Asthma pulmonary function test
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Editor(s)-in-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-632-7753; Philip Marcus, M.D., M.P.H. [2]
Overview
Asthma is defined as reversible airway obstruction that occurs spontaneously or with treatment. The basic measurement of airway function is using peak flow rates. While measurement of airway function is possible in adults, most new cases that are diagnosed constitute the pediatric age group, who are unable to perform such tests. Thereby, diagnosis in children is based on a careful compilation and analysis of the individual's medical history and demonstration of symptomatic improvement with the administration of inhaled bronchodilator. In adults, diagnosis can be made with a peak flow meter that assess any airway restriction, diurnal variation and any reversibility following inhaled bronchodilator. Young asthmatics may experience only exercise-induced asthma; hence, testing peak flow at rest and after exercise may be beneficial. If in doubt, lung function test may be conducted to ascertain the diagnosis. Once the diagnosis is established, peak flow meter testing may be conducted to monitor the severity and progression of the disease. Capnography may be used in the emergency situations, to measure the amount of exhaled carbon dioxide and if used in conjunction with pulse oximetry may be possible to estimate the amount of oxygen dissolved in the blood, in order to determine the severity of an asthma attack as well as the predict the response to therapy.[1]
Diagnostic Criteria Based On The British Thoracic Society[2]
- ≥20% difference on at least three days in a week for at least two weeks;
- ≥20% improvement of peak flow following treatment. For example:
- 10-minutes of inhaled beta-agonist such as salbutamol;
- 6-week of inhaled corticosteroid such as beclometasone;
- 14-days of 30mg prednisolone.
References
- ↑ Corbo J, Bijur P, Lahn M, Gallagher EJ (2005) Concordance between capnography and arterial blood gas measurements of carbon dioxide in acute asthma. Ann Emerg Med 46 (4):323-7. PMID: 16187465
- ↑ Pinnock H, Shah R (2007) Asthma. BMJ 334 (7598):847-50. DOI:10.1136/bmj.39140.634896.BE PMID: 17446617