Intraglottal pressure distribution computed from empirical velocity data in canine larynx

Intraglottal velocity measurements were taken using particle image velocimetry and the corresponding estimates for the intraglottal pressure were computed using the pressure Poisson equation. Results from five canine larynges showed that when the flow separated from the divergent glottal walls during closing, the vortices that were formed in the separated region of the glottis created negative pressure near the superior aspect of the folds. The magnitude of the negative pressure was directly proportional to the subglottal pressure. At low subglottal pressure, negative pressures at the superior edge were not observed when the divergence angle of the wall was minimal and the glottal flow did not separate from the wall.     

The effects of the false vocal fold gaps on intralaryngeal pressure distributions and their effects on phonation

Human phonation does not merely depend on the vibration of the vocal folds. Research by clinical and computer simulations has demonstrated that the false vocal fold (FVF) is an important laryngeal con-striction that plays a vital role during human voice production. This study explored the effects of the FVF gaps using both the three-dimensional Plexiglas model and the numerical computation methods. Twelve FVF gaps (ranging from 0.02 to 2.06 cm) were used in this study at three glottal angles (uniform and convergent/divergent 40°), two minimal glottal diameters (Dg) (0.04 cm and 0.06 cm) separately, and the constant subglottal pressure (8 cm H2O). The results suggested that (1) the intralaryngeal pressure was the lowest and the flow was the highest (least flow resistance) when the FVF gap was 1.5-2 times greater than Dg; (2) the divergent glottal angle gave lower pressure and greater flow than the conver-gent and uniform glottal angle as there were no FVF conditions; (3) the presence of the FVF decreased the effects of the glottal angle to a certain extent; and more importantly, (4) the presence of the FVF also moved the separation points downstream, straightened the glottal jet for a longer distance, decreased the overall laryngeal resistance, and reduced the energy dissipation, suggesting the significance of FVF in efficient voice production. These results may be incorporated in the phonatory models (physical or computational) for better understanding of vocal mechanics. The results might also be helpful in exploring the surgical and rehabilitative intervention of related voice problems.     

Active upper airway closure during induced central apneas in lambs is complete at the laryngeal level only.

We tested the hypotheses that active upper airway closure during induced central apneas in nonsedated lambs 1). is complete and occurs at the laryngeal level and 2). is not due to stimulation of the superior laryngeal nerves (SLN). Five newborn lambs were surgically instrumented to record thyroarytenoid (TA) muscle (glottal constrictor) electromyographic (EMG) activity with supra- and subglottal pressures. Hypocapnic and nonhypocapnic central apneas were induced before and after SLN sectioning in the five lambs. A total of 174 apneas were induced, 116 before and 58 after sectioning of the internal branch of the SLN (iSLN). Continuous TA EMG activity was observed in 88% of apneas before iSLN section and in 87% of apneas after iSLN section. A transglottal pressure different from zero was observed in all apneas with TA EMG activity, with a mean subglottal pressure of 4.3 +/- 0.8 cmH2O before and 4.7 +/- 0.7 cmH2O after iSLN section. Supraglottal pressure was consistently atmospheric. Sectioning of both iSLNs had no effects on the results. We conclude that upper airway closure during induced central apneas in lambs is active, complete, and occurs at the glottal level only. Consequently, a positive subglottal pressure is maintained throughout the apnea. Finally, this complete active glottal closure is independent from laryngeal afferent innervation.     

Geometry of human vocal folds and glottal channel for mathematical and biomechanical modeling of voice production

Current models of the vocal folds derive their shape from approximate information rather than from exactly measured data. The objective of this study was to obtain detailed measurements on the geometry of human vocal folds and the glottal channel in phonatory position. A non-destructive casting methodology was developed to capture the vocal fold shape from excised human larynges on both medial and superior surfaces. Two female larynges, each in two different phonatory configurations corresponding to low and high fundamental frequency of the vocal fold vibrations, were measured. A coordinate measuring machine was used to digitize the casts yielding 3D computer models of the vocal fold shape. The coronal sections were located in the models, extracted and fitted by piecewise-defined cubic functions allowing a mathematical expression of the 2D shape of the glottal channel. Left-right differences between the cross-sectional shapes of the vocal folds were found in both the larynges.     

