Biomedical subjects

K T Ooi

Publications and source records attributed to K T Ooi.

3 recordsLinked to original sources

PubMed2004

Frequency-dependent laminar electroosmotic flow in a closed-end rectangular microchannel.

This article presents an analysis of the frequency- and time-dependent electroosmotic flow in a closed-end rectangular microchannel. An exact solution to the modified Navier-Stokes equation governing the ac electroosmotic flow field is obtained by using the Green's function formulation in combination with a complex variable approach. An analytical expression for the induced backpressure gradient is derived. With the Debye-Hückel approximation, the electrical double-layer potential distribution in the channel is obtained by analytically solving the linearized two-dimensional Poisson-Boltzmann equation. Since the counterparts of the flow rate and the electrical current are shown to be linearly proportional to the applied electric field and the pressure gradient, Onsager's principle of reciprocity is demonstrated for transient and ac electroosmotic flows. The time evolution of the electroosmotic flow and the effect of a frequency-dependent ac electric field on the oscillating electroosmotic flow in a closed-end rectangular microchannel are examined. Specifically, the induced pressure gradient is analyzed under effects of the channel dimension and the frequency of electric field. In addition, based on the Stokes second problem, the solution of the slip velocity approximation is presented for comparison with the results obtained from the analytical scheme developed in this study.

Journal Article↗

PubMed1999

Reliability of the American Medical Association guides' model for measuring spinal range of motion. Its implication for whole-person impairment rating.

STUDY DESIGN: Repeated measures design for intra- and interrater reliability. OBJECTIVES: To determine the intra- and interrater reliability of the lumbar spine range of motion measured with a dual inclinometer, and the thoracolumbar spine range of motion measured with a long-arm goniometer, as recommended in the American Medical Association Guides. SUMMARY OF BACKGROUND DATA: The American Medical Association Guides (2nd and 4th editions) recommend using measurements of thoracolumbar and lumbar range of movement, respectively, to estimate the percentage of permanent impairment in patients with chronic low back pain. However, the reliability of this method of estimating impairment has not been determined. METHODS: In all, 34 subjects participated in the study, 21 women with a mean age of 40.1 years (SD, +/- 11.1) and 13 men with a mean age of 47.7 years (SD, +/- 12.1). Measures of thoracolumbar flexion, extension, lateral flexion, and rotation were obtained with a long-arm goniometer. Lumbar flexion, extension, and lateral flexion were measured with a dual inclinometer. Measurements were taken by two examiners on one occasion and by one examiner on two occasions approximately 1 week apart. RESULTS: The results showed poor intra- and interrater reliability for all measurements taken with both instruments. Measurement error expressed in degrees showed that measurements taken by different raters exhibited systematic as well as random differences. As a result, subjects measured by two different examiners on the same day, with either instrument, could give impairment ratings ranging between 0% and 18% of the whole person (excluding rotation), in which percentage impairment is calculated using the average range of motion and the average systematic and random error in degrees for the group for each movement (flexion, extension, and lateral flexion). CONCLUSIONS: The poor reliability of the American Medical Association Guides' spinal range of motion model can result in marked variation in the percentage of whole-body impairment. These findings have implications for compensation bodies in Australia and other countries that use the American Medical Association Guides' procedure to estimate impairment in chronic low back pain patients.

Adult↗

PubMed1999

Lumbar spine range of motion as a measure of physical and functional impairment: an investigation of validity.

OBJECTIVE: To investigate the validity of the spinal range of motion models outlined in the second and fourth editions of the American Medical Association Guides to the evaluation of permanent impairment (AMA Guides), for assessing the percentage impairment in chronic low back pain patients. DESIGN: Cross-sectional validation study. SETTING: Outpatient department in the Rehabilitation Medicine Unit. SUBJECTS: A volunteer sample of 34 subjects participated in the study, 21 females and 13 males, with a mean age of 47.7 years (1 SD = 12.1) and 40.1 years (1 SD = 11.1), respectively. Subjects had chronic low back with or without leg pain of at least six months' duration. Subjects were recruited by medical practitioners and physiotherapists through the Rehabilitation Unit at the Essendon Campus of Royal Melbourne Hospital. MAIN OUTCOME MEASURES: Lower back range of motion measured with a long arm goniometer and a dual inclinometer, Waddell Physical Impairment Scale, Waddell Disability Index, Oswestry Disability Index. RESULTS: Both range of motion measurement methods demonstrated poor validity and do not bear any consistent relationship to the level of physical or functional impairment in subjects with chronic low back pain. CONCLUSIONS: There was no evidence for a relationship between low back range of motion and impairment, and thus it would appear illogical to evaluate impairment in chronic low back pain patients using a spinal range of motion model when aiming to measure or compensate disability.

Adult↗