October 2002

Insightful Options

These techniques can add valuable, objective information to the evaluation process for people with developmental disabilities, who often cannot communicate verbally. Fit, comfort, function, and preference are often difficult to assess, and poor ability to communicate can hinder the exchange of information between providers and consumers. The use of objective measurement tools is designed to give the clinician critical information about the skin, circulatory system, respiratory status, digestive processes, and other vital functions to ensure that the postural devices provided meet the basic physiologic needs of the consumer. Additionally, the results of assessments utilizing such tools can provide concrete data for research in an area that often lacks opportunity for controlled study.

PULSE OXIMETRY

Pulse oximetry is a noninvasive technique to measure pulse rate and saturation of oxygen in the blood. The SaO2 is computed by measuring differences in the visible and infrared absorbance of oxygenated and deoxygenated arterial blood.² SaO2 should be at least 90% or above; however, any condition that restricts blood flow may result in inaccurate SaO2 readings. Because positioning can impact a person’s ability to breathe adequately, thus compromising O2 intake, it is important to test individuals in the positions being considered. For example, upright sitting in individuals with low muscle tone or kyphosis can cause collapse of the T-spine resulting in inadequate ventilation and a drop in SaO2. Tilting the person back slightly can open the trunk, ease ventilation, and improve SaO2 levels. Similarly, people with severe scoliosis may not tolerate certain positions at all or become compromised over time. Monitoring SaO2 for a prescribed period of time is recommended.¹

When SaO2 drops repeatedly, consider the following:

• Avoiding positions that result in lowered SaO2 readings.
• Design or modification of the seating/mobility system using positions that improve or stabilize readings, such as using an open seat to back angle, multiple positions in space, and rotation or derotation of the spine through contouring or offsetting the mounting of the seating components.
• Avoiding prone positioning in certain individuals because breathing can be compromised and gastro- esophageal reflux can be facilitated because of pressure on the abdomen.

DOPPLER ULTRASOUND

High-frequency ultrasound is a technique used to detect peripheral arterial pulses. When distal pulses are not easily palpable or cannot be detected with a regular stethoscope, the Doppler can be used to find and measure blood flow.¹ The equipment consists of two piezoelectric crystals that emit and receive ultrasound waves. As the ultrasonic waves reach the moving red blood cells, they are reflected and their pitch is slightly altered. The change in the pitch is called the Doppler shift. Further processing converts the shifted waves into audible sounds.³ Use of the Doppler during a seating evaluation can help determine the presence or absence of peripheral blood flow in a range of positions such as supine, or sitting, and in various degrees of postural recline and elevation of the extremities.

Table 1. ABI reading indicators.

ANKLE BRACHIAL INDEX

ABI is a standard noninvasive test used to assess the severity of peripheral arterial occlusive disease. Positioning is affected when arterial flow is insufficient and cannot move against gravity when the legs are elevated.⁴ ABI is calculated by dividing the ankle systolic pressure by the brachial systolic pressure (see Table 1 for reading indicators).

If the systolic pressure is exceedingly high, an ABI is not considered accurate. This is common among diabetic patients where the vessels of the lower leg have become calcified and cannot be compressed by the blood pressure cuff.⁵ Other difficulties that can affect the accuracy of measurement with a standard blood pressure cuff include contractures, obesity, and severe edema.

RUBOR OF DEPENDENCY

Rubor of dependency is used to test the adequacy of arterial circulation.⁶

To perform this test:

1. Place the individual in the supine position and note the color of the soles of the feet. In individuals with normal arterial circulation, the feet will be pinkish in appearance. In individuals with impaired circulation, the feet may appear chalky white.
2. Elevate the legs to approximately 45°. If a quick loss of color occurs, resulting in a dead grayish white appearance, arterial involvement may be suspected.
3. Bring individual to a sitting position. In individuals with normal circulation, a quick, pink flush will appear in the feet. In individuals with impaired circulation, the color change may take longer than 30 seconds to occur and will be a very bright red.⁶

When arterial insufficiency is suspected, positioning and other therapeutic considerations include:



• The use of gravity to facilitate circulation; do not elevate feet or arms above the heart.
• Definition of tilt features in the positions where the strongest circulatory evidence is achieved.
• Assuring adequate thigh support.
• Slightly opening the knee angle, if possible.
• Providing foot support that reduces pressure areas and provides optimal support.
• Avoiding constrictive clothing such as elastic banded sweats, socks, and some house slippers.
• Elevating the head of the bed or lowering the foot of the bed at least 5°.
• Monitoring skin for signs of breakdown.
• Encouraging movement or providing multiple positions in space for nonambulatory individuals.
• Discouraging long-term static positioning.



