Inspiratory pressure threshold training for glottal airway limitation in laryngeal papilloma

A single-subject design was used to determine if inspiratory pressure threshold training increases inspiratory muscle strength and reduces the sensation of dyspnea during exercise and speech. The subject was a 23-year-old female with congenital juvenile papilloma which has been in remission for 10 years. A 4-week inspiratory muscle training program was implemented using an inspiratory pressure threshold trainer. The pressure threshold of the trainer was set by the experimenter. The pressure threshold setting of the trainer was based on a percentage of the subject's maximum inspiratory pressure measured prior to training. The average range of the pressure threshold was 40 to 70 cmH2O. In order for inspiratory air to flow, the subject generated inspiratory pressure, independent of airflow rate. Maximum inspiratory pressure (MIP) was the dependent variable used as the index of inspiratory muscle strength. Exercise dyspnea was a dependent variable rated by the subject during a progressive treadmill test. Dyspnea associated with speech was rated following production of a comfortable and loud speech task. MIP increased by 57% following the training program with a 2-scale point reduction in the perception of dyspnea during exercise. Dyspnea during loud speech decreased from moderate to mild. The changes in dyspnea, both during exercise and speech, are directly related to inspiratory muscle strengthening. The results suggest that inspiratory muscle training may improve respiratory related function in patients with restrictive upper airway disorders.     

Phonation threshold pressure and onset frequency in a two-layer physical model of the vocal folds

The influence of vocal fold geometry and stiffness on phonation onset was experimentally investigated using a body-cover physical model of the vocal folds. Results showed that a lower phonation threshold pressure and phonation onset frequency can be achieved by reducing body-layer or cover-layer stiffness, reducing medial surface thickness, or increasing cover-layer depth. Increasing body-layer stiffness also restricted vocal fold motion to the cover layer and reduced prephonatory glottal opening. Excitation of anterior-posterior modes was also observed, particularly for large values of the body-cover stiffness ratio. The results of this study were also discussed in relation to previous theoretical and experimental studies.     

Phonation threshold pressure: comparison of calculations and measurements taken with physical models of the vocal fold mucosa

In an important paper on the physics of small amplitude oscillations, Titze showed that the essence of the vertical phase difference, which allows energy to be transferred from the flowing air to the motion of the vocal folds, could be captured in a surface wave model, and he derived a formula for the phonation threshold pressure with an explicit dependence on the geometrical and biomechanical properties of the vocal folds. The formula inspired a series of experiments [e.g., R. Chan and I. Titze, J. Acoust. Soc. Am 119, 2351-2362 (2006)]. Although the experiments support many aspects of Titze's formula, including a linear dependence on the glottal half-width, the behavior of the experiments at the smallest values of this parameter is not consistent with the formula. It is shown that a key element for removing this discrepancy lies in a careful examination of the properties of the entrance loss coefficient. In particular, measurements of the entrance loss coefficient at small widths done with a physical model of the glottis (M5) show that this coefficient varies inversely with the glottal width. A numerical solution of the time-dependent equations of the surface wave model shows that adding a supraglottal vocal tract lowers the phonation threshold pressure by an amount approximately consistent with Chan and Titze's experiments.     

Radiation and vorticity: the missing link

In the context of general relativity, radiation, either gravitational or electromagnetic, is closely associated to vorticity of observers world lines. We stress in this letter that the factor that relates the two phenomena is a circular flow of energy (electromagnetic) and/or superenergy on the planes orthogonal to vorticity vector. We also stress the potential relevance of the abovementioned relationship in experiments to detect gravitational radiation.     

The induction of reentry in cardiac tissue. The missing link: How electric fields alter transmembrane potential

