Assessing interactions among multiple physiological systems during walking outside a laboratory: An Android based gait monitor.

Gait function is traditionally assessed using well-lit, unobstructed walkways with minimal distractions. In patients with subclinical physiological abnormalities, these conditions may not provide enough stress on their ability to adapt to walking. The introduction of challenging walking conditions in gait can induce responses in physiological systems in addition to the locomotor system. There is a need for a device that is capable of monitoring multiple physiological systems in various walking conditions. To address this need, an Android-based gait-monitoring device was developed that enabled the recording of a patient's physiological systems during walking. The gait-monitoring device was tested during self-regulated overground walking sessions of fifteen healthy subjects that included 6 females and 9 males aged 18-35 years. The gait-monitoring device measures the patient's stride interval, acceleration, electrocardiogram, skin conductance and respiratory rate. The data is stored on an Android phone and is analyzed offline through the extraction of features in the time, frequency and time-frequency domains. The analysis of the data depicted multisystem physiological interactions during overground walking in healthy subjects. These interactions included locomotion-electrodermal, locomotion-respiratory and cardiolocomotion couplings. The current results depicting strong interactions between the locomotion system and the other considered systems (i.e., electrodermal, respiratory and cardiovascular systems) warrant further investigation into multisystem interactions during walking, particularly in challenging walking conditions with older adults.

The effects of increased fluid viscosity on stationary characteristics of EEG signal in healthy adults.

Electroencephalography (EEG) systems can enable us to study cerebral activation patterns during performance of swallowing tasks and possibly infer about the nature of abnormal neurological conditions causing swallowing difficulties. While it is well known that EEG signals are non-stationary, there are still open questions regarding the stationarity of EEG during swallowing activities and how the EEG stationarity is affected by different viscosities of the fluids that are swallowed by subjects during these swallowing activities. In the present study, we investigated the EEG signal collected during swallowing tasks by collecting data from 55 healthy adults (ages 18-65). Each task involved the deliberate swallowing of boluses of fluids of different viscosities. Using time-frequency tests with surrogates, we showed that the EEG during swallowing tasks could be considered non-stationary. Furthermore, the statistical tests and linear regression showed that the parameters of fluid viscosity, sex, and different brain regions significantly influenced the index of non-stationarity values. Therefore, these parameters should be considered in future investigations which use EEG during swallowing activities.

Baseline characteristics of cervical auscultation signals during various head maneuvers.

Cervical auscultation (CA) is an emerging method of assessing swallowing disorders that is both non-invasive and inexpensive. This technique utilizes microphones to detect acoustic sounds produced by swallowing activity and characterize its behavior. Though some properties of swallowing sounds are known, there is still a need for a complete understanding of the baseline characteristics of cervical auscultation signals as well as how they change due to the patient's head motion, age, and sex. In order to examine these parameters, data was collected from 56 healthy adult participants that performed six different head movement tasks without swallowing. After preprocessing the signal, features were extracted. Dependent variables were time domain, frequency domain and time-frequency domain features. Statistical tests showed that only the skewness and peak frequency were not statistically different for all tasks. The peak frequency results indicate that head movement does not significantly affect the microphone signal, and that it is unnecessary to filter out the lowest frequency components. No sex differences were observed in the extracted features, but several features exhibited age dependence.

Spinal cord injury models in non human primates: are lesions created by sharp instruments relevant to human injuries?

The worldwide incidence of traumatic spinal cord injury (SCI) is approximated at 180,000 new cases per year. Experiments using nonhuman primates (NHP) are often used to replicate the human condition in order to advance the understanding of SCI and to assist in the development of new treatments. Experimental spinal cord lesions in NHP have been created by a number of methods including blunt trauma, epidural balloons, circumferential cuffs, and dropping a precision weight over the spinal cord. As well, experimental lesions have been created with sharp instruments after opening the dura mater. However, spinal cord lesions that are created with a sharp instrument in NHP experiments may not replicate the clinical and pathological features of human spinal cord injury. Researchers should recognize the challenges associated with making clinical inferences in human SCIs based on NHP experiments that created experimental lesions with a sharp surgical instrument.

Variability in execution of the chin-down maneuver by healthy adults.

OBJECTIVE: The chin-down maneuver is commonly used in dysphagia management to facilitate greater airway protection. However, the literature suggests that variation in maneuver execution may threaten the effectiveness of the intervention. Our goal was to study variation in chin-down maneuver execution given a uniform instruction. METHODS: Sagittal view digital video recordings were acquired from 408 healthy adults who performed sequences of reiterated water swallows in head-neutral and chin-down positions. Head angle measurements were extracted from the recordings, using markers on goggles worn by 176 participants. RESULTS: We observed considerable variation in head angle in the head-neutral swallowing task, with a trend to greater flexion in participants over the age of 65. Male participants showed greater variation in head angle than females. Head flexion during the chin-down swallowing tasks averaged 19°, in the range reported to yield clinical benefit in radiographic studies. CONCLUSION: We conclude that a clear, uniform instruction is adequate to facilitate execution of the chin-down maneuver to a degree that is likely to be of clinical benefit. The variation in head angle observed in this study warrants further research, particularly regarding the relationship between anatomical cervical spine curvature and head angle influence on swallowing.