Michael C. K. Khoo

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Previous studies on ventilatory control in obstructive sleep apnea (OSA) have generally indicated depressed chemosensitivity, implying greater stability of the chemical control of breathing in these subjects. However, these results were based on tests involving steady-state or quasi-steady measurements obtained in wakefulness. We have developed a method for(More)
Detection and quantification of sleep arousals is an important issue, as the frequent arousals are known to reduce the quality of sleep and cause daytime sleepiness. In typical sleep staging, electroencephalograph (EEG) is the core signal and based on the visual inspection of the frequency content of EEG, non-rapid eye movement sleep is staged into four(More)
Recent studies suggest that exposure to repetitive episodes of hypoxia and transient arousal can lead to increased risk for cardiovascular disease in patients with obstructive sleep apnea syndrome (OSAS). To obtain an improved understanding of and to quantitatively characterize the autonomic effects of arousal from sleep, a time-varying closed-loop model(More)
GOAL We demonstrate a novel and robust approach for visualization of upper airway dynamics and detection of obstructive events from dynamic 3-D magnetic resonance imaging (MRI) scans of the pharyngeal airway. METHODS This approach uses 3-D region growing, where the operator selects a region of interest that includes the pharyngeal airway, places two seeds(More)
Deep breaths akin to sighs have been reported to cause peripheral vasoconstriction. Our previous simulation studies have shown that this phenomenon cannot be reproduced in existing circulatory control models without inclusion of a respiratory-vascular coupling mechanism. To better understand this "sigh-vasoconstriction reflex", we investigated the effect of(More)
The transition of the fetus at birth to extrauterine life is an extremely complex process. As part of the hemodynamic transition, the closure of ductus arteriosus, a fetal shunt, is among the key steps to achieve normal postnatal cardiovascular function. However, significant gaps remain in our knowledge pertaining to the hemodynamics of normal ductal(More)
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