Airflow limitation

The Global Initiative for Chronic Obstructive Lung Disease (GOLD) has defined COPD as a disease state characterized by airflow limitation that is not fully... 

During COPD, the following symptoms occur, usually in the order mucus hypersecretion, ciliary dysfunction, airflow limitation, pulmonary hyperinflation, gas exchange abnormalities, pulmonary hypertension and cor pulmonale. Acute exacerbations appear to be mainly triggered by bacteria, viruses or environmental pollutants. They lead to a worsening of lung functions, wasting and increased mortality their psychosocial impacts include depression and anxiety that may be associated with the will to die. 

COPD includes chronic bronchitis and emphysema. Chronic bronchitis is defined clinically as a chronic productive cough for at least 3 months in each of two consecutive years in a patient in whom other causes have been excluded.1 Emphysema is defined pathologically as the presence of permanent enlargement of the airspaces distal to the terminal bronchioles, accompanied by destruction of their walls without obvious fibrosis.1 The major risk factor for both conditions is cigarette smoking, and many patients share characteristics of each condition. Therefore, new consensus guidelines have moved away from using these subsets and instead focus on chronic airflow limitation. 

A suspected diagnosis of COPD should be based on the patient s symptoms and/or history of exposure to risk factors. Spirometry is required to confirm the diagnosis. The presence of a postbronchodilator FEV,/FVC ratio less than 70% [the ratio of FEV, to forced vital capacity (FVC)] confirms the presence of airflow limitation that is not fully reversible.1,2 Spirometry results can further be used to classify COPD severity (Table 12-1). Full pulmonary function tests (PFTs) with lung volumes and diffusion capacity and arterial blood gases are not necessary to establish the diagnosis or severity of COPD. 

Obtain spirometry measurements to assess airflow limitation and aid in severity classification and treatment decisions. Measure arterial blood gases if FEV is less than 40% predicted or if the patient has clinical signs suggestive of respiratory failure or right heart failure. 

Hogg JC. Pathophysiology of airflow limitation in chronic obstructive pulmonary disease. Lancet 2004 364 709-721. 

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible. The airflow limitation is usually both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases. The most common conditions comprising COPD are chronic bronchitis and emphysema. 

Initial symptoms of COPD include chronic cough and sputum production patients may have these symptoms for several years before dyspnea develops. The physical examination is normal in most patients who present in the milder stages of COPD. When airflow limitation becomes severe, patients may have cyanosis of mucosal membranes, development of a barrel chest due to hyperinflation of the lungs, an increased resting respiratory rate, shallow breathing, pursing of the lips during expiration, and use of accessory respiratory muscles. 

Assessment of airflow limitation through spirometry is the standard for diagnosing and monitoring COPD. The forced expiratory volume after 1 second (FEVj) is generally reduced except in very mild disease. The forced vital capacity (FVC) may also be decreased. The hallmark of COPD is a reduced FEVpFVC ratio to less than 70%. A postbronchodilator LEV, that is less than 80% of predicted confirms the presence of airflow limitation that is not fully reversible. 

Pike, V.W., F.I.Aigbirhio, C.A.J.Freemantle, B.C.Page, C.G.Rhodes, S.L.Waters, T.Jones, P.Olsson, G.P.Ventresca, R.J.N.Tanner, M.Hayes, and J.M.B. Hughes. 1995. Disposition of inhaled 1,1,1,2-tetrafluoroethane (HFA134a) in healthy subjects and in patients with chronic airflow limitation. Drug Metab. Disp. 23 832-839. 

Simpson, E. G., Belfield, P. W., and Cooke, N. J. (1985). Chronic airflow limitation after inhalation of overheated cooking oil fumes. Postgrad. Med. J. 61,1001-1002. 

Exposure of silica has also been related to chronic airflow limitation without radiographic changes. Epidemiological studies of quartz-exposed workers reported statistically signifi-... 

