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  • 1
    ISSN: 1573-9686
    Keywords: Human respiratory control ; Mechanical loading ; Respiratory muscles ; Diaphragm electromyogram ; Breathing pattern regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract We used an esophageal electrode to measure the amplitude and timing responses of diaphragmatic electrical activity and airflow in response to flow resistive and elastic loads at or below the threshold for conscious detection, applied pseudorandomly to the oral airway of eight normal human subjects. The mechanical and neural parameter responses to mechanical loading were cross-correlated with the pseudorandom loading sequence to obtain estimates of the impulse responses. We convolved the resultant impulse response estimates with the loading sequence to obtain the responses predicted from the linear component of the generalized Wiener kernel model. Highly significant correlations and close correspondence were found between the model-predicted and ensemble-averaged experimental responses for nearly all neural and mechanical parameters in all subjects. For nearly every aspect of the pattern, with few exceptions, the response to these small load perturbations in all eight subjects was adequately explained by an impulse response, leaving negligible nonlinearity to require higher-order cross-correlations. These results indicate that the estimated impulse responses accurately model the dynamics of the neural and mechanical responses in human subjects for the types and magnitudes of loads applied. This study supports use of the pseudorandom loading technique to determine the neural and mechanical responses to imperceptible mechanical loads in conscious humans.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-9686
    Keywords: Acoustic reflection method ; Upper airway area ; Vocal cord movement ; Larynx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The acoustie reflection method provides a noninvasive way to determine the airway geometry. Based on a discrete upper airway model, an inverse scheme is developed to infer the upper airway area as a function of distance. We incorporate this scheme into a system that can generate multiple acoustic pulses to sample the upper airway geometry at a maximum frequency of 30 Hz, making possible determination of the airway area-distance relation as a function of time. Therefore, we can monitor the dynamic behavior of the upper airway during breathing. To validate the approach, we visualized vocal cord movements in three normal subjects via laryngoscopy; simultaneously acoustic measurements were made at 10 Hz. Video images of vocal cord movement were recorded and digitized. We compared the laryngeal area from analysis of the video images with the acoustic assessment at the level of the glottis. Linear regression analysis shows that the correlation coefficients are between 0.85 and 0.9 for all three subjects. We conclude that the acoustic reflection method is a useful tool for measuring vocal cord movement without the use of laryngoscopy, and the approach promises to be a useful one to measure the movement of the whole upper airway. This paper also discusses the limitations inherent in the algorithm and some useful procedures to ensure accurate and reliable area computation during implemention.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-9686
    Keywords: Event related potentials ; Time–frequency analysis ; Supraglottic mechanoreceptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Respiratory related evoked potentials (RREPs) were recorded from eight normal subjects in response to brief pressure pulses of −10 cm H2O with a duration of 200 ms to identify the contribution of supralaryngeal mechanoreceptors to the evoked responses by constraining application of the stimulus to the larynx and sublaryngeal regions through insertion of a laryngeal mask airway (LMA). Wavelet decomposition of RREP responses from 30 electrodes on the right side of the scalp was performed for eight frequency scales in time. The RREPs at each wavelet scale were enhanced by eliminating the wavelet coefficients due to artifacts and noise. After denoising, the third (125–150 Hz), fourth (62.5–125 Hz), fifth (31.25–62.5 Hz) and sixth (13.62–31.25 Hz) wavelet scales were used for estimation of the Laplacian. In addition, the global field power was calculated to quantify the wavelet-filtered RREP activity and to extract features for statistical analysis. Our results show that estimates of the global field power at the fourth and fifth wavelet scales are more significantly decreased after the insertion of the LMA than was true for scales 3 and 6. Further, after the LMA was inserted, the Laplacian showed reduced activity in the posterior-lateral region in four subjects and reductions in other places in the rest. © 2000 Biomedical Engineering Society. PAC00: 8719Nn, 8780Tq, 8719Uv, 8719Ff
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-9686
    Keywords: Event related potentials ; Time-frequency analysis ; Evoked potentials ; Respiratory system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract In this study, the respiratory related evoked responses (RREPs) from ten normal subjects in response to brief varying pressure pulses at —6, —10 and —17cm H2O with a duration of 200 ms were recorded to investigate how mid-latency cortical evoked potentials measured on the scalp are affected in response to pressure pulses of varying magnitude at the mouth. Wavelet decomposition was performed for eight frequency scales in time for the RREPs. The RREPs at each wavelet scale were enhanced by eliminating the wavelet coefficients due to the artifacts and noise. After denoising, the third (125–250 Hz), fourth (62.5–125 Hz), fifth (31.25–62.5 Hz) and sixth (15.62–31.25 Hz) wavelet scales were quantified using the global field power estimates which serve to reduce the contamination by facial electromyogram responses evoked by the pressure stimulus. Our results show that the estimates of the global field power (GFP) at the third, fourth and fifth wavelet scales between 25 and 100 ms poststimulus were significantly increased when the pressure pulse was increased from —6 to —17cm H2O. On average, the total GFP from all scales, summed over the period 30–90 ms poststimulus, doubled from baseline with the —6 and —17 H2O stimulus, and increased linearly by 40% between —6 and —17 H2O. This supports the use of the GFP as an index of respiratory mechanoreceptor input to the central nervous system. © 2000 Biomedical Engineering Society. PAC00: 8719Nn, 8719Bb, 8719Uv
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Annals of biomedical engineering 9 (1981), S. 409-424 
    ISSN: 1573-9686
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The adult human breathing pattern is a complex product of neural, humoral, and perceptual factors, each of which is influenced by changes in the respiratory mechanics. The regulation of this pattern is qualitatively consistent with hypotheses based upon optimization criteria and involves alteration of both the respiratory frequency (f) and tidal volume (VT) as their product of minute ventilation ( $$\dot V$$ ) varies. The particular f-VT relationship followed both in theory and observed response is influenced by changes in respiratory mechanics produced by loading. Within the breath, volume and durations of inspiration and expiration also respond to applied loads. The inspiratory terminating threshold curve is shifted to the left by elastic (E) loading and to the right by flow resistive (R) loading. Regulation of the end-expiratory volume (EEV) is provided by regulation of laryngeal resistance, control of inspiratory muscle tone during expiration, and activation of expiratory muscles. Separation of the contributions of humoral, subconscious neural, and perceptual reflexes responding to loading is important to enable assessment of the effects of sleep or pathology upon specific aspects of pattern regulation. A loading technique is described that permits the reliable estimation of breathing pattern responses to mechanical loads below the threshold for conscious perception, producing immediate response estimates attributable only to neural reflexes and intrinsic muscle characteristics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0034-5687
    Keywords: CO"2 regulation ; Central respiratory neural output ; Non-REM sleep ; Respiratory mechanics ; Respiratory muscle EMG signals ; Ventilatory control
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Respiration Physiology 47 (1982), S. 97-106 
    ISSN: 0034-5687
    Keywords: Alveolar carbon dioxide ; Breathing patter ; Hypercapnia ; Inspiratory flow ; Periodic respiration ; Ventilation
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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