Asthma pulmonary function tests

Spirometry, an objective measure of pulmonary function, can be used to assist in confirming the diagnosis of asthma. The primary pulmonary function tests used to assist in the diagnosis of asthma are the forced expiratory volume in... 

Enright PL, Lebowitz MD, Cockroft DW. Physiologic measures pulmonary function tests. Asthma outcome. Am J Respir Crit Care Med 1994 149 S9-18 discussion S19-20. 

Contraindications Asthma, wheezing, or very low baseline pulmonary function tests concomitant useof beta-blockers hypersensitivity to the drug, because of the potential for severe bronchoconstriction... 

HPI KG is a 39-year-old woman with asthma on fluticasone and albuterol complaining of SOB associated with exercise. Three months ago she started an aerobic exercise program that has been hampered by chest tightness and SOB shortly after she begins running. She admits to poor compliance with her corticosteroid inhaler and requests an oral medication to control her asthma symptoms. Her PMH is significant for mild, persistent asthma for 35 years and allergic rhinitis. Her medications include fluticasone and albuterol inhalers and fexofenadine. Pulmonary function tests (PFTs) reveal her forced expiratory volume in the first second (FEV,) = 89% of predicted. 

In clinical practice, pulmonary function testing is the primary measurement used to assess disease and monitor asthma pharmacotherapy. Pulmonary function testing methods vary. The two most common measures of lung function include forced expiratory volume exhaled in one second (FEVi) and peak expiratory flow rate (PEE). FEV], measured in milliliters, represents the amount of air that patients can forcibly blow out in 1 second. 

Exhaled nitric oxide was used as the marker of airway inflammation after patients who had asthma were found to have increased levels of exhaled nitric oxide and nitric oxide synthase expression [17]. Exhaled nitric oxide correlated with a response to steroid, defined as change in pulmonary function testing, asthma symptoms, and BHR [18]. Patients who have symptoms of asthma who respond to steroids have higher exhaled nitric oxide than those who do not, implying inadequate anti-inflammatory treatment. The cutoff of exhaled nitric oxide for steroid response was determined to be approximately 48 parts per billion in one study [18], but no standards are widely used. 

IV. Diagnosis requires a careful occupational history. Pulmonary function testing may document an obstructive deficit or may be normal. Variable airflow or changing measures of airway reactivity (methacholine or histamine challenge) temporally linked to exposure strongly support the diagnosis of isocyanate-induced asthma. 

Spirometry demonstrates obstruction (forced expiratory volume in 1 second [FEVJ/forced vital capacity less than 80%) with reversibility after inhaled P2-agonist administration (at least a 12% improvement in FEVj). Failure of pulmonary function to improve acutely does not necessarily rule out asthma. If baseline spirometry is normal, challenge testing with exercise, histamine, or methacholine can be used to elicit BHR. 

Components of the assessment of control include symptoms, nighttime awakenings, interference with normal activities, pulmonary function, quality of life, exacerbations, adherence, treatment-related adverse effects, and satisfaction with care. The categories of well controlled, not well controlled, and very poorly controlled are recommended. Validated questionnaires can be administered regularly, such as the Asthma Therapy Assessment Questionnaire, Asthma Control Questionnaire, and Asthma Control Test. 

Histamine should not be given to patients with asthma (except as part of a carefully monitored test of pulmonary function) or to patients with active ulcer disease or gastrointestinal bleeding. 

The manufacturers have on record in the USA several pulmonary adverse effects during isotretinoin therapy, including worsening of asthma (SEDA-21,162), recurrent pneumothorax, pleural effusion, interstitial fibrosis, pulmonary granuloma, and deterioration in lung function tests. Exercise-induced asthma (35) may be caused by a significant reduction in the forced expiratory flow rate (36) and a drying effect of isotretinoin on the mucous membranes of the respiratory tract (37). 

As with other obstructive pulmonary diseases (e.g., asthma), spirometric tests will indicate a decrease in FEVj and an increase in the total forced expiratory time (the total time required to exhale the entire vital capacity of the lung). In emphysema, all of these pulmonary function parameters are altered due to a loss of the elastic recoil properties of the lung and a collapse of the intrathoracic airways during forced expiration, both of these phenomena being caused by the destruction of the interstitial connective tissue. 

Schwartz J, Weiss S. Relationship of skin test reactivity to decrements in pulmonary function in children with asthma or frequent wheezing. Am J Respir Crit Care Med 1995 152 2176-2180. 

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