Papers by Andrew Daubenspeck
phy measures breathing in unrestrained neonatal mice. J Appl
Journal of Applied Physiology, 2001
Evidence of the Hering-Breuer reflex has been found in humans during anesthesia and sleep but not... more Evidence of the Hering-Breuer reflex has been found in humans during anesthesia and sleep but not during wakefulness. Cortical influences, present during wakefulness, may mask the effects of this reflex in awake humans. We hypothesized that, if lung volume were increased in awake subjects unaware of the stimulus, vagal feedback would modulate breathing on a breath-to-breath basis. To test this hypothesis, we employed proportional assist ventilation in a pseudorandom sequence to unload the respiratory system above and below the perceptual threshold in 17 normal subjects. Tidal volume, integrated respiratory muscle pressure per breath, and inspiratory time were recorded. Both sub- and suprathreshold stimulation evoked a significant increase in tidal volume and inspiratory flow rate, but a significant decrease in inspiratory time was present only during the application of a subthreshold stimulus. We conclude that vagal feedback modulates respiratory timing on a breath-by-breath basis i...
Journal of applied physiology (Bethesda, Md. : 1985), 2003
Midlatency respiratory-related evoked potentials were measured during wakefulness by using a 60-e... more Midlatency respiratory-related evoked potentials were measured during wakefulness by using a 60-electrode array placed over the cortical region of the scalp. We studied the responses evoked by 200-ms pressure pulses at -5 and -10 cmH(2)O applied at inspiratory onset and during control tests (no pressure applied) in 14 subjects with obstructive sleep apnea syndrome (OSAS) and 18 normal subjects. Wavelet decomposition was used to smooth and dissect the respiratory-related evoked potentials in frequency and time in 8 frequency bands. After denoising, selected wavelet scales were used to reconstruct the respiratory-related evoked potentials, which were quantified by using global field power estimates. The time course of the global field power activity in OSAS subjects compared with normal subjects was significantly depressed in the period 55-70 ms poststimulus onset, a time when afferent traffic from upper airway receptors arrives in normal subjects. The reduced evoked response in subje...
Advances in Experimental Medicine and Biology, 2001
We investigated the role of V(T) and V(T)/T(I) modulation of breathing in awake human subjects. W... more We investigated the role of V(T) and V(T)/T(I) modulation of breathing in awake human subjects. We applied a PRBS of volume (incrementing ramp) or flow (decrementing wave) assist at levels below the perceptual threshold in order to stimulate respiratory feedback. We modeled the PRBS data with linear difference equations to obtain impulse-response profiles of V(T), V(T)/T(I), T(I) and factorial(P(MUS)). We limited cortical responses to our stimuli by applying sub-threshold levels of assist, and we limited humoral effects (O2 and CO2) by augmenting mechanical respiratory output intermittently and by small amounts. We found that flow or volume assist elicited similar significant increases in V(T) and V(T)/T(I). During flow assist there was a significant decrease in factorial(P(MUS)) and T(I) was reduced, albeit not significantly; however, volume assist did not modify T(I) or factorial(P(MUS)). The earlier onset of flow assist, relative to volume assist, may explain the difference between the responses. We conclude that vagally mediated inspiratory flow receptors in the chest wall or lungs may modulate breathing on a breath by breath basis when small, imperceptible increases in airflow occur early during inspiration. Furthermore, lung volume feedback during imperceptible unloading (occurring at the end of inspiration) was less effective. Finally, pseudorandom unloading with imperceptible stimuli provides a useful tool to study reflex regulation of ventilation in awake subjects without confounding cortical influences.