The development of coordinated singing in cooperatively displaying long-tailed manakins

Long-tailed manakins (Chiroxiphia linearis) have a puzzlingsocial system in which teams of two males display cooperativelyin dispersed lek arenas, but only the alpha partner mates withvisiting females. One benefit of performing as a nonmatingpartner might be to gain experience as an "apprentice" to improvethe performance of the complex duet song and joint dance. Weexamined the relationship between the age of singers and twomeasures of singing performance: song variability and soundfrequency matching. Singing performance improved with age;variability in four song characteristics of males less than3 years old was greater than that in their older partners,and frequency matching increased with the age of the younger partner. Randomization tests of song samples from seven well-establishedteams showed that males did not track the song-to-song variationin their partners' singing. Another randomization test showedthat frequency matching by these teams was higher than thatof randomly paired partners. We considered three alternativehypotheses for the congruent songs: (1) short-term accommodation to the partner's song; (2) active choice of partners with similarintrinsic frequencies; and (3) long-term development of congruentsong through either practice or song copying. Our results andevidence from long-term monitoring of banded birds best supportthe hypothesis that frequency matching develops over severalyears during the complex and protracted process of partner formation. Nonmating males may benefit from increasing theircompetence at display, eventually enjoying increased matingsuccess when they inherit display sites from older males.     

Changes in intra-abdominal pressure during postural and respiratory activation of the human diaphragm.

In humans, when the stability of the trunk is challenged in a controlled manner by repetitive movement of a limb, activity of the diaphragm becomes tonic but is also modulated at the frequency of limb movement. In addition, the tonic activity is modulated by respiration. This study investigated the mechanical output of these components of diaphragm activity. Recordings were made of costal diaphragm, abdominal, and erector spinae muscle electromyographic activity; intra-abdominal, intrathoracic, and transdiaphragmatic pressures; and motion of the rib cage, abdomen, and arm. During limb movement the diaphragm and transversus abdominis were tonically active with added phasic modulation at the frequencies of both respiration and limb movement. Activity of the other trunk muscles was not modulated by respiration. Intra-abdominal pressure was increased during the period of limb movement in proportion to the reactive forces from the movement. These results show that coactivation of the diaphragm and abdominal muscles causes a sustained increase in intra-abdominal pressure, whereas inspiration and expiration are controlled by opposing activity of the diaphragm and abdominal muscles to vary the shape of the pressurized abdominal cavity.     

Dissociation between diaphragmatic and rib cage muscle fatigue

To assess rib cage muscle fatigue and its relationship to diaphragmatic fatigue, we recorded the electromyogram (EMG) of the parasternal intercostals (PS), sternocleidomastoid (SM), and platysma with fine wire electrodes and the EMG of the diaphragm (DI) with an esophageal electrode. Six normal subjects were studied during inspiratory resistive breathing. Two different breathing patterns were imposed: mainly diaphragmatic or mainly rib cage breathing. The development of fatigue was assessed by analysis of the high-to-low (H/L) ratio of the EMG. To determine the appropriate frequency bands for the PS and SM, we established their EMG power spectrum by Fourier analysis. The mean and SD for the centroid frequency was 312 +/- 16 Hz for PS and 244 +/- 48 Hz for SM. When breathing with the diaphragmatic patterns, all subjects showed a fall in H/L of the DI and none had a fall in H/L of the PS or SM. During rib cage emphasis, four out of five subjects showed a fall in H/L of the PS and five out of six showed a fall in H/L of the SM. Four subjects showed no fall in H/L of the DI; the other two subjects were unable to inhibit diaphragm activity to a substantial degree and did show a fall in H/L of the DI. Activity of the platysma was minimal or absent during diaphragmatic emphasis but was usually strong during rib cage breathing. We conclude that fatigue of either the diaphragm or the parasternal and sternocleidomastoid can occur independently according to the recruitment pattern of inspiratory muscles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiac and respiratory patterns synchronize between persons during choir singing

Dyadic and collective activities requiring temporally coordinated action are likely to be associated with cardiac and respiratory patterns that synchronize within and between people. However, the extent and functional significance of cardiac and respiratory between-person couplings have not been investigated thus far. Here, we report interpersonal oscillatory couplings among eleven singers and one conductor engaged in choir singing. We find that: (a) phase synchronization both in respiration and heart rate variability increase significantly during singing relative to a rest condition; (b) phase synchronization is higher when singing in unison than when singing pieces with multiple voice parts; (c) directed coupling measures are consistent with the presence of causal effects of the conductor on the singers at high modulation frequencies; (d) the different voices of the choir are reflected in network analyses of cardiac and respiratory activity based on graph theory. Our results suggest that oscillatory coupling of cardiac and respiratory patterns provide a physiological basis for interpersonal action coordination.     

