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Airway Resistance (airway + resistance)
Kinds of Airway Resistance Terms modified by Airway Resistance Selected AbstractsThe effect of fetal tracheal occlusion on lung tissue mechanics and tissue composition,PEDIATRIC PULMONOLOGY, Issue 2 2009Jacques C. Jani MD Abstract Fetal tracheal occlusion (TO) is currently used to treat severe cases of congenital diaphragmatic hernia (DH). Clinical and experimental studies suggest an improved postnatal outcome, but lung tissue mechanics after TO have not been studied. We determined the effect of TO on mechanical impedance and lung tissue components in a rabbit model for DH. At 23 days of gestation (term,=,31 days) either a sham thoracotomy or a diaphragmatic defect was induced. DH fetuses were randomly assigned to undergo 5 days later TO. Fetuses were delivered by term cesarean section to determine lung to body weight ratio (LBWR), dynamic lung mechanics and lung impedance. Airway resistance (Raw), elastance (HL), tissue damping (GL) and hysteresivity (GL/HL) were calculated from impedance data. Collagen I and III and elastin were quantified histologically. LBWR was significantly increased by TO compared to DH (P,<,0.001) and resistance and compliance of the respiratory system (Rrs, Crs) were improved as well. TO resulted in a significant decrease of Raw comparable to observations in sham-fetuses, without effect on lung tissue mechanics HL, GL and hysteresivity. This coincides with a significant decrease of collagen I, III and elastin in comparison to DH fetuses. In this first report on lung tissue mechanics in a rabbit model of DH, TO had a substantial effect on tissue morphology yet this was not mirrored in lung mechanics. We conclude that the effect of TO on lung mechanics without in utero reversal of occlusion, is dominated by airway remodeling. Pediatr Pulmonol. 2009; 44:112,121. © 2009 Wiley-Liss, Inc. [source] Mechanisms of genioglossus responses to inspiratory resistive load in rabbitsACTA PHYSIOLOGICA, Issue 3 2002N. P. ALEKSANDROVA ABSTRACT The purpose of the present study has been to determine whether pharyngeal dilator muscles participate in inspiratory load compensatory responses and if so, to elucidate role of upper airway mechanoreceptors in these responses. The experiments were performed on anaesthetized rabbits. Each animal was tested in three ways by the imposition of inspiratory resistive load: (1) at upper airways via face mask, (2) at the tracheostomic cannula placed below larynx (all upper airway receptors were `bypassed') and (3) at the mouth after the section of the hypoglossus nerves (motor denervation of genioglossus muscle). The inspiratory load applied to the upper airways evoked significant increases in integrated genioglossus activity (to 129 ± 14.7% of control) and its inspiratory duration (to 113 ± 5% of control) already within the first loaded breath (P < 0.05). The increases in the inspiratory activity of musculius genioglossus were relatively greater than the simultaneous increases in the activity of the diaphragm. Motor denervation of the pharynx dilator muscles (including m. genioglossus) increased airway resistance to 184 ± 19% of control (P < 0.05) and induced obstructive alterations in the breathing pattern during unloaded breathing: decrease in maximal inspiratory flow (,13%) and increase in the level of negative oesophageal pressure (+14%) and the peak diaphragm activity (+6%). After nervi hypoglossus sections additional increases in motor and pressure outputs were required in order to maintain unaltered ventilation at the same degree of loading as before denervation. The results indicate that the pharyngeal dilator muscles have a role in compensation of added inspiratory load. Activation of these muscles facilitate the load compensating function of `pump' muscles by decreasing airway resistance. Tracheostomy did not reduce the genioglossus response to inspiratory loading, ruling out any role for upper airways receptors in the genioglossus response to inspiratory load compensations. [source] Clinical application of continuous spirometry with a pitot-based flow meter during equine anaesthesiaEQUINE VETERINARY EDUCATION, Issue 7 2010Y. P. S. Moens Summary This report documents the feasibility and clinical information provided by a new method for spirometric monitoring adapted for equine anaesthesia. Monitoring of ventilatory function was done with continuous spirometry during general anaesthesia of client-owned horses presented for various diagnostic and surgical procedures. An anaesthetic monitor with a spirometry unit for human anaesthesia was used. To allow the measurement of large tidal volumes, a remodelled larger version of the pitot tube- based flow sensor was used. This technology provided reliable spirometric data even during prolonged anaesthesia when water condensation accumulated in the anaesthetic circuit and the sensor. In addition to flow and volume measurement and respiratory gas analysis, the continuous display of flow-volume and pressure-volume loops offered visually recognisable information about compliance, airway