been reported that have used the IOPI or IOPI-like instruments to measure tongue strength (see References). The tongue can create pressure in an IOPI bulb in three basic ways:

• It can elevate and push the tongue bulb against the hard palate, or
• Push laterally against a tongue bulb attached to a small plate held between the molar teeth, or
• Push forward (protrusion) against a tongue bulb attached to a small plate held between the incisors.

To fully characterize the strength of a patient's tongue, it would be useful to have measurements of all of these tongue movements. The IOPI system can accomplish such an examination. How is this done and what do we currently know about the results?

Tongue Elevation Strength

The strength of tongue elevation against a tongue bulb placed in the IOPI "standard" position, against the hard palate just behind the alveolar ridge (see drawing), has been measured almost exclusively in published reports concerning tongue strength. Therefore, there is a great deal of information, derived from many different laboratories and clinics, about tongue elevation strength. This information suggests the following generalization:

(1) Repeated measures of tongue strength in the same individual are quite reliable, particularly after they've done the task a few times.

(2) There is considerable variability in tongue strength in a population of adults reporting no swallowing or speech problems, i.e. "normals." There is a clear central tendency, however, with an average maximum pressure of about 65 kPa, and a range of 35-85 kPa.

Lateral Tongue Strength

The IOPI may be adapted to obtain an objective measurement of the ability of a subject or patient to produce a laterally-directed movement of the tongue. This involves a plastic holder, a narrow handle with a small plate on the side of one end. Double-sided medical adhesive tape is used to secure an IOPI bulb to the small plate. The end of the handle that goes in the mouth has silicone rubber pads on both sides; these are held between the premolars and first molars on one side of the mouth. This secures the IOPI bulb in a fixed position against the lingual surface of the teeth. The tongue is then used to push laterally against the IOPI bulb. Both sides can be tested using the same bulb without detaching it from the holder.

Protrusive Tongue Strength

The IOPI lateral tongue bulb holder may also be used to measure the strength of protrusive movements of the tongue. In this case, the rubber pads of the holder are held between the patient's incisors, and the tongue tip is used to push against the IOPI bulb.