This review examines the initiation of reentry in cardiac muscle by strong electric shocks. Specifically, it concentrates on the mechanisms by which electric shocks change the transmembrane potential of the cardiac membrane and create the physiological substrate required by the critical point theory for the initiation of rotors. The mechanisms examined include (1) direct polarization of the tissue by the stimulating current, as described by the one-dimensional cable model and its two- and three-dimensional extensions, (2) the presence of virtual anodes and cathodes, as described by the bidomain model with unequal anisotropy ratios of the intra- and extracellular spaces, (3) polarization of the tissue due to changing orientation of cardiac fibers, and (4) polarization of individual cells or groups of cells by the electric field ("sawtooth potential"). The importance of these mechanisms in the initiation of reentry is examined in two case studies: the induction of rotors using successive stimulation with a unipolar electrode, and the induction of rotors using cross-field stimulation. These cases reveal that the mechanism by which a unipolar stimulation induces arrhythmias can be explained in the framework of the bidomain model with unequal anisotropy ratios. In contrast, none of the examined mechanisms provide an adequate explanation for the induction of rotors by cross-field stimulation. Hence, this study emphasizes the need for further experimental and theoretical work directed toward explaining the mechanism of field stimulation. (c) 1998 American Institute of Physics.     

A missing link: What is behind de Broglie's “periodic phenomenon”?

The present work constitutes an attempt to give the interpretation of de Broglie's internal periodic phenomenon which ascribes the frequencym ₀ c ²/h to each single entity in its eigensystem of coordinates. This phenomenon provides existence in principle of the ideal proper-time scale, making it possible to identify the geometric proper-time interval with a physically existing one, thus ensuring the realization of basic postulates of the relativity theory. According to the latter, neither time nor de Broglie's frequency are invariant with respect to the Lorentz transformation of the coordinate system. A search for the fundamental invariant demands passing over to dimensionless quantities, and we suggest to consider as such the integer numbers. Then it is the entity's periodic phenomenon which, after multiplying by the lasting proper-time, results in the open ordered sequence of natural numbers. The progressing course of numbers is ensured by the time course, whilst their ordering is connected with coherence. Such a sequence of numbers, once appeared in time, has to be conserved in space-time, demanding the periodic phenomenon's phase to be invariant with respect to the Lorentz transformation. This, in its turn, yields de Broglie's waves of matter, which are at the bottom of quantum physics. Thus, the most intrinsic feature of a fundamental entity has to be identified with its internal frequency, in order to ensure the actual existence of the sequence of natural numbers as the basic object of arithmetic.     

Polyphosphate-dependent nicotinamide adenine dinucleotide (NAD) kinase: A novel missing link in human mitochondria

Polyphosphate [poly(P)] is described as a homopolymer of inorganic phosphates. Nicotinamide adenine dinucleotide kinase (NAD kinase) catalyzes the phosphorylation of NAD⁺ to NADP⁺ in the presence of ATP (ATP-NAD kinase). Novel NAD kinase that explicitly phosphorylates NAD⁺ to NADP⁺ using poly(P), besides ATP [ATP/poly(P)-NAD kinase], was found in bacteria, in particular, Gram-positive bacteria, and the gene encoding ATP/poly(P)-NAD kinase was also newly identified in Mycobacterium tuberculosis H37Rv. Both NAD kinases required multi-homopolymeric structures for activity expression. The enzymatic and genetic results, combined with their primary and tertiary structures, have led to the discovery of a long-awaited human mitochondrial NAD kinase. This discovery showed that the NAD kinase is a bacterial type of ATP/poly(P)-NAD kinase. These pioneering findings, i.e., ATP/poly(P)-NAD kinase, NAD kinase gene, and human mitochondrial NAD kinase, have significantly enhanced research on the biochemistry, molecular biology, and evolutionary biology of NAD kinase, mitochondria, and poly(P), including some biotechnological knowledge applicable to NADP⁺ production.     

Investigation of a glottal related harmonics-to-noise ratio and spectral tilt as indicators of glottal noise in synthesized and human voice signals

The harmonics-to-noise ratio (HNR) of the voiced speech signal has implicitly been used to infer information regarding the turbulent noise level at the glottis. However, two problems exist for inferring glottal noise attributes from the HNR of the speech wave form: (i) the measure is fundamental frequency (f0) dependent for equal levels of glottal noise, and (ii) any deviation from signal periodicity affects the ratio, not just turbulent noise. An alternative harmonics-to-noise ratio formulation [glottal related HNR (GHNR')] is proposed to overcome the former problem. In GHNR' a mean over the spectral range of interest of the HNRs at specific harmonic/between-harmonic frequencies (expressed in linear scale) is calculated. For the latter issue [(ii)] two spectral tilt measures are shown, using synthesis data, to be sensitive to glottal noise while at the same time being comparatively insensitive to other glottal aperiodicities. The theoretical development predicts that the spectral tilt measures reduce as noise levels increase. A conventional HNR estimator, GHNR' and two spectral tilt measures are applied to a data set of 13 pathological and 12 normal voice samples. One of the tilt measures and GHNR' are shown to provide statistically significant differentiating power over a conventional HNR estimator.     

