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Spirometry (meaning the measuring of breath) is the most common of the pulmonary function tests (PFTs). It measures lung function, specifically the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. Spirometry is helpful in assessing breathing patterns that identify conditions such as asthma, pulmonary fibrosis, cystic fibrosis, and COPD. It is also helpful as part of a system of health surveillance, in which breathing patterns are measured over time. Spirometry generates pneumotachographs, which are charts that plot the volume and flow of air coming in and out of the lungs from one inhalation and one exhalation. Testing Spirometer The spirometry test is performed using a device called a spirometer, which comes in several different varieties. Most spirometers display the following graphs, called spirograms: a volume-time curve, showing volume (litres) along the Y-axis and time (seconds) along the X-axis a flow-volume loop, which graphically depicts the rate of airflow on the Y-axis and the total volume inspired or expired on the X-axis Procedure The basic forced volume vital capacity (FVC) test varies slightly depending on the equipment used. It can be in the form of either closed or open circuit. Regardless of differences in testing procedure providers are recommended to follow the ATS/ERS Standardisation of Spirometry. The standard procedure ensures an accurate and objectively collected set of data, based on a common reference, to reduce incompatibility of the results when shared across differing medical groups. The patient is asked to put on soft nose clips to prevent air escape and a breathing sensor in their mouth forming an air tight seal. Guided by a technician, the patient is given step by step instructions to take an abrupt maximum effort inhale, followed by a maximum effort exhale lasting for a target of at least 6 seconds. When assessing possible upper airway obstruction, the technician will direct the patient to make an additional rapid inhalation to complete the round. The timing of the second inhale can vary between persons depending on the length of the proceeding exhale. In some cases each round of test will be proceeded by a period of normal, gentle breathing for additional data. Limitations Clinically useful results are highly dependent on patient cooperation and effort and must be repeated for a minimum of three times to ensure reproducibility with a general limit of ten attempts. Given variable rates of effort, the results can only be underestimated given an effort output greater than 100% is not possible. Due to the need for patient cooperation and an ability to understand and follow instructions, spirometry can typically only be done in cooperative children when they at least 5 years old or adults without physical or mental impairment preventing effective diagnostic results. In addition, General anesthesia and various forms of sedation are not compatible with the testing process. Another limitation is that persons with intermittent or mild asthma can present normal spirometry values between acute exacerbation, reducing spirometry's effectiveness as a diagnostic tool in these circumstances. Supplemental diagnostics Spirometry can also be part of a bronchial challenge test, used to determine bronchial hyperresponsiveness to either rigorous exercise, inhalation of cold/dry air, or with a pharmaceutical agent such as methacholine or histamine. To assess the reversibility of a particular condition, a bronchodilator can be administered before performing another round of tests for comparison. This is commonly referred to as a reversibility test, or a post bronchodilator test (Post BD), and is an important part in diagnosing asthma versus COPD. Other complementary lung functions tests include plethysmography and nitrogen washout. Indications Spirometry is indicated for the following reasons: to diagnose or manage asthma to detect respiratory disease in patients presenting with symptoms of breathlessness, and to distinguish respiratory from cardiac disease as the cause to measure bronchial responsiveness in patients suspected of having asthma to diagnose and differentiate between obstructive lung disease and restrictive lung disease to follow the natural history of disease in respiratory conditions to assess of impairment from occupational asthma to identify those at risk from pulmonary barotrauma while scuba diving to conduct pre-operative risk assessment before anaesthesia or cardiothoracic surgery to measure response to treatment of conditions which spirometry detects to diagnose the vocal cord dysfunction. Contraindications Forced expiratory maneuvers may aggravate some medical conditions. Spirometry should not be performed when the individual presents with: Hemoptysis of unknown origin Pneumothorax Unstable cardiovascular status (angina, recent myocardial infarction, etc.) Thoracic, abdominal, or cerebral aneurysms Cataracts or recent eye surgery Recent thoracic or abdominal surgery Nausea, vomiting, or acute illness Recent or current viral infection Undiagnosed hypertension Parameters The most common parameters measured in spirometry are vital capacity (VC), forced vital capacity (FVC), forced expiratory volume (FEV) at timed intervals of 0.5, 1.0 (FEV1), 2.0, and 3.0 seconds, forced expiratory flow 25–75% (FEF 25–75) and maximal voluntary ventilation (MVV), also known as Maximum breathing capacity. Other tests may be performed in certain situations. Results are usually given in both raw data (litres, litres per second) and percent predicted—the test result as a percent of the "predicted values" for the patients of similar characteristics (height, age, sex, and sometimes race and weight). The interpretation of the results can vary depending on the physician and the source of the predicted values. Generally speaking, results nearest to 100% predicted are the most normal, and results over 80% are often considered normal. Multiple publications of predicted values have been published and may be calculated based on age, sex, weight and ethnicity. However, review by a doctor is necessary for accurate diagnosis of any individual situation. A bronchodilator is also given in certain circumstances and a pre/post graph comparison is done to assess the effectiveness of the bronchodilator. See the example printout. Functional residual capacity (FRC) cannot be measured via spirometry, but it can be measured with a plethysmograph or dilution tests (for example, helium dilution test). Forced vital capacity (FVC) Forced vital capacity (FVC) is the volume of air that can forcibly be blown out after full inspiration, measured in liters. FVC is the most basic maneuver in spirometry tests. Forced expiratory volume in 1 second (FEV1) FEV1 is the volume of air that can forcibly be blown out in first 1-second, after full inspiration. Average values for FEV1 in healthy people depend mainly on sex and age, according to the di.... Discover the Robert J Bambery popular books. Find the top 100 most popular Robert J Bambery books.