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Biomedical subjects

S T Kuna

Publications and source records attributed to S T Kuna.

At least 19 recordsLinked to original sources
PubMed2001

Effects of pharyngeal muscle activation on airway size and configuration.

Fiberoptic imaging was performed in six decerebrate, tracheotomized cats to determine the effect of pharyngeal muscle activation on the pharyngeal airway. The fiberoptic scope was advanced through the rostral trachea into the pharynx. Computer-based planimetry was used to measure airway area and maximum anteroposterior and lateral diameters in the rostral oropharynx, velopharynx, and caudal oropharynx. Cuff electrodes stimulated the bilateral distal cut ends of the following nerves: medial hypoglossus (MHG), lateral hypoglossus (LHG), glossopharyngeus, and pharyngeal branch of vagus (PBV). The velopharyngeal area increased with stimulation of the MHG, MHG plus LHG, and glossopharyngeus. The velopharyngeal area decreased with PBV stimulation. Similar effects occurred in the caudal oropharynx. The percent increase in velopharyngeal area with combined MHG and LHG stimulation was greater than the sum of the increases stimulating either branch alone. In the rostral oropharynx, airway area increased with individual and combined stimulation of the MHG and LHG. Changes in airway area at the different levels were concentric with the HG stimulations, but glossopharyngeal stimulation resulted in a greater increase in lateral than anteroposterior wall movement. The results indicate that the mechanical effects of pharyngeal muscle contraction depend on the airway level and the specific muscles that are activated.

Animals↗
PubMed2001

Effect of nasal continuous positive airway pressure on neuropsychological function in sleep apnea-hypopnea syndrome. A randomized, placebo-controlled trial.

A placebo-controlled, partial cross-over, double-blind, randomized study was performed with 46 adults with sleep apnea-hypopnea syndrome (SAHS) to determine the effect of therapeutic and subtherapeutic (0-1 cm H(2)O) nasal continuous positive airway pressure (CPAP) treatment on polysomnographic and neuropsychological testing. The following neuropsychological tests were administered: Geriatric Depression Scale, Trail Making A and B, Digit Span Test Forward and Backward, Epworth Sleepiness Scale, SteerClear, Digit Symbol, Controlled Oral Word Association, and Complex Figure Recall. Compared with results without CPAP, subtherapeutic CPAP did not affect any measured polysomnographic parameter. Comparison of neuropsychological test results obtained between the initial periods of effective treatment (Group 1, 16.1 d; Group 2, 19.6 d; p = NS) in all subjects showed significant improvements in Digit Symbol, Digit Span Backward, and Complex Figure tests. However, there were no group differences in changes in test results during the period when one group was on effective CPAP and the other on ineffective CPAP (Group 1, 16.1 d; Group 2, 13.9 d; p = NS). The results indicate the feasibility and importance of using ineffective CPAP as a placebo treatment and the importance of including a placebo control in studies evaluating the effect of treatment on neuropsychological function in SAHS.

Adult↗
PubMed2000

Respiratory-related activation and mechanical effects of the pharyngeal constrictor muscles.

We have examined the respiratory-related activation of pharyngeal constrictor (PC) muscles in decerebrate cats, normal adult humans and patients with obstructive sleep apnea. In decerebrate cats and awake normal adult humans, phasic expiratory PC activity is uniformly present under hypercapnic and hypoxic conditions. While the PC muscles are electrically silent during quiet breathing in normal adult humans in NREM sleep, an activation pattern very similar to that of other upper airway dilators, such as the genioglossus muscle, is present during spontaneous and induced apneas in patients with obstructive sleep apnea. Experiments using an isolated, sealed upper airway preparation in decerebrate cat show that selective activation of the PC muscles stiffens the pharyngeal airway. The results also show that activation of the PC muscles constricts the airway at relatively high airway volumes but dilates the airway at relatively low airway volumes. These results suggest that PC muscle activation at the end of an apneic episode, when airway volume is relatively low, may help restore airway patency in patients with obstructive sleep apnea.

Humans↗
PubMed2000

An oral elastic mandibular advancement device for obstructive sleep apnea.

