Archive for the ‘Bronchial Hyperresponsiveness’ Category

Patients with transection of the cervical spine (quadriplegia) manifest a unique situation of selective interruption of sympathetic pulmonary innervation with retained intact parasympathetic tone. Although human airways seem to lack tonic sympathetic bronchodilator tone,” it is believed that sympathetic nerves in the lung serve in a neuromodulatory capacity, acting to counteract cholinergic bronchoconstrictor effect. Such unopposed parasympa thetic airway tone most likely explains the hyperresponsiveness to methacholine demonstrated by all of our patients. Selective blockade of sympathetic input to the lung also may account for the prior observation of significant bronchodilator response to inhaled metaproterenol sulfate in a group of otherwise healthy quadriplegic nonsmokers.
A third source of innervation, the nonadrenergic noncholinergic nervous system, exists in human airways. Nonadrenergic inhibitory nerves, which relax airway smooth muscle, have been demonstrated in vitro and in vivo.’29 Since there is no tonic sympathetic influence on human airway smooth muscle, this nonadrenergic inhibitory system serves as the only direct neural bronchodilator pathway Source http://antimicrobialmed.com. The effect of transection of the cervical spine on the pulmonary nonadrenergic noncholinergic nervous system is unknown. Whether interruption of nonadrenergic inhibitory nerves in quadriplegia plays a role in the bronchial hyperresponsiveness we have observed remains to be elucidated.
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Bronchial Hyperresponsiveness After Cervical Spinal Cord Injury: ResultsBaseline spirometry revealed no evidence of obstruction (Table 1). All patients demonstrated hyperresponsiveness to methacholine (Table 2). Values of FEVi and FVC at baseline and after provocation were 3.06 ±0.61 (SD) L vs 1.91 ±0.60 L (p=0.002), and 3.46 ±0.75 L vs 2.73 ±0.69 L (p=0.062), respectively. Percentage predicted values for FEVi and FVC before and after methacholine challenge were 71.9 ±13.9 L vs 45.0 ±14.5 L (p= 0.002), and 62.5 ± 13.8 L vs 49.4 ± 12.6 L (p=0.067), respectively. Baseline values of FEVi/FVC ratio (percent) decreased after bronchoprovocation from 89.0 ± 6.0 to 71.6 ± 18.8 (p=0.026). Seven of the eight subjects experienced a feeling of chest tightness after inhalation of the concentration of methacholine producing a greater than 20 percent fall in FEVi. Administration of nebulized metaproterenol sulfate resulted in resolution of symptoms and return to baseline FEVi in all patients. No correlation was observed between airway reactivity (PC20) and either the level of cervical lesion or baseline FEVi. The baseline FVC did correlate with the level of the lesion.
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Eight male outpatients with traumatic lesions of the cervical spinal cord (level of injury, C4-7) underwent bronchoprovocation testing with methacholine (Provocholine, Roche Laboratories, Nutley, NJ). Time elapsed since spinal cord injury ranged from 3 to 23 years. Mean age was 34.5 ±5.8 (SD) years (Table 1). None of the subjects had ever been cigarette smokers, nor had they had any history of pulmonary disease or respiratory symptoms prior to their injury. None of the patients required assisted ventilation. Subjects were without respiratory complaints or evidence of recent or active infection at the time of the study, though two subjects reported infrequent episodes of mild dyspnea in the past. None of the patients was receiving any medications expected to alter airway reactivity except for one study participant who ingested 5 mg daily of prazosin, a drug reported to have bronchodilator activity after oral administration.9 All subjects granted informed consent for the study, which was approved by the institutional review board of the Veterans Affairs Medical Center. canada health and care mall

Spirometry was performed with subjects seated in their own wheelchairs, using a SensorMedics 2100 Automated Pulmonary Function Laboratory (Yorba Linda, Cal). Baseline values were obtained for each patient in compliance with current American Thoracic Society criteria.10 Results were expressed as percent predicted based on the spirometric standards of Morris et al.
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Bronchial Hyperresponsiveness After Cervical Spinal Cord InjuryThe degree of pulmonary dysfunction following spinal cord injury is dependent upon the level of injury sustained. Lesions above the third cervical segment result in complete paralysis of all muscles of respiration and therefore necessitate mechanical ventilation, whereas lesions at lower cervical levels will, to varying extents, spare the major muscles of inspiration, ie, the diaphragm (C3-5), scalene muscles (C4-8), and intercostal muscles (Tl-12). The expiratory muscles receive their innervation from the first thoracic segment and below. Hence, transection of the cervical spinal cord (quadriplegia) renders expiratory function severely compromised. As a result, inability to clear secretions, mucous plugging, atelectasis, and respiratory infections are common pulmonary complications in this patient population.
Traumatic injury to the spinal cord causes a restrictive ventilatory impairment, the severity of which parallels the level of injury. Spirometry and measurement of static lung volumes have demonstrated reductions in vital capacity, inspiratory capacity, and expiratory reserve volume, as well as elevated residual volume. Measures of airflow, including the FEVi and mean forced expiratory flow during the middle half of the forced vital capacity (FVC), are also reduced. Because flow rates were believed to be decreased in proportion to the reduction in vital capacity in subjects with spinal cord injury, the presence of an obstructive component of respiratory dysfunction in this population was not suggested by previous investigators.” mycanadianpharmacy

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