spirometry functional lung test

spirometry

1. spirometry Harith riyadh & Bassam hamid

2. • Spirometry (meaning the measuring of breath ) is the most common of the pulmonary function tests (PFTs), measuring lung function, specifically the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. •

3. 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 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

4. Contraindications: • Hemoptysis of unknown origin • Pneumothorax • Unstable angina pectoris • Recent myocardial infarction • Thoracic aneurysms, abdominal aneurysms, cerebral aneurysms • Recent eye surgery (within 2 weeks due to increased intraocular pressure during forced expiration) • Recent abdominal or thoracic surgical procedures • Patients with a history of syncope associated with forced exhalation. • Patients with active tuberculosis should not be tested

5. MEASUREMENTS: There are four lung volumes and four lung capacities. A lung capacity consists of two or more lung volumes. The lung volumes are: 1. Tidal volume (VT) 2. Inspiratory reserve volume (IRV) 3. Expiratory reserve volume (ERV) 4. Residual volume (RV). The four lung capacities are: 1. Total lung capacity (TLC) 2. Inspiratory capacity (IC) 3. Functional residual capacity (FRC) 4. Vital capacity (VC).

6. 1. Tidal volume: It is the volume of air moved into or out of the lungs during quiet breathing. Value: 500ml 2 . Inspiratory reserve volume : It is the maximal volume that can be inhaled from the end inspiratory level(after the inspiration of a normal tidal volume). Value: 3100 ml 3. Expiratory reserve volume: It is the maximal volume of air that can be exhaled from the end expiratory position(after the expiration of a normal tidal volume). Value: 1200 ml 4. Residual volume: It is the volume of air remaining in the lungs after a maximal exhalation. Value: 1200 ml

7. 1. Total lung capacity: It is the volume in the lungs at maximal inflation or maximum amount of air that can fill the lungs. Value: 6000 ml (TLC = TV + IRV + ERV + RV). 2. Vital capacity: It is the total amount of air that can be expired after fully inhaling. Value: 4800 ml (VC = TV + IRV + ERV = approximately 80 percent TLC). The value varies according to age and body size. 3. Inspiratory capacity: It is the maximum amount of air that can be inspired. Value: 3600 ml (IC = TV + IRV). 4. Functional residual capacity: It is the amount of air remaining in the lungs after a normal expiration. Value: 2400 ml (FRC = RV + ERV)

8. 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 (liters) 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.

9. Parameters • The most common parameters measured in spirometry are 1. Vital capacity (VC), 2. Forced vital capacity (FVC), 3. Forced expiratory volume (FEV) at timed intervals of 0.5, 1.0 (FEV1), 2.0, and 3.0 seconds, 4. Forced expiratory flow 25 –75% (FEF 25–75) and 5. Maximal voluntary ventilation (MVV), [5] also known as Maximum breathing capacity. * 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)

10. 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 one second, after full inspiration. • Average values for FEV1 in healthy people depend mainly on sex and age. • Values of between 80% and 120% of the average value are considered normal. • FEV1/FVC ratio (FEV1%) • FEV 1 /FVC (FEV1%) is the ratio of FEV 1 to FVC. • In healthy adults this should be approximately 75 –80%. • Forced expiratory flow (FEF) • Forced expiratory flow (FEF) is the flow (or speed) of air coming out of the lung during the middle portion of a forced expiration. • It can be given at discrete times, generally defined by what fraction remains of the forced vital capacity (FVC). • The usual intervals are 25%, 50% and 75% (FEF25, FEF50 and FEF75), or 25% and 50% of FVC.

11. HOW IS THE TEST PERFORMED The patient is instructed to inhale as much as possible and then exhale rapidly and forcefully for as long as flow can be maintained. The patient should exhale for at least six seconds. At the end of the forced exhalation, the patient should again inhale fully as rapidly as possible. The FVC should then be compared with that inhaled volume to verify that the forced expiratory manoeuvre did indeed start from full inflation. The FVC and the FEV1 should be repeatable to within 0.15 L upon repeat efforts unless the largest value for either parameter is less than 1 L. In this case, the expected repeatability is to within 0.1 L of the largest value.

12. Risks Spirometry is generally a safe test. You may feel short of breath or dizzy for a moment after you perform the test. Because the test requires some exertion, it isn't performed if you've had a recent heart attack or some other heart condition. Rarely, the test triggers severe breathing problems

13.  Measured (actual) spirometry values are compared with predicted values- age , height, weight & gender; expressed as a % of predicted value.(>80% normal limits).  During expiration floating drum moves up , counter wt comes down , downward deflection on the graph.  Inspiration the drum moves down, counter wt comes up, upward deflection on the graph.  Spirometry test –measured twice both before and after given a bronchodilator.  Improvement in measurements means patient will respond well

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