Oral mandibular advancement devices are becoming an increasingly important treatment alternative for obstructive sleep apnea (OSA). The first aim of the study was to determine whether a new oral elastic mandibular advancement device (EMA) prevents pharyngeal airway closure during sleep in patients with OSA. The second aim of the study was to determine if the polysomnographic response to the oral mandibular advancement device was dependent on the site of airway closure. Overnight polysomnograms were performed in 28 untreated OSA subjects with and without EMA. A third polysomnogram was performed in 12 of the subjects to determine the site of airway closure without the device. Site of airway closure above or below the oropharynx was determined by measuring the respective presence or absence of respiratory fluctuations in oropharyngeal pressure during induced occlusions in non-rapid eye movement (NREM) sleep. Mean apnea-hypopnea index (AHI) was 52.6 +/- 28.2 (SD) events/h without the device and 21.2 +/- 19.3 events/h with the device. Nineteen subjects (68%) had at least a 50% reduction in AHI with the device. The change in AHI with the device (AHI without device - AHI with device) was directly related to the AHI without the device. All three subjects with airway closure in the lower pharyngeal airway had a greater than 80% reduction in AHI with the device. Two of the nine subjects with airway closure in the velopharynx had a similar therapeutic response. The results show the effectiveness of EMA in the treatment of OSA. The results also indicate that polysomnographic severity of OSA and the site of airway closure should not be used to exclude patients from this oral device treatment.

Adult↗
PubMed1999

Premotor input to hypoglossal motoneurons from Kölliker-Fuse neurons in decerebrate cats.

Experiments were performed in 18 paralysed, ventilated, decerebrate adult cats to characterise projections from the Kölliker-Fuse nucleus(KFN) to hypoglossal(HG) motoneurons. Efferent neural activity was recorded from the medial branch of both HG nerves, right recurrent laryngeal(RL) nerve, and C3 branch of the left phrenic nerve. Electrical stimulation(1 Hz, 1 msec pulse duration) of discrete areas within the KFN coordinates elicited a preferential, predominantly ipsilateral burst of HG action potentials with an average stimulus-response latency of 8 msec. Tonic stimulation(5-20 Hz) frequently produced considerable HG temporal summation and the appearance of phasic inspiratory HG activity. Injection of 40-100 nl kainic acid(6.37 mM) into the rostral pontine site with the lowest electrical threshold for HG activation elicited a prolonged tonic HG activation. Following kainate injection, the electrical stimulation threshold for HG excitation increased. Pressure injections of 5-100 nl of 2 mM N-methyl-D-aspartic acid (NMDA)and 2 mM(+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid hydrobromide(AMPA) into the KFN were associated with activation and/or suppression of HG motor output. The results indicate that HG motoneurons innervating protrusor tongue muscles receive a selective projection from the KFN that can be activated by glutamate receptors on KF neurons.

Action Potentials↗
PubMed1999

Mechanical effects of pharyngeal constrictor activation on pharyngeal airway function.

The mechanical effects of pharyngeal constrictor (PC) muscle activation on pharyngeal airway function were determined in 20 decerebrate, tracheotomized cats. In 10 cats, a high-compliance balloon attached to a pressure transducer was partially inflated to just occlude the pharyngeal airway. During progressive hyperoxic hypercapnia, changes in pharyngeal balloon pressure were directly related to phasic expiratory hyopharyngeus (middle PC) activity. In two separate protocols in 10 additional cats, the following measurements were obtained with and without bilateral electrical stimulation (0.2-ms duration, threshold voltage) of the distal cut end of the vagus nerve's pharyngeal branch supplying PC motor output: 1) pressure-volume relationships in an isolated, sealed upper airway at a stimulation frequency of 30 Hz and 2) rostrally directed axial force over a stimulation frequency range of 0-40 Hz. Airway compliance determined from the pressure-volume relationships decreased with PC stimulation at and below resting airway volume. Compared with the unstimulated condition, PC stimulation increased airway pressure at airway volumes at and above resting volume. This constrictor effect progressively diminished as airway volume was brought below resting volume. At relatively low airway volumes below resting volume, PC stimulation decreased airway pressure compared with that without stimulation. PC stimulation generated a rostrally directed axial force that was directly related to stimulation frequency. The results indicate that PC activation stiffens the pharyngeal airway, exerting both radial and axial effects. The radial effects are dependent on airway volume: constriction of the airway at relatively high airway volumes, and dilation of the airway at relatively low airway volumes. The results imply that, under certain conditions, PC muscle activation may promote pharyngeal airway patency.

