Respiration physiology
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Respiration physiology · Sep 2001
Sublingual electrical stimulation of the tongue during wakefulness and sleep.
Pharyngeal obstruction in patients with obstructive sleep apnea (OSA) is thought to result from decreased upper airway muscle tone during sleep. The goal of the present study was to estimate the role of the tongue muscles in maintaining pharyngeal patency during sleep. Using non-invasive, sub-lingual surface electrical stimulation (ES), we measured tongue protrusion force during wakefulness and upper airway resistance during sleep in seven healthy subjects and six patients with OSA. ⋯ We conclude that non-invasive ES of the tongue improves flow dynamics during sleep. Combined activation of tongue protrusors and retractors may have a beneficial mechanical effect. The magnitude of responses observed suggests that in addition to the stimulated muscles, other muscles and/or forces have a substantial impact on pharyngeal patency.
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Respiration physiology · Sep 2001
Clinical Trial Controlled Clinical TrialEffects of respiratory muscle training versus placebo on endurance exercise performance.
We evaluated the effects of a 5 week (25 sessions); (30-35 min/day, 5 days/week), respiratory muscle training (RMT) program in nine competitive male cyclists. The experimental design included inspiratory resistance strength training (3-5 min/session) and hyperpnea endurance training (30 min/session), a placebo group which used a sham hypoxic trainer (n=8), and three exercise performance tests, including a highly reproducible 8 km time trial test. RMT intensity, measured once a week in terms of accumulated inspiratory pressure and the level of sustainable hyperpnea increased significantly after 5 weeks (+64% and +19%, respectively). ⋯ Heart rate, ventilation, or venous blood lactate, at equal work-rates during the incremental exercise test or at equal times during the fixed work-rate endurance test were not changed significantly across these exercise trials in either group. We propose that the effect of RMT on exercise performance in highly trained cyclists does not exceed that in a placebo group. Significant placebo and test familiarization effects must be accounted for in experimental designs utilizing performance tests which are critically dependent on volitional effort.
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Respiration physiology · Aug 2001
Airway ammonia negates the normal ventilatory response to airway CO(2) in garter snakes.
Earlier studies from this lab showed that unidirectionally ventilated snakes, maintained on high airway [CO(2)], breathe slowly with a large tidal volume. If airway [CO(2)] is abruptly reduced during inspiration, inspiratory duration (TI) and tidal volume increase. On the other hand, in an animal normally receiving fresh air (no CO(2) in the inspired air) on each inspiration, if fresh air is withheld for one breath, TI and tidal volume decrease. ⋯ However, for one breath, [CO(2)] was maintained high during inspiration and airway NH(3) (3--4%) was simultaneously introduced into the airstream. During this breath, TI was expected to decrease, owing to the elevated [CO(2)]; however, there was no significant difference in the TI of the test breath compared with the previous breath, indicating that ammonia interfered with the expected CO(2) response. This study suggests that pH (probably intracellular) rather than P(CO(2)) produces this ventilatory reflex.
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Respiration physiology · Jul 2001
Lack of positive interaction between CO2 and hypoxic stimulation for P(CO2)-VAS response slope in humans.
To compare the effect of hypoxia on ventilatory responses and respiratory sensation to carbon dioxide, 29 young adults were examined using a modified Read's rebreathing method with four experimental conditions. We used varying gas mixtures and kept PET(O2) constant at >300, 100, 80 and 60 mmHg for each four rebreathing tests. Respiratory sensation was measured by visual analog scale (VAS). ⋯ However, the slope of the CO2-VAS response curve remained unchanged. The V(E)-VAS relation slope tended to become depressed with advancing hypoxia, i.e. the magnitude of VAS elicited by a given ventilation decreased with hypoxia, signifying that dyspneic sensation was effectively mitigated during hypoxic hyperventilation. We suggest that this relief of dyspneic sensation might be due to the inhibitory respiratory effect from augmented pulmonary stretch receptor (PSR) activity.
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Respiration physiology · Jun 2001
Comparative StudyRegulation of secretion from mucous and serous cells in the excised ferret trachea.
Mucus hypersecretion is an important characteristic of many airway diseases. Mucin is the major component of mucus, and is secreted from surface goblet cells of the airway epithelium and mucous cells of submucosal glands. Lysozyme is an enzyme secreted by serous cells of airway submucosal glands. ⋯ We showed that there is an anatomic gradient for constitutive and stimulated mucin and lysozyme secretion with the distal tracheal segments secreting more mucin and lysozyme per gram of tissue than the proximal segments. This robust model system can be used to evaluate the regulation of airway mucous and serous cell secretion and to assess the effect of agents that might alter the secretory response. We confirm that on an equimolar basis, HNE is one of the most potent mucus secretagogues.