Phonation Threshold Pressure Across the Pitch Range: Preliminary Test of a Model

This study sought to examine the specific relationship between phonation threshold pressure (PTP) and voice fundamental frequency (F(0)) across the pitch range. A published theoretical model of this relationship described a quadratic equation, with PTP increasing exponentially with F(0). Prospective data from eight adults with normal, untrained voices were collected. Subjects produced their quietest phonation at 10 randomly ordered pitches from 5% to 95% of their semitone pitch range at 10% intervals. Analysis included curve fitting for individual and group data, as well as comparisons to the previous model. The group data fit a quadratic function similar to that proposed previously, but the specific quadratic coefficient and constant values differed. Four of the individual subjects' data were best fit by quartic functions, two by quadratic functions, and one by a linear function. This preliminary study indicates that PTP may be minimal at a "comfortable" pitch rather than the lowest pitch tested, and that, for some individuals, PTP may be slightly elevated during the passaggio between modal and falsetto vocal registers. These data support the general form of the theoretical PTP-F(0) function for these speakers, and indicate the possibility of potential refinements to the model. Future studies with larger groups of male and female subjects across a wider age range may eventually reveal the specific nature of the function.     

Soft Phonation in the Male Singing Voice: A Preliminary Study

Sustained high notes, diminishing gradually from the loudest to the softest phonation within a maneuver called messa di voce, are examined in two contrasting professional tenor voices. Signals of the sound pressure level, electroglottograph, and mean esophageal pressure are recorded, and similar maneuvers by the same subjects are examined stroboscopically. The lyric voice is found to make a gradual diminuendo while maintaining nearly constant posture of the vocal tract together with a phase of complete closure in the glottal cycle. The robust voice, by contrast, passes abruptly from a production of high subglottal pressure and a high closed quotient to one of low pressure and incomplete closure, and the transition is marked by a sudden opening of the previously constricted laryngeal collar. It is proposed that the mode of soft voice production demonstrated by the robust voice be recognized as a distinct register of the singing voice.     

Perceived phonatory effort and phonation threshold pressure across a prolonged voice loading task: a study of vocal fatigue

Although the problem of vocal fatigue is not uncommon in people with voice disorders, research on objective quantifiable indicators of vocal fatigue is limited. It has been suggested that a speaker's perception of increased phonatory effort associated with periods of prolonged voice use is related to increased lung pressure required to initiate and sustain phonation. The purpose of this study was to examine the relationship among perceived phonatory effort (PPE), which was used as a subjective index of vocal fatigue, and phonation threshold pressure (PTP), a quantifiable measure defined as the minimal lung pressure required to initiate and sustain vocal fold oscillation. PTP and PPE were recorded before, during, and after five adult male and five adult female speakers engaged in a prolonged oral reading task designed to induce vocal fatigue. The results supported a direct, moderately strong relationship between PTP and PPE, particularly when PTP was measured during speech produced at comfortable and low-speaking pitch levels. No gender effects were found. PTP returned to baseline levels within 1 hour after the fatiguing task. PPE returned to baseline within 1 day. The data support the use of PTP as an objective index of vocal fatigue.     

Inspiratory pressure threshold training for upper airway limitation: a case of bilateral abductor vocal fold paralysis

A single subject design was used to determine if pressure threshold training strengthens the inspiratory muscles in a subject with a limited glottal airway as well as diminish dyspnea and improve parameters of speech. The subject was a 19-year-old woman whose glottal airway was limited due to bilateral abductor vocal fold paralysis following a thyroidectomy. A 5-week inspiratory muscle strength-training program was implemented using a pressure-threshold trainer to strengthen the inspiratory muscles with the intent of enabling the generation of higher inspiratory pressures. The pressure threshold on the trainer was set at 75% of the subject's maximum inspiratory pressure (MIP). The subject was required to generate sufficient inspiratory pressure to bring air through the trainer during an inspiratory maneuver. MIP was the dependent variable used as an indication of inspiratory muscle strength. MIP increased by 47% following the training program. Maximal minute ventilation and oxygen uptake increased posttraining. Dyspnea during exercise and speech decreased as reported by the subject. Total reading duration and pause duration demonstrated a declining trend during connected speech. The results indicated that inspiratory muscle training using a pressure threshold device improves functional tasks such as exercise and speech in a subject with upper airway limitation.     

