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Biomedical subjects

S T Kuna

Publications and source records attributed to S T Kuna.

46 records · Page 3Linked to original sources
PubMed1988

Response of genioglossus muscle activity to nasal airway occlusion in normal sleeping adults.

To determine the combined effect of increased subatmospheric upper airway pressure and withdrawal of phasic volume feedback from the lung on genioglossus muscle activity, the response of this muscle to intermittent nasal airway occlusion was studied in 12 normal adult males during sleep. Nasal occlusion at end expiration was achieved by inflating balloon-tipped catheters located within the portals of a nose mask. No seal was placed over the mouth. During nose breathing in non-rapid-eye-movement (NREM) sleep, nasal airway occlusion resulted in multiple respiratory efforts before arousal. Mouth breathing was not initiated until arousal. Phasic inspiratory genioglossus activity was present in eight subjects during NREM sleep. In these subjects, comparison of peak genioglossus inspiratory activity on the first three occluded efforts to the value just before occlusion showed an increase of 4.7, 16.1, and 28.0%, respectively. The relative increases in peak genioglossus activity were very similar to respective increases in peak diaphragm activity. Arousal was associated with a large burst in genioglossus activity. During airway occlusion in rapid-eye-movement (REM) sleep, mouth breathing could occur without a change in sleep state. In general, genioglossus responses to airway occlusion in REM sleep were similar in pattern to those in NREM sleep. A relatively small reflex activation of upper airway muscles associated with a sudden increase in subatmospheric pressure in the potentially collapsible segment of the upper airway may help compromise upper airway patency during sleep.

Adult↗
PubMed1988

Thyroarytenoid muscle activity during wakefulness and sleep in normal adults.

To determine the respiratory-related activity of the thyroarytenoid (TA) muscle in normal adults, intramuscular electromyographic recordings were performed in eight normal adult males during wakefulness and sleep. Phasic expiratory TA activity was present during normal tidal breathing in all subjects during wakefulness. Tonic activity was frequently present during inspiration. After an initial rapid rise in activity near the onset of expiration, phasic TA activity generally exhibited one of three different discharge patterns: a plateau, a progressive increase, or, less commonly, a progressive decrease in activity. In four of five subjects examined, peak TA activity during quiet breathing in wakefulness appeared to be directly related to time of expiration. At a particular lung volume above end-expiratory volume during wakefulness, measurements of expiratory resistance were directly related to the level of TA activity. TA activity disappeared during stable periods of non-rapid-eye-movement sleep and exhibited paroxysmal bursts of activity during rapid-eye-movement sleep. The results during wakefulness indicate that the TA contributes to an active adduction of the vocal cords in expiration and suggest the presence of an active laryngeal braking mechanism during exhalation.

Adult↗
PubMed1988

Effect of laryngeal anesthesia on pulmonary function testing in normal subjects.

Pulmonary function tests (PFT) were performed on 11 normal subjects before and after topical anesthesia of the larynx. The PFT consisted of flow volume loops and body box determinations of functional residual capacity and airway resistance, each performed in triplicate. After the first set of tests, cotton pledgets soaked in 4% lidocaine were held in the pyriform sinuses for 2 min to block the superior laryngeal nerves. In addition, 1.5 ml of 10% cocaine was dropped on the vocal cords via indirect laryngoscopy. PFT were repeated 5 min after anesthesia. Besides routine analysis of the flow volume loops, areas under the inspiratory (Area I) and expiratory (Area E) portions of the loops were calculated by planimetry. Area I, peak inspiratory flow (PIF), as well as forced inspiratory flow at 25, 50, and 75% forced vital capacity (FVC), decreased after anesthesia. Peak expiratory flow decreased after anesthesia, but Area E and forced expiratory flow at 25, 50, and 75% FVC were unchanged. This protocol also was performed in 12 normal subjects with isotonic saline being substituted for the lidocaine and cocaine. In this group, no significant differences were observed when flow volume loop parameters were compared before and after topical application of saline. In 5 spontaneously breathing anesthetized dogs, posterior cricoarytenoid muscle and afferent superior laryngeal nerve activity were recorded before and after laryngeal anesthesia performed with the same procedure used in the human subjects. Laryngeal anesthesia resulted in a substantial decrease or a complete disappearance of afferent SLN activity recorded during unobstructed and obstructed respiration. The data suggest that laryngeal receptors help modulate upper airway patency in man.

Adult↗
PubMed1988

Effect of nasal airway positive pressure on upper airway size and configuration.

The effect of nasal airway positive pressure (NAPP) on upper airway size and configuration during wakefulness was studied by computerized tomography in 12 obese subjects with obstructive sleep apnea (OSA), seven weight- and age-matched subjects without OSA, and 12 normal subjects. NAPP of 10 to 12 cm H2O was associated with a significant increase in airway area throughout the upper airway in all three groups. The change in airway area per cm H2O NAPP increased from nasopharynx to hypopharynx. The change in airway area per cm H2O NAPP was significantly smaller in the OSA than in the normal subjects in the region of the soft palate. Electromyographic recordings of the genioglossus and alae nasi muscles with and without NAPP during wakefulness in five of the OSA and five of the normal subjects showed either a decrease or no change in phasic and tonic activity with NAPP. In a separate series of experiments in an additional five OSA and five normal subjects, NAPP of zero, 5, 10, and 15 cm H2O was associated with a linear increase in airway area at a given airway level. These results indicate that (1) the increase in pharyngeal cross-sectional area with application of NAPP during wakefulness is smaller in OSA than in normal subjects in the region of the soft palate and (2) changes in upper airway muscle activity may accompany changes in upper airway size and configuration.