The Journal of Physiology, 2011
Perception & Psychophysics, 1988
Agreement has not emerged either on the sensory attributes that underlie psychophysical decisions... more Agreement has not emerged either on the sensory attributes that underlie psychophysical decisions in respiratory magnitude scaling tasks or on the physical stimuli giving rise to human judgments. Accordingly, sensory attributes of respiratory sensations were explored in the present study by adopting scaling techniques designed to help uncover the organization of sensory experiences elicited by various breathing maneuvers. Physical stimulus characteristics underlying human judgments were also considered. Subjects rated the dissimilarity between 45 pairs of breathing maneuvers on a scale ranging from 0 ("no difference at all") to 10 ("very much difference"). Cluster analysis and multidimensional scaling were employed to uncover the perceived grouping among different types of maneuvers and the relative organization of maneuvers in a Euclidean space. Dissimilarity judgments varied primarily as a function of a single attribute, degree or magnitude of external loading, ranging from an infinite respiratory load to no load at all. This continuum may depend on interactions among pressure or tension, airflow, and lung volume displacement. A secondary attribute may relate to airflow direction (inspiration or expiration). Many types of breathing sensations have been studied, including the sensations of excessive ventilation, tightness in the chest, tracheobronchial irritation, breath holding, and sensations associated with partial or complete occlusion of the airways. Unlike the visual and auditory systems, sensations accompanying breathing do not depend on a single receptor system. In human and animal experiments both direct and indirect evidence is accumulating to suggest that sensory feedback from the upper airways, lung, chest wall, and diaphragm underlie the perception of respiratory stimuli in humans. The multiplicity of receptors that could underlie perceptual judgments reduces the likelihood that the receptor systems subserving respiratory sensations will be easily identified. Since 1970 (Bakers & Tenney, 1970), various breathing maneuvers have been examined with Stevens's (1975) magnitude scaling techniques. These maneuvers include producing respiratory efforts against a closed airway and breathing through external devices that impede changes in the rate or volume of breathing. From these types of investigations, a cohesive set of exponents has been gathered both for different scaling tasks and for performance on these tasks by various subpopulations.
American journal of physiology. Regulatory, integrative and comparative physiology, Jan 12, 2017
The neuropeptide, pituitary adeniylate cyclase-activating polypeptide (PACAP), has emerged as a pr... more The neuropeptide, pituitary adeniylate cyclase-activating polypeptide (PACAP), has emerged as a principal and rate-limiting regulator of physiological stress responses in adult rodents and has been implicated in SIDS (Sudden Infant Death Syndrome). Recent studies show that PACAP plays a role in neonatal cardiorespiratory responses to hypoxia, hypercapnia and hypothermia, but not hyperthermia, which is often associated with SIDS. Here we tested the hypothesis that, consistent with a role in SIDS, PACAP is involved in regulating the neonatal cardiorespiratory responses to severe heat. To address this, we studied the cardiorespiratory physiology of conscious neonatal PACAP-null and wild-type mice at ambient temperatures of 32°C (baseline) and 40°C (heat stress), using head-out plethysmography and surface ECG electrodes. We also assessed body surface temperature, to give an indication of cutaneous heat loss. Our results show that wild-type neonatal mice respond to heat stress by increasi...
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 6, 2016
Sudden infant death syndrome (SIDS) cases often have abnormalities of the brainstem raphe seroton... more Sudden infant death syndrome (SIDS) cases often have abnormalities of the brainstem raphe serotonergic (5-HT) system. We hypothesize that raphe dysfunction contributes to a failure to autoresuscitate from multiple hypoxic events, leading to SIDS. We studied autoresuscitation in two transgenic mouse models in which exocytic neurotransmitter release was impaired via conditional expression of the light chain from tetanus toxin (tox) in raphe neurons expressing serotonergic bacterial artificial chromosome driversPet1orSlc6a4 These used recombinase drivers targeted different portions of medullary raphe serotonergic, tryptophan hydroxylase 2 (Tph2)(+)neurons by postnatal day (P) 5 through P12: approximately one-third in triple transgenicPet1::Flpe, hβactin::cre, RC::PFtoxmice; approximately three-fourths inSlc6a4::cre, RC::Ptoxmice; with the first model capturing a near equal number ofPet1(+),Tph2(+)versusPet1(+),Tph2(low or negative)raphe cells. At P5, P8, and P12, "silenced" m...
The Faseb Journal, Apr 1, 2010
Journal of applied physiology
ABSTRACT
The Journal of Physiology
Proceedings of 17th International Conference of the Engineering in Medicine and Biology Society, 1995
Page 1. 1995 IEEE-EMBC and CMBEC Theme 4 Signal Processing Enhancement of Respiratory Related Evo... more Page 1. 1995 IEEE-EMBC and CMBEC Theme 4 Signal Processing Enhancement of Respiratory Related Evoked Responses using Matching Pursuits Metin Akay, J. Andrew Daubenspeck, Lisa M. Lim Dept .of Biomedical Engineering, Rutgers University Dept. ...