Animals↗
PubMed1997

Differential activity of the pars recta and pars oblique in fundamental frequency control.

This study was designed to determine if differences exist in pars recta and pars oblique muscle activity during speech and singing. Hooked wire electrodes were implanted in the muscle bundles under direct vision during thyroid surgery in two men and three women. It was found that the pars recta and pars oblique do not function in a similar manner across fundamental frequencies (fo's), tasks, or subjects. Large inter- and intrasubject variability was evident in the contribution of the cricothyroid bundles to fundamental frequency (fo) control. It is speculated that the effect of pars recta and pars oblique contraction may be a function of individual anatomic variations.

Adult↗
PubMed1997

Respiratory-related pharyngeal constrictor muscle activity in decerebrate cats.

Respiratory-related activity of the hyopharyngeus (middle pharyngeal constrictor) and thyropharyngeus (inferior pharyngeal constrictor) muscles was determined in decerebrate, tracheotomized adult cats and compared with the electromyographic activity of the thyroarytenoid, a vocal cord adductor. During quiet breathing, the hyopharyngeus and usually the thyroarytenoid exhibited phasic activity during expiration and tonic activity throughout the respiratory cycle. Respiratory-related thyropharyngeus activity was absent under these conditions. Progressive hyperoxic hypercapnia and progressive isocapnic hypoxia increased phasic expiratory activity in both pharyngeal constrictor (PC) muscles but tended to suppress thyroarytenoid activity. Passively induced hypocapnia and the central apnea that followed the cessation of the mechanical hyperventilation were associated with tonic activation of the hyopharyngeus and thyroarytenoid but no recruitment in thyropharyngeus activity. The expiratory phase of a sigh and progressive pneumothorax were associated with an increase in phasic thyroarytenoid activity but no change in phasic PC activity. The results indicate that a variety of stimuli modulate respiratory-related PC activity, suggesting that the PC muscles may have a role in the regulation of upper airway patency during respiration.

Animals↗
PubMed1997

Activation of intrinsic laryngeal muscles during cough.

We studied the pattern of discharge of the posterior cricoarytenoid (PCA), cricothyroid (CT), thyroarytenoid (TA), and arytenoideus transversus (AR) muscles during cough in 12 anesthetized dogs. Diaphragm electromyographic (EMG) activity was also recorded, together with subglottic and esophageal pressures. Trains of repetitive coughs were induced by mechanically stimulating the tracheobronchial airway. Trials with the upper airway isolated from and connected to the lower airway were performed before and following bilateral sectioning of the internal branch of the superior laryngeal nerve (SLN). The immediate effect of tracheal stimulation was an "apneic" period at FRC, during which the PCA, a laryngeal abductor, showed a progressive increase in activity accompanied by small, variable increases in the activity of the CT and the laryngeal adductors, the TA and AR. The subsequent cough efforts were divided into three phases: inspiration, glottic narrowing, and forced expiration. PCA activity was greatest during the inspiratory phase and CT activity was greatest during the expiratory phase. Peak subglottic pressure occurred during glottic narrowing and coincided with the greatest activation of the TA and AR during the cough effort, and suppression of the PCA and CT. The patterns of EMG activation were not affected by the route of breathing or SLN section. The results suggest the presence of a uniquely central process controlling laryngeal muscles during cough, independent of laryngeal sensory feedback.

Animals↗
PubMed1997

Respiratory-related pharyngeal constrictor muscle activity in normal human adults.

Electromyographic activity of the superior, middle, and inferior pharyngeal constrictor (PC) muscles was examined in 10 normal adult humans during wakefulness and sleep. Wire electrodes were inserted close to the midline of the posterior pharyngeal wall at the level of the soft palate (superior PC), tip of the epiglottis (middle PC), and corniculate tubercle (inferior PC). In general, the three PC muscles exhibited similar patterns of activation. The PCs were activated during swallows, repetitive "pa" sounds, changes in head position, and the last portions of slow inspiratory and expiratory vital capacity maneuvers. Respiratory-related PC activity was infrequent during quiet breathing during wakefulness; variable and inconsistent phasic activation in expiration in one or more of the PCs was present in seven of the 10 subjects, particularly after a swallow. Progressive hyperoxic hypercapnia and progressive isocapnic hypoxia were associated with recruitment of phasic PC activity, which was predominantly expiratory; however, variable discharge patterns were observed within a given muscle and a given subject. When phasic PC activity was present, preactivation during late inspiration was frequently observed. PC activity was absent in NREM sleep and exhibited sporadic, nonrespiratory-related bursts of activity during REM sleep. Passively induced hypocapnic hyperventilation in NREM sleep was not associated with PC activation. The results indicate that the PCs have very similar patterns of activation and exhibit phasic expiratory activity during relatively high ventilatory output states in wakefulness.