Capsaicin-induced activation of pulmonary vagal C fibers produces reflex laryngeal closure in the rat.

Our recent studies show that intravenous administration of capsaicin induces enhancement of the intralaryngeal thyroarytenoid (TA) branch but a reduction of the intralaryngeal abducent branch, suggesting that the glottis is likely closed by capsaicin. The aim of the present study was to examine whether the glottis is adducted by intravenous administration of capsaicin. Electromyographic (EMG) activity of the TA muscle, subglottal pressure (SGP), and glottal behavior were evaluated before and after intravenous administration of capsaicin in male Wistar rats that were anesthetized and tracheostomized. Catheters were placed in the femoral artery and vein, as well as in the right jugular vein. Low and high doses of capsaicin (0.625 and 1.25 microg/kg) produced apnea and increases in the amplitude of the TA EMG. This enhancement of the TA EMG was observed during apnea as well as during recovery from apnea. Moreover, the onset of the TA EMG was advanced such that it commenced earlier during inspiration. Concomitantly, the SGP substantially increased. Increases in both the TA EMG and SGP were abolished after bilateral sectioning of the recurrent laryngeal nerve. In some animals, movement of the vocal folds was recorded by taking a motion picture with a digital camera under a surgical microscope. With intravenous administration of capsaicin, a tight glottal closure, decreases in blood pressure, and bradycardia were observed. These results strongly suggest that glottal closure is reflexively induced by intravenous administration of capsaicin and that closure of the glottis is beneficial for the defense of the airway and lungs when an animal is exposed to environmental irritants.     

Inhibition of breathing associated with gallbladder stimulation in dogs

The effect of mechanical stimulation of the gallbladder on breathing was studied in anesthetized spontaneously breathing dogs. Measurements of tidal volume, breathing frequency, rib cage and abdominal diameter, transdiaphragmatic pressure, and electrical activity of the diaphragm were made while traction or compression was applied to the gallbladder for periods of 30 s. Both forms of mechanical stimulation produced similar changes, including large decreases in tidal volume, respiratory rate, electrical activity of the diaphragm, and transdiaphragmatic pressure swings. Inspiratory rib cage expansion was little affected, but abdominal expansion was greatly reduced, and swings in gastric pressure were reduced more than swings in pleural pressure, indicating a selective decrease in diaphragmatic activity. Recovery of all measured parameters returned toward control values, despite continued traction or compression. Some inhibition persisted after the stimulus was withdrawn. The very brief interval between stimulus and response suggested that the mechanism was a neural reflex. The afferents involved are unknown but are not purely vagal in nature, since qualitatively similar results were seen in animals after vagotomy. The alteration in breathing frequency indicates that at least part of the reflex is supraspinally mediated. The change in pattern of breathing closely resembles that seen in subjects after abdominal surgery and supports the theory that reflex inhibition of breathing contributes to postoperative pulmonary complications seen in those subjects.     

Effect of abdominal compression on maximum transdiaphragmatic pressure

Transdiaphragmatic pressure (Pdi) is lower during maximum inspiratory effort with the diaphragm alone than when maximum inspiratory and expulsive efforts are combined. The increase in Pdi with expulsive effort has been attributed to increased neural activation of the diaphragm. Alternatively, the increase could be due to stretching of the contracted diaphragm. If this were so, Pdi measured during a combined maximum effort would overestimate the capacity of the diaphragm to generate inspiratory force. This study determined the likely contribution of stretching of the contracted diaphragm to estimates of maximum Pdi (Pdimax) obtained during combined inspiratory and expulsive effort. Three healthy trained subjects were studied standing. Diaphragmatic Mueller maneuvers were performed at functional residual capacity and sustained during subsequent abdominal compression by either abdominal muscle expulsive effort or externally applied pressure. Measurements were made of changes in abdominal (Pab) and pleural (Ppl) pressure, Pdi, rib cage and abdominal dimensions and respiratory electromyograms. Three reproducible performances of each maneuver from each subject were analyzed. When expulsive effort was added to maximum diaphragmatic inspiratory effort, Pdimax increased from 86 +/- 12 to 148 +/- 14 (SD) cmH2O within the 1st s and was 128 +/- 14 cmH2O 2 s later. When external compression was added to maximum diaphragmatic inspiratory effort, Pdimax increased from 87 +/- 16 to 171 +/- 19 cmH2O within the 1st s and was 152 +/- 16 cmH2O 2 s later.(ABSTRACT TRUNCATED AT 250 WORDS)     

Absence of inspiratory laryngeal constrictor muscle activity during nasal neurally adjusted ventilatory assist in newborn lambs

