The objective of this proposed research is to improve our understanding of the resistance of upper airway and of the strength and electrical activation of its respiratory muscles in patients with obstructive sleep apnea (OSA). We will test 5 hypotheses. First that patients with OSA have a narrow airway with a high resistance and that this contributes to the development of OSA. A narrow airway would be more likely to collapse than would a normal sized one because it would have a lower pressure in it. Preliminary work supports this hypothesis but investigators have not controlled their studies for the effect of obesity, an accompanying feature of OSA. Resistance will be measured with the pulse flow method and with another more conventional method. Computed tomographic scans of the pharynx will access pharyngeal cross-sectional area. A second hyphothesis is that pharyngeal airway obstruction can be induced in awake patients with OSA but not in normals by the application of subatmospheric pressure to the nose during nasal breathing. Subjects lying on their back will wear a tightly fitting face mask in which the pressure is periodically lowered for 2 to 4 breaths to between - 10 and - 60 cmH2O. This may be a useful screening test for OSA, possibly eliminating many expensive and time consuming nocturnal sleep studies. It may also be useful to study the forcefulness of pharyngeal muscle contraction and the effect of pharmacologic agents and chemical stimuli on the pharyngeal airway. Third we will test the hypothesis that there is an inverse relationship between upper airway resistance during sleep and genioglossal and alae nasi electromyograms (EMG's ). We will also try to determine whether the observed decreased upper airway muscle EMG signals during apneic episodes could be produced by muscle fatigue. This will be tested by loading and fatiguing upper airway dilator muscles in normal subjects. Fourth we will test the hypothesis that treatment with weight loss, progesterone and protriptyline alters pharyngeal airway resistance and the ability of the airway to resist collapse from the application of subatmospheric pressure. Double blind cross over comparisons with placebo will be performed with progesterone and protriptyline. The fifth hypothesis we will test is that sleep deprivation or fragmentation, an important feature of the sleep syndrome, increase pharyngeal airway resistance and decreases the ability of the pharynx to resist collapse from the application of subatmospheric pressure in normal subjects.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL030218-03
Application #
3341280
Study Section
Respiratory and Applied Physiology Study Section (RAP)
Project Start
1983-12-01
Project End
1987-06-30
Budget Start
1985-12-01
Budget End
1987-06-30
Support Year
3
Fiscal Year
1986
Total Cost
Indirect Cost
Name
University of Virginia
Department
Type
Schools of Medicine
DUNS #
001910777
City
Charlottesville
State
VA
Country
United States
Zip Code
22904
Suratt, P M; McTier, R F; Findley, L J et al. (1992) Effect of very-low-calorie diets with weight loss on obstructive sleep apnea. Am J Clin Nutr 56:182S-184S
Griggs, G A; Findley, L J; Suratt, P M et al. (1989) Prolonged relaxation rate of inspiratory muscles in patients with sleep apnea. Am Rev Respir Dis 140:706-10
Suratt, P M; McTier, R F; Wilhoit, S C (1988) Upper airway muscle activation is augmented in patients with obstructive sleep apnea compared with that in normal subjects. Am Rev Respir Dis 137:889-94
Suratt, P M; McTier, R F; Findley, L J et al. (1987) Changes in breathing and the pharynx after weight loss in obstructive sleep apnea. Chest 92:631-7
Suratt, P M; Turner, B L; Wilhoit, S C (1986) Effect of intranasal obstruction on breathing during sleep. Chest 90:324-9
Findley, L J; Barth, J T; Powers, D C et al. (1986) Cognitive impairment in patients with obstructive sleep apnea and associated hypoxemia. Chest 90:686-90
Suratt, P M; Wilhoit, S C; Brown, E D et al. (1986) Effect of doxapram on obstructive sleep apnea. Bull Eur Physiopathol Respir 22:127-31
Suratt, P M; McTier, R F; Wilhoit, S C (1985) Collapsibility of the nasopharyngeal airway in obstructive sleep apnea. Am Rev Respir Dis 132:967-71
Suratt, P M; McTier, R; Wilhoit, S C (1985) Alae nasi electromyographic activity and timing in obstructive sleep apnea. J Appl Physiol 58:1252-6
Wilhoit, S C; Suratt, P M; Evans, R J et al. (1985) Comparison of indices used to detect hypoventilation during sleep. Respiration 47:237-42

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