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P.w. Davenport - One of the best experts on this subject based on the ideXlab platform.

  • Detection of inspiratory Resistive Loads in double-lung transplant recipients.
    Journal of applied physiology (Bethesda Md. : 1985), 2002
    Co-Authors: Weiying Zhao, A. Daniel Martin, P.w. Davenport
    Abstract:

    The afferent pathways mediating respiratory Load perception are still largely unknown. To assess the role of lung vagal afferents in respiratory sensation, detection of inspiratory Resistive Loads was compared between 10 double-lung transplant (DLT) recipients with normal lung function and 12 healthy control (Nor) subjects. Despite a similar unLoaded and Loaded breathing pattern, the DLT group had a significantly higher detection threshold (2.91 ± 0.5 vs. 1.55 ± 0.3 cmH2O · l−1 · s) and Weber fraction (0.50 ± 0.1 vs. 0.30 ± 0.1) compared with the Nor group. These results suggest that inspiratory Resistive Load detection occurs in the absence of vagal afferent feedback from the lung but that lung vagal afferents contribute to inspiratory Resistive Load detection response in humans. Lung vagal afferents are not essential to the regulation of resting breathing and Load compensation responses.

  • inspiratory Resistive Load detection in children with life threatening asthma
    Pediatric Pulmonology, 2001
    Co-Authors: P.w. Davenport, Yemiserach Kifle
    Abstract:

    The detection of inspiratory Resistive (R) Loads was studied in nonasthmatic children (NA), asthmatic children (A), and children with a history of life-threatening asthma (LTA). It was hypothesized that the LTA children would have a reduced ability to detect added mechanical Loads as measured by the Weber fraction, which assesses the Resistive Load detection threshold (ΔR50/R0). Subjects were separated from the investigator, were seated in a soundproofed room, and breathed through a nonrebreathing valve with the inspiratory port connected to the Loading manifold. The subject's inspiratory baseline resistance (Raw) was measured by the interrupter method. Ten magnitudes of R Loads and no-Load were presented randomly 10 times each for a single inspiration. The Loads were presented in three trials. Subjects pressed a button if they detected the presence of a Load. The ΔR50 was determined from the % detection-ΔR curve. R0 was the sum of the subject's Raw and the minimal resistance of the apparatus. The ΔR50/R0 for children with life- threatening asthma was significantly greater than for asthmatic and nonasthmatic children. The increased ΔR50/R0 suggests that children with LTA are at risk of life-threatening asthma attacks, in part because it requires a greater change in resistance above their baseline resistance before they sense an increased mechanical Load such as presented to them by bronchoconstriction during an asthmatic attack. Pediatr Pulmonol. 2001; 32:44–48. © 2001 Wiley-Liss, Inc.

  • Inspiratory strengthening effect on Resistive Load detection and magnitude estimation.
    Medicine & Science in Sports & Exercise, 2000
    Co-Authors: Barbara Kellerman, Anatole D. Martin, P.w. Davenport
    Abstract:

    KELLERMAN, B. A., A. D. MARTIN, and P. W. DAVENPORT. Inspiratory strengthening effect on Resistive Load detection and magnitude estimation. Med. Sci. Sports Exerc., Vol. 32, No. 11, pp. 1859–1867, 2000.PurposeThis study investigated effects of inspiratory muscle training (IMT) on maximal inspiratory

  • Inspiratory Resistive Load detection in conscious dogs.
    Journal of applied physiology (Bethesda Md. : 1985), 1991
    Co-Authors: P.w. Davenport, D. J. Dalziel, B. Webb, J. R. Bellah, C. J. Vierck
    Abstract:

    The physiological mechanisms mediating the detection of mechanical Loads are unknown. This is, in part, due to the lack of an animal model of Load detection that could be used to investigate specific sensory systems. We used American Foxhounds with tracheal stomata to behaviorally condition the detection of inspiratory occlusion and graded Resistive Loads. The Resistive Loads were presented with a Loading manifold connected to the inspiratory port of a non-rebreathing valve. The dogs signaled detection of the Load by lifting their front paw off a lever. Inspiratory occlusion was used as the initial training stimulus, and the dogs could reliably respond within the first or second inspiratory effort to 100% of the occlusion presentations after 13 trials. Graded resistances that spanned the 50% detection threshold were then presented. The detection threshold resistances (delta R50) were 0.96 and 1.70 cmH2O.l-1.s. Ratios of delta R50 to background resistance were 0.15 and 0.30. The near-threshold Resistive Loads did not significantly change expired PCO2 or breathing patterns. These results demonstrate that dogs can be conditioned to reliably and specifically signal the detection of graded inspiratory mechanical Loads. Inspiration through the tracheal stoma excludes afferents in the upper extrathoracic trachea, larynx, pharynx, nasal passages, and mouth from mediating Load detection in these dogs. It is unknown which remaining afferents (vagal or respiratory muscle) are responsible for Load detection.