resistance and integrity of the circuit. Continuous spirometry with this monitoring system was helpful in evaluating the efficacy of spontaneous ventilation, in adjusting intermittent positive pressure ventilation and detecting technical faults in the anaesthetic apparatus and connection with the patient. This adapted spirometry method represents a practical and reliable measuring system for use during equine anaesthesia. The variety of information provides an opportunity to optimise anaesthetic management in this species. [source] The Kölliker-Fuse nucleus gates the postinspiratory phase of the respiratory cycle to control inspiratory off-switch and upper airway resistance in ratEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2006Mathias Dutschmann Abstract Lesion or pharmacological manipulation of the dorsolateral pons can transform the breathing pattern to apneusis (pathological prolonged inspiration). Apneusis reflects a disturbed inspiratory off-switch mechanism (IOS) leading to a delayed phase transition from inspiration to expiration. Under intact conditions the IOS is irreversibly mediated via activation of postinspiratory (PI) neurons within the respiratory network. In parallel, populations of laryngeal premotoneurons manifest the IOS by a brief glottal constriction during the PI phase. We investigated effects of pontine excitation (glutamate injection) or temporary lesion after injection of a GABA-receptor agonist (isoguvacine) on the strength of PI-pool activity determined from respiratory motor outputs or kinesiological measurements of laryngeal resistance in a perfused brainstem preparation. Glutamate microinjections into distinct parts of the pontine Kölliker-Fuse nucleus (KF) evoked a tonic excitation of PI-motor activity or sustained laryngeal constriction accompanied by prolongation of the expiratory phase. Subsequent isoguvacine microinjections at the same loci abolished PI-motor or laryngeal constrictor activity, triggered apneusis and established a variable and decreased breathing frequency. In summary, we revealed that excitation or inhibition of defined areas within the KF activated and blocked PI activity and, consequently, IOS. Therefore, we conclude, first, that descending KF inputs are essential to gate PI activity required for a proper pattern formation and phase control within the respiratory network, at least during absence of pulmonary stretch receptor activity and, secondly, that the KF contains large numbers of laryngeal PI premotor neurons that might have a key role in the regulation of upper airway resistance during reflex control and vocalization. [source] Bruxism physiology and pathology: an overview for clinicians,JOURNAL OF ORAL REHABILITATION, Issue 7 2008G. J. LAVIGNE Summary, Awake bruxism is defined as the awareness of jaw clenching. Its prevalence is reported to be 20% among the adult population. Awake bruxism is mainly associated with nervous tic and reactions to stress. The physiology and pathology of awake bruxism is unknown, although stress and anxiety are considered to be risk factors. During sleep, awareness of tooth grinding (as noted by sleep partner or family members) is reported by 8% of the population. Sleep bruxism is a behaviour that was recently classified as a ,sleep-related movement disorder'. There is limited evidence to support the role of occlusal factors in the aetiology of sleep bruxism. Recent publications suggest that sleep bruxism is secondary to sleep-related micro-arousals (defined by a rise in autonomic cardiac and respiratory activity that tends to be repeated 8,14 times per hour of sleep). The putative roles of hereditary (genetic) factors and of upper airway resistance in the genesis of rhythmic masticatory muscle activity and of sleep bruxism are under investigation. Moreover, rhythmic masticatory muscle activity in sleep bruxism peaks in the minutes before rapid eye movement sleep, which suggests that some mechanism related to sleep stage transitions exerts an influence on the motor neurons that facilitate the onset of sleep bruxism. Finally, it remains to be clarified when bruxism, as a behaviour found in an otherwise healthy population, becomes a disorder, i.e. associated with consequences (e.g. tooth damage, pain and social/marital conflict) requires intervention by a clinician. [source] Nasal CpG oligodeoxynucleotide administration induces a local inflammatory response in nonallergic individualsALLERGY, Issue 9 2009A. Mĺnsson Background:, We have previously demonstrated the presence of toll-like receptor 9 in the nasal mucosa of both healthy and allergic individuals. CpG motifs, found in bacterial and viral DNA, elicit strong immunostimulatory effects via this receptor. CpG is known to skew the immune system towards a T helper 1 (Th1) profile, thereby suppressing Th2-driven allergic responses. This study was designed to examine the effects of CpG administration in the human nose. Methods:, Twenty subjects, of whom 10 suffered from seasonal allergic rhinitis (AR), were challenged intranasally with CpG outside pollen season. Symptom scores, nasal airway resistance (NAR), and nasal and pulmonary nitric oxide (NO) levels were assayed prior to challenge and 30 min, 6, 24 and 48 h post challenge. The presence of leukocytes and various cytokines were analyzed in nasal lavage (NAL) fluids before and after CpG exposure. Results:, Increased NAR, nasal NO production and secretion of interleukin (IL)-1,, IL-6, and IL-8 were seen after CpG exposure. Further analysis revealed that this inflammatory response was more marked in healthy subjects than among patients with AR, although a higher basal inflammatory response was recorded in the allergic group. In vitro experiments suggest that the effects induced by CpG are mediated by epithelial cells and neutrophils. Conclusion:, Nasal administration of CpG induces a local airway inflammation, more distinct among healthy than allergic individuals. The reduced responsiveness to CpG in allergic patients might be related to the ongoing minimal persistent inflammation. Results from cytokine analyses reflect the ability of CpG to induce a pro-inflammatory Th1-like immune response. [source] Resistive load of laryngeal mask airway and proseal laryngeal mask airway in mechanically ventilated patientsACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2003G. Natalini Background:, The ProSeal Laryngeal Mask Airway (PLMA) ventilation tube is narrower and shorter than the standard Laryngeal Mask Airway (LMA) and is without the vertical bars at the end of the tube. In this randomized, crossover study, PLMA and LMA resistances were compared. Methods:, Respiratory mechanics was calculated in 26 anesthetized, mechanically ventilated patients with both LMA and PLMA. The laryngeal mask positioning was fiberoptically evaluated. Differences in the respiratory mechanics of the LMA and the PLMA were attributed to the differences between the laryngeal masks. Results:, In the total study population the airway resistance was 1.5 ± 2.6 hPa.l,1.s,1 (P = 0.005) higher with the PLMA than with the LMA. During the PLMA use, the peak expiratory flow reduced by 0.02 ± 0.05 l min,1 (P = 0.046), the expiratory resistance increased by 0.6 ± 1.3 hPa.l,1.s,1 (P = 0.022), and the time constant of respiratory system lengthened by 0.09 ± 0.18 s (P = 0.023). These differences doubled when the LMA was better positioned than the PLMA, whereas they disappeared when the PLMA was positioned better than the LMA. Conclusions:, The standard LMA offers a lower resistive load than the PLMA. Moreover, the fitting between the laryngeal masks and the larynx, as fiberoptically evaluated, plays a major role in determining the resistive properties of these devices. [source] Mechanisms of force failure during repetitive maximal efforts in a human upper airway muscleMUSCLE AND NERVE, Issue 1 2002Christiana DelloRusso BS Abstract The upper airway respiratory muscles play an important role in the regulation of airway resistance, but surprisingly little is known about their contractile properties and endurance performance. We developed a technique that allows measurement of force and the electromyogram (EMG) of human nasal dilator muscles (NDMs). Endurance performance was quantified by measuring NDM "flaring" force and EMG activity as healthy human subjects performed 10 s maximal voluntary contractions (MVCs), separated by 10 s rest, until the area under the force curve fell to 50% MVC (the time limit of the fatigue task, Tlim), which was reached in 34.2 ± 3.1 contractions (685.0 ± 62.3 s). EMG activity was unchanged except at Tlim, where it averaged 78.7 ± 3.6% of pretest activity (P < 0.01). M-wave amplitude did not change, suggesting that neuromuscular propagation was not impaired. MVC force increased to 80% of the pretest level within 10 min of recovery but twitch force failed to recover, suggesting low-frequency fatigue. The data suggest that a failure of the nervous system to excite muscle could explain at most only a small fraction of the NDM force loss during an intermittent fatigue task, and then only at Tlim. Thus, the majority of the force failure during this task is due to impairment of mechanisms that reside within the muscle fibers. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 94,100, 2002 [source] Natural surfactant combined with beclomethasone decreases oxidative lung injury in the preterm lambPEDIATRIC PULMONOLOGY, Issue 12 2009Carlo Dani MD Abstract We performed a randomized study in preterm lambs to assess the hypothesis that the treatment with natural surfactant combined with beclomethasone might decrease pulmonary oxidative stress in an animal model of respiratory distress syndrome (RDS). Animals received 200,mg/kg of porcine natural surfactant or 200,mg/kg of natural surfactant combined with 400 or 800,µg/kg of beclomethasone. Lung tissue oxidation was studied by measuring total hydroperoxide (TH), advanced oxidation protein products (AOPP), and non-protein bound iron (NPBI) in bronchial aspirate samples. In addition, lung mechanics was evaluated. TH was lower in the groups treated with surfactant plus 400 or 800,µg/kg of beclomethasone than in the surfactant group; AOPP was lower in the group treated with surfactant plus 800,µg/kg of beclomethasone than in the other groups; NPBI was similar in all groups. Surfactant treatment was followed by a sustained improvement of tidal volume (TV) and airway resistance, while dynamic compliance did not vary. However, the mean airway pressure needed to obtain similar values of TV was lower in the group treated with surfactant plus 800,µg/kg of beclomethasone than in other groups. We concluded that natural surfactant combined with beclomethasone at 800,µg/kg is effective in reducing the oxidative lung stress and improving the respiratory function in an animal model of RDS. Pediatr Pulmonol. 