In nonsedated newborn lambs, nasal pressure support ventilation (nPSV) can lead to an active glottal closure in early inspiration, which can limit lung ventilation and divert air into the digestive system, with potentially deleterious consequences. During volume control ventilation (nVC), glottal closure is delayed to the end of inspiration, suggesting that it is reflexly linked to the maximum value of inspiratory pressure. Accordingly, the aim of the present study was to test whether inspiratory glottal closure develops at the end of inspiration during nasal neurally adjusted ventilatory assist (nNAVA), an increasingly used ventilatory mode where maximal pressure is also reached at the end of inspiration. Polysomnographic recordings were performed in eight nonsedated, chronically instrumented lambs, which were ventilated with progressively increasing levels of nPSV and nNAVA in random order. States of alertness, diaphragm, and glottal muscle electrical activity, tracheal pressure, Spo(2), tracheal Pet(CO(2)), and respiratory inductive plethysmography were continuously recorded. Although phasic inspiratory glottal constrictor electrical activity appeared during nPSV in 5 of 8 lambs, it was never observed at any nNAVA level in any lamb, even at maximal achievable nNAVA levels. In addition, a decrease in Pco(2) was neither necessary nor sufficient for the development of inspiratory glottal constrictor activity. In conclusion, nNAVA does not induce active inspiratory glottal closure, in contrast to nPSV and nVC. We hypothesize that this absence of inspiratory activity is related to the more physiological airway pressurization during nNAVA, which tightly follows diaphragm electrical activity throughout inspiration.     

一种喉部疾病口语声诊断新方法

本文提出了声带的三质量块模型,并应用这模型模拟病噪产生的嘶哑语声,这些嘶声包括有声带闭合不全,声带小结,声带麻痹,喉炎,声带淀粉样变和声门癌等十六种典型情况。采用快速傅里叶变换,线性预测,倒谱技术和离荼余弦变换等分析各类喉病引起的嘶哑语声,实验结果表明声带模型分析法是喉病诊断的一种有效方法。     

Effect of abdominal compression on diaphragmatic tendon organ activity.

Previous studies suggest that afferents in the diaphragm participate in the reflex reduction in phrenic nerve efferent activation when the length of the diaphragm is increased by abdominal compression. The present study determined the response of tendon organ afferents in the diaphragm to increases in abdominal pressure. Five cats were anesthetized with thiopental sodium (60 mg/kg ip to induce, supplemented intravenously). Extracellular recordings from nine individual tendon organ afferents were made from right cervical dorsal root ganglia 5 and 6. Right crural electromyographic activity was recorded. The right extrathoracic phrenic nerve was isolated and stimulated to identify tendon organs on the basis of conduction velocity and response to twitch. The response to ramp-and-hold stretch of the diaphragm was used as an additional test to differentiate tendon organs from muscle spindles. The mean level of activity of the tendon organs during the 1st s of the inspiratory phase was 47 +/- 10 (SD) Hz. Abdominal compression was associated with a significant increase in the activity of these afferents to 61 +/- 11 Hz. Results indicate that increases in the activity of diaphragmatic tendon organs are associated with moderate increases in abdominal pressure and are likely the result of elevations in the active tension developed by the diaphragm. Combined with results from previous studies, it is possible that diaphragmatic tendon organs may play a role in the attenuation of respiratory muscle activation when abdominal pressure is increased.     

Immediate diaphragmatic electromyogram responses to imperceptible mechanical loads in conscious humans.

We used an esophageal electrode to measure the amplitude and neural inspiratory and expiratory (N TE) timing responses of crural diaphragmatic electrical activity in response to flow-resistive (R) and elastic (E) loads at or below the threshold for conscious detection, applied pseudorandomly to the oral airway of eight normal subjects. We observed a rapid first-breath neural reflex that modified respiratory timing such that N TE lengthened significantly in response to R loads in six of eight subjects and shortened in response to E loading in six of seven subjects. The prolongation of N TE with R loading resulted primarily from lengthening the portion of N TE during which phasic activity in the diaphragm is absent (TE NDIA), whereas E loading shortened N TE mainly by reducing TE NDIA. Most subjects responded to both types of loading by decreasing mean tonic diaphragmatic activity, the average level of muscle activity that exists when no phasic changes are occurring, as well as its variability. The observed timing responses are consistent in direction with optimally adaptive pattern regulation, whereas the modulation of tonic activity may be useful in neural regulation of end-expiratory lung volume.     

