Respiratory physiology & neurobiology
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Respir Physiol Neurobiol · Feb 2009
Comparative StudyComparisons of effects of intravenous and inhaled methacholine on airway physiology in a murine asthma model.
Airway responses to intravenous (i.v.) and inhaled (i.h.) delivery of methacholine (MCh) in BALB/c and C57BL/6 mouse strains have been compared with and without ovalbumin (OVA)-induced airway inflammation. Bronchial reactivity to MCh was assessed in anaesthetised and tracheostomised animals by using an animal ventilator (flexiVent). We partitioned the response of the lungs into airway and parenchymal components in order to compare the contributions of the airways with those of the lung parenchyma to the pulmonary mechanical responses resulting from different routes of MCh administration. ⋯ In conclusion, i.v. and i.h. MCh produced disparate effects in different murine strains and variant responses in inflamed airways and healthy controls. The two methods of MCh delivery have important advantages but also certain limitations with regard to measuring airway reactivity in a murine model of allergic asthma.
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Respir Physiol Neurobiol · Jan 2009
Impact of supplemental oxygen in mechanically ventilated adult and infant mice.
The aim of the present study was to determine the short-term effects of hyperoxia on respiratory mechanics in mechanically ventilated infant and adult mice. Eight and two week old BALB/c mice were exposed to inspired oxygen fractions [Formula: see text] of 0.21, 0.3, 0.6, and 1.0, respectively, during 120 min of mechanical ventilation. Respiratory system mechanics and inflammatory responses were measured. ⋯ Inflammatory responses did not differ between groups at either age. Hyperoxia had no impact on respiratory mechanics during mechanical ventilation with low tidal volume and positive end-expiratory pressure. Hence, supplemental oxygen can safely be applied during short-term mechanical ventilation strategies in infant and adult mice.
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Respir Physiol Neurobiol · Dec 2008
Scalene muscle activity during progressive inspiratory loading under pressure support ventilation in normal humans.
We hypothesized that (1) in healthy humans subjected to intermittent positive pressure non-invasive ventilation, changes in the ventilator trigger sensitivity would be associated with increased scalene activity, (2) if properly processed - through inspiratory phase-locked averaging - surface electromyograms (EMG) of the scalenes would reliably detect and quantify this, (3) there would be a correlation between dyspnea and scalene EMG. Surface and intramuscular EMG activity of scalene muscles were measured in 10 subjects. They breathed quietly through a face mask for 10min and then were connected to a mechanical ventilator. ⋯ With increasing values of the inspiratory trigger, inspiratory efforts, dyspnea and the scalene activity increased significantly. The scalene EMG activity level was correlated with the esophageal pressure time product and with dyspnea intensity. Inspiration-adjusted surface EMG averaging could be useful to detect small increases of the scalene muscles activity during mechanical ventilation.
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Respir Physiol Neurobiol · Dec 2008
ReviewPharmacology of vagal afferent influences on disordered breathing during sleep.
Sleep-related breathing disorders (SRBD) are a significant public health concern, with a prevalence in the US general population of approximately 2% of women and approximately 4% of men. Although significant strides have been made in our understanding of these disorders with respect to epidemiology, risk factors, pathogenesis and consequences, work to understand these factors in terms of the underlying cellular, molecular and neuromodulatory processes remains in its infancy. ⋯ Basic investigations into the neurochemistry and neuropharmacology of sleep-related changes in respiratory pattern generation and modulation will be essential to clarify the pathogenic processes underlying SRBD and to identify rational and specific pharmacotherapeutic opportunities. Here we summarize emerging work suggesting the importance of vagal afferent feedback systems in sleep-related respiratory pattern disturbances and pointing toward a rich but complex array of neurochemical and neuromodulatory processes that may be involved.