2009; 44:1159,1167. © 2009 Wiley-Liss, Inc. [source] Therapeutic bronchoscopy in a child with sand aspiration and respiratory failure from near drowning,case report and literature reviewPEDIATRIC PULMONOLOGY, Issue 10 2009N. Kapur MBBS Abstract Foreign matter aspiration occurs relatively commonly in drowning and near-drowning events. In most cases, stomach contents are aspirated. Sand aspiration rarely occurs and there are no reported cases in children with near drowning. Limited data are available on clinical presentation and management of sand aspiration with accidental burial. We report a 3-year-old boy who nearly drowned while swimming in brackish waters and was found face down in sand. Sand aspiration was suspected when the child continued to have persistent wheezing and high ventilatory requirement despite intensive bronchodilator and corticosteroids therapy with an inability to wean after 4 days post-near-drowning event. Radiology was non-specific in the absence of sand bronchogram. Presence of sand in the airways was confirmed when a bronchoscopy was undertaken and sand seen in the bronchoalveolar lavage fluid. Sequential lung washing followed by exogenous surfactant administration (3,ml/kg) was undertaken and lead to significant improvement such that within 12,hr post-therapeutic lavage, his ventilatory requirements reduced substantially. The child was extubated 4 days post-lavage and on review 2 months post-event, was clinically well with airway resistance within normal predicted values measured on forced oscillatory spirometry (IOS). Pediatr Pulmonol. 2009; 44:1043,1047. ©2009 Wiley-Liss, Inc. [source] Laryngeal sensitivity in the neonatal period: From bench to bedsidePEDIATRIC PULMONOLOGY, Issue 8 2007Philippe Reix MD Abstract Laryngeal sensitivity in the newborn has been a subject of great interest for both researchers and clinicians for a number of years. From a clinical standpoint, laryngeal sensitivity is essential for both preventing foreign substances from entering into the lower airway and for finely tuning upper airway resistance. However, heightened reflexes originating from the laryngeal receptors in newborns and infants, due to neural immaturity, can lead to potentially dangerous cardiorespiratory events. The latter have been linked to apneas of prematurity, apparent life-threatening events, and sudden infant death syndrome (SIDS). From a physiological standpoint, many mechanisms pertaining to reflexes originating from laryngeal receptors are yet to be fully understood. This short review is an attempt to summarize current knowledge on laryngeal sensitivity and its potential consequences upon control of breathing abnormalities encountered within the first weeks of life. Pediatr Pulmonol. 2007; 42:674,682. © 2007 Wiley-Liss, Inc. [source] Viral and atypical bacterial infections in the outpatient pediatric cystic fibrosis clinic,PEDIATRIC PULMONOLOGY, Issue 12 2006Hanne Vebert Olesen MD Abstract Background Respiratory viral and atypical bacterial infections are associated with pulmonary exacerbations and hospitalisations in cystic fibrosis patients. We wanted to study the impact of such infections on children attending the outpatient clinic. Methods Seventy-five children were followed for 12 months at regular clinic visits. Routine sputum/laryngeal aspirations were tested with PCR for 7 respiratory viruses. Antibodies against C. pneumoniae, M. pneumoniae and B. pertussis were measured every 3,4 months. FEV-1, FEF25,75 and specific airway resistance, "viral" symptoms and bacterial culture were recorded. Results Ninety-seven viral and 21 atypical bacterial infections were found. FEV-1 was significantly reduced during viral infection (,12.5%, p=0.048), with the exception of rhinovirus infection. A small change in FEV-1 (,3%) was seen during atypical bacterial infection (p=0.039). Viral and atypical bacterial infections caused no change in type and frequency of bacterial culture. Positive predictive value of "viral symptoms" was low (0.64%). Eight patients received "unnecessary" antibiotics because of viral symptoms. Conclusions Some viral infections and atypical bacterial infections affect FEV-1 acutely. Viral infections did not precipitate bacterial infection or change of colonisation. Clinical symptoms failed to diagnose viral infection accurately. Routine surveillance for virus or atypical bacteria seems not to be justified in this patient category. Pediatr Pulmonol. 