Electromyography↗
PubMed1987

Interaction of hypercapnia and phasic volume feedback on motor control of the upper airway.

The effect of hypercapnia on the suppression of efferent hypoglossal and recurrent laryngeal nerve activity by phasic volume feedback was studied in decerebrate paralyzed intubated cats ventilated with a phrenic-driven servo-respirator. The gain of the respirator was altered for single inspirations, and the resulting changes in neural activities were quantified by comparison with respective neural activities without phasic volume feedback. This maneuver was performed when the end-tidal CO2 concentration was 5, 7, and 9%. Changes in the level of CO2 did not alter the slope or position of the volume thresholds for suppression of hypoglossal and recurrent laryngeal activities. The slope of the volume-time isopleths for specific levels of graded suppression also remained constant for each nerve at the different levels of CO2. Under hypercapnic conditions, greater volumes were required at a given time into inspiration to achieve any particular level of suppression, but these differences generally did not reach statistical significance. These data demonstrate a lack of effect of the CO2 stimulus on the suppression of upper airway motoneuron activity by phasic volume feedback. Despite the absence of this interaction, a CO2-induced increase in central inspiratory activation of upper airway motoneurons, in the presence of a very sensitive volume feedback system, would help maintain airway patency in the face of upper airway narrowing or closure.

Animals↗
PubMed1986

Inhibition of inspiratory upper airway motoneuron activity by phasic volume feedback.

The effects of phasic volume feedback on efferent hypoglossal, recurrent laryngeal and phrenic nerve activity were studied in decerebrate, paralyzed intubated cats ventilated with a phrenic-driven servo-respirator. The gain of the respirator was altered for single inspirations, and the resulting changes in neural activities were quantified by comparison with respective neural activities without phasic volume feedback. The volume thresholds for suppression of hypoglossal and recurrent laryngeal activities were time independent. Above these two thresholds and extending over a substantial range, volume feedback caused graded inhibition of upper airway motoneuron outputs. At any particular time during inspiration the relationships between hypoglossal or recurrent laryngeal inhibition and volume were concave to the volume axis. Rate of airflow appeared to exert an effect on upper airway motoneuron activity independent of volume. These results indicate that for hypoglossal and recurrent laryngeal efferent activity 1) volume feedback can cause a sustained graded inhibition throughout inspiration; 2) the volume thresholds are time independent; and 3) partial inhibition decreases susceptibility to additional inhibition. These actions of volume feedback on upper airway motoneuron output differ from those on phrenic efferent discharge and show that phasic vagal volume feedback has a marked and differential effect on upper airway motoneuron activity. The vagus, in this preparation, appears to play a critical role in the regulation of upper airway motoneuron activity and therefore maintenance of upper airway patency.

Animals↗
PubMed1986

The irregularly irregular pattern of respiratory dyskinesia.

The respiratory pattern during wakefulness and sleep was characterized in a 70-year-old woman with respiratory dyskinesia. During wakefulness, both respiratory frequency and tidal volume exhibited an irregularly irregular pattern. In addition, wide fluctuations occurred in the position of the rib cage and abdomen at end expiration. A normal respiratory pattern appeared during non-REM and REM sleep.

Aged↗
PubMed1984

Nasal airway positive pressure in patients with occlusive sleep apnea. Methods and feasibility.

Nasal airway positive pressure (NAPP) effectively eliminates obstructive sleep apnea. This report describes construction and evaluation of a convenient NAPP apparatus used successfully in 15 patients with obstructive sleep apnea. An impeller blower with high flow, low pressure characteristics delivers room air to a flow divider and then to an injector attached to a custom-fitted nose mask. Of the total naris pressure supplied by the system, a large fraction derives from the kinetic energy of the air stream delivered to the naris by the injectors. This, together with the high flow rate of the system, promotes a constant naris pressure. Naris pressure is determined by the size of the flow divider and the aperture of the exhaust port(s) of the injector. A series of 10 flow divider-injector combinations are described that provide a variety of naris pressures between 2.5 and 13.6 cm H2O. Fourteen of 15 patients found the NAPP apparatus acceptable and effective. No maintenance or repair appears to be required.

Adult↗
PubMed1981

Relationship between cyclooxygenase activity (COA) inhibition and stimulation of ventilation by salicylate.

Recent investigations have demonstrated that inhibition of the cyclooxygenase enzyme of the prostaglandin synthetase complex accounts for most of the pharmacological effects of salicylate. To determine whether inhibition of cyclooxygenase activity (COA) plays a role in stimulation of ventilation (VE) by salicylate, sodium salicylate and other more potent inhibitors of COA (i.e., indomethacin and ibuprofen) were infused into anesthetized dogs. These experimental intravascular infusions lasted 1 hr; VE and oxygen consumption (VO2) were continuously measured. In the initial series of experiments, all COA inhibitors were infused at a rate of 25 mumol/kg/min. It was noted that only salicylate elicited consistent increases in either VE or VO2. The possibility that high infusion rates of potent COA inhibitors may prevent stimulation of VE by some additional toxic effect was explored in a second series of experiments in which we infused the minimal amount of COA inhibitors necessary to completely inhibit cyclooxygenase in other experimental situations. In these experiments, it was noted that none of the COA inhibitors (i.e., salicylate, meclofenamate, indomethacin or ibuprofen) stimulated either VE or VO2. These observations suggest that salicylate stimulates VE by a mechanism other than inhibition of prostaglandin synthetase. Because salicylate-induced increases in VE and VO2 followed a similar time course, these results are consistent with our concept that stimulation of VE by salicylate is related to tissue hypermetabolism.

Animals↗