Wiley Encyclopedia of Biomedical Engineering, 2006
The American review of respiratory disease, 1986
Upper airway obstruction during sleep occurs more commonly in men than in women and has been trea... more Upper airway obstruction during sleep occurs more commonly in men than in women and has been treated with progestational agents with some success. Alcohol ingestion exacerbates sleep apnea, and recent studies have established that alcohol depresses the respiratory motor activity to upper airway muscles more than that to the diaphragm, a response pattern that favors upper airway obstruction during inspiration. To investigate the possibility that progesterone provides some protection from this action of alcohol, we studied the responses of phrenic and hypoglossal nerve activities to alcohol infusion in decerebrate cats pretreated with medroxyprogesterone acetate (MPA) or with control injections. The results indicate that pretreatment with MPA reduces the alcohol-induced mismatching of hypoglossal and phrenic activities. This action of MPA may contribute to its effectiveness in the treatment of some patients with inspiratory obstruction during sleep.
Journal of applied physiology (Bethesda, Md. : 1985), 1989
We determined the influence of the background level of mechanical impedance on the respiratory re... more We determined the influence of the background level of mechanical impedance on the respiratory responses to very small mechanical loads, at or below the threshold for conscious perception. We used a pseudorandom load application technique to estimate the immediate pattern responses from the zeroth lag of the cross correlation between the load application sequence and the respiratory pattern components of tidal volume (VT), inspiratory and expiratory time (TI and TE), and the instantaneous respiratory frequency (f), minute ventilation (VI), and mean inspiratory flow (VT/TI). Elevation of the background resistance served to reduce the TI and TE responses to small perturbations in resistance from those in the control background state, which resulted in generally smaller perturbations of f, VI, and VT/TI. Elevation of the background elastance, however, served to initiate a TI reduction not seen in the control state but did not appreciably affect the rest of the pattern responses to the ...
Respiration physiology, 1990
Expiratory laryngeal restriction in normal humans is augmented immediately following expiratory f... more Expiratory laryngeal restriction in normal humans is augmented immediately following expiratory flow resistance loading applied to the mouth. The time course of this increased narrowing reflects the dynamics of the physiological stimuli that govern laryngeal control during expiration. Lung volume, expiratory airflow and upper airway pressure are possible factors influencing the larynx, and a comparison of their dynamics with those observed for laryngeal narrowing during control and loaded expirations ought to indicate the possible contribution of each source. We examined the dynamics of lung volume, airflow and laryngeal aperture subsequent to single breath applications of small flow resistance loads (2 and 5 cm H2O.L-1.sec) in 3 subjects using video image analysis techniques to define accurately the laryngeal aperture variation with time. The earliest deviation of the loaded expired volume time course from the control trajectory lagged the earliest occurrence of a significant incre...
Respiration physiology, 1979
Respiratory responses to hypercapnia and isocapnic hypoxia were evaluated in vagotomized decerebr... more Respiratory responses to hypercapnia and isocapnic hypoxia were evaluated in vagotomized decerebrate cats prior to and following lesions in the midline at the pontomedullary junction. Subsequent to these lesions, frequency responses to hypercapnia were significantly elevated whereas the concomitantly determined tidal volumes were significantly lowered. In the post-lesion phase, the durations of inspiration, expiration and the total respiratory cycle at maximum hypercapnia-induced tidal volumes were lower than comparable values at maximum tidal volumes in the pre-lesion phase. The same lesions produced no significant alteration of respiratory responses to hypoxia. Mesencephalic or rostral pontile lesions caused no systematic changes in either hypercapnia- or hypoxia-induced responses. It is concluded that the lesions at the pontomedullary junction produce ventilatory alterations by interrupting a pathway interconnecting the caudal pontile apneustic center with the medullary respirato...
Journal of applied physiology (Bethesda, Md. : 1985), 2001
A direct relationship exists within subjects between midlatency features (<100 ms poststimulus... more A direct relationship exists within subjects between midlatency features (<100 ms poststimulus) of respiratory-related evoked potentials and the perceived magnitude of applied oral pressure pulse stimuli. We evaluated perception in 18 normal subjects using cross-modality matching of applied pressure pulses via grip force and estimated mechanoafferent activity in these subjects by computing the global field power (GFP) from respiratory-related evoked potentials recorded over the right side of the scalp. We compared across subjects 1) the predicted magnitude production for a standard pressure pulse and 2) the slope (beta) and 3) the intercept (INT) of the Stevens power law to the summed GFP over 20-100 ms poststimulus. Both the magnitude production for a standard pressure pulse and the beta showed an inverse relationship with the summed GFP over 20-100 ms poststimulus, although there was no relationship between INT and the summed GFP. This may partially reflect characteristics of t...
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Papers by Andrew Daubenspeck