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Professor, BIO5 Institute
Professor, Evelyn F Mcknight Brain Institute
Professor, Speech/Language and Hearing
My research focus is the neural control of breathing in human and nonhuman mammals. My earlier work assessed the role of pulmonary stretch receptors and central chemoreceptors in the genesis and relief of dyspnea or shortness of breath in healthy adults. These studies led to studies in the mammalian (rodent) airway that explored the modulation of upper airway muscles activities by chemical and pulmonary afferent feedback and the potential for selective electrical stimulation of the cranial nerve XII to alter airway geometry and volume (NIH/NIDCD RO3). Beginning in 2005, with the support of an NIH/NIDCD K23 I began work in neural control of upper airway muscles using tungsten microelectrodes to record from single motor units in adult human subjects. This work led in turn, to studies of regional (or segmental) muscle and motor unit activities in human subjects under volitional, state-dependent (i.e., wake/sleep) and chemoreceptor drives, in health and disease (NIH/NIDCD RO1). On the basis of the experimental work in muscle and motor units I have pursued additional lines of enquiry focused on clinical respiratory dysfunction in two specific populations a) infants at risk for SIDS and b) adults diagnosed with obstructive sleep apnea (OSA). Both lines of enquiry are highly innovative and have diagnostic and clinical applications. One recent line of enquiry explores the potential for a non-pharmacologic intervention daily to lower blood pressure and to improve sleep in patients diagnosed with mild-moderate obstructive sleep apnea. This training protocol shows promise as a cheap, effective and safe means of lowering blood pressure and improving autonomic-cardiovascular dysfunction in patients who are unwilling or unable to use the standard CPAP therapy.
Bailey, E. F. (2016). Evaluating the control: minipump implantation and breathing behavior in the neonatal rat. Journal of Applied Physiology.
Fregosi, R. F., Bailey, E. F., & Fuller, D. D. (2011). Respiratory muscles and motoneurons. Respiratory physiology & neurobiology, 179(1), 1-2.
Vranish, J. R., & Bailey, E. F. (2015). A comprehensive assessment of genioglossus electromyographic activity in healthy adults. Journal of neurophysiology, 113(7), 2692-9.
The genioglossus (GG) is an extrinsic muscle of the human tongue that plays a critical role in preserving airway patency. In the last quarter century, >50 studies have reported on respiratory-related GG electromyographic (EMG) activity in human subjects. Remarkably, of the studies performed, none have duplicated subject body position, electrode recording locations, and/or breathing task(s), making interpretation and integration of the results across studies extremely challenging. In addition, more recent research assessing lingual anatomy and muscle contractile properties has identified regional differences in muscle fiber type and myosin heavy chain expression, giving rise to the possibility that the anterior and posterior regions of the muscle fulfill distinct functions. Here, we assessed EMG activity in anterior and posterior regions of the GG, across upright and supine, in rest breathing and in volitionally modulated breathing tasks. We tested the hypotheses that GG EMG is greater in the posterior region and in supine, except when breathing is subject to volitional modulation. Our results show differences in the magnitude of EMG (%regional maximum) between anterior and posterior muscle regions (7.95 ± 0.57 vs. 11.10 ± 0.99, respectively; P 0.2).
Van Zutphen, C., Janssen, P., Hassan, M., Cabrera, R., Bailey, E. F., & Fregosi, R. F. (2007). Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction. NMR in biomedicine, 20(7), 682-91.
The velopharynx is the most collapsible segment of the upper airway in patients with obstructive sleep apnea. However, we do not know if velopharyngeal compliance is uniform throughout its length, or if compliance is modified by contraction of upper airway muscles. We tested the hypothesis that rostral and caudal velopharyngeal (VP) compliance differs, and that tongue muscle contraction reduces compliance. High-resolution MR images of the VP were made at nasopharyngeal pressures ranging from -9 to 9 cmH(2)O in anesthetized rats. Images were obtained twice at each pressure, once with and once without bilateral hypoglossal nerve stimulation. The volume of the caudal and rostral VP was computed at each pressure. The caudal VP was significantly (P = 0.0058) more compliant than the rostral VP, but electrical stimulation of the tongue muscles did not change compliance. VP critical pressure (Pcrit; pressure at zero airway volume) averaged -25.2 and -12.1 cmH(2)O in the rostral and caudal VP, respectively (P
John, J., Bailey, E. F., & Fregosi, R. F. (2005). Respiratory-related discharge of genioglossus muscle motor units. American journal of respiratory and critical care medicine, 172(10), 1331-7.
Little is known about the respiratory-related discharge properties of motor units driving any of the eight muscles that control the movement, shape, and stiffness of the mammalian tongue.