2006; 41:1197,1204. © 2006 Wiley-Liss, Inc. [source] Inhaled drugs for the prevention and treatment of bronchopulmonary dysplasiaPEDIATRIC PULMONOLOGY, Issue 8 2006T. Pantalitschka MD Abstract Bronchopulmonary dysplasia (BPD) is one of the most common long-term complications and treatment challenges in preterm infants. Theoretically, inhaled corticosteroids may suppress pulmonary inflammation without causing systemic side-effects, while bronchodilators will improve airway resistance and thereby work of breathing. This article reviews current data on these drugs in BPD prevention or treatment. Trials published to date have not demonstrated that regular bronchodilator administration influences the incidence of BPD or improves long-term outcome. Inhaled steroids started before 2 weeks of age may improve rates of successful extubation and reduce the need for rescue systemic glucocorticoids, but have not been shown to reduce the incidence of BPD. Thus, their use cannot be generally recommended. The data currently available are not sufficient to give any clearer recommendation on the use of these drugs in infants at high risk of, or established, BPD. Pediatr Pulmonol. 2006; 41: 703,708. © 2006 Wiley-Liss, Inc. [source] Guidelines for mechanical lung function measurements in psychophysiologyPSYCHOPHYSIOLOGY, Issue 5 2002Thomas Ritz Studies in psychophysiology and behavioral medicine have uncovered associations among psychological processes, behavior, and lung function. However, methodological issues specific to the measurement of mechanical lung function have rarely been discussed. This report presents an overview of the physiology, techniques, and experimental methods of mechanical lung function measurements relevant to this research context. Techniques to measure lung volumes, airflow, airway resistance, respiratory resistance, and airflow perception are introduced and discussed. Confounding factors such as ventilation, medication, environmental factors, physical activity, and instructional and experimenter effects are outlined, and issues specific to children and clinical groups are discussed. Recommendations are presented to increase the degree of standardization in the research application and publication of mechanical lung function measurements in psychophysiology. [source] Resistance and reactance in oscillation lung function reflect basal lung function and bronchial hyperresponsiveness respectivelyRESPIROLOGY, Issue 7 2009Hyeong Yoon KIM ABSTRACT Background and objective: Currently there are few data available regarding the use of impulse oscillometry parameters to assess airflow obstruction during standardized methacholine challenge testing. Methods: Methacholine challenge tests were performed using impulse oscillometry and conventional spirometry in 64 healthy and 39 asthmatic children, in order to determine airway resistance (R) and reactance (X) at frequencies of 5,35 Hz, as well as FEV1. Results: Baseline R and X were significantly different between the healthy and asthmatic children, with the most discriminating parameter being resistance at 5 Hz (R5). In asthmatic children BHR was well demonstrated by FEV1, X5 and X10, but not by R5. However, when the actual R5 values obtained in this study were compared with the predicted values, there appeared to be differences in the lung function measures that corresponded to varying methacholine concentrations. In addition, the PC20_FEV1 and PC70_X5 were significantly more sensitive than other parameters for methacholine challenge testing. Conclusions: Measuring resistance at 5 Hz using impulse oscillometry facilitates significant differentiation of baseline lung function between asthmatic and healthy children. Additionally, X may be a suitable replacement for PC20 in methacholine challenge testing. [source] Exploring the phonatory effects of external superior laryngeal nerve paralysis: An In vivo model,THE LARYNGOSCOPE, Issue 4 2009Nelson Roy PhD Abstract Objectives/Hypothesis: Little is known regarding the phonatory consequences of unilateral external superior laryngeal nerve (ESLN) paralysis. By selectively blocking the ESLN with lidocaine HCl (with laryngeal electromyography verification), we modeled acute, unilateral cricothyroid (CT) muscle dysfunction to explore possible acoustic, aerodynamic, auditory-perceptual and auto-perceptive effects. Study Design: Prospective, repeated measures, experimental design. Methods: Ten, vocally-normal adult males underwent lidocaine block of the right ESLN. Multiple measures of phonatory function across a variety of vocal tasks/conditions were acquired before and during the block using standard data acquisition and analysis protocols. Results: During ESLN block, phonatory frequency range was significantly reduced with compression of both upper and lowermost regions of the pitch range. Mean speaking fundamental frequency increased significantly during oral reading. Acoustic analysis, aerodynamic assessment, and auditory- perceptual evaluation by blinded listeners revealed modest increases in phonatory instability (jitter), increased laryngeal airway resistance with no objective evidence of glottic insufficiency, and mild deterioration