Airflow obstruction

Sink within the infinite surface w ith an airflow obstruction from one side... 

Cell BR, Cote CG, Marin JM et al (2004) The body-mass index, airflow obstruction, dyspnea, and exercise capacity index in chronic obstructive pulmonary disease. New Engl J Med 350 1005-1012... 

In advanced COPD, airflow obstruction, damaged bronchioles and alveoli, and pulmonary vascular abnormalities lead to impaired gas exchange. This results in hypoxemia and eventually hypercapnia. Hypoxemia is initially present only during exercise but occurs at rest as the disease progresses. Inequality in the ventilation/perfusion ratio (VAQ) is the major mechanism behind hypoxemia in COPD. 

The National Asthma Education and Prevention Program (NAEPP) defines asthma as a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role. In susceptible individuals, inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness, and coughing. These episodes are usually associated with airflow obstruction that is often reversible either spontaneously or with treatment. The inflammation also causes an increase in bronchial hyperresponsiveness (BHR) to a variety of stimuli. 

The major characteristics of asthma include a variable degree of airflow obstruction (related to bronchospasm, edema, and hypersecretion), BHR, and airway inflammation. 

The goals of treatment include (1) correction of significant hypoxemia (2) rapid reversal of airway obstruction (within minutes) (3) reduction of the likelihood of recurrence of severe airflow obstruction and (4) development of a written action plan in case of a future exacerbation. 

Objective measurements of airflow obstruction with a home peak flow meter may not necessarily improve patient outcomes. The NAEPP advocates use of PEF monitoring only for patients with severe persistent asthma who have difficulty perceiving airway obstruction. 

An improvement in FEVj of less than 12% after inhalation of a rapidacting bronchodilator is considered to be evidence of irreversible airflow obstruction. 

The TP receptor requires the G/G protein to activate the Src-Ras-ERKl/2 (extracellular signal-regulated kinase 1 and 2) cascade to induce the proliferative response, which in turn promotes the rapid nuclear translocation of activated ERKl/2 (201). Because TP receptor may be activated by many inflammatory mediators (202-204), these findings suggest new therapeutic strategies that alter the ASM hypertrophy or hyperplasia observed in the chronic airflow obstruction and airway inflammation that characterizes asthma, chronic bronchitis, bronchiolitis obliterans, and chronic obstructive pulmonary disease. 

Nishimura, H., Tokuyama, K., Inoue, Y., et al. (2001) Acute effects of prostaglandin D-2 to induce airflow obstruction and airway microvascular leakage in guinea pigs role of thromboxane A(2) receptors. Prostaglandins Other Lipid Medial. 66, 1-15. 

Chronic obstructive pulmonary disease (COPD) associated with chronic bronchitis For the twice-daily maintenance treatment of airflow obstruction in patients with COPD associated with chronic bronchitis. Fluticasone propionate/salmeterol 250 meg per 50 meg twice daily is the only approved dosage for the treatment of COPD associated with chronic bronchitis. Fligher doses, including fluticasone propionate/salmeterol 500 meg per 50 meg, are not recommended. 

The American Thoracic Society (ATS) defined COPD as a disease state characterized by the presence of airflow obstruction due to chronic bronchitis or emphysema the airflow obstruction is generally progressive, may be accompanied by airway hyperreactivity, and may be partially reversible. 

Reversibility tests to bronchodilators are recommended at all stages of obstructive airways diseases. They are helpful in differentiating patients with COPD with those of asthma. Many patients with COPD and even those with severe airflow obstruction can demonstrate (partial) reversibility. Patients with a positive bronchodilator response i.e. reversibility are more likely to respond to a trial of oral or inhaled corticosteroids. 

Yellowlees PM, Alpers JH, Bowden JJ, et al Psychiatric morbidity in patients with chronic airflow obstruction. Med J Aust 146 305-307, 1987 Yeragani VK, Pohl R, Berger R, et al Decreased heart rate variability in panic disorder a study of power-spectral analysis of heart rate. Psychiatry Res 46 89-103,... 

The respiratory actions of the methylxanthines may not be confined to the airways, for they also strengthen the contractions of isolated skeletal muscle in vitro and improve contractility and reverse fatigue of the diaphragm in patients with COPD. This effect on diaphragmatic performance—rather than an effect on the respiratory center—may account for theophylline s ability to improve the ventilatory response to hypoxia and to diminish dyspnea even in patients with irreversible airflow obstruction. 

Of the xanthines, theophylline is the most effective bronchodilator, and it has been shown repeatedly both to relieve airflow obstruction in acute asthma and to reduce the severity of symptoms and time lost from work or school in patients with chronic asthma. Theophylline base is only slightly soluble in water, so it has been administered as several salts containing varying amounts of theophylline base. Most preparations are well absorbed from the gastrointestinal tract, but absorption of rectal suppositories is unreliable. 

If asthmatic symptoms occur frequently or if significant airflow obstruction persists despite bronchodilator therapy, inhaled corticosteroids should be started. For patients with severe symptoms or severe airflow obstruction (eg, FEVi < 50% predicted), initial treatment with a combination of inhaled and oral corticosteroid (eg, 30 mg/d of prednisone for 3 weeks) treatment is appropriate. Once clinical improvement is noted, usually after 7-10 days, the oral dose should be discontinued or reduced to the minimum necessary to control symptoms. 

It is recommended that patients with persistent allergic rhinitis be evaluated for asthma by history, chest examination and, if possible and when necessary, assessment of airflow obstruction before and after bronchodilator. 

CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) A general term to describe airflow obstruction due to emphysema and chronic bronchitis. 

Airflow obstruction in asthma is due to bronchoconstriction resulting from contraction of bronchial smooth muscle, inflammation of the bronchial wall, and increased mucous secretion. Asthmatic attacks may be related to recent exposure to allergens, inhaled irritants leading to bronchial hyperactivity and inflammation of the airway mucosa. The symptoms of asthma may be effectively treated by several drugs, but none of the agents provide a cure for this obstructive lung disease. 

Theophylline [the OFF i lin] is a bronchodilator that relieves airflow obstruction in chronic asthma, and decreases the symptoms of the chronic disease. Previously the main-stay of asthma therapy, theophylline has been largely replaced with (3-agonists and corticosteroids. Theophylline is well absorbed by the gastrointestinal tract, and several sustained-release preparations are available. The drug has a narrow therapeutic window, and an overdose of the drug may cause seizures or potentially fatal arrhythmias. Further, theophylline interacts adversely with many drugs. See pp. 450-451 for a description of newly approved drugs, zileuton, zafirlukast, and montelukast. 

Breathlessness Airflow obstruction, due to airway and Shortness of parenchymal damage as a result of chronic breath inflammation that is progressive, not fully reversible. 

The degree of airflow obstruction should be assessed using ... 

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