Gila Benchetrit - One of the best experts on this subject based on the ideXlab platform.

John C Baird - One of the best experts on this subject based on the ideXlab platform.

  • neuromodulatory effect of endogenous opioids on the intensity and unpleasantness of breathlessness during Resistive Load breathing in copd
    COPD: Journal of Chronic Obstructive Pulmonary Disease, 2011
    Co-Authors: Alex H Gifford, Donald A Mahler, Laurie A Waterman, Joseph Ward, William J Kraemer, Brian R Kupchak, John C Baird
    Abstract:

    Background: Endogenous opioids are naturally occurring peptides released by the brain in response to noxious stimuli. Although these naturally occurring peptides modulate pain, it is unknown whether endogenous opioids affect the perception of breathlessness associated with a specific respiratory challenge. The hypothesis is that intravenous administration of naloxone, used to block opioid signaling and inhibit neural pathways, will increase ratings of breathlessness during Resistive Load breathing (RLB) in patients with chronic obstructive pulmonary disease (COPD). Methods: Fourteen patients with COPD (age, 64 ± 9 years) inspired through resistances during practice sessions to identify an individualized target Load that caused ratings of intensity and/or unpleasantness of breathlessness ≥ 50 mm on a 100 mm visual analog scale. At two intervention visits, serum beta-endorphins were measured, naloxone (10 mg/25 ml) or normal saline (25 ml) was administered intravenously, and patients rated the two dimension...

C Guilleminault - One of the best experts on this subject based on the ideXlab platform.

  • Load detection in subjects with sleep-induced upper airway obstruction.
    American journal of respiratory and critical care medicine, 1994
    Co-Authors: A A Clerk, S R Dunan, C Guilleminault
    Abstract:

    Respiratory flow-Resistive Load detection in obese patients has been shown to be impaired. We tested the hypothesis that there is no difference in inspiratory flow-Resistive Load detection measured in nonobese obstructive sleep apnea patients, nonobese snorers, and normal control subjects. Eleven male obstructive sleep apnea patients and seven male snorers were investigated and compared with 10 normal male control subjects. Severely obese patients (body mass index, BMI > 35 kg/m2) were excluded. Patients were investigated by nocturnal polysomnography with measurement of esophageal pressure (Pes). Awake pulmonary function tests were performed before the investigation. Airway resistance (Raw) and lung volumes were measured with plethysmography. Resistive Loads were investigated according to Tapper and associates (13) and Killian and associates (12). Resistances were applied for the duration of one inspiratory cycle and a minimum of two breaths allowed between each Resistive Load. Six different resistances plus background shams were presented 10 times in random order. Flow, pressure, and subject response were recorded with a calibrated multichannel recorder. Subjects signaled detected changes of inspiratory resistance with a hand-held signaling device. The probability of detecting a particular resistance was calculated as the ratio of correct identification to the number of presentations (i.e., 10). The resistance corresponding to a 0.5 probability of detection was determined. The Weber fraction (wf) calculated as delta R/R(apparatus) +Raw. There were no differences between nonobese subjects and controls in terms of Resistive Load detection.

Edgar Williams - One of the best experts on this subject based on the ideXlab platform.

  • effect of Resistive Load on the inspiratory work and power of breathing during exertion
    PLOS ONE, 2012
    Co-Authors: Thomas Powell, Edgar Williams
    Abstract:

    Resistive Loads are used to train respiratory muscles in athletes and in rehabilitation of people with pulmonary disease or spinal injuries [1–3]. Other studies use external Resistive Load detection as a tool to study dyspnoea sensitivity [4]. Resistive work is dependent on ventilation, and different exercise modes, for example walking and cycling place different metabolic demands on the body. A measure of the work performed during breathing can be derived from the product of the volume and pressure change generated during the respiratory cycle. The mechanical work of breathing which includes the elastic and Resistive components, defined per litre of ventilation in resting healthy subjects is around 0.3560.1 JL21 while the power generated is around 2.460.7 W [5]. The power generated is thus influenced by respiratory rate and volume of air moved. Measuring these parameters often involve using invasive techniques and require an estimate of chest wall compliance [6]. At rest the inspiratory work of breathing is consistently larger than expiratory work. However this changes with exercise when expiration also becomes an active process. Measuring work only during the inspiratory phase of the respiratory cycle provides a simple index of the muscle-driven work irrespective of the expiratory phase. This study aims to use a new non-invasive method to measure the Resistive work of breathing and the subsequent power generated (WRI and PRI respectively) while breathing against added Resistive Loads and explore this relationship with ventilation during sub-maximal exercise, sitting, walking or cycling. This study while observational is unique in that the Loading was applied in ‘‘real-time’’ using a servo-controlled variable orifice pneumotachograph allowing both Resistive inspiratory work and power to be assessed simultaneously.