Assessment of venous dysfunction is generally performed to ascertain a possible cause of edema and to prevent ulceration from venous stasis. Evaluation is performed by observation of skin color, the presence of tortuous veins, palpation of edema, trial elevation of limbs with girth measurements, and other special tests. Positioning and compression are among the options that are successfully employed to manage this aspect of care.¹




If venous insufficiency is suspected, consider the following:

• Use of multiple positions in space to elevate extremities and lessen the effects of gravity.
• Planning a positioning routine, using appropriate equipment, throughout the day.
• Opening the knee angle slightly, if possible.
• Use of compressive hosiery.
• Monitoring of skin for signs of breakdown.
• Encouraging movement or providing multiple positions in space for nonambulatory individuals.
• Discouraging long-term static positioning.



It is possible for both arterial and venous insufficiency to occur simultaneously. In this event, arterial problems rule decisions of elevation and compression because of the serious consequences of arterial insufficiency. For example, compression may still be used but at a milder degree, eg, 20 mm Hg vs 40 mm Hg. Positioning can be used by specifically defining the angle of tilt and elevation.




PRESSURE MAPPING

Pressure mapping refers to the clinical use of a tool that enables the user to identify areas of concern, to select appropriate equipment, and to assist in positioning persons at risk for pressure sores. The system uses an array of individual pressure sensing elements to determine the pressure between the individual being tested and the sitting surface, then it presents the information in measurable units and as a color-coded display.^7,8 Pressure is usually recorded in mm Hg. Individuals who register low pressures, <80 mm Hg, coupled with no active skin problems, generally require no additional intervention. Individuals who record pressures higher than 80 mm Hg may need additional intervention that could include changing seat or foot cushions, altering the angle of tilt, replacing the wheelchair frame, or other actions.⁹




VIDEOFLUOROSCOPY

Videofluoroscopic evaluation of swallowing refers to a moving x-ray examination of swallowing using various densities of food and liquid impregnated with barium, a radiopaque substance. Such studies should include oral, pharyngeal, esophageal, and gastric components to present a comprehensive evaluation of dysphagia.¹⁰ Appropriate assessment should involve a routine that incorporates both erect and recumbent positions including supine and prone oblique positions to assess esophageal motility, gastroesophageal reflux, and gastric emptying. Such testing can lead to a number of treatment options.




Interventions may utilize individualized positioning regimes and equipment to address the range of medical, orthopedic, respiratory, digestive, and neurological considerations that are frequently displayed by individuals with severe developmental disabilities. The use of seating and positioning systems can enhance digestive function, respiration, and daily living skills by assisting in alignment of body structures and by the use of gravity.¹¹ Appropriate positioning may be upright, reclining, side-lying, sitting, standing, prone, or a combination of positioning routines depending on the problem that is revealed during the assessment.^12,13




Simple positioning procedures may also be used to control symptoms of dysphagia in individuals who are ambulatory. These include conservative antireflux techniques, such as raising the head of the bed to use gravity to control reflux, and maintaining upright positioning at least 30 minutes to an hour after meals.




Karen Davis Hardwick, PhD, OTR, FAOTA, is director of habilitation therapies at Austin State School, a residential facility serving individuals with mental retardation and other developmental disabilities in Austin, Tex. She is also discipline coordinator for therapies and physical nutrition management for the Texas Department of Mental Health and Mental Retardation and a consultant in private practice.




References

1. Hanson S, Hardwick K, Nichols R, Yeager C. Clinical assessment technologies. Presented at: 16th Annual Seating Symposium; February 24-26, 2003; Vancouver, BC.
2. Mendelson Y. Pulse oximetry: theory and applications for non-invasive monitoring. Clin Chem. 1992;38:1601-1607.
3. Doppler Stethoscope [user’s manual]. Trumbull, Conn: MedaSonics®; 1998.
4. Gardner AW, Mongomery PS. Comparison of three blood pressure methods used for determining ankle/brachial index in patients with intermittent claudication. Angiology. 1998;49:723-728.
5. Collier P, Boyd C, Merwath D. Noninvasive vascular assessment of the lower extremity. Presented at: Second Annual Wound Management Symposium; February 27, 1999; Austin, Tex.
6. McCulloch J. Peripheral vascular disease. In: O’Sullivan S, Schmitz T, eds. Physical Rehabilitation: Assessment and Treatment. Philidelphia: FA Davis Co; 1988:377.
7. Clinseat [user’s manual]. South Boston: Tekscan; 1998.
8. XSensor® Pressure Mapping System [user’s manual]. Belleville, Ill: The ROHO Group; 1998.
9. Shapcott N, Levy B. By the numbers. TeamRehab Report. 1999;January:16-21.
10. Jones B, Donner MW. Interpreting the study. In: Donner MW, Jones B, eds. Normal and Abnormal Swallowing Imaging in Diagnosis and Therapy. New York: Springer-Verlag; 1991:52-72.
11. Hardwick KD. Clinical manifestations of dysphagia individuals with developmental disabilities: an exploratory study. Ann Arbor, Mich: University of Michigan; 1993.
12. Hardwick KD, Feichtinger L. Issues in evaluation and fabrication of seating and mobility systems for multiply handicapped individuals. Presented at: 7th International Seating Symposium.
13. Morris SE, Klein MD. Pre-feeding Skills. Tucson, Ariz: Therapy Skill Builders; 1987.

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