Neukirch F, CooremanJ, KorobaeffM, et al Silica exposure and chronic airflow limitation in pottery workers. Arch Environ Health 49 459M64, 1994... 

COPD is a chronic, slowly progressive disorder characterized by airways obstruction (FEVi < 80% predicted FEViA C ratio < 70%) which does not change markedly over several months. The airways obstruction is largely fixed but may be partially reversible by bronchodilator therapy. Unlike asthma, airflow limitation in COPD can never be returned to normal values. The diagnosis of COPD is usually suggested by symptoms. A firm diagnosis can only be made by objective measurement of airways obstruction with spirometric tests, which may be enhanced by radio diagnostic techniques (Table 4). 

Asthma is considered as a chronic inflammatory disorder of the airways. This inflammation causes recurrent episodes of symptoms, variable airflow limitation, and increased airway responsiveness. Prevention of asthma involves both the prevention of the initial development of asthma (= primary prevention) and the prevention of exacerbation in patients with asthma (= secondary prevention). Primary prevention methods include reducing exposure to indoor allergens, particularly domestic mites, avoidance of passive smoking, especially by infants, and avoidance of vehicle emission pollutants, largely from incomplete combustion of petrol by car engines. 

Vincken WG, Gauthier SG, Dollfuss RE, Hanson RE, Darauay CM, Cosio MG. Involvement of upper-airway muscles in extrapyramidal disorders a cause of airflow limitation. N Engl J Med 1984 311 438442. 

Peak flow measurement of peak expiratory flow rate (PEFR) on waking, before bed, before and after bronchodilator medication is useful to assess the extent of airflow limitation and the characteristic of the disease in terms of reversibility. There is some evidence of diurnal variability. PEFR is also useful in assessing the disease progression longer term and the response to therapy. Patients are advised to keep an asthma diary and record regularly the peak flows to ascertain their diurnal pattern. 

This patient s PEFR (150 L/min) is very limited. In a patient of her age and weight her normal value would be 300-350 L/min hence she is showing 50% or <50% of her best value which indicates substantial airflow limitation. 

Begin R, Boileau R, Peloquin S. 1987a. Asbestos exposure, cigarette smoking, and airflow limitation in long-term Canadian chrysotile miners and millers. Am J Ind Med 11 55-66. 

Papi A, Romagnoli M, Baraldo S, Braccioni F, Guzzinati I, Saetta M, Ciaccia A, Fabbri LM. Partial reversibility of airflow limitation and increased exhaled NO and sputum eosinophilia in chronic obstructive pulmonary disease. Am. J. Respir. Crit. Care Med. 2000 162 1773-1777. 

Crystalline silica Dusts generated by mining, other industrial activities. Dusts produced by erosion of friable, silica-rich rocks (i.e., some ash flow tuffs, diatomaceous earth deposits). Inhalation. Silicosis, industrial bronchitis with airflow limitation, progressive massive Hbrosis. Associated illnesses include opportunistic infections, silica nethropathy, lung cancer. 

Tiotropium is inhaled from the HandiHaler, a dry-powder, breath-activated inhaler system that delivers particles to the lung over a wide range of airflow limitations in patients with chronic obstructive pulmonary disease (COPD) it can be effectively delivered at inspiratory flow rates as low as 201/minute (2). Pharmacodynamic steady-state studies have shown that most of the bronchodUator activity is achieved with one to two doses within 48 hours, although a carryover effect on forced vital capacity was observed beyond 48 hours (3). 

OUerenshaw, S.L. and Woolcock, A.J. (1992). Characteristics of the inflammation in biopsies from large airways of subjects with asthma and subjects with chronic airflow limitation. Am. Rev. Respir. Dis. 145, 922-927. 

Guyatt GH, Townsend MB, Pugsley SO, et al. Quality of life in patients with chronic airflow limitations. Br J Dis Chest 1987 81 45-54. 

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