Active control of expiratory airflow by the respiratory muscles influences gas exchange, the degree of emptying of the lungs, and the work of breathing; may help optimize inspiratory muscle function; and is important during coughing and speech. Alterations in expiratory timing and velocity of flow occur in response to hypoxia, hypercapnia and exercise, and in diseases such as asthma, chronic obstructive pulmonary disease and sleep apnea. Recent studies of medullary and pontine respiratory centers suggest that neurophysiologically expiration may consist of tow distinct phases. In the proposed studies we will focus on the peripheral mechanisms by which abdominal, thoracic and upper airway muscles actively modulate expiration during these two phases. Specifically, in anesthetized dogs and cats we will 1) examine the manner in which multiple abdominal and thoracic expiratory muscles act in a coordinated fashion during resting and stimulated breathing; 2) study the relationship between the late expiratory activity of the above muscles and the early expiratory activity of the thoracic inspiratory muscles; 3) assess the extent to which upper airway dilators and constrictors are reciprocally active during the two phases of expiration, and how this os modified by respiratory stimuli; 4) record activity from single motor units of selected respiratory muscles, and examine how different motor unit subpopulations fire during expiration; and 5) assess the relationship between expiratory electrical activity of the above muscles and the mechanical consequences of muscle contraction, including respiratory changes in muscle length, expiratory flow rates and respiratory pressures. Studies will be performed during eupnea, when breathing is stimulated by hypercapnia and hypoxia, and following bronchoconstriction; in addition we will assess the roles that different chemoreceptors and mechanoreceptors play in mediating the responses to these stimuli. Finally, in chronically instrumented awake cats we will analyze expiratory activity recorded from several abdominal, thoracic and upper airway muscles to 1) ensure that conclusions derived from studies in anesthetized animals are not unduly influenced by the effects of anesthesia, and 2) assess the effects of spontaneous changes in posture on respiratory muscle activity during expiration.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL038701-01
Application #
3355038
Study Section
Respiratory and Applied Physiology Study Section (RAP)
Project Start
1987-07-01
Project End
1992-06-30
Budget Start
1987-07-01
Budget End
1988-06-30
Support Year
1
Fiscal Year
1987
Total Cost
Indirect Cost
Name
Case Western Reserve University
Department
Type
Schools of Medicine
DUNS #
077758407
City
Cleveland
State
OH
Country
United States
Zip Code
44106
van Lunteren , E; Dick, T E (2001) Heterogeneity within geniohyoid motor unit subpopulations in firing patterns during breathing. Respir Physiol 124:23-33
Haxhiu, M A; Erokwu, B; van Lunteren, E et al. (1993) Central and spinal effects of sodium cyanide on respiratory activity. J Appl Physiol 74:574-9
Van Lunteren, E; Vafaie, H (1993) Force potentiation in respiratory muscles: comparison of diaphragm and sternohyoid. Am J Physiol 264:R1095-100
van Lunteren, E; Martin, R J (1993) Pharyngeal dilator muscle contractile and endurance properties in neonatal piglets. Respir Physiol 92:65-75
Haxhiu, M A; Cherniack, N S; Mitra, J et al. (1992) Nonvagal modulation of hypoglossal neural activity. Respiration 59:65-71
van Lunteren, E; Dick, T E (1992) Intrinsic properties of pharyngeal and diaphragmatic respiratory motoneurons and muscles. J Appl Physiol 73:787-800
van Lunteren, E; Manubay, P (1992) Contractile properties of feline genioglossus, sternohyoid, and sternothyroid muscles. J Appl Physiol 72:1010-5
van Lunteren, E; Dick, T E (1992) Breath-to-breath variability in hypoglossal motor unit firing. Respir Physiol 89:37-46
van Lunteren, E; Arnold, J S; Haxhiu, M A (1991) Abdominal muscle length during respiratory defensive reflexes. Respir Physiol 86:199-213
Salmone, R J; Van Lunteren, E (1991) Effects of hypoxia and hypercapnia on geniohyoid contractility and endurance. J Appl Physiol 71:709-15

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