Adult↗
PubMed1997

Superior pharyngeal constrictor activation in obstructive sleep apnea.

Respiratory-related superior pharyngeal constrictor (SPC) muscle activity was determined in 18 obstructive sleep apnea (OSA) patients during wakefulness and sleep. Hooked-wire electrodes were implanted into the SPC muscle via a nasopharyngoscope. During quiet breathing in wakefulness, phasic expiratory SPC-muscle activity was consistently present in six subjects and intermittently present in 12 subjects, particularly following a swallow. The SPC muscle showed two patterns of activation during spontaneous obstructive apneic episodes in non-rapid-eye-movement (NREM) sleep: (1) activation during airway reopening, with or without waning phasic or tonic activation in the first half of the ensuing apnea (n = 13); and (2) absence of activation during apneas or arousals (n = 5). Activation on airway reopening following spontaneous apneas usually occurred on inspiration. When the apneic episodes were eliminated by application of nasal continuous positive airway pressure (CPAP), SPC-muscle activity was absent in NREM sleep in 16 subjects, but phasic expiratory activity persisted in two subjects. Sudden withdrawal of nasal CPAP in NREM sleep induced airway closure without a change in SPC-muscle activity. Arousal prior to or immediately after reapplication of nasal CPAP was associated with SPC-muscle activation during inspiration or expiration, and airway reopening. The results in OSA subjects indicate that SPC-muscle activation is similar to that of pharyngeal dilator muscles during spontaneous and induced apneas, and is not necessary to induce upper-airway closure during NREM sleep in OSA subjects.

Adult↗
PubMed1996

Comparison of direct and indirect calculations of laryngeal airway resistance in connected speech.

Direct measures of subglottal pressure obtained through a tracheal puncture were used to calculate laryngeal airway resistance. Six subjects completed tasks including syllable trains and more natural speech samples produced at three loudness levels. Direct calculations of natural speech resistance values were compared with indirect estimates obtained during syllable train production. The degree of correspondence between direct and indirect calculations varied by subject. Overall, the smallest relative errors among calculations occurred for syllable trains, with higher relative errors for the monologue and sentence. For loudness conditions, the smallest and largest relative errors occurred for soft and loud productions, respectively. The clinical utility of indirect estimation is questioned and suggestions for improving its validity are provided.

Adult↗
PubMed1996

Effect of airway surface liquid composition on laryngeal muscle activation.

The effects of aerosolized distilled water and isosmolal dextrose in the isolated larynx on laryngeal muscle activity were studied in eight anesthetized dogs. Water aerosol was associated with an increase in peak posterior cricoarytenoid activity but no change in thyroarytenoid activity. Saline or isosmolal dextrose aerosols did not have any effect on the activity of either muscle. The reflex increase in posterior cricoarytenoid activity due to laryngeal negative pressure was enhanced when the negative pressure challenge was repeated following distilled water aerosol. The results suggest that alteration in laryngeal surface liquid composition modifies the response of pressure-responsive laryngeal receptors and, thereby, the reflex activation of airway patency maintaining muscles.

Animals↗
PubMed1995

Effect of changes in airway surface liquid on laryngeal receptors and muscles.

The effects of aerosolizing distilled water and isosmolal dextrose in the isolated larynx on the activity of pressure-responsive receptors and laryngeal muscles were studied in anesthetized dogs. Following water aerosolization, the mean discharge of pressure-responsive laryngeal mechanoreceptors during upper airway breathing and occlusion was 151% and 138% respectively of that present after saline aerosolization. During delivery of water aerosol, the peak activity of the posterior cricoarytenoid muscle increased to 229 +/- 56% of control; no effects were present on the thyroarytenoid muscle activity. Saline or isosmolal dextrose aerosols did not have any effect on the activity of either muscle. The reflex increase in posterior cricoarytenoid muscle activity due to laryngeal negative pressure was enhanced (163%) when the negative pressure challenge was repeated following distilled water aerosol. These results suggest that alteration in laryngeal surface liquid composition modifies the response of pressure-responsive laryngeal receptors and thereby the reflex activation of airway patency maintaining muscles.