in voice quality most evident during high pitched voice productions, respectively. Participants uniformly rated their speaking and singing voices as worse during the block with significant weakness, effort, and tightness that they perceived as a mild level of impairment. Conclusions: These data support generally mild changes to the speaking voice, which extend beyond reductions in pitch range only, and shed light on the potential untoward phonatory effects of acute, unilateral CT dysfunction. Laryngoscope, 2009 [source] Modeling Flow in a Compromised Pediatric Airway Breathing Air and HelioxTHE LARYNGOSCOPE, Issue 12 2008Mihai Mihaescu PhD Abstract Objectives/Hypothesis: The aim of this study was to perform computer simulations of flow within an accurate model of a pediatric airway with subglottic stenosis. It is believed that the airflow characteristics in a stenotic airway are strongly related to the sensation of dyspnea. Methodology: Computed tomography images through the respiratory tract of an infant with subglottic stenosis, were used to construct the three-dimensional geometry of the airway. By using computational fluid dynamics (CFD) modeling to capture airway flow patterns during inspiration and expiration, we obtained information pertaining to flow velocity, static airway wall pressure, pressure drop across the stenosis, and wall shear stress. These simulations were performed with both air and heliox. Results: Unlike air, heliox maintained laminar flow through the stenosis. The calculated pressure drop over stenosis was lower for the heliox flow, in contrast to the airflow case. This lead to an approximately 40% decrease in airway resistance when using heliox, and presumably causes a decrease in the level of effort required for breathing. Conclusions: CFD simulations offer a quantitative method of evaluating airway flow dynamics in patients with airway abnormalities. CFD modeling illustrated the flow features and quantified flow parameters within a pediatric airway with subglottic stenosis. Simulations with air and heliox conditions mirrored the known clinical benefits of heliox as compared with air. We anticipate that computer simulation models will ultimately allow a better understanding of changes in flow caused by specific medical and surgical interventions in patients with conditions associated with dyspnea. [source] Optimising the unprotected airway with a prototype Jaw-Thrust-Device , a prospective randomised cross-over studyANAESTHESIA, Issue 11 2009A. Von Goedecke Summary Despite being a standard procedure during induction of anaesthesia, facemask ventilation can be a major challenge especially for inexperienced anaesthetists. We manufactured a Jaw-Thrust-Device designed to keep the patient's jaws in an optimised position, and thus to maintain the airway in a permanently patent state. Using a cross over design, we compared the influence of using the Esmarch manoeuvre (bimanual jaw-thrust), a nasopharyngeal airway, an oropharyngeal airway, or the Jaw-Thrust-Device on airway physiology in 50 healthy adults with body mass index < 35 kg.m,2, undergoing standard facemask ventilation for routine induction of anaesthesia. The main study endpoints were expiratory tidal volumes, airway resistances, and gas flow rates. The Jaw-Thrust-Device was more effective in increasing expiratory tidal volumes and peak inspiratory flow than a standard Esmarch manoeuvre, and was more effective than both nasopharyngeal and oropharyngeal airways in decreasing airway resistance. [source] Effects of 7,8-dihydro-8-oxo-deoxyguanosine on antigen challenge in ovalbumin-sensitized mice may be mediated by suppression of RacBRITISH JOURNAL OF PHARMACOLOGY, Issue 7 2009JY Ro Background and purpose:, Earlier we reported that 7,8-dihydro-8-oxo-deoxyguanosine (8-oxo-dG), an oxidatively modified guanine nucleoside, exerted anti-inflammatory activity through inactivation of the GTP binding protein, Rac. In the present study, the effects of 8-oxo-dG were investigated on responses to antigen challenge in sensitized mice, as Rac is also involved at several steps of the immune process including antigen-induced release of mediators from mast cells. Experimental approach:, Mice were sensitized and challenged with ovalbumin without or with oral administration of 8-oxo-dG during the challenge. Effects of 8-oxo-dG were assessed by measuring lung function, cells and cytokines in broncho-alveolar lavage fluid (BALF) and serum levels of antigen-specific IgE. Rac activity in BALF cells was also measured. Key results:, 8-oxo-dG inhibited the increased airway resistance and decreased lung compliance of sensitized and challenged mice to the levels of non-sensitized control mice and lowered the increased leukocytes particularly, eosinophils, in BALF. Furthermore, 8-oxo-dG suppressed allergy-associated immune responses, such as raised anti- ovalbumin IgE antibody in serum, increased expression of CD40 and CD40 ligand in lung, increased interleukin-4, -5, -13, interferon-, and tumour necrosis factor-, in BALF and mRNA levels of these cytokines in BALF cells, dose-dependently. The corresponding