Effects of a vocally fatiguing task and systemic hydration on phonation threshold pressure

Phonation threshold pressure (PTP), effort for speaking, and vibratory closure pattern were assessed in 4 women with normal untrained voices after 2 hours of loud reading. PTP generally increased after this vocally fatiguing task at conversational pitch and 10%, 50%, and especially 80% of the pitch range. Increased systemic hydration by drinking water appeared to attenuate and/or delay the elevation of PTP for 3 subjects, at least at the highest pitch tested. Effort for speaking increased consistently throughout the loud reading task and subsequently decreased after 15 minutes of vocal silence. Upon videostroboscopic examination of the larynx, 3 subjects demonstrated spindle-shaped vibratory closure patterns on occasion after loud reading. The results provide preliminary support for increasing water consumption to reduce or delay some vocal-function changes after prolonged loud phonation in untrained speakers.     

Approximations of open quotient and speed quotient from glottal airflow and egg waveforms : Effects of measurement criteria and sound pressure level

Noninvasive measures of vocal fold activity are useful for describingnormal and disordered voice production. Measures of open and speed quotient from glottal airflow and electroglottographic (EGG) waveforms have been used to describe timing events associated with vocal fold vibration. To date, there has been little consistency in the measurement criteria used to calculate quotient values. In this study, criteria of 20% and 50% were applied to the AC amplitude of glottal airflow and inverted EGG waveforms for measurement of open quotient. Criteria of 20%, 50%, and 80%, and a midslope criterion that segmented the waveform between 20% and 80% of the waveform amplitude, were used for the calculation of speed quotient. Subjects produced waveforms at sound pressure levels (SPL) of 70, 75, 80 and 85 dB. Results indicated that approximations of open quotient obtained from the glottal airflow waveform significantly decreased using both the 20% and 50% criteria as SPL increased from 80 to 85 dB. No significant changes were found in open quotient from the EGG waveform as a function of SPL. Results of speed quotient measures from the glottal airflow and EGG waveforms showed a generally increasing trend as SPL increased, although the differences were not statistically significant. The data suggest that the signal type, measurement criterion and SPL must be considered in interpreting quotient measures.     

Whereabouts of missing atoms in a laser-injected Si: Part 1

In a stealth dicing of Si wafers, voids are formed in laser-induced modified volumes (LIMVs). Most of the voids are free from apparent defects such as dislocations and cracks. Needless to say, in what will become a void (pre-void) upon laser injection, Si atoms are present prior to the laser injection. The critical issue is where these missing atoms are after the laser injection. Two obvious possibilities are that (1) they remain inside the Si wafer as interstitials (I’s) or (2) these I’s reach the surface of the wafer to disappear. If (1) is the case, I’s are to coagulate to form dislocation loops of I-type upon post laser-injection annealing. However, it has been shown that this is not the case. In order to see whether (2) is the case, surfaces of a laser-injected Si wafer were studied by a scanning electron microscope in detail. No evidence of I’s having reached the surfaces was obtained.     

Direct-numerical simulation of the glottal jet and vocal-fold dynamics in a three-dimensional laryngeal model

An immersed-boundary method based flow solver coupled with a finite-element solid dynamics solver is employed in order to conduct direct-numerical simulations of phonatory dynamics in a three-dimensional model of the human larynx. The computed features of the glottal flow including mean and peak flow rates, and the open and skewness quotients are found to be within the normal physiological range. The flow-induced vibration pattern shows the classical "convergent-divergent" glottal shape, and the vibration amplitude is also found to be typical for human phonation. The vocal fold motion is analyzed through the method of empirical eigenfunctions and this analysis indicates a 1:1 modal entrainment between the "adduction-abduction" mode and the "mucosal wave" mode. The glottal jet is found to exhibit noticeable cycle-to-cycle asymmetric deflections and the mechanism underlying this phenomenon is examined.