Aerosols↗
PubMed1995

Comparison of direct and indirect calculations of laryngeal airway resistance in various voicing conditions.

Calculation of laryngeal airway resistance using intraoral pressure divided by airflow has become a widely accepted clinical tool. The estimation is based largely on theoretical assumptions, particularly regarding the relationship between intraoral and subglottal pressure. To determine the estimate's validity, direct measures of airflow and subglottal, intraoral and pharyngeal pressures were obtained for four men and four women. Subjects produced normal, loud, soft and simulated breathy and strained syllable trains. Comparison of direct and indirect calculations of laryngeal airway resistance revealed generally good correspondence, particularly for [pi] syllables, although the estimate's accuracy varied among individual subjects. Some interpretive caution is warranted for the extremes of laryngeal airway resistance, with resistance likely to be underestimated in the strained condition, and overestimated in the breathy condition.

Adult↗
PubMed1994

Sleep apnea and vigilance performance in a community-dwelling older sample.

Impaired vigilance performance has been reported in older subjects with sleep apnea syndrome (SAS). The current study is an attempt to extend these findings and to investigate additional factors that might have implications for vigilance in the older adult. Fifty-nine older adults [age: 62 +/- 5 (mean +/- SD), range 54-75 years; respiratory disturbance index (RDI): 8.8 +/- 14.4 (mean +/- SD), range 0-67.5] were categorized as SAS or NotSAS, based on various classification criteria [i.e. apnea index (AI) > or = 5, and 10, RDI > or = 5, 10 and 15], and were compared on their vigilance performance as assessed by the computer program "Steer Clear". Vigilance performance did not discriminate the groups, independent of how they were formed. Groups were then formed based on vigilance performance (HiVig vs. LowVig) and compared on assorted sleep variables, periodic leg movements, and self-reported hypersomnolence and depression. Only age discriminated vigilance performance (an inverse relationship), accounting for 31% of the observed variance. Our findings suggest that subject selection may unintentionally bias findings regarding the neuropsychological functioning of individuals with SAS, that vigilance may be impaired only in relatively more "severe" SAS, and that severity of SAS in older adults may not be well characterized by current classification standards. Age clearly impacted vigilance performance, despite the constricted age range sampled, and should be taken into account in future research.

Age Factors↗
PubMed1994

Cricothyroid muscle activity during sleep in normal adult humans.

Previous investigators reported that cricothyroid (CT) muscle usually exhibits phasic inspiratory activity in normal adult humans during wakefulness. The purpose of this study was to determine respiratory-related CT activity in normal adult humans during sleep. Nighttime polysomnograms were performed in 16 subjects. Hooked-wire electrodes were percutaneously implanted in CT with 21-gauge needle-catheter unit that allowed artifact-free monopolar recordings during electrode placement. During wakefulness, CT was usually phasically active on inspiration, with tonic activity throughout the respiratory cycle. Phasic inspiratory activity was present throughout sleep in all subjects, even those without respiratory-related CT activity during wakefulness. Compared with non-rapid-eye-movement (NREM) sleep, phasic CT activity uniformly increased in rapid-eye-movement (REM) sleep. No differences were apparent in height of phasic CT activity between phasic and tonic REM sleep. Application of nasal continuous positive pressure in stage 3/4 NREM sleep was associated with a decrease in phasic CT activity. Passively induced hypocapnia with positive-pressure ventilation via a nose mask in stage 3/4 NREM sleep was associated with a disappearance of phasic CT activity. Cessation of positive-pressure ventilation under hypocapnic conditions frequently resulted in apnea. Phasic CT activity remained absent during apnea but reappeared coincident with or soon after resumption of spontaneous respiration. In summary, CT's phasic inspiratory activity and respiratory-related response to various stimuli during sleep were very similar to those of posterior cricoarytenoid muscle, the principal vocal cord abductor.

Adult↗