SPIROMETRY BASICS ROSEMARY STINSON MSN, CRNP THE CHILDREN’S HOSPITAL OF PHILADELPHIA DIVISION OF ALLERGY AND IMMUNOLOGY PORTABLE COMPUTERIZED SPIROMETRY WITH BUILT IN INCENTIVES WHAT IS SPIROMETRY? Use to obtain objective measures of lung function Physiological test that measures how an individual inhales or exhales volume of air Primary signal measured–volume or flow Essentially measures airflow into and out of the lungs Invaluable screening tool for respiratory health compared to BP screening CV health Gold standard for diagnosing and measuring airway obstruction. ATS, 2005 SPIROMETRY AND ASTHMA At initial assessment After treatment initiated and symptoms and PEF have stabilized During periods of progressive or prolonged asthma control At least every 1-2 years: more frequently depending on response to therapy WHY NECESSARY? o To evaluate symptoms, signs or abnormal laboratory tests o To measure the effect of disease on pulmonary function o To screen individuals at risk of having pulmonary disease o To assess pre-operative risk o To assess prognosis o To assess health status before beginning strenuous physical activity programs ATS, 2005 SPIROMETRY VERSUS PEAK FLOW Recommended over peak flow meter measurements in clinician’s office. Variability in predicted PEF reference values. Many different brands PEF meters. Peak Flow is NOT a diagnostic tool. Helpful for monitoring control. EPR 3, 2007 WHY MEASURE? o Some patients are “poor perceivers.” o Perception of obstruction variable and spirometry reveals obstruction more severe. o Family members “underestimate” severity of symptoms. o Objective assessment of degree of airflow obstruction. o Pulmonary function measures don’t always correlate with symptoms. o Comprehensive assessment of asthma. ATS, 2005 ; EPR 3, 2007 EPR 3,1997 SPIROMETRY MYTHS Can’t be performed on children It takes a long time It can only be performed by respiratory therapists The curves and numbers are hard to interpret TEST PROCEDURE Three Phases: o Maximal inspiration- Deep breath in o Exhalation- Blast of air: Takes at least 6 seconds to fully empty air o Continue completion to end of time Vital Capacity: o Maximum amount of air emptied from lungs o Average 3-5 liters o Dependent on age, sex, height COMMONLY MEASURED VARIABLES Forced Vital Capacity (FVC) Forced Expiratory Volume in first second (FEV1) FEV1/FVC Forced Expiratory Flow from 25-75% of FVC (FEF25-75%) Peak Expiratory Flow (PEF) Flow volume loop/expiratory curve FEV1 Defined: Forced expired volume in 1st second of FVC maneuver; Normal > 80% Expressed as a percent of the predicted value A proportion of the forced vital capacity (FVC) or FEV1 /FVC. Approximately 2.5 - 4 Liters Depends upon age, height, sex Measure of speed exhalation (volume/liters) Value most used to diagnose obstructive disease and degree of improvement with bronchodilator The test most used for assessing the risk of future of exacerbations ATS, 2005; EPR 3 ,2007 FEV1 FVC Defined: Forced vital capacity-Maximal volume of air exhaled with maximum force Measures the amount of air blown out after full inspiration Total lung capacity minus Residual Volume Their “umph” factor FVC FEV1/FVC RATIO Defined: Amount of air expired in the 1st second/ Total amount air expired during maneuver o Decreased in obstructive, normal in restrictive o Calculated result o Measured FEV1 / Measured FVC o Percentage o Example: FEV1 3 L and FVC 4 L ; FEV1/FVC= 75% o Compared to predicted normal value ( age, sex, height) PEFR Defined: Peak expiratory flow rate- The maximum flow attained during a FVC maneuver. Effort dependent! The top of the blast Value indicative of large airway function Used to determine baseline in peak flow meters Measure PEFR (in meters/second) x 60 = baseline Must have baseline minimum of ~ 240 Liters FEF 25-75% Defined: Measures the average amount of air in the small airways during the middle half of test (From 1-3 seconds) Forced expiratory flow rate between 75% and 25% of FVC Flow in the middle of the curve Measures small airways function Effort dependent Useful in children over 10 yrs old Most sensitive test to detect the presence of early small airways disease! FEF 25-75% THE EXPERT PANEL RECOMMENDED SPIROMETRY MEASUREMENTS: • FEV1 • FEV 6 Before AND after use of • Forced expiratory volume in 6 seconds short-acting • FVC bronchodilator • FEV1/FVC Should be performed for patients where a diagnosis of asthma is being considered Including children ≥ 5 years of age. EPR 3- Guidelines, 2007 TESTING METHOD o Patient has 3 acceptable tests o Pre bronchodilator o Drug administered (Albuterol 4 puffs 90 mcg/puff) o Testing repeated: > 10 to 15 minutes post SABA > 30 minutes post anticholinergic agents o Significant reversibility an increase in FEV1 > 200 ml and 12 % from baseline o Degree of airway reversibility- correlates with airway inflammation ATS 2005 ; EPR 3 ,2007 TESTING… o Aim of test –to determine whether patient lung function can improve with therapy- in addition to their regular medications. o Baseline testing: when not taking any drugs • SABA> 4 hours • LABA, Theophylline> 12 hours • No smoking> 1 hour prior to testing ATS, 2005 SUMMARY Pulmonary functions are important o Gold standard used to confirm diagnosis of asthma (≥ 12% FEV1, ≥ 200 ml) o Determine the degree of obstruction o Determine severity o To assess one aspect of response to therapy o To monitor for future remodeling SUPPLEMENTAL SLIDES BRONCHODILATOR RESPONSE FEV1 may improve within about 10 minutes of using inhaled bronchodilator If reverses by ≥ 12% “reversibility” or “bronchial hyper-responsiveness” has been demonstrated If reversible, suggests asthma If not reversible, does not exclude asthma PRE-POST SPIROMETRY REPORT .