purine, 8-oxo-guanine, showed no effects in the same experiments. Finally, 8-oxo-dG, but not 8-oxo-guanine, inhibited the increased Rac activity in sensitized and challenged mice. Conclusion and implications:, 8-Oxo-dG had anti-allergic actions that might be mediated by Rac inactivation. This compound merits further evaluation of its therapeutic potential in allergic asthma. [source] Adrenergic mechanisms in canine nasal venous systemsBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2003Min Wang We investigated the adrenergic mechanisms of the two venous systems that drain the nasal mucosa, thereby their exact role in eliciting nasal decongestion. The action of endogenously released noradrenaline and exogenous adrenergic agonists on different segments of the nasal venous systems, i.e. collecting (LCV, SCV) and outflow (SPV) veins of posterior venous system, collecting (ACV) and outflow (DNV) veins of anterior venous system and venous sinusoids of the septal mucosa (SM), were studied. In vitro isometric tension of the vascular segments was measured. Transmural nerve stimulation (TNS) produced constriction in ACV, DNV and SM, primary constriction followed by secondary dilatation in LCV and SCV and dilatation in SPV. Tetrodotoxin (10,6M) abolished all responses. Phentolamine (10,6M), prazosin (10,6M) and rauwolscine (10,7M) inhibited the constriction in all venous vessels. Propranolol (10,6M), atenolol (10,6M) and ICI 118,551 (10,6M) inhibited the relaxation in SPV but not in LCV and SCV. Phenylephrine and clonidine constricted whereas dobutamine and terbutaline relaxed all venous vessels dose-dependently. These results indicate ,1 -, ,2 -, ,1 - and ,2 -adrenoceptors are present in both venous systems. TNS causes constriction of anterior venous system, venous sinusoids and posterior collecting veins primarily via postjunctional ,2 -adrenoceptors but relaxation of posterior outflow vein equally via postjunctional ,1 - and ,2 -adrenoceptors. The combined action of the two adrenergic mechanisms can reduce nasal airway resistance in vivo by decreasing vascular capacitance and enhancing venous drainage via the posterior venous system. British Journal of Pharmacology (2003) 138, 145,155. doi:10.1038/sj.bjp.0705020 [source] Respiratory muscle strength and muscle endurance are not affected by acute metabolic acidemiaCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2009Tessa A. C. Nizet Summary Respiratory muscle fatigue in asthma and chronic obstructive lung disease (COPD) contributes to respiratory failure with hypercapnia, and subsequent respiratory acidosis. Therapeutic induction of acute metabolic acidosis further increases the respiratory drive and, therefore, may diminish ventilatory failure and hypercapnia. On the other hand, it is known that acute metabolic acidosis can also negatively affect (respiratory) muscle function and, therefore, could lead to a deterioration of respiratory failure. Moreover, we reasoned that the impact of metabolic acidosis on respiratory muscle strength and respiratory muscle endurance could be more pronounced in COPD patients as compared to asthma patients and healthy subjects, due to already impaired respiratory muscle function. In this study, the effect of metabolic acidosis was studied on peripheral muscle strength, peripheral muscle endurance, airway resistance, and on arterial carbon dioxide tension (PaCO2). Acute metabolic acidosis was induced by administration of ammonium chloride (NH4Cl). The effect of metabolic acidosis was studied on inspiratory and expiratory muscle strength and on respiratory muscle endurance. Effects were studied in a randomized, placebo-controlled cross-over design in 15 healthy subjects (4 male; age 33·2 ± 11·5 years; FEV1 108·3 ± 16·2% predicted), 14 asthma patients (5 male; age 48·1 ± 16·1 years; FEV1 101·6 ± 15·3% predicted), and 15 moderate to severe COPD patients (9 male; age 62·8 ± 6·8 years; FEV1 50·0 ± 11·8% predicted). An acute metabolic acidemia of BE ,3·1 mmol.L,1 was induced. Acute metabolic acidemia did not significantly affect strength or endurance of respiratory and peripheral muscles, respectively. In all subjects airway resistance was significantly decreased after induction of metabolic acidemia (mean difference ,0·1 kPa.sec.L,1 [95%-CI: ,0·1 ,,0·02]. In COPD patients PaCO2 was significantly lowered during metabolic acidemia (mean difference ,1·73 mmHg [,3·0 ,,0·08]. In healthy subjects and in asthma patients no such effect was found. Acute metabolic acidemia did not significantly decrease respiratory or peripheral muscle strength, respectively muscle endurance in nomal subjects, asthma, or COPD patients. Metabolic acidemia significantly decreased airway resistance in asthma and COPD patients, as well as in healthy subjects. Moreover, acute metabolic acidemia slightly improved blood gas values in COPD patients. The results suggest that stimulation of ventilation in respiratory failure, by induction of metabolic acidemia will not lead to deterioration of the respiratory failure. [source] Optimising the unprotected airway with a prototype Jaw-Thrust-Device , a prospective randomised