Dr. Tony Szturm, Ph.D. 
Associate Professor, School of Medical Rehabilitation, University of Manitoba
 

Acoustic Modeling of Tracheal Sounds
Reduced mobility and falls are common and potentially preventable sources of disability, mortality and morbidity in disabled individuals and in older adults. Reduced mobility and falls have multiple contributing factors. Intrinsic factors include a) central nervous system disorders such as Stroke, Parkinson's, MS, b) peripheral nervous system deficits in visual, vestibular, proprioceptive and cutaneous sensor systems, c) arthritis and other musculo-skeletal disorders d) leading to deconditioning (reduced muscle strength and endurance, range of motion, reduced reaction time) and e) use of psychotropic drugs. Extrinsic factors include environmental factors, such as, presence of obstacles, uneven or compliant ground surfaces, slippery surfaces, poor lighting etc. Balance is an important factor when considering function, mobility and falls Dynamic balance is highly correlated to the ability to perform daily living skills and maintenance of mobility necessary for outdoor walking and community independence. Balance is a functional term and involves many essential neural processes which include a) sources of spatial information form a variety of sensors; visual, vestibular and somatosensory systems (proprioceptive, cutaneous) and b) higher level integrative processes essential for mapping sensation to action and ensuring predictive (feedforward control) and unpredictive (feedback control) aspects of balance maintenance and restoration. Sensing the "state" of balance or threat to balance, and timely selection of appropriate motor strategies is determined both by the function of the task (static or dynamic, degree of difficulty) and the demands of the environment in which it is being performed. These can change substantially according to the characteristics of the support surface (uneven, compliant, slippery). Nashner (Neurocom Inc) developed a sophisticated laboratory test "the sensory organization test" (SOT), with an objective to measure the contribution of each sensor in maintaining equilibrium when other senses are either absent/eliminated, conflicting or receive distorted information. A number of studies have used the SOT to examine balance impairment and fall risk in different patient groups and in the elderly. A different experimental paradigm, the moving platform paradigm, has been used to examine motor processes involved in balance control. The platform upon which the subject stands is suddenly translated at different amplitudes and frequencies, which systematically disturbs one's balance by changing the position of center of mass relative to the base of support. Both predictive (feedforward) and automatic (feedback) control mechanisms can be evaluated by this procedure. A number of studies abruptly and unexpectedly moved the platform. This causes the subject to lose their balance momentarily, which requires a rapid compensatory response to restore balance. A good analogy to this test is what happens when you are standing on a bus that suddenly accelerates.In contrast, when a platform is moved sinusoidally (10-20 continuous cycles) subjects after a few cycles can anticipate the platform movements and thus can produce preparatory adjustments in advance, as a function of frequency of platform motion. Slow or minor perturbations, and at low frequencies of sinusoidal platform motions, elicit an "Ankle strategy". Here the body acts as an inverted pendulum with the ankle as the pivot point. As the movement of an inverted pendulum is completely rigid, the trunk and lower limb's motion is in the same direction. For faster or larger disturbances, and at higher frequencies of sinusoidal platform motion, a "Hip Strategy" is observed. In this strategy, the body behaves as a dual-segment inverted pendulum, with the trunk as one segment and the lower limbs as the second. The Laboratory tests described above require expensive devices, are not portable and require specially trained personnel, which makes their use unavailable to the average clinician requiring balance screening, in particular in the home. The goal of our research program is to provide insights into early physical decrements that precede development of disability, i.e. basis for identifying older adults at risk of becoming disabled and at risk of falling. The purpose is to develop a clinical measurement tool of dynamic balance, which includes the main features of the Sensory Organization Test and platform motion paradigms used to evaluate feedforward and feedback balance control mechanisms.