Dependence of diaphragmatic length on lung volume and thoracoabdominal configuration

Changes in lung volume can be partitioned into volume displacements of the rib cage and abdomen. Abdominal displacements are often used as estimates of diaphragmatic displacements and changes in lengthening of diaphragmatic muscle. We used X-rays, ultrasound, and linear measurements of thoracic and abdominal diameters to estimate relationships among lung volume, thoracoabdominal configuration and diaphragmatic length, and we found that diaphragmatic length was strongly dependent on rib cage as well as abdominal displacement. In three subjects, the diaphragm shortened 57-85% as much during a breath made without abdominal displacement as during a normal breath in which the abdominal wall moved outward with the rib cage. We conclude that changes in diaphragmatic length can be estimated from surface measurements without radiation and that the length of the diaphragm cannot be estimated from displacements of the abdominal wall alone.     

Temporal Aspects of Singing Interactions among Territorial Ovenbirds (Seiurus aurocapillus)

The temporal aspects of singing interactions among birds have received relatively little attention. To determine if the song delivery of one individual is affected by that of its territorial neighbor, I recorded singing interactions between territorial ovenbirds (Seiurus aurocapillus). Ovenbirds appeared to adopt one of two roles during singing interactions, Type I or Type II singers. Type II singers placed more of their songs immediately after the song of their neighbor than expected. The singing pattern of Type I singers could not be distinguished from a random pattern with respect to their neighbor's songs. In each observed pair of interacting birds, one individual was a Type I singer and one was a Type II singer. Although there was some intra-individual variation, most birds maintained the same role with each of their recorded territorial neighbors. Variation occurred between the two study sites in the extent that individuals overlapped the songs of their neighbors. Song overlap was common at one site, but occurred as, or less, often than expected at the other site.     

Scintigraphic evaluation of shape of lung and chest in upright and head-down posture

We determined the configuration of lungs and chest in six healthy young subjects using anteroposterior and lateral technetium-99m-labeled scintigraphic images obtained in upright and in 90 degree head-down posture at 0, 25, 50, 75, and 100% vital capacity (VC). The lung shape was evaluated from curves relating vertical height vs. cumulative volume of 20 apicodiaphragmatic lung zones of equal height. S-shaped curves were obtained, which, after size normalization, were largely independent of volume or posture (P greater than 0.1). However, the apical zones tended to become relatively wider and the diaphragmatic zones relatively smaller with increasing volume, especially between 0 and 25% VC in upright posture and 0-50% VC in head-down posture. Changing posture from upright to head-down also tended to slightly widen the apical zones and to narrow the diaphragmatic zones, which is in line with a greater intrathoracic penetration of the diaphragm/abdomen. The shape of the chest was evaluated from the ratio of the transverse-thoracic and anteroposterior distances over height. These ratios did not clearly change with posture (P greater than or equal to 0.05) but increased by approximately 30% with decreasing volume (P less than 0.01). The fact that these shape changes of the chest were not accompanied by similar changes in lung shape can be explained mainly by widening of the mediastinum when volume decreases. In conclusion, the shape of the lung and chest are similar in head-down and upright humans, in contrast to the reversal of the apicodiaphragmatic differences in alveolar expansion and in transpulmonary pressure.     

Preferential fatigue of the rib cage muscles during inspiratory resistive loaded ventilation

Because the inspiratory rib cage muscles are recruited during inspiratory resistive loaded breathing, we hypothesized that such loading would preferentially fatigue the rib cage muscles. We measured the pressure developed by the inspiratory rib cage muscles during maximal static inspiratory maneuvers (Pinsp) and the pressure developed by the diaphragm during maximal static open-glottis expulsive maneuvers (Pdimax) in four human subjects, both before and after fatigue induced by an inspiratory resistive loaded breathing task. Tasks consisted of maintaining a target esophageal pressure, breathing frequency, and duty cycle for 3-5 min, after which the subjects maintained the highest esophageal pressure possible for an additional 5 min. After loading, Pinsp decreased in all subjects [control, -128 +/- 14 (SD) cmH2O; with fatigue, -102 +/- 18 cmH2O; P less than 0.001, paired t test]. Pdimax was unchanged (control, -192 +/- 23 cmH2O; fatigue, -195 +/- 27 cmH2O). These data suggest that 1) inability to sustain the target during loading resulted from fatigue of the inspiratory rib cage muscles, not diaphragm, and 2) simultaneous measurement of Pinsp and Pdimax may be useful in partitioning muscle fatigue into rib cage and diaphragmatic components.