cross-over studyANAESTHESIA, Issue 11 2009A. Von Goedecke Summary Despite being a standard procedure during induction of anaesthesia, facemask ventilation can be a major challenge especially for inexperienced anaesthetists. We manufactured a Jaw-Thrust-Device designed to keep the patient's jaws in an optimised position, and thus to maintain the airway in a permanently patent state. Using a cross over design, we compared the influence of using the Esmarch manoeuvre (bimanual jaw-thrust), a nasopharyngeal airway, an oropharyngeal airway, or the Jaw-Thrust-Device on airway physiology in 50 healthy adults with body mass index < 35 kg.m,2, undergoing standard facemask ventilation for routine induction of anaesthesia. The main study endpoints were expiratory tidal volumes, airway resistances, and gas flow rates. The Jaw-Thrust-Device was more effective in increasing expiratory tidal volumes and peak inspiratory flow than a standard Esmarch manoeuvre, and was more effective than both nasopharyngeal and oropharyngeal airways in decreasing airway resistance. [source] The efficacy and safety of QVAR (hydrofluoroalkane-beclometasone diproprionate extrafine aerosol) in asthma (part 2): clinical experience in childrenINTERNATIONAL JOURNAL OF CLINICAL PRACTICE, Issue 8 2004C. P. Van Schayck Summary QVAR [hydrofluoroalkane-134a beclometasone dipropionate (BDP)] produces equivalent asthma control to chlorofluorocarbon-based BDP inhalers, at approximately half the daily dose in adults, a probable consequence of the increased lung deposition of QVAR that results from its greater fine particle fraction. Recent studies have relied on the clinical experience with QVAR in adults as a basis for investigations in childhood asthma. Design considerations, such as the use of the breath-actuated AutohalerÔ delivery device and measurement of direct health benefits, account for problems of variation in inspiratory flow, handling difficulties and low airways resistance that are associated with children. QVAR appears to be well tolerated in children with no clinically relevant adverse effects on adrenal function, bone metabolism or growth at recommended doses. [source] Suppression of histamine-induced tachypnoea in the rhesus monkey by sibenadet: no role for dopamine D2 receptorsAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 1 2004J. R. Fozard Summary 1 Sibenadet (Viozan®), a dual dopamine D2/,2 -adrenoceptor agonist, suppresses histamine-induced tachypnoea in the dog by activating dopamine D2 receptors. We here compare the effects of sibenadet and formoterol, a selective ,2 -adrenoceptor agonist, on histamine-induced tachypnoea in the rhesus monkey. 2 Anaesthetized, spontaneously breathing, rhesus monkeys were set up for measuring airways resistance, respiratory rate, blood pressure and heart rate. 3 Both sibenadet and formoterol administered by aerosol, induced inhibition of the bronchoconstrictor response to aerosolized methacholine accompanied by tachycardia. Sibenadet, but not formoterol, also reduced blood pressure. 4 Administration of histamine by inhalation induced tachypnoea which was accompanied by bronchoconstriction. Tachypnoea to histamine was suppressed by both sibenadet and formoterol at doses which manifest anti-bronchoconstrictor activity. These effects and the accompanying tachycardia but not the hypotension induced by sibenadet were abolished by pretreatment with propranolol. 5 The dopamine D2 receptor agonist, quinagolide, did not suppress tachypnoea to histamine despite inducing a fall in blood pressure indicating activation of dopamine D2 receptors. 6 Thus, both sibenadet and formoterol suppress histamine-evoked tachypnoea in the rhesus monkey. The effect arises exclusively through activation of ,2 -adrenoceptors and probably reflects the anti-bronchoconstrictor effects of these agents. The results reveal a fundamental difference in the role of dopamine receptors in the airways of dog and rhesus monkey. [source] A Pressure-controlled Rat Ventilator With Electronically Preset RespirationsARTIFICIAL ORGANS, Issue 12 2006Valentin L. Ordodi Abstract:, Major experimental surgery on laboratory animals requires adequate anesthesia and ventilation to keep the animal alive throughout the procedure. A ventilator is a machine that helps the anesthesized animal breathe through an endotracheal tube by pumping a volume of gas (oxygen, air, or other gaseous mixtures), comparable with the normal tidal volume, into the animal's lungs. There are two main categories of ventilators for small laboratory rodents: volume-controlled and pressure-controlled ones. The volume-controlled ventilator injects a preset volume into the animal's lungs, no matter the airways' resistance (with the peak inspiratory pressure allowed to vary), while the pressure ventilator controls the inspiratory pressure and allows the inspiratory volume to vary. Here we show a rat pressure ventilator with a simple expiratory valve that allows gas delivery through electronic expiration control and offers easy pressure monitoring and frequency change during ventilation. [source] | ||||||||||||||||||||||||||||